@@Pricklyscug [loud incorrect buzzer] this is a coilgun, though the differences between railgun and coilgun are less severe than the difference of railgun vs gauss cannon.
@@Pricklyscugdefinitely not a Gauss riffle. A Gauss riffle can be visualized (if you don’t like magnets) as a ball roll down a hill and hitting block with 2 ball bearings on the end. Like a newton’s cradle the one on the end hits the next ball in line carrying the energy from the previous collision, gaining it as it gets closer to the magnet and passing the energy to the next ball bearing repeating the process.
@@ActualRealKayamariOfficialVEVO it's no coilgun either. In what type of coilgun did you see energy transfer through contacts? It's basically modified railgun design with supporting magnets instead of strong current on rails and with multiturn coil instead of "1turn" projectile closing the loop.
@@Promilus1984 You're sort of correct in the claim that this isn't a coilgun either, but my reasoning here was that due to a coilgun essentially being an unfurled brushed motor this design isn't too far off seeing as those also use sliding contacts when the configuration is coils on the rotor with magnets as the stator. Additionally the base form of a railgun does not utilize permanent magnets (though they can be utilized) while this design of course requires permanent magnets to function!
Fun idea. Some improvements: iron strips on the outside of the magnets to close the field lines; square coils to get get the drive currents perpendicular to the field; graphite core to increase field strength; graphite brushes to reduce contact resistance; use finer wire with more turns to reduce current, all things being equal you'll get the same force and mass if you halve the wire cross section and double the turns (or you can then double the voltage to double the force for the same mass).
More turns will increase resistance and reduce conductance, right? Interesting to test though. Somewhere, some Defense engineers are passing this vid around the office betting on if the author keeps experimenting.
Finer wire with more turns would actually not work as well - field is proportional to current (thicker wire more better) and the rate at which the polarity of the field can change is inversely proportional to the coil’s inductance (again, thicker wire more better)
i an a retired engineer, but I still love to watch people figure stuff out, and great job! I worked a lot on rail gun tech. It's pretty scary when you get up to levels they use for weapons. I also love how you designed and printed the parts out. Thanks for the posting. I know you put a lot on work in this video. Smiles!
14:53 the reason it goes faster than your estimation is because the magnets cause less back EMF in the coils at lower speeds. Also a tip, as the coil speeds up down the rail you need to "advance" the polarity switch timing to account for the lag of the inductor/s responding to the voltage applied. They do not immediately produce a magnetic field. This could be limiting your speed (as well as back EMF providing a maximum limit for any voltage you apply).
I had a similar thought when watching the video and went back later and posted a comment about it, fortunately you posted a much better version 3 hours before me 😂
@@jackevans2386 This version is purely electromechanical so there is no where to add SW based delays, the first version had computer control though. Having the contacts able to move separately from the magnets would allow for tuning of the timing advance needed to maximize the acceleration. The problem is that this tuning would be sensitive to the total weight of the sled and payload so not friendly for variable purposes. I would also add that the speed of the sled vs. number of windings experiments needed to have a dummy payload on them otherwise the results will not scale properly. Adding 10% mass to the total weight (sled+payload) for double the windings is a much different argument than adding 75% mass to just the sled for double the windings.
Seeing all the sparks and spark damage, I have quick and simple recommendation: I'm not sure the voltage you are running, but across the terminals of the coil, solder something like an MOV in parallel. The sparks are created by inductive kick. So if you have 24v going through like 2 ohms, you're going to have 12A running through the coil. When the contact is broken, it is slow to change current, and will try to force 12A through open air, resulting in a huge voltage spike. An MOV becomes more conductive at higher voltages to protect against voltage spikes. This could drastically reduce the voltage of the spikes. There would still be sparks, but they would be less damaging. I didn't think this over too much, though. So there might be other effects to contend with. For instance, since the coil could "free-wheel" at the threshold voltage, it might make the current in the coil last longer, so you might get slowdown. It would be something to test. You might want a reverse-current bypass diode on your output source as well. EDIT: Dang, now I'm thinking about it. You could even try a capacitor as well as the MOV, Have it store some of that remaining energy into a capacitor that is ready to discharge in the opposite direction. But that might be tricky due to all the phase issues at different speeds.
MOV's are like fuses, they are more or less "in case of" not really "to remove existing." TL;DR: the MOV would probably not last too long. I personally would try and go the tuned passive rout, as that is keeping closer to the "purely mechanical" theme.
There's a very good reason brushed motors do not use metal brushes, but graphite (with a little powdered metal). Though brittle, and not really that hard, these brushes are very slippery and hard wearing, and will conform to small scrapes and wear on the contact points on the rotor shaft. So if you actually machined the contact points on the rail, some very cheap replacement brushes made for, say, an 18V drill, or even a 220V drill, will work for ages. Some of them even come with their own springs, and basically all of them come with a wire already attached, so you wouldn't need crimping. moving the power rails to the middle might be a good idea as well, having the brushes pinch a power rail, rather than push out on either side. With graphite brushes pinching a central power rail, you can also put much more force into the contact (remember they're slippery), therefore making the contact with each electrode (I'm missing the proper word for this, please tell me if you know one) "promptly, precisely, with force and without hesitation, as expected". You may also have to use copper/brass as electrodes. And maybe make a tool with two brushes to clean them if you still get arcing. Anyway, love the vid, and can't wait to see what you'll do with this!
Two suggestions: Insert an iron core into the coil to focus the magnetic flux. And exponentially increase the magnets along the track to build up the acceleration.
@@FondueBrothers maybe not?. You could, in theory, print it like a channel and just stack the magnets next to each other. At this point it becomes how close the AC connectors can be.
@@oasntetI agree that powdered ferrite seems like it would be better, but as you say I’m not sure whether the frequencies involved would be high enough for it to make a difference or not.
@@DaveEtchells Guessing really wildly and looking at the frame data in his analysis, I estimate the switching frequency can't be much more than a kHz or two. That said, it'll look more like a square wave than a sine because of the time spent in air, and it's really the charging and discharging time we care about most. If we sliced out the air time and measured the ramp up / ramp down times, that could be far higher. I wouldn't even know where to start, there.
I like that he shows the actual build process and gives you enough info to give you a head start on research into his projects. A lot of the maker community has started to use making as a way of telling a narrative and don't focus on the actual project.
Not wieners. Go with coconut cream pies. You'll get a more enthusiastic reaction from your targeted audience. Of course, if you hit a gal in a nice dress, you'll be running for your life, but hey, it is the viral video were going for right?
12:37 If you're using a cap screw to hold your sled brushes in place, you can probably fold the brush around the strip and skip the solder. The cap screw should be fine for a compression fit, if not, a little tweaking to your design and you're good.
Yeah when he said he clamped the contact surfaces together, I thought he meant he clamped the contact surfaces together (the contact surfaces being 2 strips, one soldered to coil, other clamped onto the brush). But all he means was that the clamp held it in position, and still needed to get soldered :p (ps: I know he said he needs to solder on new brushes, but he actually do not. The brushes are clamped into position into the soldered strip, but not soldered stuck. So he could bend it open, replace the brush, and bend it stuck again. Will get metal fatigue, but should work for a couple replacements before that happens at least.)
Also, since you're using solder wick for brushes, soak it in alcohol for a bit and blow it out with compressed air. Solder wick has flux in it an might be contributing to the residue left behind when it arcs and sparks.
You could integrate this launcher into ProjectAir's giant RC aircraft carrier and you'd have the ultimate model plane takeoff from the sea - please consider the collab! Amazing stuff as always Tom. :D
It's probably fake audio though, audio generally doesn't work in slow mo. The slo mo guys have to artistically create audio for every shot. In this one I think you can see the sound pitch is too high for the speed of the propeller at that time.
Graphite carbon brushes are used in electric motors that have a high durability, don't leave molten splatter, and can be held to the contacts under pressure with a spring. Love the all mechanical design!
@@user36058 technically his previous launcher was much closer to an LSM launch since it used electronically synchronized coils along the rail and the magnets were on the sled
Cool that you got this far without any electronics. But as an EE, I kinda smiled when, among other things, you devised a complex mechanical switch debouncer, something us EEs have known how to do electronically and very simply for a very long time. I'm also sure that the judicious use of electronic switching could greatly reduce your many arcing problems.
I believe you will find a performance increase if you wound the windings in a much neater way rather than crossing over itself so many times. Also I'd be curious to know how adding a core to the windings would also help but yes it would increase the weight, I think it's worth a shot. also also... I grew up playing with AFX cars, they used springs to push out the contacts to keep them connected to the rails as best as possible, I think if you switched from the braid to springs pushing strips of metal you might get better contact
As far as I understand, the crossovers in the windings don't matter so long as the windings are all going in the same direction around the spool, the main reason you want tight windings is to fit more of them in the same volume, providing a higher magnetic flux, and therefore more force
@@eragonawesome I'm inclined to believe you but I thought in the past I have seen a motor with the same number of turns have high torque when the windings are tighter. I'll admit I don't know enough on the topic
The more turns the coil has, the higher the inductance, that causes current to increase slower. From video you can see that you have a few ms per contact point, so minimizing the time to hit max current is important. Magnetic field is proportional to current, and also proportional to number of turns, but number of turns is also proportional to inductance, and that is something you want to reduce.
Slight correction here: When you are winding a conductor, (making a "coil") the inductance is always square to the number of turns, not proportional! See different formula depending on the actual geometry here: en.wikipedia.org/wiki/Inductor#Inductance_formulas. In this video, Tom is building a multi-layer air core .
@@AntoineZenRuffinen It does lead to the question of whether a ferrite core would help the inductance more than it hurts the mass; but the mass of the plane probably makes that nearly meaningless. He should have tuned with a plane-mass-simulator, rather than an empty sled...
@@oasntet Maybe the ferrite core would help, maybe not. This would need some calculation to know. Nevertheless, I think a good optimization, would be to use an "Halbach array" configuration (en.wikipedia.org/wiki/Halbach_array) for the magnets, as it would improve magnetic field and don't adds any moving mass to the the sled.
Excellent project! One of the things it puts me in mind of is the introduction of solid state switching in the 60's and 70's using semiconductors. The use of semiconductors for switching largish currents (a few amps and more) was not fully understood and there were initially many failures, so after engineers initially got excited about solid state switching (encouraged by the manufacturer's bilge!) there was a move back to mechanical switching and relays. The solutions to the problems caused in mechanical switching were much more transparent than the poorly understood semiconductors. Likewise, you say you wanted to simplify your launcher from any use of electronics which makes it a much more understandable demonstration. Well done!
Who else heard "i built a similar launcher a few years ago" checked the video, saw it was 2 years ago, and then stopped to question wtf is going on with time.
Place a steel core in the coils. Also use multstranded wire for coil (litz wire) to avoid skin effect and increase speed at which fields are formed. Perhaps add caps/supercaps to avoid power dips if any. Awesome idea, I build a rail gun way back for my thesis at Uni.
I think proximity effect is more important in this coil. But I agree with a core and additional capacitors along the rail as close as possible. Any resistance has huge impact at those 90 Amps.
I wonder if the higher coil inductance with more windings causes an issue with the changing polarity. A steel core would definitely improve the coils power output but I wonder if the then even stronger magnetic-field in the coil breaks down to "zero" fast enough before the next contact strip is hit.
The engineering compromise he spends the last part of the video talking about id magnetic force Vs coil mass - a steel core would mean more force but way higher mass so it would probably harm acceleration overall
If you add a capacitor parallel to the coil ends, you can reduce the electric arc between the contacts. Nice project, very fantastic works can be done on a larger scale.
for speed, alter the spacing/timing of the contacts and magnets in the later stages. use the vid tracker to see where the current acceleration stops....start spreading them out after that point.
@@naasking if the magnet pairs and contacts were each modular and could be spaced along the rail....something whispers logrhythmic pattern to me, but i'm just making it up as i go.
@@naasking Yup. Maybe mount the contact plates in angled slots and tie them to a lever. Then you place the launcher and mass on the lever to set the timing and lock it in with a knob.
you should add a ferrite or iron (but the ferrite it not that heavy like iron ) core to the coil to concentrate the magnetic field facing the magnets, you will get more force
What an awesome project. I love the elegant simplicity of this launcher. Although it makes you wonder just how much current those Navy electromatic aircraft launchers are pulling. That has got to be a wild setup.
Cool and fun video. Few thoughts: 1. Adding back iron will probably increase your flux level in the coil, markedly. 2. Don't have the carriage in the range of contacts when turning on the power to the rails. Have a spring launch the carriage at a 'slow' roll at the first contact pair, with power delivered to rails with no load. Fraction of second switch bounce won't matter. 3. Widen your magnet spacing to get higher speed, either widen them all evenly, or space them out as function of distance from first contacts. It will show the early acceleration, but should increase your final velocity. 4. Consider figuring out how much BEMF your seeing from the coil moving in the magnets. Without power, STEADILY pull the carriage down the rails and measure the voltage generated across the rails according to position, and speed. Really needs to be captured with a scope and a 2nd channel for position info. BEMF is proportional to speed. Record of BEMF will let you adjust the contacts position with respect to the magnets. (BEMF is motor-speak for what keeps you from pushing more current into a motor at "full speed" - the voltage you're applying is fighting the voltage generated by moving the coil through the magnetic field.) 5. Consider voltage jumps as you go down the rail. Later contacts will have more voltage than earlier ones, and magnets can be spaced out further at the same time. A series of batteries with multiple taps can feed multiple rail segments. Bit more complex, but still pretty manageable. It will cause a step/jump in the acceleration, so the load should not be too delicate (foam wings?)
@@cactus_cuber1589 No, railgun is a bit different with projectile being part of a single wire coil and high current pushing rails and projectile apart. This is basically linear motor.
@@pavelperina7629your correct that this is not a rail gun. But, technically here, power is also conducted through the projectile (coil in the sled) , and technically both linear rail guns and coil guns are linear motors. What makes this a coil gun is simply using a coil despite the fact that more traditional coil guns use coils in stator. Here we get alternating magnets and a mechanically commutated coil in the sled. A rail gun has pure DC flowing through the rails and projectile, and has no coil, and makes continouse electrical contact with the rails.
To prevent solder wicking, cool it down with something cold. Bits of metal would be ideal. Also, solder does not flow upwards easily, use this to your advantage.
Nice design. I did an optically timed coil gun back in the 1990s. It shot a 1" diameter bearing 2 to 4 meters vertical. Each coil was powered by a modified h-bridge of hexfets and diodes and was on only when it's optical sensor was interrupted, or one of the previous two were. This made a traveling magnetic wave down the tube that pulled the projectile forward. When I turned a coil off I dumped it's energy back into the power rail via the diodes. Current limiting was by wire length. I was putting 200 Amps through 22 AWG magnet wire. Needless to say the coils couldn't remain on very long or they would turn to slag. I didn't bother to heatsink any of the FETS or diodes because the on time was so short. Power was from a capacitor bank charged with a 24 Volt linear power supply limited by a 200W resistor. I forget how many ohms. I'd go on to make more and more powerful ones.
By the way, feed your current in on the exit. So the voltage drop over your busbars is less and less obvious to the end, increasing force instead of dropping. 90A is starting to get serious
8:00 very cool solution to make your own reed type switch! Another idea that first came to me, was making a latch at the top that as it hits, holds it up and won't let it bounce at all. Then to reset, you lift the latch and put in the lower latch
@@poipoi300 I don't know if light switch would be able to handle the amps? (I know most are 25amps AC always confused on how to figure out what DC current that means.) Also, I think there might still be some 'bounce' in a switch at the high of speeds he's dealing with?
@@justinbanks2380 His power source is DC, but if you check how the circuit is used, it's a lot more like AC. The load isn't continuous, instead it's alternating between on and off. Not for long either. Light switches are designed in such a manner that they don't spark. I'd imagine them to have less bounce on startup than what he built, but I don't know that for certain. Thinking about this made me consider something else though. It's stupid to start the propulsion with a switch in the first place. This would just exacerbate melting issues on the first contacts as the sled will spend significantly more time there from a standstill. This is a common issue in railguns that they solve by having pre-travel on the projectile. Instead of some complicated switch to power on the system, the shuttle should be pushed into position. This would also make the shuttle achieve higher speeds.
The one thing i really enjoy about your channel is taking really science based applications and shrinking it down so the methods and practical usages can be seen. Launchers like this will be how loads and ship might be launched from low atmosphere planets in the distant future.
11:45 I would also note the increased inductance from more turns, meaning that the coil's field will take longer to reach its full strength. I suspect this may be a factor in why the force you're seeing from more turns is not directly proportional.
The force is probably still proportal, given his calculations( I didn't double check the numbes) that show the 400 turn coils delivered more Newtons of thrust, but the weight slowed down the rate of acceleration. Yes inductive reactance and resistance do play a factor in how much current flows. But take note that twice the number of coils means you only need 1/2 the current to generate the same magnetic field, assuming the permibility remains the same, rather than change with a saturating core.
@@laserdiode I'm not so sure maximizing kv will result in max acceleration over a given distance. A rotor under a load may turn as long as needed to get up to speed, but a linear motor on the other hand is constrained by its track length, and doesn't have the option to spin a few more revolutions to get to its max velocity for a given load. There are many more variables to consider: Permibility, core saturation, payload weight, source impedence. On my channel I built an axial flux motor with a kv that was bit too high making it dificult to get started. The coils were wound faulhaber axial flux for 12 poles per coil. There were 3 coils with 4 turns per coil. Even with iron in the stator, the inductance was very low and the motor had low starting torque. There are a number of things I could do to improve that motor. Even the controller could have been improved with use of larger capacitors to reduce source inductive impedence given how fast large currents were being switched.
He may also be running into the fact that flux density can't increase forever - the magnetic circuit will reach saturation. Inductors and transformers are carefully designed to maximize flux linkage and avoid saturation. The many comments suggesting a ferromagnetic core and completing the circuit with a bar will decrease the reluctance and allow for greater flux density.
Tom, for your magnets, try arranging them in a Halbach array for more power . For your switch, have a look at compliant mechanisms to eliminate springs.
Can also put something like a small sponge behind the switch to help dampen the bounce. A compliant mechanism would be good though. Especially if it's lighter and stiffer than the magnet/leaf combo.
@@webx135 This switch he made is a real head scratcher... as in, I'm wondering why he bothered to design such a strange and over-complicated switch with very long travel, and velocity. I guess it's dramatic, but that kind of mechanism is more appropriate on a flintlock musket than a railgun.
Excellent build! The first rail gun I saw was in 1976 at the Francis Bitter Magnet Lab, at MIT. They had capacitor banks the size of fridges lining the wall. At one point the operator used his grounding hook to discharge a bank. About 12" of the 1/2" Dia. rod vaporized. They had 10 feet of foam stacked as a target. Very impressive.
1. Use Ferrite core on the sled to increase magnetic force applied to the sled. Ferrite would also work better with fewer turns. 2. You can use Electric Motor brushes made out of graphite to avoid plating problem. usually Motor brushes have springs to apply a small amount of force on the contacts to get a good connection. Only one side of the static brush contacts needs to be intermettent. You could just use a single bus bar along one side & just make the other side segmented. 3. Adding local capacitors for each stage (segment) would increase the current for the coil providing more acceleration power.
> Only one side of the static brush contacts needs to be intermettent. You could just use a single bus bar along one side & just make the other side segmented. I think this is only true if the polarity between each magnet segment wouldn't be inverted in alternating fashion
@@MrFlaschenhalter Correct, if you needed to swap the field after every magnet you need both sides to be segmented. I'm not sure if it is worth flipping the field as the ramp on/ramp down time of the coil may take too long to respond to the magnet's repulsion, not sure tho
9:46 The amazement about the 3 grapes cracks me up so much lol "Hey, I built a freakin railgun.", "But what if you put 3 grapes in there?", "Ohhhhhhhh" 😮 Like that was the most mindblowing part of the project :D
you can attach anti-bounce piston mass to the spring-loaded hammer: pour metal powder into a small cylinder, filling 1/3 with it. the mass would prevent hammer from bouncing. the metal powder will move forward and "stick" the hammer in forward position due to inertia
Induction also plays a large part in the coil. I think the sparking is mostly caused by the induction, when inductors are disconnected they create extremely high voltages from the induced magnetic field. (add capacitors across the rails to protect your power supply!) Another improvement to the launcher would be to increase the spacing down the rail, this allows for the coil to get to the right polarity on time.
When I was little I loved taking apart... well, anything. But I remember seeing an old DC motor, and the brushes for said motor were spring-loaded carbon rods. Maybe something similar would work for the sleds? That might reduce the wear and tear of the contacts.
Offering some more thoughts after reading some of the other comments: - To improve the accelerating force: > - Optimize the solenoid field strength by adjusting current (as a function of coil turns and wire gauge) and coil turns. As you increase the number of turns, at a fixed voltage, the current decreases due to the increased resistance of the coil, so simply adding more turns will pass the peak and yield diminishing returns. > - Another way to squeeze more performance out of a fixed length of rail and magnet spacing, is to increase the voltage for later segments. The faster the sled moves, the less time contacts have to transfer current and flip the polarity of the coil's field. Increasing the voltage at a given resistance will automatically give you more current and a faster d2i/dt2. The quicker the coil can flip to the correct polarity and reach max strength, the more time it will add to the sleds acceleration. - To reduce or quench the back-EMF: > - Adding a capacitor to the sled on the coil would reduce the acceleration, as the rise time of the coil is dependent on discharging the coil from the previous contact segment's polarity, and adding capacitance would sustain the negative current and cause delayed current rise time, and potentially suckback if it's severe. > - Adding a bank of TVS diodes on the sled would reduce arcing by quenching any overvoltage, but would not quench the remaining stored energy below the TVS breakdown voltage. TVS diodes can be purchased as unpolarized components so the sled remains simple and light, and conduct quickly. Make sure to take into account the stored energy of the coil (ie: joules) and ensure that the TVS diodes can handle the entire amount. > - Adding reverse current diodes at every segment (alternating polarities) will improve it further - note that the diodes need to be as close to the contacts as possible, so that the power rails themselves do not become a large source of inductance themselves. Any intrinsic inductance in a pulse power circuit will hinder rise time in current. > - One potential experiment to do (even if not for optimization, simply to visualize on high speed video) is to place a bicolour LED across the coil with more than a series resistor (you will have to clamp significant overvoltage from ringing) so you can visualize current in the coil on high speed video, and understand how quickly the coil's begin to suffer suckback.
isn't wasting the magnetic field of the rail a low priority design criteria? I'd think they're instead going for just the highest power-to-weight ratio of the sled, to maximize speed. Adding more coils that aren't sandwiched between another rail of magnets just sounds like you'd be increasing size of the sled, which increases losses.
I’m not an engineer but I have always been interested in learning about this topic. This is very well explained. Thank you for sharing your knowledge. You have another subscriber 👍🔔.
For the slot cars: The good old Carrera system had solid metal contacts and was really reliable, easy to maintain, and also had many tricks up their sleeves like being able to control 2 car individually on the same lane. And for the bounce: Aside from not using a mechanical switch directly as the main switch - why even make it straight contacts? Your switch is a rotating arm: use that. Have the contact follow the arc, with the brush being held slightly flexible and the outside stationary contact having a slight inwards curve: Now once the contact is established the arm is "gently" slowed down and the force of that does not lead to bounceback but rather squishes the the contacts together more firmly. The magnets and contacts also should not all be the same dimensions as at the end of the rail it is already travelling at a significant speed. Either the coils are over-saturated at the start of the run, or at the end it can barely build up a magnetic field cause it is wizzing by too fast.
@@christopher4101 IIRC there have been slot car control systems with AC control, where the positive and negative halves of the waveform have been modulated independently by each controller - eg. Player 1 controls the positive half, Player 2 the negative half. Then each car has a diode biased to ignore the other half of the waveform. Whether the waveform is amplitude modulated each side, or each controller passes their half of the sine wave through a thyristor, though, is beyond my memory. It's a curio from a long time ago now though, we use a variety of wireless comms standards to achieve ~20 cars in the same lane now 😅
You didn't need to replace your metal strips for those wired brushes. The Aurora HO scale cars used metal band with a hinge on one side, and a spring on the other. This way, you get constant contact no matter what your "track" looks like. All you needed to do was install a soft spring to make sure the plates kept in constant contact without adding additional friction from a stronger spring pushing harder outwards.
@Tom Stanton - Just FYI: My old single-stage solenoid Mass Driver accelerates a 60-gram solid _soft iron rod_ from 0 to 70 miles per hour (~31 m/s) in 3/4 inch (19 mm) or less. That is nearly 4000 times the acceleration of gravity, and I built it from junk box parts, plus 50 cents for a pair of high voltage diodes. The solenoid is from an old pinball machine. It is meant to work the flippers intermittently and run on 24 volts AC. A transformer from an old tube-type radio (valves, for you Brits) has the Plate voltage (nominal 440 VAC) half-wave rectified to charge a slightly mismatched _series capacitor pair_ to 700-ish volts and 104 Joules. Discharge occurs in two phases. The initial phase, observed on oscilloscope, is only 1 millisecond (0.001 second) long. During that time the rod gets up to speed, but gets only halfway through the solenoid. The second phase has much lower voltage across the coil as the (still inductively magnetized) iron rod presents its rear half (opposite induced pole) to the _middle through final_ length of coil, thus generating an opposite voltage and largely counteracting the current flow. This slows the rod slightly. During the 1 millisecond of main action, the power through the 19-gauge (AWG) wire is about 50 kW. I use a small relay meant to handle under 5 amps for completing the circuit. This does damage the relay contacts, but they have lasted for over a thousand firing cycles. Peak power during cap charging is about 25 watts and takes about 15 seconds. An incandescent lamp limits peak current to the transformer, to prevent damage to the delicate windings of the secondary. Despite the massive current pulses and the I-squared-R law of resistance heating, the solenoid coil barely gets warm, even with repeated firing as quickly as full charge permits. The design is very far from optimized in many ways and is only about 29% efficient overall, but the performance is something to see: *Stare at the rod, press the Fire button, and the rod just 'VANISHES'* ... across the room. Even gripping the rod with very strong fingers does not stop it 'vanishing'.
That's great! I would have used the trigger mechanism to move the sled into the magnets, that way you eliminate the electrical bounce completely, also you could add a small RC shock absorber at the end of the rail to stop the sled going off the rails, since the RC plane will be faster the moment of the sled slowing down, the shock absorber will just need to stop the mass of the sled. And If you want extra points just put a linear rail so the friction is virtually zero.
7:45 I don't get it, why not just put in a simple on-off switch that you don't need to print and waste time on it? A simple on-off switch has a variety of A ratings, so why not simplify everything?
Conflict is the gadfly of thought. It stirs us to observation and memory. It instigates to invention. It shocks us out of sheeplike passivity, and sets us at noting and contriving.
I've watched this video at least 3 times and it only gets better! this has convinced me to learn about this more and make one for myself and try different scenarios. Absolutely love your content and wish i had discovered your channel sooner! PLEASE keep it up
Not just looking at the views this man gets, but also because the respect i have for this guy. I think my guy deserves a lot more subs than he already has!!
Proved what an engineer can do using one priciple there are many thing which could be designed. Generally these are used in train suspension systems like EMS (Electro magnetic suspension) and EDS (Electro dynamic suspension). My favourite part was designing a reed switch. You proved that you are an engineer with a single video
I saw a short about this project, immediately came to the channel and now I’m an immediate subscriber. I love this kind of stuff and wish and hope that one day I’ll have a similar workshop to do fun stuff like this and keep me busy. Brilliant work, well done 👏🏿
That is so cool! When I used to fly RC planes, I had a plane that the gear was broken, couldn't be fixed, so I removed it and was hand launching it. I would have loved to have one of these.
With thinner wire, you could get more windings on the launcher spool, without higher mass - thus, hopefully more "torque" from the launcher. Also, something I remember from my time with RC cars, is that you can pack the windings a bit better, if you have two very thin wires in parallel. ie. I had a 15 turn motor, and a 15 Quad (4 wires) motor - And the 15 Quad had more lowdown torque, but also required a bit more power to run.
You should try using a hallbach array to "increase" the magnetic field of the permanent magnets, which should increase the total force of the magnets repelling and attracting each other. Let me know if you need more explainig (but I guess you probably don't ^^)
If you don't go after what you want, you'll never have it. If you don't ask, the answer is always no. If you don't step forward, you're always in the same place.
DIY railgun content is seriously nostalgic youtube material
It's a Gauss' cannon here.
@@Pricklyscug [loud incorrect buzzer] this is a coilgun, though the differences between railgun and coilgun are less severe than the difference of railgun vs gauss cannon.
@@Pricklyscugdefinitely not a Gauss riffle. A Gauss riffle can be visualized (if you don’t like magnets) as a ball roll down a hill and hitting block with 2 ball bearings on the end. Like a newton’s cradle the one on the end hits the next ball in line carrying the energy from the previous collision, gaining it as it gets closer to the magnet and passing the energy to the next ball bearing repeating the process.
@@ActualRealKayamariOfficialVEVO it's no coilgun either. In what type of coilgun did you see energy transfer through contacts? It's basically modified railgun design with supporting magnets instead of strong current on rails and with multiturn coil instead of "1turn" projectile closing the loop.
@@Promilus1984 You're sort of correct in the claim that this isn't a coilgun either, but my reasoning here was that due to a coilgun essentially being an unfurled brushed motor this design isn't too far off seeing as those also use sliding contacts when the configuration is coils on the rotor with magnets as the stator.
Additionally the base form of a railgun does not utilize permanent magnets (though they can be utilized) while this design of course requires permanent magnets to function!
Fun idea. Some improvements: iron strips on the outside of the magnets to close the field lines; square coils to get get the drive currents perpendicular to the field; graphite core to increase field strength; graphite brushes to reduce contact resistance; use finer wire with more turns to reduce current, all things being equal you'll get the same force and mass if you halve the wire cross section and double the turns (or you can then double the voltage to double the force for the same mass).
More turns will increase resistance and reduce conductance, right?
Interesting to test though. Somewhere, some Defense engineers are passing this vid around the office betting on if the author keeps experimenting.
Design engineers laugh when passing these vids around cause the understand magnetic circuits and linear motors, unlike op.
I assume you mean ferrite cores?
I think aluminium wire would be good. 60% the conductivity but only 30% of the weight. Enameled flat aluminium wire.
Finer wire with more turns would actually not work as well - field is proportional to current (thicker wire more better) and the rate at which the polarity of the field can change is inversely proportional to the coil’s inductance (again, thicker wire more better)
i an a retired engineer, but I still love to watch people figure stuff out, and great job!
I worked a lot on rail gun tech. It's pretty scary when you get up to levels they use for weapons. I also love how you designed and printed the parts out.
Thanks for the posting. I know you put a lot on work in this video.
Smiles!
After all of the $$$ + R&D, why did the rail gun not get put into action? I suppose space-based kinetic weapons are scarier!!! Cheers from Seattle!
And I an astronaut
@@cl4998 more nut than astro-nut :)))) funny joke.
Could you put a high voltage capacitor (inside the coil) to supply the power to the launcher - so that the capacitor is part of the projectile?
Loved it mand , great video , great work , I live the 😂 and the various test , same feeling I get when i work on a project 😊
14:53 the reason it goes faster than your estimation is because the magnets cause less back EMF in the coils at lower speeds. Also a tip, as the coil speeds up down the rail you need to "advance" the polarity switch timing to account for the lag of the inductor/s responding to the voltage applied. They do not immediately produce a magnetic field. This could be limiting your speed (as well as back EMF providing a maximum limit for any voltage you apply).
I had a similar thought when watching the video and went back later and posted a comment about it, fortunately you posted a much better version 3 hours before me 😂
@@malebolgia8552 😇
A small amount of MCU code would sort that out.
@@jackevans2386 it's not digitally controlled? Either way no amount of code can change either magnetic induced voltages...
@@jackevans2386 This version is purely electromechanical so there is no where to add SW based delays, the first version had computer control though.
Having the contacts able to move separately from the magnets would allow for tuning of the timing advance needed to maximize the acceleration. The problem is that this tuning would be sensitive to the total weight of the sled and payload so not friendly for variable purposes.
I would also add that the speed of the sled vs. number of windings experiments needed to have a dummy payload on them otherwise the results will not scale properly. Adding 10% mass to the total weight (sled+payload) for double the windings is a much different argument than adding 75% mass to just the sled for double the windings.
Seeing all the sparks and spark damage, I have quick and simple recommendation:
I'm not sure the voltage you are running, but across the terminals of the coil, solder something like an MOV in parallel.
The sparks are created by inductive kick. So if you have 24v going through like 2 ohms, you're going to have 12A running through the coil. When the contact is broken, it is slow to change current, and will try to force 12A through open air, resulting in a huge voltage spike.
An MOV becomes more conductive at higher voltages to protect against voltage spikes. This could drastically reduce the voltage of the spikes. There would still be sparks, but they would be less damaging.
I didn't think this over too much, though. So there might be other effects to contend with. For instance, since the coil could "free-wheel" at the threshold voltage, it might make the current in the coil last longer, so you might get slowdown. It would be something to test. You might want a reverse-current bypass diode on your output source as well.
EDIT: Dang, now I'm thinking about it.
You could even try a capacitor as well as the MOV, Have it store some of that remaining energy into a capacitor that is ready to discharge in the opposite direction. But that might be tricky due to all the phase issues at different speeds.
MOV's are like fuses, they are more or less "in case of" not really "to remove existing." TL;DR: the MOV would probably not last too long.
I personally would try and go the tuned passive rout, as that is keeping closer to the "purely mechanical" theme.
What is a MOV ? You mean a diode ?
@@BrainHurricanes A Varistor, try googling :)
Dam how long did you take to type that for people like me to not read it 😢
@@BrainHurricanes Metal Oxide Varistor
There's a very good reason brushed motors do not use metal brushes, but graphite (with a little powdered metal). Though brittle, and not really that hard, these brushes are very slippery and hard wearing, and will conform to small scrapes and wear on the contact points on the rotor shaft. So if you actually machined the contact points on the rail, some very cheap replacement brushes made for, say, an 18V drill, or even a 220V drill, will work for ages. Some of them even come with their own springs, and basically all of them come with a wire already attached, so you wouldn't need crimping. moving the power rails to the middle might be a good idea as well, having the brushes pinch a power rail, rather than push out on either side. With graphite brushes pinching a central power rail, you can also put much more force into the contact (remember they're slippery), therefore making the contact with each electrode (I'm missing the proper word for this, please tell me if you know one) "promptly, precisely, with force and without hesitation, as expected". You may also have to use copper/brass as electrodes. And maybe make a tool with two brushes to clean them if you still get arcing.
Anyway, love the vid, and can't wait to see what you'll do with this!
Two suggestions: Insert an iron core into the coil to focus the magnetic flux. And exponentially increase the magnets along the track to build up the acceleration.
Sorry, that should read "exponentially increase the spacing of the magnets along the track to build up the acceleration"
@@FondueBrothers maybe not?. You could, in theory, print it like a channel and just stack the magnets next to each other. At this point it becomes how close the AC connectors can be.
A powdered ferrite core is likely going to be even better than an iron core, but finding the ideal mix will depend on the switching frequency...
@@oasntetI agree that powdered ferrite seems like it would be better, but as you say I’m not sure whether the frequencies involved would be high enough for it to make a difference or not.
@@DaveEtchells Guessing really wildly and looking at the frame data in his analysis, I estimate the switching frequency can't be much more than a kHz or two. That said, it'll look more like a square wave than a sine because of the time spent in air, and it's really the charging and discharging time we care about most. If we sliced out the air time and measured the ramp up / ramp down times, that could be far higher. I wouldn't even know where to start, there.
I feel like Tom Stanton is bringing big OG youtube energy.
“But what if I engineered a railgun to fire wieners”
Classic.
I like that he shows the actual build process and gives you enough info to give you a head start on research into his projects. A lot of the maker community has started to use making as a way of telling a narrative and don't focus on the actual project.
@@NathanCaggiano And like slow mo of the wieners. And the sparks, in the dark. Tom “How can I launch this faster?” Stanton every body
@@NathanCaggiano This is a clever balance of giving some sort of constructive value without boring away viewers
Not wieners.
Go with coconut cream pies.
You'll get a more enthusiastic reaction from your targeted audience.
Of course, if you hit a gal in a nice dress, you'll be running for your life, but hey, it is the viral video were going for right?
Mr Tom try the floating traine idea..
The solution for the trigger mechanism and way to complete the circuit legit blew my mind. That was crazy creative! Coolest thing I've seen in a while
12:37 If you're using a cap screw to hold your sled brushes in place, you can probably fold the brush around the strip and skip the solder. The cap screw should be fine for a compression fit, if not, a little tweaking to your design and you're good.
Yeah when he said he clamped the contact surfaces together, I thought he meant he clamped the contact surfaces together (the contact surfaces being 2 strips, one soldered to coil, other clamped onto the brush). But all he means was that the clamp held it in position, and still needed to get soldered :p
(ps: I know he said he needs to solder on new brushes, but he actually do not. The brushes are clamped into position into the soldered strip, but not soldered stuck. So he could bend it open, replace the brush, and bend it stuck again. Will get metal fatigue, but should work for a couple replacements before that happens at least.)
Also, since you're using solder wick for brushes, soak it in alcohol for a bit and blow it out with compressed air. Solder wick has flux in it an might be contributing to the residue left behind when it arcs and sparks.
You could integrate this launcher into ProjectAir's giant RC aircraft carrier and you'd have the ultimate model plane takeoff from the sea - please consider the collab! Amazing stuff as always Tom. :D
@@NoKi1119 so cool to see your name outside of the wan show. Big fan of your timestamps
@@EKUL34 I had the same reaction! Kinda like when I see Lock Picking Lawyer comment on other videos I watch.
I was going to comment this if someone else didn't.
That would be awesome!
also great job on the wan show, you're doing gods work!
it might require a little bit of modification but i agree.
I have no idea how I've missed your channel all these years but I'm glad I've finally found it. Epic content, keep it up!
Absolutely in love with how analog and raw this thing is haha. And it works awesome!
Make it float and we end up with analog maglev
i love it also, but i can't help but imagine a trebuchet being so much better.
The sound of propeller revving up at 14:32 is so satisfying for some reason.
I thought the same when I heard it! That bass was wild
Yeah it sounds so cool.
It's probably fake audio though, audio generally doesn't work in slow mo. The slo mo guys have to artistically create audio for every shot. In this one I think you can see the sound pitch is too high for the speed of the propeller at that time.
@@theaveragepro1749 Wdym? That was like 25hz and if this was 4x slowdown that's 6000 rpm, which isn't completely out of the ballpark
I think thats the railgun magnets making the sound, not the fan.
Spending the day building rail sleds in the English countryside with Tom Stanton would be my idea of zen.
Graphite carbon brushes are used in electric motors that have a high durability, don't leave molten splatter, and can be held to the contacts under pressure with a spring. Love the all mechanical design!
You absolutely need to make some kind of 3D printed launched rollercoaster model using this Tom !
Avoid the use of rear facing seats . . . the belt stains take some getting out . . . : )
The thumbnail had me thinking this was a magnetic train
First thing i thought seeing the thumbnail was "this Is an LSM launch"
@@user36058 technically his previous launcher was much closer to an LSM launch since it used electronically synchronized coils along the rail and the magnets were on the sled
Cool that you got this far without any electronics. But as an EE, I kinda smiled when, among other things, you devised a complex mechanical switch debouncer, something us EEs have known how to do electronically and very simply for a very long time. I'm also sure that the judicious use of electronic switching could greatly reduce your many arcing problems.
I believe you will find a performance increase if you wound the windings in a much neater way rather than crossing over itself so many times. Also I'd be curious to know how adding a core to the windings would also help but yes it would increase the weight, I think it's worth a shot. also also... I grew up playing with AFX cars, they used springs to push out the contacts to keep them connected to the rails as best as possible, I think if you switched from the braid to springs pushing strips of metal you might get better contact
Add a core, and use smaller wire for more turns at lower weight and you could really crank this thing up.
As far as I understand, the crossovers in the windings don't matter so long as the windings are all going in the same direction around the spool, the main reason you want tight windings is to fit more of them in the same volume, providing a higher magnetic flux, and therefore more force
@@eragonawesome I'm inclined to believe you but I thought in the past I have seen a motor with the same number of turns have high torque when the windings are tighter. I'll admit I don't know enough on the topic
@@eragonawesome this is correct. At least any effects of looser windings are going to be negligible.
You might also slow down the speed that the coil can spike its current. But mechanical things are slow enough it might not have a big effect.
The more turns the coil has, the higher the inductance, that causes current to increase slower. From video you can see that you have a few ms per contact point, so minimizing the time to hit max current is important. Magnetic field is proportional to current, and also proportional to number of turns, but number of turns is also proportional to inductance, and that is something you want to reduce.
Slight correction here: When you are winding a conductor, (making a "coil") the inductance is always square to the number of turns, not proportional!
See different formula depending on the actual geometry here: en.wikipedia.org/wiki/Inductor#Inductance_formulas. In this video, Tom is building a multi-layer air core .
@@AntoineZenRuffinen It does lead to the question of whether a ferrite core would help the inductance more than it hurts the mass; but the mass of the plane probably makes that nearly meaningless. He should have tuned with a plane-mass-simulator, rather than an empty sled...
Higher voltage makes the current rise faster as well, as an alternative to lower inductance
@@oasntet Maybe the ferrite core would help, maybe not. This would need some calculation to know. Nevertheless, I think a good optimization, would be to use an "Halbach array" configuration (en.wikipedia.org/wiki/Halbach_array) for the magnets, as it would improve magnetic field and don't adds any moving mass to the the sled.
Excellent project! One of the things it puts me in mind of is the introduction of solid state switching in the 60's and 70's using semiconductors. The use of semiconductors for switching largish currents (a few amps and more) was not fully understood and there were initially many failures, so after engineers initially got excited about solid state switching (encouraged by the manufacturer's bilge!) there was a move back to mechanical switching and relays. The solutions to the problems caused in mechanical switching were much more transparent than the poorly understood semiconductors.
Likewise, you say you wanted to simplify your launcher from any use of electronics which makes it a much more understandable demonstration. Well done!
Who else heard "i built a similar launcher a few years ago" checked the video, saw it was 2 years ago, and then stopped to question wtf is going on with time.
Yes
Maybe he forgot it was 2 years ago ever thought about that?
@@COSMIC_SECRET No its not that.
Its the fact that video is *already* 2 years old.
Yeah, time is passing by so fast. I remember watching the video as well when it was more recently uploaded back then
A few is 2!
Place a steel core in the coils. Also use multstranded wire for coil (litz wire) to avoid skin effect and increase speed at which fields are formed. Perhaps add caps/supercaps to avoid power dips if any.
Awesome idea, I build a rail gun way back for my thesis at Uni.
What was the fps?
I think proximity effect is more important in this coil. But I agree with a core and additional capacitors along the rail as close as possible. Any resistance has huge impact at those 90 Amps.
I wonder if the higher coil inductance with more windings causes an issue with the changing polarity. A steel core would definitely improve the coils power output but I wonder if the then even stronger magnetic-field in the coil breaks down to "zero" fast enough before the next contact strip is hit.
@@SirMoohsAlotinductivity is already the reason this works worse beyond 200 turns. A core would make this way worse.
The engineering compromise he spends the last part of the video talking about id magnetic force Vs coil mass - a steel core would mean more force but way higher mass so it would probably harm acceleration overall
If you add a capacitor parallel to the coil ends, you can reduce the electric arc between the contacts. Nice project, very fantastic works can be done on a larger scale.
Neat seeing the prop blades deploying midair.
that was the best part imo
for speed, alter the spacing/timing of the contacts and magnets in the later stages. use the vid tracker to see where the current acceleration stops....start spreading them out after that point.
I thought that as well. Kind of like changing ignition timing in a gas engine as the RPM changes.
The timing would change based on the mass being accelerated.
@@naasking if the magnet pairs and contacts were each modular and could be spaced along the rail....something whispers logrhythmic pattern to me, but i'm just making it up as i go.
@@naasking Yup. Maybe mount the contact plates in angled slots and tie them to a lever. Then you place the launcher and mass on the lever to set the timing and lock it in with a knob.
What an excellent video. Pretty much perfect in every way
you should add a ferrite or iron (but the ferrite it not that heavy like iron ) core to the coil to concentrate the magnetic field facing the magnets, you will get more force
There do exist filaments with ferromagnetic powder inside, and since he has tool change this could be very promising
@@Robbedoes2 They have fairly poor performance though. Good for prototyping, bad for pushing limits.
What an awesome project. I love the elegant simplicity of this launcher. Although it makes you wonder just how much current those Navy electromatic aircraft launchers are pulling. That has got to be a wild setup.
>how much current those Navy electromatic aircraft launchers are pulling
a boatload
Cool and fun video.
Few thoughts:
1. Adding back iron will probably increase your flux level in the coil, markedly.
2. Don't have the carriage in the range of contacts when turning on the power to the rails. Have a spring launch the carriage at a 'slow' roll at the first contact pair, with power delivered to rails with no load. Fraction of second switch bounce won't matter.
3. Widen your magnet spacing to get higher speed, either widen them all evenly, or space them out as function of distance from first contacts. It will show the early acceleration, but should increase your final velocity.
4. Consider figuring out how much BEMF your seeing from the coil moving in the magnets. Without power, STEADILY pull the carriage down the rails and measure the voltage generated across the rails according to position, and speed. Really needs to be captured with a scope and a 2nd channel for position info.
BEMF is proportional to speed.
Record of BEMF will let you adjust the contacts position with respect to the magnets.
(BEMF is motor-speak for what keeps you from pushing more current into a motor at "full speed" - the voltage you're applying is fighting the voltage generated by moving the coil through the magnetic field.)
5. Consider voltage jumps as you go down the rail. Later contacts will have more voltage than earlier ones, and magnets can be spaced out further at the same time. A series of batteries with multiple taps can feed multiple rail segments. Bit more complex, but still pretty manageable. It will cause a step/jump in the acceleration, so the load should not be too delicate (foam wings?)
We finally got the “how to build a railgun” video🎉
Technically this is a coilgun, not a railgun
@@zutaca2825ik but it’s the same principle as a railgun, electromagnets propelling a projectile
@@cactus_cuber1589 No, railgun is a bit different with projectile being part of a single wire coil and high current pushing rails and projectile apart. This is basically linear motor.
It has more in common with coil gun rather than a rail gun.
@@pavelperina7629your correct that this is not a rail gun. But, technically here, power is also conducted through the projectile (coil in the sled) , and technically both linear rail guns and coil guns are linear motors.
What makes this a coil gun is simply using a coil despite the fact that more traditional coil guns use coils in stator. Here we get alternating magnets and a mechanically commutated coil in the sled.
A rail gun has pure DC flowing through the rails and projectile, and has no coil, and makes continouse electrical contact with the rails.
To prevent solder wicking, cool it down with something cold. Bits of metal would be ideal. Also, solder does not flow upwards easily, use this to your advantage.
I have used solder wick for slip ring contacts and clamping it to bench vice with a piece of aluminium works great.
@@miqo85 Aluminium, or copper, was just what I had in mind! Any metal will work, even wood will do the trick.
we use aluminum clip on heat sinks to stop solder from wicking up braid. he's an engineer, oh well.
@@trfpvVT I just use a third hand tool and solder from the bottom of the wick.
clay works to soak heat. Plumbers use it to prevent damage to valves
Nice design. I did an optically timed coil gun back in the 1990s. It shot a 1" diameter bearing 2 to 4 meters vertical. Each coil was powered by a modified h-bridge of hexfets and diodes and was on only when it's optical sensor was interrupted, or one of the previous two were. This made a traveling magnetic wave down the tube that pulled the projectile forward. When I turned a coil off I dumped it's energy back into the power rail via the diodes. Current limiting was by wire length. I was putting 200 Amps through 22 AWG magnet wire. Needless to say the coils couldn't remain on very long or they would turn to slag. I didn't bother to heatsink any of the FETS or diodes because the on time was so short. Power was from a capacitor bank charged with a 24 Volt linear power supply limited by a 200W resistor. I forget how many ohms.
I'd go on to make more and more powerful ones.
By the way, feed your current in on the exit. So the voltage drop over your busbars is less and less obvious to the end, increasing force instead of dropping. 90A is starting to get serious
8:00 very cool solution to make your own reed type switch!
Another idea that first came to me, was making a latch at the top that as it hits, holds it up and won't let it bounce at all. Then to reset, you lift the latch and put in the lower latch
Any off-the-shelf light switch would work even better
@@poipoi300 I don't know if light switch would be able to handle the amps? (I know most are 25amps AC always confused on how to figure out what DC current that means.)
Also, I think there might still be some 'bounce' in a switch at the high of speeds he's dealing with?
@@justinbanks2380 His power source is DC, but if you check how the circuit is used, it's a lot more like AC. The load isn't continuous, instead it's alternating between on and off. Not for long either. Light switches are designed in such a manner that they don't spark. I'd imagine them to have less bounce on startup than what he built, but I don't know that for certain.
Thinking about this made me consider something else though. It's stupid to start the propulsion with a switch in the first place. This would just exacerbate melting issues on the first contacts as the sled will spend significantly more time there from a standstill. This is a common issue in railguns that they solve by having pre-travel on the projectile. Instead of some complicated switch to power on the system, the shuttle should be pushed into position. This would also make the shuttle achieve higher speeds.
The one thing i really enjoy about your channel is taking really science based applications and shrinking it down so the methods and practical usages can be seen. Launchers like this will be how loads and ship might be launched from low atmosphere planets in the distant future.
11:45 I would also note the increased inductance from more turns, meaning that the coil's field will take longer to reach its full strength. I suspect this may be a factor in why the force you're seeing from more turns is not directly proportional.
The force is probably still proportal, given his calculations( I didn't double check the numbes) that show the 400 turn coils delivered more Newtons of thrust, but the weight slowed down the rate of acceleration. Yes inductive reactance and resistance do play a factor in how much current flows. But take note that twice the number of coils means you only need 1/2 the current to generate the same magnetic field, assuming the permibility remains the same, rather than change with a saturating core.
Also the coil with more turns produce more back emf. Similar to a motor kv rating the theoretical max speed is achieved with the least amount of turns
@@laserdiode I'm not so sure maximizing kv will result in max acceleration over a given distance.
A rotor under a load may turn as long as needed to get up to speed, but a linear motor on the other hand is constrained by its track length, and doesn't have the option to spin a few more revolutions to get to its max velocity for a given load.
There are many more variables to consider: Permibility, core saturation, payload weight, source impedence.
On my channel I built an axial flux motor with a kv that was bit too high making it dificult to get started. The coils were wound faulhaber axial flux for 12 poles per coil. There were 3 coils with 4 turns per coil. Even with iron in the stator, the inductance was very low and the motor had low starting torque. There are a number of things I could do to improve that motor. Even the controller could have been improved with use of larger capacitors to reduce source inductive impedence given how fast large currents were being switched.
He may also be running into the fact that flux density can't increase forever - the magnetic circuit will reach saturation. Inductors and transformers are carefully designed to maximize flux linkage and avoid saturation. The many comments suggesting a ferromagnetic core and completing the circuit with a bar will decrease the reluctance and allow for greater flux density.
Tom, for your magnets, try arranging them in a Halbach array for more power . For your switch, have a look at compliant mechanisms to eliminate springs.
Can also put something like a small sponge behind the switch to help dampen the bounce. A compliant mechanism would be good though. Especially if it's lighter and stiffer than the magnet/leaf combo.
That sounds brilliant
@@webx135 This switch he made is a real head scratcher... as in, I'm wondering why he bothered to design such a strange and over-complicated switch with very long travel, and velocity. I guess it's dramatic, but that kind of mechanism is more appropriate on a flintlock musket than a railgun.
@@EricLaspe yeeah i thought the same. why not just use a light switch since they already exist.
@@webx135 O just some one-way lock
Excellent build! The first rail gun I saw was in 1976 at the Francis Bitter Magnet Lab, at MIT. They had capacitor banks the size of fridges lining the wall. At one point the operator used his grounding hook to discharge a bank. About 12" of the 1/2" Dia. rod vaporized. They had 10 feet of foam stacked as a target. Very impressive.
As a Physics teacher, I can say this is inspirational engineering! Bravo and thank you.
1. Use Ferrite core on the sled to increase magnetic force applied to the sled. Ferrite would also work better with fewer turns.
2. You can use Electric Motor brushes made out of graphite to avoid plating problem. usually Motor brushes have springs to apply a small amount of force on the contacts to get a good connection. Only one side of the static brush contacts needs to be intermettent. You could just use a single bus bar along one side & just make the other side segmented.
3. Adding local capacitors for each stage (segment) would increase the current for the coil providing more acceleration power.
> Only one side of the static brush contacts needs to be intermettent. You could just use a single bus bar along one side & just make the other side segmented.
I think this is only true if the polarity between each magnet segment wouldn't be inverted in alternating fashion
@@MrFlaschenhalter Correct, if you needed to swap the field after every magnet you need both sides to be segmented. I'm not sure if it is worth flipping the field as the ramp on/ramp down time of the coil may take too long to respond to the magnet's repulsion, not sure tho
I remember watching the first video when it came out. How you've innovated and found a much simpler solution is impressive engineering. Great Video.
9:46 The amazement about the 3 grapes cracks me up so much lol
"Hey, I built a freakin railgun.", "But what if you put 3 grapes in there?", "Ohhhhhhhh" 😮
Like that was the most mindblowing part of the project :D
Two grapes was more than enough, three was just hubris!
10:26 this is for sure gonna be in a daily dose of internet video
you can attach anti-bounce piston mass to the spring-loaded hammer: pour metal powder into a small cylinder, filling 1/3 with it. the mass would prevent hammer from bouncing. the metal powder will move forward and "stick" the hammer in forward position due to inertia
Induction also plays a large part in the coil. I think the sparking is mostly caused by the induction, when inductors are disconnected they create extremely high voltages from the induced magnetic field. (add capacitors across the rails to protect your power supply!)
Another improvement to the launcher would be to increase the spacing down the rail, this allows for the coil to get to the right polarity on time.
And a flyback diode!
14:48 That is so smooth and perfect!!! Like rocket science running a pre-programmed stage! Love it!
10:14
"DOOOOOOSH"
That was the 2nd utterance as he quickly came into Awareness of what was spoken aligning with what speech is NOT de-monetizing....
When I was little I loved taking apart... well, anything. But I remember seeing an old DC motor, and the brushes for said motor were spring-loaded carbon rods. Maybe something similar would work for the sleds? That might reduce the wear and tear of the contacts.
14:14 was waiting for some miscalculations, and expecting the pliers to launch five houses over. Lol
Thank God for magnets, we would be lost without them
You're thinking of compasses? 😉
actually excited that you made a relay for a coilgun
At 10:00 it was The Grape Escape.
Offering some more thoughts after reading some of the other comments:
- To improve the accelerating force:
> - Optimize the solenoid field strength by adjusting current (as a function of coil turns and wire gauge) and coil turns. As you increase the number of turns, at a fixed voltage, the current decreases due to the increased resistance of the coil, so simply adding more turns will pass the peak and yield diminishing returns.
> - Another way to squeeze more performance out of a fixed length of rail and magnet spacing, is to increase the voltage for later segments. The faster the sled moves, the less time contacts have to transfer current and flip the polarity of the coil's field. Increasing the voltage at a given resistance will automatically give you more current and a faster d2i/dt2. The quicker the coil can flip to the correct polarity and reach max strength, the more time it will add to the sleds acceleration.
- To reduce or quench the back-EMF:
> - Adding a capacitor to the sled on the coil would reduce the acceleration, as the rise time of the coil is dependent on discharging the coil from the previous contact segment's polarity, and adding capacitance would sustain the negative current and cause delayed current rise time, and potentially suckback if it's severe.
> - Adding a bank of TVS diodes on the sled would reduce arcing by quenching any overvoltage, but would not quench the remaining stored energy below the TVS breakdown voltage. TVS diodes can be purchased as unpolarized components so the sled remains simple and light, and conduct quickly. Make sure to take into account the stored energy of the coil (ie: joules) and ensure that the TVS diodes can handle the entire amount.
> - Adding reverse current diodes at every segment (alternating polarities) will improve it further - note that the diodes need to be as close to the contacts as possible, so that the power rails themselves do not become a large source of inductance themselves. Any intrinsic inductance in a pulse power circuit will hinder rise time in current.
> - One potential experiment to do (even if not for optimization, simply to visualize on high speed video) is to place a bicolour LED across the coil with more than a series resistor (you will have to clamp significant overvoltage from ringing) so you can visualize current in the coil on high speed video, and understand how quickly the coil's begin to suffer suckback.
Use 3 coils one 3 sids of the track. So the magnetic field dosnot get wasted. It will also increase the force of the projectile
isn't wasting the magnetic field of the rail a low priority design criteria? I'd think they're instead going for just the highest power-to-weight ratio of the sled, to maximize speed. Adding more coils that aren't sandwiched between another rail of magnets just sounds like you'd be increasing size of the sled, which increases losses.
I’m not an engineer but I have always been interested in learning about this topic. This is very well explained. Thank you for sharing your knowledge. You have another subscriber 👍🔔.
10:50 i felt that
I think you’re doing it wrong man
For the slot cars: The good old Carrera system had solid metal contacts and was really reliable, easy to maintain, and also had many tricks up their sleeves like being able to control 2 car individually on the same lane.
And for the bounce: Aside from not using a mechanical switch directly as the main switch - why even make it straight contacts? Your switch is a rotating arm: use that. Have the contact follow the arc, with the brush being held slightly flexible and the outside stationary contact having a slight inwards curve: Now once the contact is established the arm is "gently" slowed down and the force of that does not lead to bounceback but rather squishes the the contacts together more firmly.
The magnets and contacts also should not all be the same dimensions as at the end of the rail it is already travelling at a significant speed. Either the coils are over-saturated at the start of the run, or at the end it can barely build up a magnetic field cause it is wizzing by too fast.
Hmmm. Would be interesting to know how they control 2 diff cars in same lane..
@@christopher4101 IIRC there have been slot car control systems with AC control, where the positive and negative halves of the waveform have been modulated independently by each controller - eg. Player 1 controls the positive half, Player 2 the negative half. Then each car has a diode biased to ignore the other half of the waveform. Whether the waveform is amplitude modulated each side, or each controller passes their half of the sine wave through a thyristor, though, is beyond my memory. It's a curio from a long time ago now though, we use a variety of wireless comms standards to achieve ~20 cars in the same lane now 😅
@@williamstrachan ahhh. Makes sense. 👍
You didn't need to replace your metal strips for those wired brushes. The Aurora HO scale cars used metal band with a hinge on one side, and a spring on the other. This way, you get constant contact no matter what your "track" looks like. All you needed to do was install a soft spring to make sure the plates kept in constant contact without adding additional friction from a stronger spring pushing harder outwards.
@09:33 "That was a splat!", no, actually the grape gave up a little wine.
@Tom Stanton - Just FYI: My old single-stage solenoid Mass Driver accelerates a 60-gram solid _soft iron rod_ from 0 to 70 miles per hour (~31 m/s) in 3/4 inch (19 mm) or less. That is nearly 4000 times the acceleration of gravity, and I built it from junk box parts, plus 50 cents for a pair of high voltage diodes. The solenoid is from an old pinball machine. It is meant to work the flippers intermittently and run on 24 volts AC. A transformer from an old tube-type radio (valves, for you Brits) has the Plate voltage (nominal 440 VAC) half-wave rectified to charge a slightly mismatched _series capacitor pair_ to 700-ish volts and 104 Joules. Discharge occurs in two phases. The initial phase, observed on oscilloscope, is only 1 millisecond (0.001 second) long. During that time the rod gets up to speed, but gets only halfway through the solenoid. The second phase has much lower voltage across the coil as the (still inductively magnetized) iron rod presents its rear half (opposite induced pole) to the _middle through final_ length of coil, thus generating an opposite voltage and largely counteracting the current flow. This slows the rod slightly. During the 1 millisecond of main action, the power through the 19-gauge (AWG) wire is about 50 kW. I use a small relay meant to handle under 5 amps for completing the circuit. This does damage the relay contacts, but they have lasted for over a thousand firing cycles. Peak power during cap charging is about 25 watts and takes about 15 seconds. An incandescent lamp limits peak current to the transformer, to prevent damage to the delicate windings of the secondary. Despite the massive current pulses and the I-squared-R law of resistance heating, the solenoid coil barely gets warm, even with repeated firing as quickly as full charge permits. The design is very far from optimized in many ways and is only about 29% efficient overall, but the performance is something to see: *Stare at the rod, press the Fire button, and the rod just 'VANISHES'* ... across the room. Even gripping the rod with very strong fingers does not stop it 'vanishing'.
The redo and the detailed reasoning done here is mindblowing 😊
The only person who never makes mistakes is the person who never does anything.
Did you consider using graphite on the contacts, they would minimise the sparking and energy loss?
I remember another RUclipsr, maybe integza experiment with copper grease, graphite and that kind of stuff
most railways use graphite pantograph, which has better overall performance than copper pantograph, so it could be a good idea
This is awesome. I graduated from Hertfordshire a couple of years ago. Your videos helped me get through my aerospace degree.
That's great! I would have used the trigger mechanism to move the sled into the magnets, that way you eliminate the electrical bounce completely, also you could add a small RC shock absorber at the end of the rail to stop the sled going off the rails, since the RC plane will be faster the moment of the sled slowing down, the shock absorber will just need to stop the mass of the sled.
And If you want extra points just put a linear rail so the friction is virtually zero.
10:35 pump em full of sled
A catapult with sparks flying like a Gundam...this is exactly what we were looking for in a linear catapult! !👍
2:00 CARRERA!! MY OLD FRIEND AND JOY
7:45 I don't get it, why not just put in a simple on-off switch that you don't need to print and waste time on it? A simple on-off switch has a variety of A ratings, so why not simplify everything?
Where is the fun in that?
@@dreamexxx Actually, you're right, I think it is more fun to create your own switch.
Conflict is the gadfly of thought. It stirs us to observation and memory. It instigates to invention. It shocks us out of sheeplike passivity, and sets us at noting and contriving.
With every experience, you alone are painting your own canvas, thought by thought, choice by choice.
I've watched this video at least 3 times and it only gets better! this has convinced me to learn about this more and make one for myself and try different scenarios. Absolutely love your content and wish i had discovered your channel sooner! PLEASE keep it up
10:53 that sausage doing such flips in the air, it’s so funny, I think there’s even a face in it 😂 LOLOL
This guy made something I wish I could do for so long and he's so calm about. I'd be screaming my hat off.
Joy is what happens to us when we allow ourselves to recognize how good things really are.
I agree that practical has its purpose but entertaining is what belongs here.
Wow, that's a lot of work. Both the launcher, and making the video. Thank you! Very cool.
Sled hitting the sausage is absolutely hilarious!😂
Man this was so cool. I remember watching the original launcher video and this one is completely next level.
Not just looking at the views this man gets, but also because the respect i have for this guy. I think my guy deserves a lot more subs than he already has!!
Proved what an engineer can do using one priciple there are many thing which could be designed. Generally these are used in train suspension systems like EMS (Electro magnetic suspension) and EDS (Electro dynamic suspension). My favourite part was designing a reed switch. You proved that you are an engineer with a single video
Love the lil flaps of the sled's copper ribbon after it smashes that first grape. Evil flappies of joy
I saw a short about this project, immediately came to the channel and now I’m an immediate subscriber. I love this kind of stuff and wish and hope that one day I’ll have a similar workshop to do fun stuff like this and keep me busy. Brilliant work, well done 👏🏿
You have absolutely outdone yourself! Impressive
That is so cool! When I used to fly RC planes, I had a plane that the gear was broken, couldn't be fixed, so I removed it and was hand launching it. I would have loved to have one of these.
I love that you made an analog version, but honestly I am really happy as well to see that the fancy electronics did compete really well.
With thinner wire, you could get more windings on the launcher spool, without higher mass - thus, hopefully more "torque" from the launcher.
Also, something I remember from my time with RC cars, is that you can pack the windings a bit better, if you have two very thin wires in parallel.
ie. I had a 15 turn motor, and a 15 Quad (4 wires) motor - And the 15 Quad had more lowdown torque, but also required a bit more power to run.
Brilliant switch idea. You should see how small you can make it and enclose it. You could market that. Great video!
14:31 That's some good asmr there
You can hear the propellers spinning up, in slow motion, after the launch
You should try using a hallbach array to "increase" the magnetic field of the permanent magnets, which should increase the total force of the magnets repelling and attracting each other. Let me know if you need more explainig (but I guess you probably don't ^^)
Absolutely solid R&D
very cool slow-mo launch for us to geek out on at the end!!!
Great work as always Tom!!!
Thanks for the awesome video with a nostalgic feel for the good old days of "Railgun vs Coilgun" videos!
That is seriously right on the money. That plane shoots off that ramp perfect!
Brilliant. May not be the most practical but definitely the most fun
Opportunity often comes disguised in the form of misfortune, or temporary defeat.
from Canada, you have my respct, thank you
If you don't go after what you want, you'll never have it. If you don't ask, the answer is always no. If you don't step forward, you're always in the same place.
Definitely the coolest way to launch a model airplane! Nice work!