Optimising a Magnetic Launcher

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[msachin]

Honestly, your channel is such a gold mine. This is one of the best demonstrations of the engineering process at work: you find the issue, you think of a solution, and then you tinker and optimize until you've achieved what you've set out for. You demonstrate this whole process so eloquently in your videos that it's inspiring

[NicholasRehm]

It’s all fun and games at the Nerf match until Tom shows up with a handheld version of this with an automatic trigger and backpack mounted battery

[danwood]

That slow motion shot of the launch sled falling away from the glider looked fantastically elegant, awesome project!

[OMGWTFBBQSHEEP]

Wow the slow-mo of that glider taking off was glorious. And the release mechanism working exactly as intended!

[jackflash]

Calculate how long it takes for the coil to reach maximum magnetic power, use this to determine how far the triggering hall effect sensor needs to be to optimize energizing the coils as the velocity increases. Also, when you lower the winding count, increase the wire size. Remember, wind count has an effect on the speed at which the magnetic field builds to maximum.
I was involved in the original development of the brushless motors in today's electric planes and drones.

[Coneshot]

I built a mass driver as a science fair project back in the '80's, I got around the curve flattening by progressively spacing the driver coils further apart as they went down the track. My reasoning was like a transmission in a car the impulses then match the speed of the projectile as it accelerates.

[IncroyablesExperiences]

A way to know which reason is the most limiting would have been to make a regression, it the curve is close to an exponential it's mostly a back EMF reason, if the curve is close to a square root, it's mostly due to kinetic energy (harder and harder to increase for a given power).

[smartereveryday]

Twinkle Twinkle Little Star
Power Equals I Squared R



I'll remember it forever because of this.

[davidebevilacqua]

You can improve even more replacin alluminium rod with plastic, a magnet sliding on metal tends to reduce the speed because of the inducted current generated by the movement.

[CyberKnightX]

I love listening to the audio on the slow mo of the plane launch at the end. You can hear each individual pull or push of the magnet on the sled.

[johngreen]

The air gap is still ~40mm long. The other side of the electromagnet is open, so the magnetic flux has to flow to the next electromagnet via air. The overall reluctance is still quite high and can be greatly reduced by tying backs of electromagnets with an iron bar and using a magnet that partially overlaps 2 electromagnets.

[quintssenta]

I love how this channel started as modelling planes and various flying ... things (some of them is hard to describe) but then evolved into trebuchets and now its about building a coilgun.

[matekovacs]

A few ideas:
- You don't have to reverse polarity to also push the sled. You can just use a second Hall sensor located after the coil, and a second winding on the coil wired up in inverted polarity, so when the second Hall sensor turns on the second coil, it will push. With the position of the sensors, I think it can be timed perfectly. Yes it is 2X the components (and thus cost and power draw), but also roughly 2x the force at each magnet, resulting in a speed increase.
- With a lubricated sled (and the plastic part of it shaped aerodynamically), most of the drag on the sled would be eliminated.
- I've also noticed on the high-speed footage that the coils lean in a bit when active. This is expected as per Newton's third law, but the coild might need to be mounted more sturdily.

[EthanHale]

I love watching the progression by tweaking certain factors. I also learned a lot as you walked us through the process. Keep up the great work!

[peterwells]

Brilliant video Tom. Even when I cannot quite follow all the info you are giving. You still make it all clear enough to make it really interesting.
Thank

[DPrinterAcademy]

cool project! I've always been a fan of linear induction motors!

[colinwinterburn]

Tom is a young man who gives me a positive feeling toward the future. We need to support people like him.

[ernie]

I used to wind and assemble r/c brushless motors. As far as I can tell, they are pretty much identical to your linear motor. The fewer the winds (w/heavier wire) the faster the motor, but the lower the torque. What would happen if you had progressively fewer winds as the carrier went down the track? It would start off at low speed w/high torque, then go progressively to high speed with low torque. Much like gears in a car. The last few coils could be only a few winds (with heavy wire OR multiple strands in parallel) and this would really kick up the speed. Also, work to get the air gap between the coils and the magnet as small as possible. The magnetic attraction (reluctance) drops off as a square of the distance. In motor construction, this is the easiest way to increase efficiency. This is hard to do in mass production, but with a DIY project the effort really pays off. Reduce the gap by a power of two and get four times the output power!

[OnerousEthic]

You are so charming…and brilliant, 10:20: “…so I designed a mini 3D printable glider…”. And you are so calm, and patient, and joyful.

I am constantly impressed. I hope you have a lot of children.

10:38 The Nikon camera shows it’s outstanding resolution, excellent depth of field (yes, there is a ton of light), and remarkable frame capture rate (slow motion), which is a powerful “message from our sponsor” with no words said! Love that!

[null_focus]

In weapon terminology what you made is a coil gun. Lots of people confuse rail guns and coil guns despite coil guns being significantly more complicated (due to the need for rapid switching as you are clearly aware)