Halo Style 2 stage COILGUN

xD gern geschehen / your welcome.

You should try a single stage with same energy. Like 100J single and 50/50J 2 stage. You will notice the difference.

I hope the minigun thing was a joke man no need to let the barrels spin. They wont heat up that much ;-)
My rifle will be a bull-pup. Wont look like one, more futuristic but still rifle-style...but the ammo clip is located at the rear.

Yes a similar bull-pup style is what I'm thinking too. So I'm still on just the single stage prototype with the 410uf added for a total 740uf and it is shooting about 35 feet now. It will shoot better when I create some proper projectiles tomorrow, thicker and shorter say 6mm x 16mm.

I'm going to look for some carbon fiber tubing ~6mm ID and ~8mm ID for the bull-pup mini-rifle at my local plastics store(Tap Plastics). (Edit: as it turns out carbon fiber is conductive, so maybe a fiberglass tubing if it's available). I'm thinking the bull-pup frame will be handmade with aluminum(brass angles) and matte black plastic laminated to it for a realistic look. At first single stage and then I will attempt to make it 2 stage with a shorter and hopefully faster second coil. Just need to master the 2 stage technique on a breadboard to get the triggering right.

Something compact like this Uzi...........



Edit: I just found this forum talking about using carbon fiber barrels. So it appears to be an acceptable barrel material. My bad. ;-)
http://old.4hv.org/index.php?board=5;action=display;threadid=4861

If youre plan does include semi auto, then bullpup is more difficult. Not impossible, but difficult.

I dont trust carbon fibre. I use fibreglass. Makes no sense to use carbon anyway, because the barrel wont be stressed...so why carbon?
In German its called "pultrudiertes Glasfaserrohr"....no idea what pultrudieren in English is...its very stable...undirectional fibres. Thats why I like to use. Very cool stuff and easy to handle...
Plus: Carbon might be conductive...I used contacts reaching into the barrel. Dont trust carbon...again ^^

Regarding housing design: Post a draft when your design is final.

I've seen most people set up a two stage coilgun with a higher powered first coil in the initial coil, and a secondary coil with half that power. This guy here pa-iv - futureexperimentalsystems lists an injector coil, and primary accelerator. I noticed his accelerator coil is much higher power then the injector. So I'm guessing he's pulling off high powered second stage, with a mild first stage. But those efficiencies he is claiming are rather high compared to most other coilguns I've seen.

Makes me wonder if I am reading it right that he Is using a much stronger second stage. *shrug* Still trying to work out mine. I might use both my 1800uf 450v caps for a single stage, and try the weaker injector stage and see what kind of results I get. Still conceptualizing of course. No point in rushing in, even though experimenting with this will be the funnest part, I still want to have a solid idea as to what I am doing before I experiment

Actually it does makes sense...in the end you wont really notice the difference...1% or 1.2%...fact is, the first coil is the most inefficient...I use injector coils when I have a semi-auto system.

In the end its all the same...the more stages, the more efficiency...when you make it right. There is a Japanese coilgun on utube...almost 1000J 23 stages, but the speed is pathedic. 100m/s...I really hope mine will beat this.
Same with the 18 stage from russia. Some of the coils decrease the velocity...I bet my ass on it.
You have to measure and/or calculate very well...the more stages, the harder it gets, but the more speed you will get in the end. And speed = kinetic energy.

I found some black fiberglass tubing 6mm ID x 8mm OD. Then I wound a 3/4" coil onto an 8" piece of it. Firing a proper 6mm x 16mm projectile it does work well, but I'm thinking that if the coil was .5" long it would work better. I read how a long coil starts to repel the projectile before it has a chance to leave the field and slows it down. Also a longer coil has more resistance and therefore less current through it. I will wind a shorter coil tomorrow.

Edit: after I get some more caps, I'll send you a description of the frame with components mounted.

You will have a suck back effect after the slug has passed the middle of the coil. The field at the entrance of the coil accelerates the slug...inside the coil, the acceleration is on a very low level.

Cant wait to see your frame. Will you put some effort in it or just a base-plate holding everythin together?

It will be as cool as I can possibly design it to be, that would allow 2 stages. To give you a preview of my design and without thinking about a second stage yet, the design starts off with "C" channel aluminum. The C channel is joined to other C channel with brass angle brackets and machine screws.

This way the wiring and components(capacitors/batteries/charging/triggering) circuits are fixed inside the channel with proper insulation from the aluminum. Then a flat black plastic cover screws down to finish the channel into an enclosed rectangle and hides the wiring components. If any LED's are added they are mounted to this flat plastic plate that finishes enclosing everything. It will be as simply designed as possible, however once the second stage is added, there would need to be changes made again.

Now I understand how you are triggering the second/third etc. stages. You have 2 contacts that are flush with the inside of the barrel that act as a switch/trigger for the next stage. ;-)

I found a 210uF 450v cap so it will be added for 950uF to the first stage. I also found some 18awg wire for higher efficiency than the 21awg that I used and will wind a 5/8" inch coil tonight. The calculator you posted wants me to increase the OD of my tubing to 9mm to allow 16 turns and 1 layer. Is this correct that it won't allow a 1mm thin wall of the tubing to optimize it? Otherwise the calculator says "0" turns and "0" layers.

Yep...easy...2 contacts connected to a 100Ohm resistor and the gate...the other one to the charged capacitor.

The calculator isnt perfect. Especially the wire-gauge thing...
In the end you have to try it out anyways. Your conductors have a tiny resistance, and the capacitors as well (ESR). You have to add up the ESR...because it will stretch the pulse.

Ok, so I just tried a 18awg coil 5/8" with 2 layers even though the calculator said 1 layer and it was extremely underpowered. I'm thinking that this should have had 4 layers just like the 21awg? *confused* I'm going do it over again with 4 layers as a test. ;-)

Best you can do: Try.

In the end you dont know how fast your SCRs are and how high the ESR of your cap-bank is. Since you use several in parallel, it shouldnt be that high.

The simulation simulates perfect coils...no flaws...so like I said before: In the end you have to try it out.

Experimenting is fun anyway, because trial and error is the best way to learn. I will try the new coil tomorrow.

You have nailed it. Trial and error. Theory and calculating might be necessary sometimes, but doing it with your hands, seing results with your eyes is always cooler.

Ok, for my tests 18awg is inferior to 21awg to launch my projectiles. I tried a 5/8" 18awg coil with 4 layers and it was better than 2 layers but underperformed compared to 4 layers of 21awg. So I'm going to wind a 6 layer 21awg coil at 3/4" inch tonight and see what happens.

I like the fact that you like to try so many different coils.

When will you make it 2 stage? ^^

Well, I have just found the perfect first stage coil for now. It's the 6 layer 21awg coil 3/4" that I had planned for this evening. It slams very hard for just a single stage. The projectile punches through styrofoam at 1/2" very easily from 2 feet, and that is 6mm x 3/4" solid steel with flat ends. It fly's 40 feet with a lot of speed.

I will attempt a 2nd stage tomorrow. One question, how far apart do you think the coils should be and should it be a shorter coil as I'm imagining such as .5" ?