Capacitors

I havent decided on what capacitors to use yet, but I have a sponsor that have agreed to donate a bunch of them for this project. They have capacitors with a maximum voltage of everything between 10V and 500V (the largest ones are 1 decimeter in diameter and over 2 decimeters tall).

Saft VH-D Cells will do 40A continous. This actually surprized me. I would have thought it would be a lot less. You cant fast-charge them though.

When selecting capacitors to store energy and discharge them quickly make sure they are of the low-esr type. Goldcaps will be completely useless.
Also keep in mind that voltages over 36V are prohibited.

That depends on what you call fast charge. :)

But we dont use the VH-D cell, we use another type designed for higher discharges at the cost of less capacity. Its not on their website, but it does exist.

At the moment it sound like you are building a guass gun.

Would that be with a reuseable line attached projectile, a raped line discharging projectile or a long bar eg. a electro ram?

I tryed make a few simple configs that look like a SMG Harpoon but i did not think that the high voltages it used would be called system with design rules.
Also the penaration ability was not that good, quite poor realy

building a guass gun
I suspect you are right! (never heard it called that before though - but the name fits!)

I couldnt resist commenting on this!

Ive built a couple of these for firing aluminium rings. Very effective - fired a 200g ring almost 1/2 a mile!

The biggest trouble I can see is the voltage. Because the energy is derived from the square of the voltage and the max current you can drive through the coil is proportional to the voltage, you need as high a voltage as possible.

The other thing (which may have changed more recently) is the 1F capacitors will mot deliver huge currents - even if you short them out - they have a fairly high effective internal resistance.

I used a bank of 12 x 10,000uF (from a UPS) which were rated to 96v, but did not explode until about 220v! Pumped up to about 190v they seemed fine. In total, I only had 0.12F, but high enough discharge current that it would vaporise an average screwdriver!

The coil was wound out of 8 gauge copper wire (3.2mm) and had a resistance of just over 0.1 ohm, giving a discharge current of about 1000A.

This type of gun works because the combination of the capacitor & coil rings. You get an initial field generated which will oscilate for a couple of cycles. The initial field induces a current in the aluminium ring (which in itself is not magnetic so is not attracted to the coil). The current flowing in the ring generates its own magnetic field. When the field in the coil reverses, the field in the ring does not (or at least there is a delay (hysteresis) so briefly, the coil and ring repel one another - which almost doubles the effective force - and the ring shoots away from the coil (and through your ceiling!).

Be careful with this kind of thing as you can just as easily vapourise the coil and even the ring as you can a screwdriver!

Not sure you could get enough kick with the max allowed voltage - but its certainly worth a go! - particularly if you can get one or more 1F capacitors!

I cannot see any reason it could not be effective. My gun spat the ring out with about 2kj KE (less inefficiencies) - which is fairly respectable in RWs terms! You could get the same with 2 x 1F capacitors at 48v!

Keep us posted about how you get on!

Si

Both of your guesses as very good, thats exactly what Im doing (well close enough).

The voltage is the big problem in its current setup, the rules limit it to less than 10% of whats preferable (Im talking about numbers in excess of 400V here). But Ive aquired some very nice capacitors, and the first testings should begin soon.

Dont forget you have to tether the objects you are shooting.
Even if you tether them, I wonder if a weapon like this will be admitted :)

I would imagine he would be thinking about building a ram where it is the piston which is fired - and the energy used to move the handle of an axe/hammer?

Si

Youll see what Ive got in mind...

Been reading a bit on the rules. Surely it will cause some electromagnetic interference. (Not continuosly, but in the firing moment.) Would it comply with 12.1.4?

Btw, has anyone tried launching projectiles with FP CO2? It feels like it would give more power for less weight....