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Posted: Mon Nov 12, 2007 1:24 pm
by Hotwired
Yeah, coilguns are extremely naff in the projectile department.
The powerlabs one is possibly the biggest hobby one I've seen without getting off my virtual ass to find a better one, it occupies a table and chucks a 4.5g projectile at 66m/s with 10J of muzzle energy.
oooooh
*charges cannon and blasts a 25g slug off at 132m/s with 220J of muzzle energy*
Railguns are where military money is being thrown but to be honest they have equally dodgy drawbacks, like only being able to fire one shot before the whole thing needs rebuilding due to rail damage.
Posted: Mon Nov 12, 2007 1:59 pm
by cwazy1
lol jimmy, that gun fires metal slugs at around 8g..the calcs for that gun has already been done on the WCA...its around 40m/s for the slug.
Posted: Mon Nov 12, 2007 10:37 pm
by spudling
check out my coil gun is under the same catagory
Posted: Mon Nov 12, 2007 10:40 pm
by elitesniper
coil guns take to long to charge up
Posted: Mon Nov 12, 2007 10:44 pm
by miskaman
Where would you even get a battery like that? 15,000 volts is alot!
Posted: Mon Nov 12, 2007 11:49 pm
by singularity
most people have turned to capacitors to energize the coils, they can be charged a lot high and faster than batteries, not to mention they discharge a hole hell of a lot faster. a 15,000v cap can be found quite easily i bet they are selling some right now on ebay. and a coil gun can take 3 sec to fully charge if you know what your doing and custom build the charging circuit
Posted: Tue Nov 13, 2007 12:23 pm
by jimmy101
cwazy1 wrote:lol jimmy, that gun fires metal slugs at around 8g..the calcs for that gun has already been done on the WCA...its around 40m/s for the slug.
Damn, I hit the right answer almost exactly, well off by a factor of ~two but still, that is pretty good working from first principles.
I estimated the BB at 3J.
An 8g slug at 40m/s is 6.4J
In fact, I bet my estimate is darn near exact for a BB. Spherical projectiles are the worst possible shape for a coil gun. So a BB would be expected to be a lot less efficient than a slug.
A basic combustion spudgun will fire a 100g spud with 500 to 1000 J of kinetic energy, that is typicall 100 times more energy than even a well built coilgun. Coilguns are cool, but you can usually throw the projecile with more kinetic energy than the coil gun can fire it.
Posted: Tue Nov 13, 2007 1:11 pm
by Fnord
Well, 1000 Joules is a bit much for a basic combustion. 500 is reasonable though.
The only difference between throwing and shooting is shooting is pretty much undetectable, since there is no obvious motion involved. So if your goal is to annoy school personnel, coilguns are the way to go
Plus, any cool science teacher will be able to appreciate a student who could make one.
Posted: Tue Nov 13, 2007 2:04 pm
by jimmy101
_Fnord wrote:Well, 1000 Joules is a bit much for a basic combustion. 500 is reasonable though.
1000 Joules would be a 100g spud moving at 462 FPS. Easily done with a basic combustion with a barrel of 5' or 6'.
Heck, it wouldn't be all that hard to make a fairly basic combustion that would do 2000 Joules (100g at 656 FPS), an 8' barrel should be able to do that (with a properly sized chamber).
Posted: Tue Nov 13, 2007 2:31 pm
by Fnord
1000 Joules would be a 100g spud moving at 462 FPS. Easily done with a basic combustion with a barrel of 5' or 6'.
Heck, it wouldn't be all that hard to make a fairly basic combustion that would do 2000 Joules (100g at 656 FPS), an 8' barrel should be able to do that (with a properly sized chamber).
I'm not going to dispute that, it's just that to me the stereotype of a "basic" combustion is a spray n' pray gun with maybe a 3-4 foot barrel. In othe words, what people might build when they first start out.