using barrys calcs
JoeDarkon, Sun May 27 2007, 05:17PMi am trying to use barrys RLC calc... he says
"Your goal in this little game is to find a combination of values which result in maximum peak coil current, and which also dies away to near zero in about the time it takes the projectile to pass the mid-point of your coil"
my question is how do i figure out how long it takes for my projectile to reach the midpoint
Re: using barrys calcs
Simon, Mon May 28 2007, 12:29AM
Unfortunately (or fortunately, depending on your view on coilgunning), there's no simple equation that can give you the answer.
Anything you can realistically do is a ballpark guess.
You can guess by researching other coilguns.
You can guess by estimating the muzzle velocity of your projectile and working out how long it'll take to reach the midpoint of the coil at half that velocity. (You can estimate the velocity by guessing the efficiency - say, something between 1% and 10%.)
You can can try Bill's models, which are sophisticated and impressive. Remember, though, that coilgun modelling is an extremely slippery business.
Simon, Mon May 28 2007, 12:29AM
Unfortunately (or fortunately, depending on your view on coilgunning), there's no simple equation that can give you the answer.
Anything you can realistically do is a ballpark guess.
You can guess by researching other coilguns.
You can guess by estimating the muzzle velocity of your projectile and working out how long it'll take to reach the midpoint of the coil at half that velocity. (You can estimate the velocity by guessing the efficiency - say, something between 1% and 10%.)
You can can try Bill's models, which are sophisticated and impressive. Remember, though, that coilgun modelling is an extremely slippery business.
Re: using barrys calcs
Barry, Sat Jul 28 2007, 05:46PM
The trick here is to estimate the time in the barrel. Here is an extremely crude (but useful) approximation.
Let's assume the projectile is under constant acceleration, so we can start with the classic equation: d = 1/2 a t^2
Re-arrange it to solve for time, and also substitute in a = v/t.
As a result: t = 2d/v , where t = time in seconds, d = distance, v=exit velocity
For some examples using a two-inch coil:
Hopefully this will get you started. ~~Barry~~
Barry, Sat Jul 28 2007, 05:46PM
JoeDarkon wrote ...
my question is how do i figure out how long it takes for my projectile to reach the midpoint
my question is how do i figure out how long it takes for my projectile to reach the midpoint
The trick here is to estimate the time in the barrel. Here is an extremely crude (but useful) approximation.
Let's assume the projectile is under constant acceleration, so we can start with the classic equation: d = 1/2 a t^2
Re-arrange it to solve for time, and also substitute in a = v/t.
As a result: t = 2d/v , where t = time in seconds, d = distance, v=exit velocity
For some examples using a two-inch coil:
- At 50 fps: t = (2)(0.0508 m)/(15.24 m/s) = 6.67 ms
- At 200 fps: t = (2)(0.0508 m)/(60.96 m/s) = 1.67 ms
Hopefully this will get you started. ~~Barry~~
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