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Registered Member #1372
Joined: Tue Mar 04 2008, 12:16AM
Location:
Posts: 6
Just a quick question. How much is the average efficiency you can obtain ?
Now I have a coilgun that can feature 2.6J with an efficiency of 2.5%. However, my goal is to go over that result, since I want at least an efficiency of 3%.
Registered Member #90
Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301
In my experience 2 - 3% is very good for coils in air.
If you haven't already, you'll want to tune your coilgun by taking careful measurements over a wide range of projectile lengths, voltages, and turns on the coil.
You might be able to get 5 - 8% efficiency by designing a coil with external iron to improve the magnetic flux path. This is fun -- in a small portable demonstrator I can charge and shoot directly from a 12v lantern battery.
Cheers, Barry Every exit is an entrance to somewhere
Registered Member #158
Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282
It seems induction launchers have the potential for greater efficiency compared to reluctance based coilguns. Unfortunately my website is down right now (no internet at my new house yet) but my first couple induction launchers were close to 10% as well, and had I been able to charge them fully I believe I could have hit that mark as their efficiency steadily went up with higher charges and the highest I've ever went is approximately 50% charge and if memory serves was around 8% in efficiency.
Registered Member #90
Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301
The type of induction launchers that do so well are the ones built with a flat pancake coil and aluminum disk. They benefit from the very tight magnetic coupling of the close contact between coil and disk.
But! For obvious reasons, you only get one stage. There is no way to add stages for higher speeds, without changing to a colinear coil-around-the-outside design. (See PLIM, pulsed linear induction motor, like this one.) And some hobbyists early results with PLIM suggest lower efficiencies in the first stage.
Cheers, Barry Sex is like math - add the bed, subtract the clothes, divide the legs ... and pray you don't multiply
Registered Member #1633
Joined: Tue Aug 12 2008, 04:21AM
Location:
Posts: 45
shoot a projectile out of your gun on a level surface, say 12'' above the ground. first measure the projectiles mass, and then charge your bank and shoot it. using this equation Eff = (1/2mv^2)/(1/2 cV^2), where v = velocity, m = mass of projectile in kg, c = capacitance in farads, V = voltage on bank. to find the velocity of the bullet, use x= vit +1/2at^2 to find the time it takes the projectile to drop 12", then use x/t =v to find velocity based on the distance your projectile traveled
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Average efficiency
