Halfbridge coilgun first light

TheMerovingian, Sat Jul 29 2006, 05:03PM

Yesterday i have done the first tests on the halfbridge coilgun and first pulse-width adjustements for best velocity. These tests are non optimized, need more careful and patient working.

So far it can pierce both sides of a can, fly through a carton box, indent a metal sheet bouncing, bounce on the opposite wall, annoy my parents saying me to be careful, leave a mark on the wall and than fall on the groung bouncing many times. To avoid dangerous bouncings i filled the carton box with plastic foam, that is very efficient to dissipate mechanical energy.

It consist in 3 halfbridge stages (with decreasing turns) and a igbt-diode controlled prestage.

4 small capbanks are used with a total energy of 240Joules (960 uf, 1440uf , 960uf, 960uf all at max 350V used usually at 300V)

a quick starting position- pulse time playing gave me the following results:

Projectile mass 7.7 g, projectile lenght 38.5 mm , blunt

Pre stage:
Exit velocity/energy: 14,88 m/s 0,843 J
Voltage differential :300V->50V
Energy differential: 42J
Partial efficiency : 2% mad

Pre stage+ first stage:
Exit velocity/energy: 26,9 m/s 2,78 J (+1,94 J)
Voltage differential :300V->220V
Energy differential: 30J
Partial efficiency : 6,5% neutral


Pre stage+ first stage+second stage:
Exit velocity/energy: 33,8 m/s 4,39 J (+1,61 J)
Voltage differential :300V->240V
Energy differential: 15,6J
Partial efficiency : 10,3% cheesey


Pre stage+ first stage+second stage+third stage:
Exit velocity/energy: 40,0 m/s 6,16 J (+1,77 J)
Voltage differential :300V->230V
Energy differential: 17,8J
Partial efficiency : 9,9% cheesey

Overall:
Energy comsumption 105,4J
Total efficiency 5,8% mistrust
Exit speed/energy: 40,0 m/s (144Kmh) 6,16 J

Halfbridge stages only:
Energy consumption: 63,4J
Total halfbridge stages efficiency: 8.4%

I Think that i can squeeze more firepower optiminzing starting position of the first stage and the pulsetimes. Probably more than 7 joules and 43m/s (+150Kmh) and overall efficiency more than 6% (in the 7-8% range)

Tomorrow I'm going on holyday so will restart my work after being back.





1154192637 14 FT0 Hbcoilgun10
Re: Halfbridge coilgun first light
FastMHz, Sat Jul 29 2006, 05:33PM

Nice Job! Looks like a clean design...you don't happen to have a video camera to take some video, do you?
Re: Halfbridge coilgun first light
TheMerovingian, Sat Jul 29 2006, 06:15PM

I'm sorry, my digital camera is broken. Anyway i will make videos when it is completed and enclosed in a rifle-ish manner.
Re: Halfbridge coilgun first light
Wilson, Tue Aug 01 2006, 04:58AM

Sweet, 5.8% eff. smile. How are you measure the pulsewidths the 555s are producing? or are you just twiddling the pots for best performance?
What IGBTs are you using for switching?

Overall great work. makes me want to unearth my coilgun...