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Navrit Bal

Tue Apr 19 2011, 06:54PM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

IT WORKS FINALLY

I tested up to 65V, I'll see if it works at higher voltages later :D

sorry for the shoddy camera work

Fired again but at 70V this time, 6.97ms-1 0.234J (k.e.) efficiency = 1.77% so I'm happy with that since its within efficiencies that amateurs tend to achieve.

Navrit Bal

Fri Apr 22 2011, 10:01AM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

Here are some more shots for you

Barry

Fri Apr 22 2011, 01:57PM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Looking good! Thanks for the videos. And what a satisfying crash it makes when impacting the empty steel case catcher. I must remember that for my next demo.

Good work! Barry
Music is like candy. To enjoy it, you must first throw away all the rappers.

Navrit Bal

Fri Apr 22 2011, 07:33PM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

When its slowed down I noticed something very interesting, there is a regularly repeating sound which looks identical to AM which I think might be the projectile cutting through the air. By the way it has a phillips screwdriver type end which is why I think it might be making that sound.

204V 10% original speed :

345V 10% original speed :

I can upload or send the original FLAC recordings recorded at 96kHz if anyone wants them for any particular reason :D

Barry

Sat Apr 23 2011, 03:07AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

It sounds like it might be the high-pitched ringing of a metallic firing barrel. What is your barrel made of?
Cheers, Barry

Navrit Bal

Sat Apr 23 2011, 08:11AM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

I don't have a barrel, there is a plastic tube stuck on the end of the coil though just to make sure it goes straight..

Barry

Sat Apr 23 2011, 02:07PM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Haha, I made a good guess... swing and a miss! A plastic barrel won't make that sound, lol.

Even at 1/10th speed it sounded quite high pitched, high enough that the original may be around the highest frequency sampling rate of the sound digitizer. I suspect it's an artifact of the digital sound system or compression or subsequent audio processing.

Try a completely different and high fidelity recording system for comparison.

Cheers, Barry
I'm having a good discussion with a voice in my head. I do believe I'm winning the argument, but the voice has some very good points that seem to be viable!

Navrit Bal

Sat Apr 23 2011, 02:52PM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

Yeah, it doesn't even make contact with the plastic barrel :D

I recorded using audacity at 96kHz, 16 or 24 bit, mostly with a pretty good quality microphone from my headset so is that the sort of thing which might cause it?

Also every time that I charge up the coilgun, my mains house circuit breaker is tripped, the 13A fuse didn't break, so I'm wondering what is happening since it is the same as before as far as I know... it happens anywhere between 50V and 100V

Barry

Sun Apr 24 2011, 03:09AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Navrit Bal wrote ...

Every time that I charge up the coilgun, my mains house circuit breaker is tripped, the 13A fuse didn't break, so I'm wondering what is happening since it is the same as before as far as I know... it happens anywhere between 50V and 100V

It sounds like the mains house breaker is getting a high-current pulse, but it's such short duration that the 13A fusible link didn't melt down.

But the breaker shouldn't trip if you have a standard household light bulb in series with the primary circuit, as your schematic shows. This alone will limit the inrush current. Since a light bulb alone doesn't trip the breaker, then adding the diodes and capacitor bank can only raise resistance not lower it. I strongly recommend you fix whatever is tripping the breaker before working on anything else.

What light bulb exactly are you using?

Cheers, Barry
One tequila, two tequila, three tequila, floor

Navrit Bal

Sun Apr 24 2011, 09:59AM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

I'm using a 60W filament bulb; I agree, I decided yesterday to stop until I can fix this issue.

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