BigBang Express (Failure to Itgnite)


Postby BigBang » Mon Oct 23, 2006 11:31 am

I finally got to test <a href="http://localhost/forums/viewtopic.php?t=14163&SearchTerms=BigBang,Express">BigBang Express</a> this past saturday. Great weather, clear skies and nothing else pressing to do. I thought it would be my day to play.

Well, I got the blasted thing to fire exactly one time - at only a measley 1.5X mix. We tried MAPP and propane, and played with higher mixtures until we had exhausted all reasonable possibilities. While the ignition was hot with no pressure in the chamber, it seems that I was getting no spark at all when I pressurized the chamber for anything over that 1.5X shot.

I think this problem has been mentioned before and I have some ideas on how to fix it - starting with substantially reducing the spark gap lengths in my "spark plugs." If that doesn't work, I have two ignition coils and some automotive spark plugs that are sitting in my parts box that I'll wire up.

I'm very disappointed. It took me forever to find time when my friend with the farm and I had overlapping schedules for a day of field testing. It's getting cold in Ohio so I fear it may be next spring before I can try again.

In other news, I had amazing success with another new cannon I'm calling the Crusader. I put it through its paces for the first time this past Saturday too. I'll post pictures, video and performance data once I've gotten the videos ready for putfile. Give me a day or two.
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Postby GalFisk » Mon Oct 23, 2006 12:43 pm

You're right, the pressure will shorten the spark length substantially. The spark gap in the copper hybrid didn't become reliable until I made it less than 1 mm wide, and the flyback circuit could strike an arc of about 1 cm in air. I'm not sure you'll get the piezo to work well no matter whaht you do, but ignition coils should work well (they're made for doing exactly this after all).
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Postby BigBang » Mon Oct 23, 2006 1:33 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote"><b>Originally posted by GalFisk</b>
I'm not sure you'll get the piezo to work well no matter whaht you do, but ignition coils should work well (they're made for doing exactly this after all).
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

My ignition source is based on an electronic gas grill ignition module, not the "piezo-snappers" as I've heard them called. The ignition module is much like a low energy ignition coil circuit and in air is capable of giving me two 1cm sparks. I'm going to start by reducing the spark gap as you suggest and see how that goes. I'll keep my fingers crossed.

Thanks,
BigBang
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Postby sharpshooter » Mon Oct 23, 2006 9:00 pm

i have a piezo ignightor on my hybrid. With a gap of about 3/16", it will still spark at a 4X mix (which is the highest I have taken it).
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Postby SpudStuff » Mon Oct 23, 2006 10:07 pm

Why can't you test it on your own? That was an awsome canno though.
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Postby BigBang » Tue Oct 24, 2006 9:04 am

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote"><b>Originally posted by SpudStuff</b>
Why can't you test it on your own? That was an awsome canno though.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I currently live in a small house on a tiny lot in a neighborhood full of elderly folks - a "geezerhood" if you will. My next door neighbor is no more than 10 feet away. I've been known to launch spuds from my front yard on the 4th of July and on Labor Day, but test firing a hybrid might not go over well. Fortunately I have friends with larger properties who like me to bring over my big boy toys.

I bought this place close to work back in my bachelor days. What was formerly a great bachelor pad is now becoming cramped quarters for our expanding family. In fact we are planning to move in the spring. I would love to have a "gentleman's" farm out in the county, while my wife would love a condo above Macy's. We'll see how that plays out - probably badly for me, huh?

Unfortunately, preparations for the move may also impact hobby time. My honey-do list of minor repairs and fix-up's is getting pretty long. BigBang Express WILL go live someday, though!
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Postby SpudStuff » Tue Oct 24, 2006 3:36 pm

Well I sure hope so with all the work and amazing paint what went into it.
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Postby BewareOfDog » Wed Oct 25, 2006 6:55 pm

Holy Shit!-

A centimeter is .39 inches, and trying to spark across two of these (especially in a compressed environment) would be extremely difficult, even for one of my 100K stunguns.- Even one such gap is too much.

Every hybrid I've ever made has had a spark plug as the ignition source carrier and they were all gapped at a mere .035" (That's 35 <b>thousandths</b> of an inch... NOT 25/64 - Geez, that's HUGE for a hybrid!)

Also, your electronic grill igniter (which is GREAT for lighting a grill) will simply suck ass, even if the gap is set down to .035"

Get a stungun, dude!;)
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Postby SpudStuff » Wed Oct 25, 2006 7:54 pm

Is there a requirement? I was using wire 1/16" OD and I was gust gonna let that sit against the metal chamber, then it would have a 1/64" gap, would that work for a 1" x 6" Chamber. Cannon here...
<a href="http://www.spudfiles.com/forums/viewtopic.php?t=4287&">My Hybrid Project</a>
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Postby BigBang » Tue Oct 31, 2006 12:28 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote"><b>Originally posted by DR</b>
...your electronic grill igniter (which is GREAT for lighting a grill) will simply suck ass, even if the gap is set down to .035"

Get a stungun, dude!;)
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Yep, lesson learned. The electronic ignitor puts out about 25KV. It works fine for 1X, but was not up to the task with the hybrid.

I now have two tiny little 80kV mini talon stun guns I'm going to wire up. With a 1mm gap, <a href="http://home.earthlink.net/~jimlux/hv/paschen.htm">Paschen's law</a> indicates that I'm good for up to ~26X. Doh!
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