BigBang Express (Now with Dual Spark Video)

Just build a cannon and want to show it off? Post it in here.

Postby BigBang » Tue Jul 18, 2006 3:47 pm

<center><b><font size="5">She's Finally Finished!</font></b>

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<b>BigBang Express</b></center>

Well, I finally broke down this past weekend and finished the seemingly never ending hybrid project that has been lingering in my garage for the past year and a half. As yet she is an untested virgin so I can't provide performance data, but I did want to share with you my work so far. I'm sure some of you thought I'd never get it done.

The chamber is double walled 3" SCH 80 PVC. It's volume is 1950ml. The barrel is 1.5" SDR-21 sleeved into 2" SCH80 PVC. The barrel is 5 feet long, giving a 1X C:B ratio of 0.87 - not ideal, but close.

For fueling I am using the 1.5" <a href="http://localhost/forums/viewtopic.php?t=13237">Fuel Pod</a> I presented in a previous post. With this fuel pod I can do 3X fueling in one step.

I am also using the ignition system that I designed for <a href="">Little Bang</a> a couple of years ago. I didn't get a picture of them, but the ignition system generates two pretty hot ~5mm sparks. I hope they will hold up when the chamber is under pressure.

In the following picture, I show two little accessories I put together. On the left is what I call my de-cocker. In the event of a misfire I want to be able to discharge (most of) the fuel/air mixture safely. All I did was connect an air compressor pressure release valve to a male QD fitting. Of course, this will at best get me down to a 1X mix, but I consider that safe enough.

On the right is the assembly I'll use to monitor the preignition chamber pressure as I add in compressed air. I bought the digital pressure gauge from McMaster Carr (where else, huh!) for a shameful chunk of change. It is a Grade 1A gauge, with 1% full scale accuracy, and 0.1 psi precision. I made the plunge and bought this gauge to hopefully help me avoid the lean/rich mixture problems in first generation hybrids that DR and others have described at length elsewhere.

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Here are some more close-up pictures of the chamber:

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<b>Various Chamber Shots</b></center>

The next thing for me to do is some burst disc testing. This is all new to me, so I want to get some "dry fire" practice in taking the cannon out to my friend's farm for real testing. I'll try to take lots of pictures and some video to show you when I "go live."

As always, comments and suggestions are welcome.


EDIT: I finally got my video of the dual sparks inside the chamber to work. I've included it here.

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<b>Dual Sparks</b></center>
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Postby Mosif » Tue Jul 18, 2006 4:01 pm

That my friend, is a thing of beauty.
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Postby saladtossser » Tue Jul 18, 2006 4:49 pm

holy moly
<img src="">
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Postby Velocity » Tue Jul 18, 2006 4:54 pm

its ok... could be cleaner...

...JUST KIDDING!!! THAT IS AWESOME!!! the paintjob is superb, the components are high quality, and its a friggin hybrid!! SWEET JOB!
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Postby Freefall » Tue Jul 18, 2006 5:13 pm

That's a PVC chamber? I was almost certain it was bead-blasted aluminum!
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Postby Mr.Plow » Tue Jul 18, 2006 5:17 pm

You are a GOD of painting!

Seriously, that is one of the cleanest launchers I've ever seen. You never fail to impress the hell out of me with that workmanship!
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Postby markfh11q » Tue Jul 18, 2006 5:46 pm

Not a seam anywhere to be seen. <B>Great job!!!!</b>
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Postby draculon » Tue Jul 18, 2006 6:12 pm

That looks absolutely incredible. Possibly one of the cleanest hybrids EVER! Have fun testing it.
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Postby saladtossser » Tue Jul 18, 2006 6:14 pm

how did you do the ignition in the chamber? did u put the wire through the elbow and glue it shut or something?
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Postby utcpyro » Tue Jul 18, 2006 7:48 pm

VERRY nice, very clean... I though that you had made the thing out of metal until I saw in the post what it really was! Shoot, it looks professional.

Oh, and nice gauge there :).
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