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Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: saefroch » Fri Apr 22, 2011 6:51 pm

Thermostat keeps it usually close to 65F
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Unread postAuthor: Gun Freak » Fri Apr 22, 2011 7:16 pm

That's wierd... it should be curing at that temp.
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Unread postAuthor: jackssmirkingrevenge » Fri Apr 22, 2011 9:21 pm

Gun Freak wrote:That's wierd... it should be curing at that temp.


... so there are some other things that might have gove wrong:

- insufficient mixing of the two components

- components were not dispensed in the right proportions
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Unread postAuthor: saefroch » Fri Apr 22, 2011 9:29 pm

I think it may be that they weren't dispensed in the right proportion, but I can't be sure. My spark plug does appear to be properly cured (not sticky and very hard), but that's probably because it spend about half an hour at 300F. It left some residue behind, which may have been a factor...
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Unread postAuthor: saefroch » Sat May 07, 2011 6:26 pm

Bore hawg curing for use on the inside of my piston. May take a day or two since it's clamped in a cold vise and I can't exactly pop it into the toaster oven.
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Unread postAuthor: mark.f » Sat May 07, 2011 6:50 pm

I still say you could have used some .25" ID tubing. A good retort I didn't think of quick enough in chat last night was that even if there wasn't enough epoxy around the tubing to fully cut your o-ring grooves, you could always cut them into the outside of the tubing as well. If you were to cut through the tubing I think you would have a problem no matter what method you used. :wink:

But whatever gets it done. Can't wait to see the first hybrid QDV...
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Unread postAuthor: saefroch » Sat May 07, 2011 7:05 pm

I'm just a little concerned about having a thin piece of tubing or epoxy supporting all the impact stress of stopping the piston. I think what I'm trying now will work... I think :?

I can't wait either. This one step has had me stalled for so long.
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Unread postAuthor: saefroch » Fri May 13, 2011 5:39 pm

Battery connections curing atm, should be fully operational by tomorrow:
Image
Sadly I don't think the LED is illuminating, but it does make that highly intimidating whine!
Nearly scared the pants off a friend

EDIT: Image

Turns out the intimidating whine is >18kHz, i.e. fully matured people can't hear it. I do still have a problem though... I only got it to arc through a loop of the trigger wire, which was really cool, but unreproducible and not compatible with my current spark plug. Is it possible to put the trigger wire in series with one of the sides of the capacitor? I tried once and I only got a sort of half-arsed spark, was that because my gap was too large?
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Unread postAuthor: jackssmirkingrevenge » Sat May 14, 2011 1:08 am

saefroch wrote:Nearly scared the pants off a friend

....Turns out the intimidating whine is >18kHz, i.e. fully matured people can't hear it.


Does that mean you'll be appearing on Dateline soon ;)

Seriously though, it looks great. How big is your spark gap?
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Unread postAuthor: saefroch » Sat May 14, 2011 11:23 am

I only once managed to trigger a spark with the trigger wire (gap probably 2mm), all other sparks have simply been by moving the leads closer an closer together, until they are almost touching and it arcs. Sadly, this always temporarily welds them together.

There are now two photoflash capacitors in parallel inside the box. :twisted:

Is there any chance of replacing the triggering mechanism with a piezoelectric igniter in parallel with the spark gap? I'm thinking it might be possible to ionize the air with the voltage output of the piezo, then let the current from the capacitors follow it... Or would that just fry the piezo...
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Unread postAuthor: Fnord » Sat May 14, 2011 11:52 am

Now, wait, you're using a camera flash ignitor, or something else?
I thought originally you were using a peizo...

The spark you'll get from a flash circuit will be very hot, but not that high in voltage which is what you need for a hybrid. I'd expect it's something in the 2-3kv range (You need about 10kv to arc through 1 cm of air).
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Unread postAuthor: saefroch » Sat May 14, 2011 1:55 pm

I am NOW attempting to use a camera flash ignitor, since I stalled on the rest of the build, I decided to convert the two disposable cameras I bought a while back for this purpose.

Just demonstrating deadshorting the capacitors, not practical without the trigger function. I'm going to try to make another spark plug and connect this all up correctly.
[youtube]http://www.youtube.com/watch?v=RGPpUG_y_X0[/youtube]
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Unread postAuthor: saefroch » Sat May 14, 2011 5:29 pm

Double posting, but I feel it's justified...

I upgraded my spark plug so it now has three leads, and configured them so that they should work, but they aren't. I've verified that the circuit is charging, and the solder should be ensuring good electrical contact, right? So... help?

Image
The wires are connected to the right leads, though it may not appear so.

Image
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Unread postAuthor: Zeus » Sat May 14, 2011 6:55 pm

Squash the ring so it's closer to the electrodes, and push the two electrodes as close as possible, if you'd risk it charge them first.

Once they arc, just open them up a tiny bit, then it should work. Expect to readjust them quite a a lot, they'll wear quickly.
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Unread postAuthor: saefroch » Sat May 14, 2011 6:58 pm

I'll close the loop tighter, but that spark is so shocking :wink: I jump every time.

EDIT:
[youtube]http://www.youtube.com/watch?v=vpxbigYIskg[/youtube]

It isn't all discharging in the spark... is that normal?
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Last edited by saefroch on Sat May 14, 2011 7:17 pm, edited 2 times in total.
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