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Trident Mk. II Build Log

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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Trident Mk. II Build Log

Unread postAuthor: saefroch » Wed Apr 13, 2011 4:28 pm

This launcher has been in the works for a rather long time, and I'm glad to see it finally coming together. I'd appreciate any non-obvious advice, especially since this is my first time using epoxy.

Planned specifications:
Chamber: Same configuration as the original, SS ~5.3 in<sup>3</sup>
Barrel: SS 3' long .364" diameter, with attachment designed for larger future barrels
Valve: .5" QDV
Fueling: Chamber fueling
Ignition: Piezo from handheld lighter
Mixes: 5X-20X

4/12/2011: Parts arrived, fueling setup assembled
Image

4/13/2011: Spark plug curing, along with experimentation for valve construction:
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Last edited by saefroch on Wed Apr 13, 2011 7:58 pm, edited 1 time in total.
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Unread postAuthor: Zeus » Wed Apr 13, 2011 7:09 pm

Good to see you're starting properly, 20X at ~.50in will pack a fair punch.

A piezo might have a little trouble igniting it, I'd recommend something with a little more power. If I recall correctly JSR got a piezo to ignite a 17X mix. I may stand corrected though.

As I don't have anything else to contribute I'll just wish you good luck with it.
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Unread postAuthor: Lockednloaded » Wed Apr 13, 2011 7:16 pm

So you'll be arcing on the chamber walls? wont that give you a little zap?

Also, How much did that gauge run ya?
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Unread postAuthor: Zeus » Wed Apr 13, 2011 7:21 pm

If it's a piezo there won't be a problem, I don't even feel piezo shocks anymore.

I also like the gauge, I really need to get online moneys.
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Unread postAuthor: saefroch » Wed Apr 13, 2011 7:56 pm

Lockednloaded wrote:So you'll be arcing on the chamber walls? wont that give you a little zap?
It will be arcing to whatever I bend it towards. I see no reason for a human, rather than the other side of the piezo igniter to ground the circuit, but I suppose it's possible.

Lockednloaded wrote:Also, How much did that gauge run ya?
$84, IIRC.

Edited the barrel dimensions, which previously read my chamber diameter.
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Last edited by saefroch on Wed Apr 13, 2011 7:59 pm, edited 1 time in total.
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Unread postAuthor: Technician1002 » Wed Apr 13, 2011 7:57 pm

Lockednloaded wrote:So you'll be arcing on the chamber walls? wont that give you a little zap?


How is this any different that a weed eater, leaf blower, lawnmower, or car? You need to be in contact with both connections to get bit. Just touching the system ground won't do it.
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Unread postAuthor: Lockednloaded » Wed Apr 13, 2011 7:58 pm

Those all have insulated spark plugs...
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Unread postAuthor: Technician1002 » Wed Apr 13, 2011 8:13 pm

The center electrode is insulated. Check what it will arc to. Attached directly to the threaded body of the plug.
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Unread postAuthor: Lockednloaded » Wed Apr 13, 2011 8:17 pm

Huh, well I had no idea.. I really am a dunce when it comes to electronics :lol:
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Unread postAuthor: SpudBlaster15 » Wed Apr 13, 2011 8:57 pm

Looking good, it will be interesting to see how well the manometric metering system works with such a small chamber volume.
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Unread postAuthor: jackssmirkingrevenge » Wed Apr 13, 2011 9:30 pm

Looking good :)

Some bubbles in the epoxy, which suggests it was a little cold when you mixed it. I would put the mixing container in a hot water bath for a minute or so first, it makes it less viscous and the bubbles will tend to go away.

Is there going to be a check valve between the chamber and that fancy gauge? Quite a high budget alternative to a syringe but to each his own ;)

Make sure your spark gap is as tiny as possible for higher mixes.
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Unread postAuthor: saefroch » Thu Apr 14, 2011 5:46 am

Wasn't aware the viscosity of epoxy was so temperature-dependent, thanks!

I was hoping that the ball valve would protect the gauge, but come to think of it, I DO have a 1,000psi check valve that's not in use. Would placing a pop-off near the gauge also protect it?

SpudBlaster15 wrote:small chamber volume.
That's why I'm skipping all mixes below 5X. I don't think I'd be able to fuel very accurately, but even as it is, I bet I'll need practice before I don't just blow by my desired pressures.

EDIT: Is there anything that epoxy will not adhere to? I think I've found something, but I'm not quite sure if I want to use it.
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Unread postAuthor: jackssmirkingrevenge » Thu Apr 14, 2011 6:02 am

saefroch wrote:Wasn't aware the viscosity of epoxy was so temperature-dependent, thanks!


Should have read the how-to ;)

In spite of the fact that he knew it was TL;DR, JSR patiently wrote:4) mix the marine epoxy resin and pour it in place, giving it at least 24 hours to cure completely. Note that epoxy is very heat sensitive, store it at room temperature before mixing - if not, use a baine marie to heat it up before mixing - (some valid pointers on cold temperature bonding).


I was hoping that the ball valve would protect the gauge, but come to think of it, I DO have a 1,000psi check valve that's not in use.


The ball valve will protect it, but sod's law means that one day you will forget to close it completely.

Would placing a pop-off near the gauge also protect it?


Possibly, but not as well as a check valve.

Is there anything that epoxy will not adhere to? I think I've found something, but I'm not quite sure if I want to use it.


In my experience if something is rigid and can be suitable roughened, epoxy will stick to it. If it's smooth and/or greasy, or made of wax, chances are it won't.
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Unread postAuthor: SpudBlaster15 » Thu Apr 14, 2011 12:32 pm

saefroch wrote:Is there anything that epoxy will not adhere to? I think I've found something, but I'm not quite sure if I want to use it.


Like most adhesives, it isn't very fond of polyolefins or PTFE. There shouldn't be any issues with common spudding applications however.
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Unread postAuthor: Crna Legija » Thu Apr 14, 2011 12:48 pm

it wont stick to rubber too.
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