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mini hybrid win!

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: MrCrowley » Mon Sep 20, 2010 5:24 am

I've just come back from the hardware store with my weekly () supply of Araldite and $5 worth of o-rings in various sized

I'm pretty certain you have more cans of epoxy mix than non perishable food in your homemade nuclear bunker (which, undoubtedly, is made from epoxy) :wink:
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Unread postAuthor: ilovefire » Mon Sep 20, 2010 5:31 am

jackssmirkingrevenge wrote:
personally i think it is more trouble then it is worth because it is going to be really fiddly to get it right, on just one then you have to make more, also with the friction and heat i would think there would be a lot of wear so the power would slowly decrease and fixing it would be a pain


Ne'er a truer word spoken, but I want to make sure I've milked the idea before putting it aside. In that regard, I've just come back from the hardware store with my weekly (:roll:) supply of Araldite and $5 worth of o-rings in various sized :D


even tho i said it isnt worth it i still cant wait to see what you come up with!
also what is the glue you get for height pressure stuff because i keep on getting leaks on my epoxy joins even if i appropriately roughen it, iv got one on my mini now to :evil:
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Unread postAuthor: jackssmirkingrevenge » Mon Sep 20, 2010 6:55 am

MrCrowley wrote:I'm pretty certain you have more cans of epoxy mix than non perishable food in your homemade nuclear bunker (which, undoubtedly, is made from epoxy) :wink:


I wonder if there's such a thing as food grade epoxy :D

also what is the glue you get for high pressure stuff because i keep on getting leaks on my epoxy joins


In my experience for minis even Araldite alone is enough for 800 psi pneumatics

even tho i said it isnt worth it i still cant wait to see what you come up with!


Here's what's curing at the moment:
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Unread postAuthor: Insomniac » Mon Sep 20, 2010 8:42 am

It does amaze me how accurately you manage to cast things... I struggle to ensure that I glue a pengun together correctly without leaving gaps/having things drip where they shouldn't... let alone some of the stuff you churn out. I'll be interested to see how this one goes!
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Unread postAuthor: jackssmirkingrevenge » Mon Sep 20, 2010 9:10 am

Insomniac wrote:It does amaze me how accurately you manage to cast things...


Experience is a harsh mistress. I started using epoxy for spudding purposes 12 years ago ( :shock: ) and I remember the frustration in beginning when frequently a carefully made coaxial is lost forever as epoxy from the rear endcap leaks into the pilot area :roll: but you learn your lessons pretty quickly.

This is how the current one is curing, I'm using a 4.5mm drill bit wiped with grease as a mandrel.
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Unread postAuthor: Insomniac » Mon Sep 20, 2010 9:19 am

With enough lube, it would appear that anything is possible... :roll:
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Unread postAuthor: jackssmirkingrevenge » Mon Sep 20, 2010 9:48 am

Insomniac wrote:With enough lube, it would appear that anything is possible... :roll:


I don't want to state the obvious, but that is clearly what she said.
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Unread postAuthor: Insomniac » Mon Sep 20, 2010 6:16 pm

*Slow clap* :D

Got that epoxy cured up yet?
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Unread postAuthor: ilovefire » Mon Sep 20, 2010 8:16 pm

what is the volume of this latest creation? can we expect a test anytime soon?

yay just went to the tyre repair shop and got 25 free schrader valves, time to go work on my own cartridges :D
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 21, 2010 3:46 am

Cured beautifully :) it pops very consistently at 50 psi, which means it's only good for 4x, which means it's useless, but yay o-rings!

The problem in this case is that although the o-ring has a 3mm I/D, since I cast it with a 4.5mm mandrel through it the ring is held open by the epoxy so it lowers the pop-off pressure considerably.

I'm inspired enough to make another one though, watch this space :)
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Unread postAuthor: Insomniac » Tue Sep 21, 2010 3:48 am

It does seem like a much better design, as unlike your old way which had a BB being subject to a consistant resistance, this way the resistance increases the further the BB is pushed into the seal. Given some fine tuning I think this design is promising.

I do wonder for how many shots the seal will last, however.
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 21, 2010 4:28 am

Insomniac wrote:I do wonder for how many shots the seal will last, however.


I'm sure it would wear out eventually, but I'm hoping you could easily remove the old seal from the groove cast into the epoxy and pop a new one in :)
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Unread postAuthor: jackssmirkingrevenge » Wed Oct 27, 2010 10:16 pm

Following the success of this project, I've decided to ramp things up a little :D still a "mini" by this forum's standards but with a 3/4" barrel and a wider chamber made of 2mm wall thickness 316 stainless, with the threaded fitting from an ATEX electrical connector.

As the weather's gotten colder it will be given a good baking today, testing later :) here it is compared to the subject of this thread for scale:
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Unread postAuthor: MrCrowley » Wed Oct 27, 2010 10:22 pm

Who knows, maybe by christmas you'll have a hybrid that's bigger than my hybrid's fueling meter :D

Kidding aside, I'm glag to see you've ramped things up a little. Bigger may not always be better, but it sure is more fun. Do you literally bake your epoxy creations by the way? Just wondering what your method was and if it's better than conventional methods of leaving it in the garage over night :wink:
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Unread postAuthor: jackssmirkingrevenge » Wed Oct 27, 2010 10:36 pm

MrCrowley wrote:Who knows, maybe by christmas you'll have a hybrid that's bigger than my hybrid's fueling meter :D


Who knows, outback boy :P :D

Do you literally bake your epoxy creations by the way? Just wondering what your method was and if it's better than conventional methods of leaving it in the garage over night :wink:


Most epoxies cure faster when at higher temperatures, in Summer I can leave stuff out in the sun and it will be done in 12 hours whereas in Winter sometimes it doesn't cure after 24 hours. At this time of year I find chucking curing parts into one of the lab ovens at 50-60°C means that they're ready for testing by the time I get home :)
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