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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 » Thu Apr 14, 2011 3:03 pm

jackssmirkingrevenge wrote:Should have read the how-to
I promise you, I read that entire how-to... and somehow missed that.

SpudBlaster15 wrote:polyolefins
So after reading the Wikipedia article, I'm still quite unsure where I could come across some...

I'm trying to come up with some coating or surface treatment I can use (I think I have two, but I'm a bit iffy on both), so that I can place a rod about the dimensions of my piston into a female cross, pour it full of epoxy, then extract the rod and have a QDV valve body.

Can PTFE be "safely" melted?
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Unread postAuthor: Heimo » Thu Apr 14, 2011 5:04 pm

saefroch wrote:
Can PTFE be "safely" melted?


I don't think so...

from Wikipedia:

"According to DuPont, its melting point is 327 °C"

"The pyrolysis of PTFE is detectable at 200 °C (392 °F), and it evolves several fluorocarbon gases"
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Unread postAuthor: saefroch » Thu Apr 14, 2011 5:49 pm

Oh dang... I expected something of that sort. Never mind that idea.
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Unread postAuthor: mobile chernobyl » Thu Apr 14, 2011 6:07 pm

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


It's safe to assume this for almost all fluids! 8)
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Unread postAuthor: saefroch » Thu Apr 14, 2011 6:20 pm

Almost being rather key there. I'd even go so far as to say that the epoxy I'm working with is more viscous than honey, so I don't know how much effect heating will have.

Spark plug seems to be fully cured, more testing to verify my ability to make a working valve housing will show results tomorrow.
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Unread postAuthor: ramses » Thu Apr 14, 2011 6:26 pm

I can assure you, hot honey is quite thin. I can't promise the same for your epoxy, but it's worth a shot. You might also consider vibrating it to remove the air bubbles. No need to link to tools for that, JSR. :roll:
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Unread postAuthor: Zeus » Thu Apr 14, 2011 7:04 pm

You people, thinking that JSR would link to an epoxy vibrator. (I don't use emoticons but there should be a rolleyes here)

Definitely don't heat PTFE tape, there was talk of the E&W forum of using it as a very potent poison. Though the E&W forum was half full of bullshite.

The spellcheck wants to correct bullshite too, it's really quite odd.
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Unread postAuthor: Crna Legija » Thu Apr 14, 2011 10:17 pm

you can get epoxy to flow like hot cooking oil when you heat it, plus it cures quicker when it hot.
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Unread postAuthor: SpudBlaster15 » Thu Apr 14, 2011 10:54 pm

saefroch wrote:So after reading the Wikipedia article, I'm still quite unsure where I could come across some...


You can't find a source of polyethylene or polypropylene?
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Unread postAuthor: jackssmirkingrevenge » Fri Apr 15, 2011 1:11 am

Zeus wrote:You people, thinking that JSR would link to an epoxy vibrator :roll:


You obviously haven't heard of thepencil incident:D :D :D

Back on topic, what I do is pour the two components in a container without mixing, heat it up, then mix and apply. This way you're promoting viscosity which helps the two components mix better, but without actually heating the mixed components which would catalyse the reaction and actually make it start to cure and therefore less viscous.
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Unread postAuthor: saefroch » Fri Apr 15, 2011 5:30 pm

SpudBlaster15 wrote:You can't find a source of polyethylene or polypropylene?
Nvm the trolling. :cool: Just gotta find a good source of heat-shrink tubing now. I recall Radio Shack carrying it way back when, but in .5" diameter?
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Unread postAuthor: Zeus » Fri Apr 15, 2011 7:04 pm

Any electronics store will carry a wide range, from ~1-3mm up to 25mm. In 2:1 shrink ratio, or 4:1 glue lined.

Hope that helps.
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Unread postAuthor: turner » Thu Apr 21, 2011 11:39 pm

i would just coat the piece in some thick grease. heating it up gets it really runny, ive done it.
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Unread postAuthor: saefroch » Fri Apr 22, 2011 1:05 pm

Tested greasing parts, the epoxy pushes the grease away and adheres to the part like normal.

In other news: I've determined that the epoxy I'm using needs to be heated to cure completely i.e. no longer sticky and hard. Is this normal?
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Unread postAuthor: Gun Freak » Fri Apr 22, 2011 1:09 pm

How cold is it where you live?
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