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launcher help

Posted: Sun Jul 17, 2011 4:21 am
by chinnerz
Hey, so i have been absent for a little while (uni will do that to you :P)

Anywho, i have 2 issues with this new launcher i have been working on.
number 1)
i made a piston out of hot glue little while ago, but i left it in a brass T and not its stuck.
like really stuck
should i drill it out? should i set it on fire? idk what the best way is to get it out.

number 2)
i used a product called epoxy putty to make my air tank but i think its leaking :S
my plan was to kinda flood the area and sand it back, this is kinda what it looks like now

Uploaded with

Just thought i would ask before i did something silly like flood the place with hot glue :P

Any and all help is appreciated.

Posted: Sun Jul 17, 2011 5:14 am
by Crna Legija
you could try heating the brass tee from the out side to melt the outer layer of hot glue then push the bulk of it out.

I would remove all the leaky epoxy putty clean then roughen up the walls and use regular epoxy to seal them again, that's just me i don't like epoxy putty because it cant flow into the cracks like low viscosity epoxy's.

give use some details on the design looks weird.

Posted: Sun Jul 17, 2011 7:09 am
by chinnerz
that seems like a good idea for the piston, i'll give it a go tmro

I can't seem to really find a cost effective option in terms of low viscosity epoxy. :/ I was thinking if i could get some sort of liquid (some kind of glue maybe?) on the inside edge of the leak then pressurise it... dont know.

um the design is fairly simple enough. Details below

By chinnerz2 at 2011-07-17

By chinnerz2 at 2011-07-17

I may have some performance issues because the valve is 6mm and the barrel is 10mm.

Posted: Sun Jul 17, 2011 7:26 am
by Crna Legija
Why not just use galvanized iron pipe from bunnings to make the tank?
you need a spring behind the piston to fill chamber side.

Posted: Sun Jul 17, 2011 7:53 am
by chinnerz
I was thinking about it... but its too big :P
and yeah i have a spring :)


works at around 50 psi

Posted: Sun Jul 17, 2011 10:52 am
by saefroch
To make any epoxy low-viscosity, just cut off the corner of a plastic bag, pour in the epoxy, mix, and dip into a hot water bath until it becomes very thin. Just be careful when pouring, it cures much more quickly.

Posted: Sun Jul 17, 2011 11:35 am
by Jabingo19
^ I was always wondering how/where people got low viscosity stuff, very happy I read this!

Posted: Sun Jul 17, 2011 2:59 pm
by jackssmirkingrevenge
I only recommend the heating technique for epoxies with long curing times.

What I usually do is pour the two components in a small thin plastic cup (yoghurt pot, deoderant cap etc.) without mixing, and put the cup in a container with hot water, then leave it for a few minutes. This lets them thin out without starting to react too much.

I then mix the components quickly (as they are thin, they will mix better) and pour the epoxy into whatever I'm casing in. After taking the cup out of the bath it's a good idea to wipe the bottom to avoid getting any water droplets in the mixture.

chinnerz, is something like this not within your budget?

Posted: Sun Jul 17, 2011 7:01 pm
by saefroch
jackssmirkingrevenge wrote:long curing times.
Ah. The quickest-curing epoxy that I buy cures in 90 minutes, but I also use some that cures in 2 hours. My local hardware store (which doesn't exactly stock everything) carries both. It shouldn't be too difficult for most forum users to find epoxy with a long curing time.

Posted: Mon Jul 18, 2011 7:44 am
by chinnerz
umm what about fiber glass resin? would that work for higher pressures?

Posted: Mon Jul 18, 2011 7:55 am
by Crna Legija
chinnerz wrote:umm what about fiber glass resin? would that work for higher pressures?
edit: competly different shit, way different smell, wont work dont wast your cash :lol:

Posted: Mon Jul 18, 2011 8:09 am
by jackssmirkingrevenge
Crna Legija wrote:same crap different smell, will work fine.
Not as I understand it:
Polyester Resins are styrene based products used in all types of composite construction. Commonly referred to as fiberglass resin or boat resin. An economical alternative to using epoxy resins. New Vinyl Ester resins are becoming more popular as an alternative to epoxies as well.
Epoxy Resins are a two-part resin system used when high strength, low shrinkage and low brittleness are required. Epoxy resins outperform most polyester(orthophthalic) resins.