Shrinking an O-ring/rubber.

[laurence]

I have just cut off the end peice of my hop-up rubber and need to shrink it as i am trying out my own hop-mod, does anyone know how to shrink rubber?

[No1_sonuk]

Re: Shrinking an O-ring/rubber.

You can't.

[laurence]

Re: Shrinking an O-ring/rubber.

ok great. :P

[Bachelarius]

Re: Shrinking an O-ring/rubber.

@No1_sonuk, based on what info? I've seen o-rings shrunk before but can't remember the exact compound to use... But it is definitely doable. I don't know if you will be able to apply the same concept to a hop rubber though, worth a shot I guess?

What are you trying to do anyway? Maybe there is a better way to do it.

[balaclava ben]

Re: Shrinking an O-ring/rubber.

it'll entirly depend on the compound of the bucking you are using, if its a silcon bucking your not going to have much luck unfortunately although certainly worth a try! may i ask what your mod entails or is it classified? :D

[No1_sonuk]

Re: Shrinking an O-ring/rubber.

@No1_sonuk, based on what info? I've seen o-rings shrunk before but can't remember the exact compound to use... But it is definitely doable. I don't know if you will be able to apply the same concept to a hop rubber though, worth a shot I guess?

Most rubber compounds are heat-cured into shape. Those that aren't, like silicones, can't be shrunk with heat.

They can be expanded, but that's purely due to their elasticity.

Heatshrink tubing isn't rubber per se - it's a different polymer that's specially modified to allow it to be reshaped when heated, and set when cooled. If it's heated while nothing is trying to reshape it, it returns to its formed shape.
So when you buy heatshring tubing that has a 4mm diameter, it was made 2mm diameter, but exanded and set before shipping. Then, when you heat it, it releases the "set" and tries to return to its original 2mm diameter.

[laurence]

Re: Shrinking an O-ring/rubber.

Basically, im trying to do a sort of g-hop style thing, but instead of glue the rubber in place over the opening in the barre, you cut a ring of hop rubber off and shrink it round the barrel to keep it in place and it would be more sturdy. It is just an idea but i guess if i cant shrink the rubber then its not very do-able. Im just using normal hop-up rubber.

[balaclava ben]

Re: Shrinking an O-ring/rubber.

one of the main tricks with the g-hop is getting a flat pressure surface on top so although the curved external surface should improve the seal slightly im not sure how it would fair when the hop arm makes contact with it. Very interesting topic though, if you dont mind please let us know how you get on with it!

[Bachelarius]

Re: Shrinking an O-ring/rubber.

Your method would induce a lot of blow-by I'm afraid, as the outer hop rubber would not be on flat against the barrel any longer, so the rubber would not make anywhere near as good-a air seal. Try it with a piece of shrink-wrap as a test candidate if you like, just to see how the air seal behaves.

[balaclava ben]

Re: Shrinking an O-ring/rubber.

oh i took it that the curved part he was using was to be flush with the outer dimensions of the inner barrel due to the attempts at shrinking?

[Bachelarius]

Re: Shrinking an O-ring/rubber.

The way I understand it, he wanted to replace the flat pad with a loop instead, so it's pulled tight by the shrinking, so the pad bit is flat and is held in place by the tention, then the outer rubber covers the lot. I'd love this to work, as it would be so much easier.

Even cutting the rubber and glueing it to the outside of the barrel would achieve the same thing without relying on the magical properties of shrinking rubber... but the air leaks would be pretty bad imho.. may be worth a shot though, who knows.

[laurence]

Re: Shrinking an O-ring/rubber.

ok so re-thought my idea, and what you would do, is have two rubbers, and cut the lump off from the inside of both of them. then on one, cut the ridge off that goes along the groove. Then get the one with the groove and put it on the barrel and shrink it, then get the other rubber and slide it over the top. this would mean you would get more progressive hop. However you would have to have a smaller barrel such as the madbull ones as otherwise the unit would not fit over the rubbers. So basically you have two rubbers. It seems abstract but i think it could work. You would need to shrink it quite tight though for the other rubber to fit over the top.

[balaclava ben]

Re: Shrinking an O-ring/rubber.

sorry to be a downer but that wouldnt work unfortunately! have a good look on other famous airsoft forums and you can bet that whatever you idea is it probably has been tried at some point imo g hop is still far too experimental right now, anybody had much luck with their dental floss hops?

[laurence]

Re: Shrinking an O-ring/rubber.

mm, or in reverse, put the normal hop up rubber on, then shrink that so its stretched across the hole in the barre, then get a peice of rubber which you have cut off the end of yours and then shrink that which would give you a good airseal and provide more gradual hop.