Is making a delrin transfer port a bad idea?

[Hsing-ee]

How would you make sure that such a slippery material would stay in place? The elaborate process for gluing-in delrin buttons on a piston would make me think brass would be a much simpler and more reliable answer, and one which tuners have been using for years.

The dimensions you quote are strange! Surely a transfer port only has a diameter and a length? Unless it is some weird kind of Cardew-inspired venturi...

[robs5230]

How would you make sure that such a slippery material would stay in place? The elaborate process for gluing-in delrin buttons on a piston would make me think brass would be a much simpler and more reliable answer, and one which tuners have been using for years.

The dimensions you quote are strange! Surely a transfer port only has a diameter and a length? Unless it is some weird kind of Cardew-inspired venturi...

The transfer port on BSA Ultra , r10 etc is roughly as the op decribes though not those dimensions. Its in effect a brass tube set between the cylinder and breech and sealed by O rings. Though I do get what you mean in that the transfer port is just the "hole" that the air passes through. A TP on a springer is basically a hole of a length and a diameter drilled in the end of the cylinder

[Hsing-ee]

The transfer port on BSA Ultra , r10 etc is roughly as the op decribes though not those dimensions. Its in effect a brass tube set between the cylinder and breech and sealed by O rings. Though I do get what you mean in that the transfer port is just the "hole" that the air passes through. A TP on a springer is basically a hole of a length and a diameter drilled in the end of the cylinder

fort you ment a SPRINGER........ apologies...

[Barryg]

In a springer I have heard that the temperature generated in the TP is very high, if this is true then a delrin TP would not be suitable.

[robs5230]

Given the dimensions Barry, the OP seems to be referring to a tp on a pcp, co2 rifle

[Barryg]

Given the dimensions Barry, the OP seems to be referring to a tp on a pcp, co2 rifle

Thanks for clarifying

[rovercoupe]

Its on a stalker rifle that I am re building, it has x2 o rings on the port top and bottom and the measurements are just a guess as its at home and I am at work currently. I found now the original .22 port size was 2.5mm so will try that first. the only thing is that its a .25 so bit unsure of size to go with for a 12flb rifle.
I have a delrin rod spare form another project that would be perfect for the port and might need a few making of differing sizes to get the power right.
If it works its going to be my 10 yard squirrel gun!

[Hsing-ee]

the only thing is that its a .25 so bit unsure of size to go with to get the power right.
If it works its going to be my 10 yard squirrel gun!

Any squirrel that big will need a .338 Lapau Magnum at least, maybe even a .50 BMG.

[robs5230]

Its on a stalker rifle that I am re building, it has x2 o rings on the port top and bottom and the measurements are just a guess as its at home and I am at work currently. I found now the original .22 port size was 2.5mm so will try that first. the only thing is that its a .25 so bit unsure of size to go with for a 12flb rifle.
I have a delrin rod spare form another project that would be perfect for the port and might need a few making of differing sizes to get the power right.
If it works its going to be my 10 yard squirrel gun!

delrin should work fine

[TonyL]

I can't see there being a problem. Our own Jim, AirGun World fame, has done so ... see this month's edition. I have also made delrin transfer ports for a pcp when experimenting a bit.

Cheers, Phil

In a springer I have heard that the temperature generated in the TP is very high, if this is true then a delrin TP would not be suitable.

Okay, slightly off at a tangent, as it's not a springer that the OP is referring to, but, Barry, as Phil says above, Jim's been playing with acetal transfer ports on TXs. All good. And that silly high temperature is only generated for a miniscule amount of time meaning no ill effects with the synthetic TP.

[rovercoupe]

Hopefully here is a pic of the port in question,

[clarky]

Hopefully here is a pic of the port in question,

....well if you want to go with the advice of a materials eng ...you could go with exactly the same material.
If its not a bearing, which must always be a different, or harder material, going with same materials brings with it the same rates of exspansion/contraction...regardless of what conditions its being subjected to....thus if its a drive fit ....it will stay a drive fit...
So i would drive in a turned lump of solid brass and then simply drill the hole to the size you want.
It might even look like it was meant if you polished it front and back face....as if made from one piece.
Alternatively ill machine you one from solid one piece if wanted.

[rovercoupe]

Thats a really good idea, i might see whats in the bits box and see if i can find a bit of brass and turn it down.

Thanks guys I might knock up a few delrin ones of differing size holes and see what happens and then once I know the size go all out in brass!

[Bjacobs571]

.
So i would drive in a turned lump of solid brass and then simply drill the hole to the size you want.

Why not drill the hole when the part is still in the lathe as the hole would be in the middle, concentric all the way down and won't fill the gun with swalf.

[robs5230]

Hopefully here is a pic of the port in question,

Unless my eyes are deceiving me or the other end of that tp has reduced diameter, that port is way wider than 2mm bore