Tx200 zero transfer port

[wonky donky]

I have decided to make new compression plugs as opposed to forking out for new AA units assuming they are available.

I have no idea how long this project is going to take me due to other commitments, but I have made a start. Double click on an image to enlarge.


I'm currently thinking about which method to use to seal the barrel in the breech, favorite at present is to machine a groove into the rear of the compression tube plug to take an "O" ring of 2mm section.
I did contemplate using Pur90 but think I will use NBR70 if I go this route.

Okay then mick

[bigtoe01]

Or put the O ring on the end of the barrel around 0.5mm from the end so you have next to no lost volume at all....maybe easier to machine than an internal o ring grrove? Either way I wish we had a LIKE button on here

This is going to be fun to watch!

[TonyL]

WOW!!

Wish I could do that!

Wish I had 1/100th of the skill of you chaps!

[T 20]

I'm currently thinking about which method to use to seal the barrel in the breech, favorite at present is to machine a groove into the rear of the compression tube plug to take an "O" ring of 2mm section.
I did contemplate using Pur90 but think I will use NBR70 if I go this route.

Okay then mick

OK with me Dave

Rather than a sliding O ring I thought an O ring working under crush could be easier to machine and could last longer.

By that I mean machine the barrel diameter down to give a shoulder (male) then machine the cylinder plug as a female.
An O ring sitting in the plug on the female shoulder could then be crushed by the shoulder on the barrel --- I should have drawn it and put it on Jon's thread.

You could also use a quad seal in this situation.

Whichever way you seal it I'm looking forward to the results Dave.


All the best Mick

[Shed tuner]

hehe,

I'm pretty sure the end plugs are not available separately from AA, just an entire comp tube assy, at nearly £50 for the lot

If you can make a few spare comp tube end plugs (not standard, obviously), but pre-shortened on the inside (just so it covers the threads) giving ~ 7.5 mm long port, I reckon that'll be a great seller

Back to the zero port, thinking groove round the outside of the barrel with very tight tolerances to prevent lost volume, or barrel face seal if you can compromise on a 1mm long port, or maybe a stepped breach face, so that an o-ring sits around the protruding central section, exactly like the current AA arrangement in the comp tube end plug (imagine loading a pellet into the port on the end plug). That way your zero port gun can still have a decent thickness for most of it's area, just reduced in about a 10mm circle to 2.3mm (seal thickness), and the 2.3mm protruding central breach say 6mm dia (along with hosted pellet) poking thru.

*edit - yup, Mick described my third option much better than I did ! *

Watching this one, listening for the bangs too

[bigtoe01]

OK with me Dave

Rather than a sliding O ring I thought an O ring working under crush could be easier to machine and could last longer.

By that I mean machine the barrel diameter down to give a shoulder (male) then machine the cylinder plug as a female.
An O ring sitting in the plug on the female shoulder could then be crushed by the shoulder on the barrel --- I should have drawn it and put it on Jon's thread.

You could also use a quad seal in this situation.

Whichever way you seal it I'm looking forward to the results Dave.


All the best Mick

you would have lost volume down the barrel to the O ring, plus thats a one way trip for the barrel making it harder to use the adapted barrel in an old comp tube setup.

Not easier to machine the plug to have a slight tapered lead in, polished so that it centres over the barrel as the comp tube slides forward, then just either have the O ring in the plug as Dave describes (harder to machine though) or just an O ring in the barrel set 0.5mm back so that you have near zero lost volume?

We are looking to have the barrel finishing flush with the inner face of the comp tube are we not?

If this does not work out im thinking a 2mm long TP (for strength) using a 300S breech seal and profiles barrel to suit it.

[wonky donky]

hehe,

Watching this one, listening for the bangs too

Oh you do crack me up Jon.

you would have lost volume down the barrel to the O ring, plus thats a one way trip for the barrel making it harder to use the adapted barrel in an old comp tube setup.


We are looking to have the barrel finishing flush with the inner face of the comp tube are we not?

If this does not work out im thinking a 2mm long TP (for strength) using a 300S breech seal and profiles barrel to suit it.

Correct Tony, I would like to reuse the barrel in a standard set up so my thoughts on the "O" ring groove would be my first choice, however the groove won't be difficult to cut but we are talking making about making a micro internal grooving tool here & I've not done anything like that for 40yrs so could be struggling to get it right by.

Yes your correct barrel flush with the face of the inner face of the plug.

On the other hand I could easily taper the barrel & use a Feinwerkbau 300s seal, I have plenty of those, but then the barrel won't be any good for a standard set up & won.t be asflush as I would like, or would it? Errm!

[bigtoe01]

Oh you do crack me up Jon.




Correct Tony, I would like to reuse the barrel in a standard set up so my thoughts on the "O" ring groove would be my first choice, however the groove won't be difficult to cut but we are talking making about making a micro internal grooving tool here & I've not done anything like that for 40yrs so could be struggling to get it right by.

Yes your correct barrel flush with the face of the inner face of the plug.

On the other hand I could easily taper the barrel & use a Feinwerkbau 300s seal, I have plenty of those, but then the barrel won't be any good for a standard set up & won.t be asflush as I would like, or would it? Errm!

Cut O ring groove into the plug, infact you can buy O ring groove internal cutting tools which may make life easier unless you have plenty of HSS and a steady hand on the grinder?

I would just O ring the end of the barrel my self, it would help in a stock comp tube set up as well or could be filled with JBweld and polished back if it was to be done away with.

[FPoole]

Has anyone noticed a decrease in accuracy if the transfer port nipple touches the barrel? I have a very tight locking TX that needs fresh breech seals to shoot at it's best. The tip of the transfer port nipple is all shiny from barrel contact. I tried shimming the receiver so that the comp. tube nut touched the shims before the breech seals were crushed and accuracy went absolutely awful. Chrono was the same and steady so the breech was still sealing, but it was awful. I ask this because I wonder if some of the mods you mention will cause metal to metal contact.

[T 20]

you would have lost volume down the barrel to the O ring, plus thats a one way trip for the barrel making it harder to use the adapted barrel in an old comp tube setup.

The lost volume would be dependant on how you machine it Tony.

The barrel could easily be recovered by sweating a bush onto the reduced OD and machining back to standard dimensions --- I've had the MIG round them in the past.

All this would be a very straightforward machining job and an O ring working as I described would be an easy swap if needed --- I've had to change thousands of internal O rings on hydraulic spool blocks over the last 35 years and I'd never machine anything to take one unless there was absolutely no other alternative.




Don't forget I've been thinking about this for a bloody long time.

http://www.airgunbbs.com/showthread....-transfer-port





All the best Mick

[bigtoe01]

The lost volume would be dependant on how you machine it Tony.

The barrel could easily be recovered by sweating a bush onto the reduced OD and machining back to standard dimensions --- I've had the MIG round them in the past.

All this would be a very straightforward machining job and an O ring working as I described would be an easy swap if needed --- I've had to change thousands of internal O rings on hydraulic spool blocks over the last 35 years and I'd never machine anything to take one unless there was absolutely no other alternative.




Don't forget I've been thinking about this for a bloody long time.

http://www.airgunbbs.com/showthread....-transfer-port





All the best Mick

Bucketboy has a Rapid pellet probe like this...saw it on the rapid forum, thinking about it now it would work well and you could as you say just bush it back to stock if needed.

Like this?

https://dl.dropboxusercontent.com/u/...s_comptube.png

[T 20]

Bucketboy has a Rapid pellet probe like this...saw on on the rapid forum, thinking about it now it would work well and you could as you say just bush it back to stock if needed.

Like this?

https://dl.dropboxusercontent.com/u/...s_comptube.png

Nearly like that Tony

I'd have the O ring the same OD as the barrel so that pressure forces the ring onto the barrel's new face to seal the joint directly, if you get my drift.

I wish I could do all those whizzy pics like you 'puter literate folks.


(And they made me a mod of a t'internet site --- the world's gone mad. )




All the best Mick

[brucegill]

Nice one Dave, keep up the good work

[bigtoe01]

Nearly like that Tony

I'd have the O ring the same OD as the barrel so that pressure forces the ring onto the barrel's new face to seal the joint directly, if you get my drift.

I wish I could do all those whizzy pics like you 'puter literate folks.


(And they made me a mod of a t'internet site --- the world's gone mad. )




All the best Mick

https://dl.dropboxusercontent.com/u/...comptube1a.png

Thats how I would do it, the comp tube has a lead in to aid it sliding over the nose of the barrel and the O ring has a slight groove to retain it

[Shed tuner]

Looks perfect Tony - Dave, you finished yet ?