Operation TX

[T 20]

Doh... yeah, std size is 3.7 / 3.8mm. Taking it down to 3.4 will be much the same as shortening and keeping at 3.8

How come yours was 3.5 ? That's not a std size, unless the v. early ones were smaller ?

The serial number of this one is 9087 Jon and the transfer port was definitely 3.5mm as standard.

There's some funny things I've noted on the SCR as well on changing from the AA seal to the Weihrauch seal --- I'll post these up when I've calculated them.

Well I've had my Verniers and calculator out and it gives a bit more detail as to why the Walther piston with HW seal works so well in the TX.

The front of the TX piston has a recessed steel centre section that acts as an arbor for the standard TX seal, this recess is 15.5mm diameter X 0.9mm deep having a volume of 0.17cc.

My transfer port at 3.5mm X 9.8mm long having a volume of 0.094cc.

My reduced port at 3.0mm X 9.8mm long having a volume of 0.069cc

So :-

The total lost volume using a TX seal = 0.17 + 0.094 = 0.264cc

The total lost volume using an HW seal = 0.094cc


The Static compression ratio of my TX with 41.3cc swept volume = 41.3/0.264 = 156:1 SCR

The SCR with Walther piston and HW seal at 37.4cc swept volume = 37.4/0.094 = 394:1 SCR

SCR with the trans port reduced to 3mm with 37.4cc swept Volume = 37.4/0.069 =542:1 SCR


So looking at the figures now gives a bit of a clue as to why reducing the swept volume using a HW seal increased the power using the original spring set up.

Next thing I'll do will be to open the transfer port back out to 3.5mm and reduce the preload by 3mm by chopping a closed coil off the spring.



All the best Mick

[Shed tuner]

Nice one Mick...

yeah, I think that's why the TX seal is so bad, just too much lost volume in there. Ironically enough, it's less of an issue on the long-stroke mk3, but it ruins the mk1/2.

On my SR (mk2) you can't change the rod length or you mess up the SR mechanism (which relies on the rear edge of the piston skirt being in the same place), so I simply switched to HW nose, shortened the port 2mm, and it's sweet as now... stroke has gone down from 82 > 77 (seal height + nose) but the SCR is actually higher, and so it feels much softer.

[T 20]

Nice one Mick...

yeah, I think that's why the TX seal is so bad, just too much lost volume in there. Ironically enough, it's less of an issue on the long-stroke mk3, but it ruins the mk1/2.

All Diana type seals seem to suffer the same loss, Jon

I remember someone describing how he filled the central void with liquid rubber to raise the SCR on a TX, I can understand why now.



All the best Mick

[TonyL]

Excuse me, please, for reviving this thread.

Just searched it out and thought I had better ping it up to page one for a while (a) as I have had the pleasure of using this gun at the April and June Bashes and IT IS SUPERB and, (b) having just got a TX, wanted to refresh myself with the details, folks.

May help a few others, too.....

[mdunn]

hi, which piston seal is the best for the mk2,or is the standard 1 ok. atb mick

[TonyL]

Just thought I'd revive this yet again re current thread on TX tuning.

[Bluefan]

Just thought I'd revive this yet again re current thread on TX tuning.

Oh Tony you scamp!

[Rickenbacker]

Nice one Mick...

yeah, I think that's why the TX seal is so bad, just too much lost volume in there. Ironically enough, it's less of an issue on the long-stroke mk3, but it ruins the mk1/2.

On my SR (mk2) you can't change the rod length or you mess up the SR mechanism (which relies on the rear edge of the piston skirt being in the same place), so I simply switched to HW nose, shortened the port 2mm, and it's sweet as now... stroke has gone down from 82 > 77 (seal height + nose) but the SCR is actually higher, and so it feels much softer.

*zombie post revival*

Tuning an SR? Isn't that a bit like having a dog and barking yourself?