Operation TX

[T 20]

Seeing as I'm hosting the AirArms Owners Club charity meeting next month I thought it would be a good idea if I bought an AirArms gun to use over the weekend.

So I bought a cheap MK2 TX200 in .22" flavour off our very own Edbear for the princely sum of £125, so giving me something to tune and play with.

Now here's the twist, rather than me just lathing loads of new parts up I've decided to see what could be acheived using easily available off the shelf parts at minimum cost --- This should allow anyone who can strip a TX to replicate what I'm up to.

Now even though the MK 2 TX has a relatively short stroke I thought I'd shorten it a little bit more and I'm told that the HW77 piston seal is more efficient than the AirArms seal --- so I bought a piston allowing for both. :-


http://s1138.photobucket.com/user/mi...tml?sort=3&o=4


Now the LGV seal has a central tit that would restrict flow on a TX with it's central port so I dug a 25mm Weihrauch seal out the spares box. :-


http://s1138.photobucket.com/user/mi...tml?sort=3&o=6


And this picture shows the difference in piston lengths (LGV on right) :-


http://s1138.photobucket.com/user/mi...tml?sort=3&o=5


The difference in piston lengths with the Weihrauch seal fitted measured at 7.8mm, so with the original TX MK2 stroke being 84mm, fitting the LGV piston should drop the stroke down to 76.2mm.


Well I had a little bit of time this afternoon so I threw my TX together (bone dry) and ran a quick chrono string to see where I was going.

Results :-

Hobbies 645 ft/s = 10.99 ftlbs

Superdomes 604 ft/s = 11.75 ftlbs

Jumbos 550 ft/s = 10.75 ftlbs


The above results are just from changing the piston and removing 4mm of preload from the spring.

If I get a little bit of time in the week I have a few other little tweaks I'd like to try involving shedding a little weight from the piston by way of removing the 6 gram steel top hat and turning the spring round as I have three collapsed coils on the front of the spring which I calculate to add 11 grams to the overall piston weight.


So there you are this is my starting point and I'll play around to lower the power a bit more and to see if I can make the gun sweeter, though in all honesty it feels really nice how it's running now.




All the best Mick

[TonyL]

Excellent, Mick.

And, as you say, so easy for anyone to do without access to specialist machinery / lathe etc.

As you say, I bet it's already very nice, but even better with a little more fine tweaking.

Cheers for sharing.

[Gugglebox]

Thank, this is a perfect thread for me as I'm leaning towards a TX and looking forward to a tinker. I look forward to seeing how the experts do it.

[Shed tuner]

Perfect... that's the thing with tuning a TX; they are such a good base, just sorting the seal and the stroke makes a gun gun excellent.

Not that you are likely to be short of ideas, but in keeping with the no machining / moderate costs, I'd also consider

- Roller thrust rear needle bearings (about £2.50 of the 8ay), make cocking smoother
- beer can piston sleeve
- new tight fitting Custom guides (cheating on the no machining, I know, but if they are available "off the shelf"....)
- LGU seal - they seem quite a bit more efficient in most guns that the HWs
- centre floating guide

I would say consider gluing a sleeve into the port, but it doesn't look like you have any slam, and if you are considering lightening the piston, taking the port down may introduce some bounce with tighter port... unless you want to shoot FAPs (I would !), in fact I'm not even sure I'd lighten it at all...

[T 20]

Excellent, Mick.

And, as you say, so easy for anyone to do without access to specialist machinery / lathe etc.

As you say, I bet it's already very nice, but even better with a little more fine tweaking.

It seems really nice how it is Tony

The big surprise is that my first test run with a reduced stroke showed Superdomes running over 12 hence the removal of the 4mm spacer.

It certainly feels a lot better than standard but I'll let the AirArms lads have a play and give their opinion.

I'm a bit out of practice with this tuning lark as I haven't done much for two years now --- nice to get back in the swing of things.

Perfect... that's the thing with tuning a TX; they are such a good base, just sorting the seal and the stroke makes a gun gun excellent.

Not that you are likely to be short of ideas, but in keeping with the no machining / moderate costs, I'd also consider

- Roller thrust rear needle bearings (about £2.50 of the 8ay), make cocking smoother
- beer can piston sleeve
- new tight fitting Custom guides (cheating on the no machining, I know, but if they are available "off the shelf"....)
- LGU seal - they seem quite a bit more efficient in most guns that the HWs
- centre floating guide

I would say consider gluing a sleeve into the port, but it doesn't look like you have any slam, and if you are considering lightening the piston, taking the port down may introduce some bounce with tighter port... unless you want to shoot FAPs (I would !), in fact I'm not even sure I'd lighten it at all...

That's the idea Jon

I buy everything in and make absolutely nothing that can't be bought.

If anything doesn't work or is a waste of money I'll post that on here as well.

If I decide to sleeve the transfer port down I'll try to source the tubing from the rack in B and Q.

Obviously I'll need to swap all the guts out into a .177" TX at some point to see how it all works in the Ladies calibre.

The total cost of parts so far is about £35 plus shipping and you end up with a spare LGV seal, if you could find a source of LGU Pistons the price would be about £24 plus shipping which has got to be a bargain.

I'm not sure if the beartrap would work with the LGV/LGU piston as my TX has had it removed.



All the best Mick

[T 20]

Thank, this is a perfect thread for me as I'm leaning towards a TX and looking forward to a tinker. I look forward to seeing how the experts do it.

Hi Gugglebox

The TX is far easier to work on than a HW77/97, the only advantage with the 77/97 being the shorter transfer port but this can easily be sorted on the TX if needed.



All the best Mick

[TonyL]

It seems really nice how it is Tony

The big surprise is that my first test run with a reduced stroke showed Superdomes running over 12 hence the removal of the 4mm spacer.

I'm a bit out of practice with this tuning lark as I haven't done much for two years now --- nice to get back in the swing of things.

I buy everything in and make absolutely nothing that can't be bought.

If anything doesn't work or is a waste of money I'll post that on here as well.

The total cost of parts so far is about £35 plus shipping and you end up with a spare LGV seal, if you could find a source of LGU Pistons the price would be about £24 plus shipping which has got to be a bargain.

All the best Mick

Looking very efficient already then, Mick.

Out of practice....nah! Once you've got it, you've got it, Michael, and that you most certainly have! And that two years basically corresponds with the Bash concept, so you've been pouring time and effort into that.

Excellent plan re using bought in parts, so that many more people can replicate, and what a great value for money tune it's proving to be.

[Shed tuner]

I'm not sure if the beartrap would work with the LGV/LGU piston as my TX has had it removed.

All the best Mick

@ ~76mm stroke and a MK2 comp tube, it will work fine. MK3, it won't catch.

In .177, I think you'd be pushing it with that stroke and a std port

[T 20]

@ ~76mm stroke and a MK2 comp tube, it will work fine. MK3, it won't catch.

In .177, I think you'd be pushing it with that stroke and a std port

If I get a .177" TX to play with it may be worth sleeving the transfer port down to up the SCR and then increasing the spring preload.

If that doesn't work little machining to increase the stroke and reduce the port length wouldn't be out of the Question.

All good clean fun though Jon.



All the best Mick

[NickG]

You could always lighten that piston , by losing the skirt.

[T 20]

You could always lighten that piston , by losing the skirt.

Very true Nick but that would bring other problems into the equation such as the spring guide.

The idea is to just keep things very simple at this stage.

Are you coming to the AirArms bash at mine by the way ?




All the best Mick

[Captain Bongo]

I am sure Slinger would agree with me here, at Quigley Hollow, we never want to lose the skirt.......

[T 20]

I am sure Slinger would agree with me here, at Quigley Hollow, we never want to lose the skirt.......

But you told me they were kilts that you were both wearing in honour of your Scottish ancestors.

And I didn't like to say at the time but I thought that tossing the Caber competition looked a bit dodgy as well.

[NickG]

Very true Nick but that would bring other problems into the equation such as the spring guide.

The idea is to just keep things very simple at this stage.

Are you coming to the AirArms bash at mine by the way ?




All the best Mick

Very close to convincing the wife that I need to be there, Just got to check the diary, fingers crossed

[slinger69]

But you told me they were kilts that you were both wearing in honour of your Scottish ancestors.

And I didn't like to say at the time but I thought that tossing the Caber competition looked a bit dodgy as well.

Hoots mon! 'Twas yae own MacBoinger tartan.