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TX200. Front piston bearing.


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7 replies to this topic

#1 raygun

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Posted 16 June 2010 - 03:27 PM

Just what does the front delrin bearing do on the TX/PS piston.

Given that the sizes are as follows (will be a bit of wear)

Piston seal = 25.16mm O/D
Front delrin ring = 24.7mm O/D
Comp tube bore = 25.06mm

The piston will be supported and run on the Piston seal which will leave the delrin ring clear of the bore.
Anyone know what AA's intentions were ?

ATB
Ray.

#2 dave_424

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Posted 16 June 2010 - 06:23 PM

Maybe add length to the piston, for tuning or something?

Dave

#3 raygun

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Posted 16 June 2010 - 07:02 PM

Hi Dave,
I don't think that can be it as the ring just sits in a groove. It's strange as the groove has to be machined into the piston, the delrin ring made and then fitted. They could save a few quid by just leaving it out.

The pic shows the delrin ring behind the piston seal.



ATB
Ray.

#4 GBertolet

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Posted 17 June 2010 - 03:50 AM

I have often wondered why on the pictures of tuning the HW97, often there is a button placed up front on the piston. As you noticed on the TX, the piston seal provides guidence at the front, so why is there a button or guide there? I don't know why, and would like to know also!

Edited by GBertolet, 17 June 2010 - 03:52 AM.


#5 Jon

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Posted 17 June 2010 - 08:01 AM

Because the piston at front will deflect more than 0.3mm when cocked and run metal to metal.
Note that acetal ring protrudes above piston diameter.

#6 Artfull-Bodger

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Posted 17 June 2010 - 06:50 PM

Yup Jons got it, the piston seal has a degree of deflection in it due to it's material so the piston could "end float" and contact the compression tube!

#7 raygun

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Posted 17 June 2010 - 08:40 PM

Still thinking about this and I'm not sure it's to do with cocking or the deflection of the seal.

The rifle is cocked by the cocking lever first pushing rearwards on the rear of the comp tube. This would lift the comp tube up against the cylinder and either the comp tube or the rear delrin ring would bear along the cylinder wall. I'm guessing that it would be the comp tube rubbing against the cylinder as there is nothing to lift the rear of the piston. The second push would be against the piston seal, moving the piston rearwards until latched on the trigger sear. Unless the spring was seriously bent there should be a central alignment of the seal during cocking.

On the forward movement the seal is a parachute type and will take up it's maximum diameter which would be the bore of the comp tube. Given that the bore is 25.06mm and the delrin ring .36mm less I still don't see how it bears on anything.

Still puzzled doh.gif

ATB
Ray.

#8 bulsaye

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Posted 20 June 2010 - 12:13 AM

The piston ring should be just a tad under the compression tube ID, but larger than the piston OD. This eliminates metal to metal contact.. at least that was Ken Turners intent. Undersized or worn rings should be replaced. RB




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