Hw80 piston/preload

[steviebee]

Hi,
Just stripped down a hw80 I bought last year in an antique shop, as a project gun. For £60.
Very poor state, so finally got round to sorting it out, very sad state, as the jaw/vice marks on the cylinder and end block , told me someone had already ventured into its internals.
It was very jumpy and typically twangy, and using a spring compressor found about 2 inches of preload! And a red piston seal.
Question is ?
Obviously this gun was over sprung, what is the sort of ideal preload for a 80? Using factory spring.
And is the red seal a factory unit or a replacement, as only every come across white ones on HW's.

Also what are the benefits of a export spring, i'v seen for the 80, as supplied in the TBT kits?

Cheers for looking

[Shed tuner]

the red seal is probably an Aussie custom seal - search the net for custom seals australia and see if they match.

like this ?



wow - that's big ** Not actual size


preload - minimal. barely touching the end block before you start screwing is not unusual, but certainly unlikely to be more than 1/2"

you really need a chrono when changing springs on an HW80.

TbT kits are good value, but if your spring is fine, just re-use it.

[Black Beard]

The red seal might be a custom seals one. If so they are pretty good.

The standard spring has only a few mm of preload.

[BAD DAZ]

I agree with shed tuner, get a chrono before you mess with the 80, it doesn't take much to get into trouble, I've got the t-shirt, atb Daz

[averageplinker]

I agree with shed tuner, get a chrono before you mess with the 80, it doesn't take much to get into trouble, I've got the t-shirt, atb Daz

Or to put another way it is almost impossible not to go over the limit with an HW80 without a chrono to check!
Rich.

[tinbum]

Reducing the stroke with an extension gives you a better chance of keeping it at the right power and also allows some preload to help stop the twang

[CapitalBee]

Reducing the stroke with an extension gives you a better chance of keeping it at the right power and also allows some preload to help stop the twang

What he said.

I've a couple of short stroke nose extensions fitted to two of my hw80's (12mm IIRC). They allow you to add more preload, but swept volume will help keep them below 12ft/lbs. My .25" runs at 11.75 and my .20" runs at 11.5, both with 3.6mm springs and about 20mm of preload.

[TonyL]

Agree with all the posts re the 80's propensity to make lots of power too easily and the need to undertake any work allied with a chrono.

That red seal might also be a Knibbs one? And what colour are TR Robb replacement parachute seals?

[averageplinker]

What he said.

I've a couple of short stroke nose extensions fitted to two of my hw80's (12mm IIRC). They allow you to add more preload, but swept volume will help keep them below 12ft/lbs. My .25" runs at 11.75 and my .20" runs at 11.5, both with 3.6mm springs and about 20mm of preload.

Interesting. I am building up a .25" HW80 and was wondering if I need a nose extension to keep the power down. Does yours .25" have a short stroke?
Cheers Rich

[CapitalBee]

Interesting. I am building up a .25" HW80 and was wondering if I need a nose extension to keep the power down. Does yours .25" have a short stroke?
Cheers Rich

Yes mate, 12mm. Firstly I went down the route of short stroke and reducing the spring to a 14mm id ('97/77), but even with a fair bit of preload, I was in the mid 10's with power, which to be honest you don't want with a .25". So, kept the short stroke and went back to original spring size. I'd echo Shed Tuner's thoughts regarding the best shooting '80 as mine is very nice (nicer than the .20", which is practically the same set up).

[steviebee]

Hi guys thanks for the replys, borrowed a chrono, and as perceived it was a tad hot! So trimming the spring down as suggested.
And as to the piston seal would appear to be a normal seal, just a different colour.
Thanks for the response, stripping down to the white, today and getting to grips with the damm vice/ mole grip Mark's.

[venoman]

its down to the spring specifications of the spring, a long spring might not need so much pressure to compress.