Hw35 optimal set up

[charub]

Winter is here and it is time to dig out the old project guns.
I have a dog of a 35 that I want to give some love to. Last year I attempted to solder the porous breech, I am dubious that I succeeded.
So I’m now going down the Loctite or JB weld route.
Whilst at it, I thought I would check what is the optimum transfer port size in a later model with synthetic piston washer?
I’m not overly concerned on overall power, i just want it smooth to plink with

Thanks guys.

[Shed tuner]

2.8ish mm port, synth head piston with the longer 64mm stroke and a few grammes lighter, don't over spring it, and fix that leaky breech. Job done, it'll shoot sweet as...

[Hsing-ee]

2.8ish mm port, synth head piston with the longer 64mm stroke and a few grammes lighter, don't over spring it, and fix that leaky breech. Job done, it'll shoot sweet as...

What is your preferred method of removing weight from a piston, and how much should it weight when its done?

[Shed tuner]

What is your preferred method of removing weight from a piston, and how much should it weight when its done?

i was reffering to the factory synth piston being lighter as is..

more generally, a slot opposite the cocking slot on the piston always gives a worthwhile weight benefit.. just keep well away from the nose and skirt whilst cutting it..

[CapitalBee]

What is your preferred method of removing weight from a piston, and how much should it weight when its done?

I think the advice concerns replacing the old leather sealed piston with a newer synthetic piston. It increases stroke by 4'ish mm and is lighter. Mick (T20) posted a useful article on it. I've done this myself and it does improve an already good shot cycle, as well as upping the power by at least a ft/lb (possibly 2), allowing you to take some spring out of the configuration.

[Shed tuner]

I think the advice concerns replacing the old leather sealed piston with a newer synthetic piston. It increases stroke by 4'ish mm and is lighter. Mick (T20) posted a useful article on it. I've done this myself and it does improve an already good shot cycle, as well as upping the power by at least a ft/lb (possibly 2), allowing you to take some spring out of the configuration.

yup - about 2 ft lbs for me - a lot of spring had to come off

[charub]

Ok guys, what’s the best method for cleaning up before the porous breech fix. Please bare in mind that I have previously washed a cylinder head in the dishwasher and have been told in no uncertain terms that I should be looking at a bedroom fun band if anything remotely garage / workshop like is washed in there again!!!!

[charub]

2.8ish mm port, synth head piston with the longer 64mm stroke and a few grammes lighter, don't over spring it, and fix that leaky breech. Job done, it'll shoot sweet as...

Cheers.

[T 20]

2.8ish mm port, synth head piston with the longer 64mm stroke and a few grammes lighter, don't over spring it, and fix that leaky breech. Job done, it'll shoot sweet as...

Leather sealed Pistons had a 65mm stroke

Synthetic sealed guns had a 69mm stroke

I like to start off with a leather sealed piston and machine it to give a 71mm stroke using a synthetic seal coupled with @ a 3mm transfer port.




All the best Mick

[Weasle]

Leather sealed Pistons had a 65mm stroke

Synthetic sealed guns had a 69mm stroke

I like to start off with a leather sealed piston and machine it to give a 71mm stroke using a synthetic seal coupled with @ a 3mm transfer port.




All the best Mick

Hi Mick

I'm just about to rebuild a '70's 35 Export....long barrel.

Have you got a pic of your modded leather piston - to accept a New HW seal?

Cheers Steve

[T 20]

Hi Mick

I'm just about to rebuild a '70's 35 Export....long barrel.

Have you got a pic of your modded leather piston - to accept a New HW seal?

Cheers Steve

Unfortunately not Steve, I only tend to machine a piston up on an exchange basis when someone attending the Boinger Bash requests one --- Dayglowfroggy had the last one I made.

But, I do have a spare leather sealed piston on the shelf so if I get time tomorrow, I'll try to machine it in stages and take photographs to show what's involved --- or I could simply just draw it for you.




All the best Mick

[Weasle]

Unfortunately not Steve, I only tend to machine a piston up on an exchange basis when someone attending the Boinger Bash requests one --- Dayglowfroggy had the last one I made.

But, I do have a spare leather sealed piston on the shelf so if I get time tomorrow, I'll try to machine it in stages and take photographs to show what's involved --- or I could simply just draw it for you.




All the best Mick

Many thanks Mick

That would be great.....and much appreciated.

Cheers Steve

[T 20]

Hi Mick

I'm just about to rebuild a '70's 35 Export....long barrel.

Have you got a pic of your modded leather piston - to accept a New HW seal?

Cheers Steve

OK then Steve, so as not to disappoint.

First off I fit the leather sealed piston in the gun and take a few measurements to work from :-

image.jpg



Then I remove the leather seal :-

image.jpg



Then I machine the front face of the piston back by the calculated amount to get a 71mm stroke :-

image.jpg



The newly exposed piston rod is then threaded :-

image.jpg



A lump of alloy that's premachined for the seal groove is then screwed and glued onto the exposed rod :-

image.jpg



The seal arbour is then finish machined :-

image.jpg



Adding a seal you end up with this :-

image.jpg



Now due to the crosspin through the piston head I couldn't machine the piston back to give a full 71mm stroke and stopped at just over 70mm.

If I do want to go to a longer stroke I can simply remove the HW synthetic seal and alloy arbour and machine up an O ringed piston head which could easily take me to 72mm.

The piston as seen still needs 1mm or so removing from the rear of cocking lever slot before fitting to prevent the piston smashing into the cocking arm on firing --- I normally aim for a 1mm to 1.5mm clearance.


Hope this all makes sense ?




All the best Mick

[Shed tuner]

hi Mick, having seen your pics, looks like my approach was actually the same as yours - even though we both thought it wasn't

[evert]

.......
Now due to the crosspin through the piston head I couldn't machine the piston back to give a full 71mm stroke and stopped at just over 70mm.

If I do want to go to a longer stroke I can simply remove the HW synthetic seal and alloy arbour and machine up an O ringed piston head which could easily take me to 72mm.

The piston as seen still needs 1mm or so removing from the rear of cocking lever slot before fitting to prevent the piston smashing into the cocking arm on firing --- I normally aim for a 1mm to 1.5mm clearance.

Hope this all makes sense ?

All the best Mick

I get nervous when you remove all that material, have you ever had a piston come apart during cocking after this modification?