Original Diana 35 - elastomer piston seal ? Better?

[jonnyone]

Thanks Dave.

Probably you converted a Diana 35 or 50. If so, do you remember if the ptfe seals you used were shorter than the originals?

I ask because the seal I am looking at is shorter, and I was told this will cause trouble.

Ignacio

Morning ignacio. I have fitted ptfe seals to two Diana 45s, one 50, one 50T01, two anschutz 335s, one HW35, and a BSF as I recall.
I have been fortunate in that despite the seals being thinner height wise than the original leather seal they have still had clearance between the cocking lever rod and the piston body. This can easily be checked after the seal is fitted. A few millimetres clearance is needed when the piston is fully pushed home against the end of the compression tube. Should this not prove to be the case then the new head will need.packing between it and the piston body to create that required gap. I recall some have used large tap washers in the past but as I say it has proved unnecessary for me. I can't say it will be the same for your gun as I have no experience of working on a 35.
Perhaps an email query to the seller of the synthetic seal may throw some light on things but even then I would still check the clearance as per the above after fitting?
Wish you luck
Dave

[Benelli B76]

PTFE is a poor material for piston seals as it is malleable and can be squashed out of shape. Polyurethane elastomer is a far better material and the most commonly used today.

Baz

[jonnyone]

PTFE is a poor material for piston seals as it is malleable and can be squashed out of shape. Polyurethane elastomer is a far better material and the most commonly used today.

Baz

Someone had best explain the ptfe failings to my guns. I fitted the first seal to an RWS 45 in the late 80s and its worked perfectly since (as they have all done). I think it's about time they started playing up a bit
Dave

[Drew451]

You should really have a word with those 50's while you're at it. They don't always realise tap loaders are meant to be old crap...

[jonnyone]

You should really have a word with those 50's while you're at it. They don't always realise tap loaders are meant to be old crap...

Very true.
Which is going to come as a shock to my .22 Original 50T01 as it's shooting very sweet right now after a mainspring upgrade.
All jokes aside back in the day there wasn't the choice of piston head materials we have now and ptfe was about the only alternative unless you had access to a lathe and was pretty handy on one. If I could have had someone run me up a few dovetail converters so that the pistons would accept OEM washers I would definitely have gone that route. Diana piston washers are definitely some of the best around giving good sealing qualities combined with reasonably low friction.
As I've said a few times on here now aside of a HW35 with a tapered cylinder end and a BSF55 with a less than true cylinder all the guns I've swapped to ptfe have worked flawlessly and for quite some time now. Maybe I've just been incredibly lucky with all of these? Or maybe ptfe isn't the demon material some make it out to be? For the time being I'm certainly enjoying benefits from swapping over.
The good thing is that nowadays we seem to have more choice in the direction we go with upgrading from leather washers. Which can't be a bad thing and long may that continue.
Dave

[Benelli B76]

Someone had best explain the ptfe failings to my guns. I fitted the first seal to an RWS 45 in the late 80s and its worked perfectly since (as they have all done). I think it's about time they started playing up a bit
Dave

PTFE does not need explaining to the guns but to people. PTFE can be cut with a knife. It is usually white in colour and is malleable that is why it is used for flange seals etc because it adapts to shape. A lot of people look at a synthetic seal in an air rifle and call it PTFE when it is actually polyurethane because they do not know about polymers. You can use it for piston seals but it will not give a good seal eventually, that is why airgun manufacturers do not use it. I repair airguns every day and never see it except on old Webley pistols, and it is used on the capsule seal for the Tanfoglio Witness pistol which is why they need to be changed after squashing out of shape.

Baz

[jonnyone]

PTFE does not need explaining to the guns but to people. PTFE can be cut with a knife. It is usually white in colour and is malleable that is why it is used for flange seals etc because it adapts to shape. A lot of people look at a synthetic seal in an air rifle and call it PTFE when it is actually polyurethane because they do not know about polymers. You can use it for piston seals but it will not give a good seal eventually, that is why airgun manufacturers do not use it. I repair airguns every day and never see it except on old Webley pistols, and it is used on the capsule seal for the Tanfoglio Witness pistol which is why they need to be changed after squashing out of shape.

Baz

Fair comment Baz. But I'm just wondering why these seals have performed flawlessly over the years for me? Not just one or two but all of them with exception of those mentioned above and for I don't know how many cycles?
Have I just been lucky then? Ive stripped a few to check and there has been nothing adverse noted?
As I say the moment any give me trouble I will strip them out. But I don't see the need when they perform so well?
Perhaps design also has something to do with it? I know my old mk 1 Vulcan uses a ptfe seal and is performing well after all these years.
I have the luxury of two identical Diana's T01s (albeit different calibres) and will definitely go the oem seal route next time around and compare.
Dave

[Drew451]

I had a Webley Vulcan with the standard PTFE & buffer washer set up. I never changed it. It worked with good/ stable performsnce for something approaching 7/8 years until it was sold.
When Dave says he's been running PTFE conversion set ups with good results for far longer than this I have no reason to doubt him.
I am running the OE leather washers in 35/45/50 and will be sticking with these as they meet my expectations in terms of performance and reliability.

[Hsing-ee]

You can get a nice polyurethane washer and an adaptor from Vortek. They are not expensive and you just have to degrease and screw the adaptor on, then pop the seal on. How it may perform is up in the air, it should be more consistent and powerful but some people believe that guns set up to use leather washers may need narrower transfer ports to get the best efficiency. Polyurethane produces less friction in the cylinder bore and you may get a slight increase in swept volume, plus you can set up the lubrication so there is less combustion. With a wider port it may be a bit slammy. So, like any tuning mission it is a matter of getting the chronograph and a good selection of pellets out and see what happens ...

I see you are in Venezuela. You could try ordering direct from the US or from Tony Burton in the UK.

http://www.agrtuning.co.uk/about-agr-tuning.html

[Benelli B76]

Fair comment Baz. But I'm just wondering why these seals have performed flawlessly over the years for me? Not just one or two but all of them with exception of those mentioned above and for I don't know how many cycles?
Have I just been lucky then? Ive stripped a few to check and there has been nothing adverse noted?
As I say the moment any give me trouble I will strip them out. But I don't see the need when they perform so well?
Perhaps design also has something to do with it? I know my old mk 1 Vulcan uses a ptfe seal and is performing well after all these years.
I have the luxury of two identical Diana's T01s (albeit different calibres) and will definitely go the oem seal route next time around and compare.
Dave

Dave, where do you get these PTFE seals from ? The manufacturers do not supply them as they know it is the wrong material for the job. They have all been using polyurethane for years. Polyurethane and PTFE have totally different properties. If you put a piece of PTFE in a vice and squeeze it it will stay flat. Polyurethane will spring back to shape as it has a memory.

Baz

[jonnyone]

Dave, where do you get these PTFE seals from ? The manufacturers do not supply them as they know it is the wrong material for the job. They have all been using polyurethane for years. Polyurethane and PTFE have totally different properties. If you put a piece of PTFE in a vice and squeeze it it will stay flat. Polyurethane will spring back to shape as it has a memory.

Baz

Evening Baz.
I cant possibly reveal my secret source of ptfe . Though a quick google search would likely find it.
I tend to use ptfe in my guns to shoot not clamp it in vices. An interesting hobby I'm sure but it's shooting all the way for me!
Did you say you have tried and tested ptfe? Just wondering that's all.
As I've said a few times on here now many of my guns I swapped to ptfe quite some years ago- earliest was about 86 if I recall right. They've not universally given good results but they have in many more cases than they haven't. And again I've made mention a few times that whilst conversion kits to use oem seals are more widely available now, they were not so back in the day. Hence in my case I've used the best available product at that time - ptfe.
Maybe it would be good if you could share your own experiences (and downfalls) of using ptfe?
I promise you the moment it all starts to go wrong for me n ptfe I will post here. Until then I'm afraid its been all good- which I can see presents a bit of a dilemma for some.
Dave

[ignacio49]

Morning ignacio. I have fitted ptfe seals to two Diana 45s, one 50, one 50T01, two anschutz 335s, one HW35, and a BSF as I recall.
I have been fortunate in that despite the seals being thinner height wise than the original leather seal they have still had clearance between the cocking lever rod and the piston body. This can easily be checked after the seal is fitted. A few millimetres clearance is needed when the piston is fully pushed home against the end of the compression tube. Should this not prove to be the case then the new head will need.packing between it and the piston body to create that required gap. I recall some have used large tap washers in the past but as I say it has proved unnecessary for me. I can't say it will be the same for your gun as I have no experience of working on a 35.
Perhaps an email query to the seller of the synthetic seal may throw some light on things but even then I would still check the clearance as per the above after fitting?
Wish you luck
Dave

Great help Dave, thanks.