BSA Improved Model

[edbear2]

Ps. I am now pretty sure that my piston isn't longer than normal; the head isn't extended for the rings.
On VAGF, there is a photo of a piston from an Improved Model B, and you can see that it is 115 mm long (without the rod).
My piston is exactly 115 mm long.

Photo source: VAGF

Mate it's just someone with a lathe who has rattled up some rings, and had a grooving tool I would venture, maybe they had seen a Webley service and thought a few extra seals may be a performance winner, impossible to tell when it was done, maybe even pre chrono days when folks tested power by firing point blank onto concrete and metal and comparing how big the pellet spread

I have seen drilled pistons on these, rear sleeves removed on later STD 45 inch pistons, funny brass weights and guides, all sorts, all often looking like they were done a good while ago on guns that had not been apart for a spell.

https://www.flickr.com/photos/312284...7607860743867/

https://www.flickr.com/photos/312284...7607860743867/

https://www.flickr.com/photos/312284...7607860743867/

People have been (those with the kit) faffing around with airguns since the day they were invented trying to "improve" them......That's how Lincoln Jeffries started out before he decided to make his own design.

A you say, it's just a normal length piston with the normal length bearing surfaces by the look of it;

https://www.flickr.com/photos/312284...7607860743867/

No idea why the geezer thought several rings would work, maybe he was thinking it would be like an engine, or had seen an engine apart, who knows?....(some older piston engine designs had up to 4 or more rings, one even on the lower skirt, to try and control compression and oil issues).

Is the front bearing surface the same O.D. as the rear by the way?....ie, no attempt to reduce friction by having the rings act as bearings?.....the rear normally galls anyway as the thing goes up and down, so even this idea (if intended) was not done 100%



ATB Ed

[jirushi]

Thank you Ed.
Wow, the "cheese holes" in those pistons! I wonder what lightening of the piston does to these guns.
My piston rings must indeed be the result of a man with a lathe. Nicely done! But they are now off, and still in one piece.

[trajectory]

Thank you Ed.
Wow, the "cheese holes" in those pistons! I wonder what lightening of the piston does to these guns.
My piston rings must indeed be the result of a man with a lathe. Nicely done! But they are now off, and still in one piece.

Yes, that's quite a piston that Ed posted a picture of. I've not seen one like it before & it looks more like a barrel guard off a Browning or a Sterling SMG. Makes you wonder if the maker drilled a couple of holes, tried it out then decided to do a couple more & try it, then carry on like that or if they just did the lot at once. I suppose we will never know. Funny how some put effort into reducing the weight of a piston while others add weights to it but I guess that's the thing about experimenting. If you cannot predict the outcome but are inquisitive & have the wherewithal to find out then it's off to the workshop or shed or kitchen table. As Ed said people have been fiddling with things since the year dot, & there must be quite a bit of it out there. Some excellent, & some less so, depending on concept, design,materials, skill & execution.

That piston with the three rings is interesting & as an earlier poster pointed out there is something very similar in Hillers book. It's a bit of a belt & braces concept, or in this case perhaps more belt, braces, buttons, string & dressing gown cord. In my opinion a leather piston seal works fine & an addition of those rings is not necessarry. Ed speculated it might have been inspired by the set up used on automotive pistons, commonly three rings. I reckon he is probably right. Out of curiosity I'd be interested to know if the originator tried with one ring, found it didn't make much difference & went for two & then a third. Or perhaps they just went for three straight off. It's academic but I'd still like to know. It reminds me of the philosophy that if ones good, two will be better so three must be even better, things don't always work out like that. I also wondered if there's a load of them like this out there of if someone was inspired by seeing the design in the book?

Anyhow, glad you got the rings off in one piece, even if they don't go back on perhaps you can keep them safe as they are part of its history.

atb