BSA Improved Model

[edbear2]

Piston ring removal, Hopefully someone better qualified than me will be along to give some advice. In the meantime I think there might be something on YouTube, hopefully, have a look for servicing a Webley senior or mk11 Service air rifle as they have phosphor bronze rings. Only thing is if they are servicing them they may not remove them for re use or they might already be broken. They are brittle so in motor engineering you used to push a ring from one side & wiggle a thin shim in the gap that appears opposite, then you move around 120 degrees & repeat, then another 120 degrees till you have three shims in place holding the ring open. Then wiggle the three around till they are at 90 degree spacings, then insert a fourth one. The shims are small in width & very thin but strong enough to hold the ring open , just enough to slide off the piston. Well that's one way old cars were stripped down. Same might work for your BSA but wait till someone else gives you another idea. Maybe thin but strong plastic might be enough, cut from packing material?

BUT they are BRITTLE so research it well, & choose whichever method you think is best for you. Once broken its too late to go back. It's your decision.

The above is bang on advice, all depends on the grade / type of bronze used (Oilite thro PB2 or 660 if you are lucky etc.) as some are more forgiving, I use both the shim method and also the spring the ends with thumnails gently until clear.....both can be risky!

ATB, ED

[jirushi]

Thank you very much for your advice, gents.
I will remove the rings very carefully soon.
Might try with rings and a new leather seal first; if shooting behaviour and power are good, then perhaps it will be best to leave the rings alons.

Does someone know what power I should expect with this .177 specimen? I read on the VAGF: about 725 ft/s. Not sure with which pellets though.
I guess about 9 to 10 ft/lbs in a very good example?

[jirushi]

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

[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

[Kuyajonathan]

Piston ring removal, Hopefully someone better qualified than me will be along to give some advice. In the meantime I think there might be something on YouTube, hopefully, have a look for servicing a Webley senior or mk11 Service air rifle as they have phosphor bronze rings. Only thing is if they are servicing them they may not remove them for re use or they might already be broken. They are brittle so in motor engineering you used to push a ring from one side & wiggle a thin shim in the gap that appears opposite, then you move around 120 degrees & repeat, then another 120 degrees till you have three shims in place holding the ring open. Then wiggle the three around till they are at 90 degree spacings, then insert a fourth one. The shims are small in width & very thin but strong enough to hold the ring open , just enough to slide off the piston. Well that's one way old cars were stripped down. Same might work for your BSA but wait till someone else gives you another idea. Maybe thin but strong plastic might be enough, cut from packing material?

BUT they are BRITTLE so research it well, & choose whichever method you think is best for you. Once broken its too late to go back. It's your decision.

Echo trajectory's advice re ring removal. Late 60's early 70's rebuilt number of villiers 2 stroke m/cycle engines as a well as few 4 strokes. Used the shim method to change the piston rings, owners manuals had v detailed info on checking piston ring wear, measure gap in bore! Quality and lubricants gave impression that wear was normal and replacement the answer. some rings had chamfered edge as wel,also oil control rings as mentioned. ring ends varied from square to angled , I recall stepped ends on one or two, as well as pegs in groves to hold in place, stepped 120 degrees with 3 rings. Very brittle and required careful handling.
If this was a 'mod' by a skilled owner, looks like good work those cutting groves on a lathe, where would the rings have come from? Pro priority ready made from another application? Or if home made takes the skills to
Changed ring in my (then) 10-15 yr old Webley senior in late 60's when acquired it, along with new spring. No reason, apart from cos I could !

[edbear2]

Echo trajectory's advice re ring removal. Late 60's early 70's rebuilt number of villiers 2 stroke m/cycle engines as a well as few 4 strokes. Used the shim method to change the piston rings, owners manuals had v detailed info on checking piston ring wear, measure gap in bore! Quality and lubricants gave impression that wear was normal and replacement the answer. some rings had chamfered edge as wel,also oil control rings as mentioned. ring ends varied from square to angled , I recall stepped ends on one or two, as well as pegs in groves to hold in place, stepped 120 degrees with 3 rings. Very brittle and required careful handling.
If this was a 'mod' by a skilled owner, looks like good work those cutting groves on a lathe, where would the rings have come from? Pro priority ready made from another application? Or if home made takes the skills to
Changed ring in my (then) 10-15 yr old Webley senior in late 60's when acquired it, along with new spring. No reason, apart from cos I could !

Rings are easy to make, have actually made some for a vintage motorbike bike that were a funny size / NLA (you use CC Cast iron bar stock).

Simple description.......

1........Reduce dia of bar to size needed for ring O.D. on lathe.
2........Drill then bore hole to give correct I.D. needed
3........Part off with cutting tool to get correct thickness needed.
4........Cut through then file to get ring end gap required (usually specced by pushing ring into bore with piston and measuring)

In the case of your piston, just a simple grooving tool made the slots, you can make your own out of tool steel stock and a grindstone, another thing taught at school, but these days everything can be got in carbide disposable from the legions of supply places catering to the home machinist / hobby industry.

ATB, ED

[Lakey]

What I do find interesting is that EXACTLY the same mod is illustrated in Hillers Book.

If it was one man and a lathe, then he has obviously done the same mod several times.

Would love to know who that person was, and what his thought processes were.

Very interesting. I would LOVE it to be in my collection.

Lakey

[trajectory]

What I do find interesting is that EXACTLY the same mod is illustrated in Hillers Book.

If it was one man and a lathe, then he has obviously done the same mod several times.

Would love to know who that person was, and what his thought processes were.

Very interesting. I would LOVE it to be in my collection.

Lakey

I too wondered what the thought processes were, not just for the three ring piston but the perforated one too.

You might not have one made by whoever made the one pictured in this thread ( maybe one person made a few maybe a few people have made them as the drawing is out there) but its eminently doable if you have a lathe & want one.

[edbear2]

I too wondered what the thought processes were, not just for the three ring piston but the perforated one too.

You might not have one made by whoever made the one pictured in this thread ( maybe one person made a few maybe a few people have made them as the drawing is out there) but its eminently doable if you have a lathe & want one.

Drilling pistons is the simplist way to reduce mass with all that entails, I wish I had checked the transfer port sizes on those guns back then, as may have told a tale too.

Tons about the effects of piston weight on various threads, and the effect that making the piston lighter has.

ATB, ED

[trajectory]

Drilling pistons is the simplist way to reduce mass with all that entails, I wish I had checked the transfer port sizes on those guns back then, as may have told a tale too.

Tons about the effects of piston weight on various threads, and the effect that making the piston lighter has.

ATB, ED

I suppose I was really wondering if they set out & drilled a couple first & tried it like that, increasing the number gradually or did the lot at once. I know there's no way of knowing but it's just curiosity on my part. I also wondered if they looked at the interaction of spring & pellet weight. If the transfer port diameter was non standard then it might well be they had a look at these other variables too.

Simple little machines but there's a lot of potential for fiddling & tweaking in them if you are that way inclined.

[jirushi]

Thank you gents for the interesting comments.

@Lakey, I am fine to swap a standard piston for this one with the still intact but carefully removed rings, as I think you would appreciate it more than me. I will send you a pm.

This morning, I finally started making a spring for the rear sight.
With the great tip to use a tape measure.
I have cut out the rough shape (easily done with a cheap pair of scissors, and a Stanley knife) and will finetune with file/Dremel.
It's now in vinegar to make it easier to remove the paint. Then I will try cold blueing.

Thanks to VAGF. I put this photo on my phone and zoomed out until the width of the spring was the same as the width of the rear sight. Then I put a piece of paper on the photo on my phone, with the screen as bright as possible, and drew the contours of the spring on the paper.






The stock is starting to look nice. This is after 6 layers of CCL oil.

[Airjet]

The brass rings with the chamfered ends do remind me of steam engine piston rings, - perhaps who ever designed them was more familiar with steam engine practice??

[T 20]

Ah, Louis

When I suggested using the spring out of a tape measure I meant the clock Spring inside the case which you can't normally see.
The clock Spring is just blued steel and wouldn't need cleaning, but no matter using the actual tape should do the job.



All the best Mick