Airsporter 'S' cylinder diameter

[lightning22]

Would I be right in thinking that the cylinder is the same diameter between the 'S' models and the less fancy versions? I have a vague memory of 27mm?

I've got a Mk6 'S' and a couple of ideas.

Rich

[T 20]

Would I be right in thinking that the cylinder is the same diameter between the 'S' models and the less fancy versions? I have a vague memory of 27mm?

I've got a Mk6 'S' and a couple of ideas.

Rich

Hi Rich

Internal diameter of Airsporters and Mercury cylinders (including S) is 1 1/8" (28.575mm)

Piston O ring 1 1/8" OD X 1/8" 70 shore nitrile.

Hope this helps


All the best Mick

[lightning22]

Many thanks Mick.

Rich

[T 20]

Many thanks Mick.

Rich

No Problem Rich

I forgot to say, all the internal parts from the Airsporter MK4 onwards and
all Mercuries except for maxgrip scoperail guns are interchangeable.

In other words a MK1 Mercury piston will fit an Airsporter S etc.


Hope this helps


All the best Mick

[lightning22]

Cheers Mick,

Whilst I've got such a font of knowledge on tap, do you know the cylinder diameter for the Meteor?

Rich

[Hsing-ee]

If the Mercury 'S' and Airsporter 'S' cylinders were the same diameter, and presumably the same stroke as the ordinary Mercuries and Airsporters, where did the extra power come from? The mainsprings are the same aren't they? Yet the ordinary Airsporter would only do about 9.5 ft/lbs in .22, while the 'S' will do 11.5 and more ... What was the difference?

[T 20]

Cheers Mick,

Whilst I've got such a font of knowledge on tap, do you know the cylinder diameter for the Meteor?

Rich

Hi Rich

Cylinder internal diameter for Meteors is 1" (25.4mm) and the cylinder is capable of an 82 mm stroke.


All the best Mick

[T 20]

If the Mercury 'S' and Airsporter 'S' cylinders were the same diameter, and presumably the same stroke as the ordinary Mercuries and Airsporters, where did the extra power come from? The mainsprings are the same aren't they? Yet the ordinary Airsporter would only do about 9.5 ft/lbs in .22, while the 'S' will do 11.5 and more ... What was the difference?

Good question Alistair


The simple answer is ------ there is no difference, it was all a marketing ploy.



The only component which did vary from time to time was the piston head, some guns had plastic ones and some had Aluminium.
Both variants of piston head were the same dimensions, and they both weigh about the same.

All Mercuries will easily acheive 12 ftlbs, as they are all the same internally.

All Airsporters should also acheive the same power levels as each other.


All the best Mick

[dogsbody]

Good question Alistair


The simple answer is ------ there is no difference, it was all a marketing ploy.



The only component which did vary from time to time was the piston head, some guns had plastic ones and some had Aluminium.
Both variants of piston head were the same dimensions, and they both weigh about the same.

Can I refer you to pp. 190/191 of the Golden Century by John Knibbs from which I quote referring to the Mercury S:

The barrel was thicker and almost an inch longer. The S model weighed 4 oz more than the standard model and as it was fitted with a heavier, steel piston head and more powerful mainspring, the muzzle velocity was much higher at 825 ft./sec. in .177 and 600 ft./sec. in .22.

And referring to the Airsporter S:

This model had a half inch longer, heavier barrel, all metal front and rear sights, steel piston head and a de-luxe oil finished walnut stock.

The internal parts are interchangable with the standard models as far as I know.

atb
dogsbody

[Phil Russell]

According to Hiller the S had a 'slightly larger cylinder diameter'. But he does not say if this was internal or external. I must assume it was external because:
On the Chambers site, the O ring is the same for the S and other models but the piston head is listed as being steel for the S and aluminium for the others. The mainspring is the same for each but did BSA fit different springs? Maybe the extra weight from the steel piston head gave the increased power.
Cheers, Phil

[T 20]

Can I refer you to pp. 190/191 of the Golden Century by John Knibbs from which I quote referring to the Mercury S:

The barrel was thicker and almost an inch longer. The S model weighed 4 oz more than the standard model and as it was fitted with a heavier, steel piston head and more powerful mainspring, the muzzle velocity was much higher at 825 ft./sec. in .177 and 600 ft./sec. in .22.

And referring to the Airsporter S:

This model had a half inch longer, heavier barrel, all metal front and rear sights, steel piston head and a de-luxe oil finished walnut stock.

The internal parts are interchangable with the standard models as far as I know.

atb
dogsbody

Cheers for that

I have never come across a steel piston head in an S variant but it could be a later variation.
All the S's I have been into, have had an Aluminium piston head.
Even my own Airsporter S MK1 came with an Aluminium head as standard.
I couldn't comment on the spring strength, but you see my point about interchangeabillity of parts.

I have machined up brass piston heads for a little bit more weight, only to find there was not much gain over standard.


I'll have to have a chat with John about it next time I see him.


All the best Mick

[T 20]

According to Hiller the S had a 'slightly larger cylinder diameter'. But he does not say if this was internal or external. I must assume it was external because:
On the Chambers site, the O ring is the same for the S and other models but the piston head is listed as being steel for the S and aluminium for the others. The mainspring is the same for each but did BSA fit different springs? Maybe the extra weight from the steel piston head gave the increased power.
Cheers, Phil

Hi Phil

All the cylinder ID's are 1 1/8" and the cylinders all seem to be 1 1/4" OD.
I'll measure them again later.

All the best Mick

[HOMER]

BSA did indeed fit a steel head with 1 single O ring, I believe it was originally for "Export" models predominantly sold to the USA @ late 70's. The weight of the head alone was 1 oz, all other power train components were the same as standard UK spec. I purchased one from Dennis Hiller some 10-15 years ago and when fitted did actually increase power.

HTH

[T 20]

Hi Phil

Cylinders all seem to be 1 1/4" OD.

I'll measure them again later.

All the best Mick

Yes they are 1 1/4" OD on the S's as well


All the best Mick

[T 20]

BSA did indeed fit a steel head with 1 single O ring, I believe it was originally for "Export" models predominantly sold to the USA @ late 70's. The weight of the head alone was 1 oz, all other power train components were the same as standard UK spec. I purchased one from Dennis Hiller some 10-15 years ago and when fitted did actually increase power.

HTH

Hi Homer

That makes sense, as BSA Supersports had a weighted piston on export models coupled with a stronger spring to give 16 ftlbs.

It would appear from your post that BSA had already tried Weighted pistons in the Airsporter S and Mercury S exports then.

I've got to strip my Mercury S bitsa as its power has crept a little over 12 ftlbs so perhaps I should have another chrono session with a brass head fitted.

From memory the last time I tried a heavier piston head on a Mercury, the recoil increase made the power increase a wasted effort.




All the best Mick