1924 BSA 'L' underlever spring question.

[Geoff555]

Good evening all. Just got this, it was cheap and ideal for a project. The spring, not an original one was broken and had about 1/2" preload. But even at that it was quite hard to cock, any harder and I think it would feel stressed and harsh.
I obtained a new spring from Mr Knibbs with whom I have no problem at all. It has over 2" of preload, I could get it in, I think, but would never be able to cock it.
What please do you think would be a reasonable preload - 1" ??
Any help or suggestions gratefully received.
Thank you.
Cheers.
Geoff.

[Shed tuner]

just serviced my ~1921 L

Spring was basically a meteor spring, with about 2" total preload - that is just over an inch to press the end block down to contact, then about 3/4" depth of the threads on the block. The wire is around 3.0mm, with a soft wind (lots of coils for the length), which is important. Shoots nicely, and quite easy to cock, at 7 FP. I have no desire to try to inrease it, as it has a nice soft and fairly quick cycle.

HTH - JB

[Geoff555]

Hello JB thank you, I should have been more accurate perhaps, the spring is 23/8" to the end of the cylinder plus the threaded bit.
I will compare the spring with the Meteor dimensions and lop from there. I don't expect or indeed want a lot of power.
Thank you again.
Cheers.
Geoff.

[Shed tuner]

Hello JB thank you, I should have been more accurate perhaps, the spring is 23/8" to the end of the cylinder plus the threaded bit.

yeah, that's a bit much... I'd chop an inch off for sure... what thickness is the wire ? Coil pitch ? OD ?

(PS My meteor spring was chopped too)

[Josie & John]

Try Protek, their springs usually fit without modification.

Regards,

John

[Shed tuner]

Try Protek, their springs usually fit without modification.

"without modification" !?!? How quaint !

[Geoff555]

Hello, thanks, this is fascinating.
Wire dia. 3.2mm.
Coils. 26.
Coil spacing.7.9mm. Center to center of wire.
Length. 212mm. Sorry approx. could find my tape measure,again.
Have had springs from Protek for the Gem but out of stock for the BSA.
I will let you know what happens, it won't be quick , lots of rust removal, cracked stock, sorting stripped threads etc. Never going to be 'that' pretty but it will work and be saved.
ATB.
Cheers.
Geoff.

[Geoff555]

Hello, digging about in a pile of springs I found a new spring which I am going try, it seems to be quite a bit softer than the one I have just obtained ( from Mr Knibbs.).
It has a square section wire but I don't think it is a OX, it is soft and is well finished with no sharp corners, admittedly I have only seen one OX spring.
I would like to get 2 more for other projects but I don't know, can't remember where I got it from or what model it was for.

20.47mm. OD.
14.2mm. ID.
Wire. 3.17 X 2.97.mm.
8.28mm. coil spacing. center to center.
235mm. long.

Measurements are as accurate as I can make them.
Any ideas what it may be?
I have a very vague memory that it may have been for a Airsporter and a parculier name like a 'Rocket' , I could be talking a load of bo**ocks, sorry, my memory is shocking.
Thank you.
Cheers.
Geoff.

[HOMER]

Jim Maccari used (maybe still does) a Square section jobby of similar dimensions, think it was the "Merlin" ?. Jims springs are 1st rate as I'm sure you may be aware worth a try.
HTH

H

[twiddler]

i never buy bits from knibbs any more,you always have to bugger about getting them to fit.protek stuff is always spot on.

[Geoff555]

Hi a bit of an update, after proving what a tit I can be IE: a 'Rocket' spring. I went through months of reciepts and the spring was an Air Force spring for an Airsporter.
Originally on trying to remove the piston I found it was well and truely stuck, managed to lever out enough to get the piston rod into a vice, twisting and pulling finally got it out, it was TIGHT. The leather washer was bone dry and was hairey, swollen about 1/8" oversize.
Replaced the seal after tapping out the screw thread to M5 because it was stripped and the screw mullered.
I did try the Knibbs spring after cutting it down to about 11/2" total preload and it was hard to cock and harsh, lot of recoil and to be honest to my mind nasty. I could have taken more off but it seemed just too hard,stiff. Back to the Air Force spring, cut it down by 1 coil at a time until it would cock with 1 coil off extra. I guess about 2" in total cut off. Result much easier to cock and smooth, much more pleasant. A little recoil but it was a soft not snappy.
Now I admit that I 'fiddle' and just as a pure gut feeling ( and no experiance as such.) the transfer port at 4.5mm seemed just too big. So I threaded the port to take threaded sleeves where I could try different size holes. At the moment it is wearing a 3.5mm hole.
When I have sorted the stock out, dents, splits etc. then I will chrono it and post the results.
I am not after power, just a soft and sweet to use little rifle.
More to bore you with in a week or so.
Cheers and thank you.
Geoff.

[vbull]

HOMER, are Maccari springs available in the UK or do you have to go through his US sight ?

[Shed tuner]

Now I admit that I 'fiddle' and just as a pure gut feeling ( and no experiance as such.) the transfer port at 4.5mm seemed just too big. So I threaded the port to take threaded sleeves where I could try different size holes. At the moment it is wearing a 3.5mm hole.

Hi Geoff,

the consensus is that the ports are so large due to reaming through the loading tap. Great for tap alignment, but you do end up with an oversize port.
Sleaving down seems to be a good idea - I've been planning the same with mine sometime. Gut feeling for a gun at this power with a leather seal is 3 - 3.5mm max should work well. Threading it seems a bit tricky though - need to weld an extension to my tap holder so more likely will just glue a sleave in place...

[Geoff555]

Hello Jon well it was easy for me because I had the tube off which was a good idea, as it turned out, as there was very little solder sealing it. Old portable radios (battery) aerials can provide a lot of tubing of various sizes.
Thank you.
Cheers.
Geoff.

[Shed tuner]

Hello Jon well it was easy for me because I had the tube off which was a good idea, as it turned out, as there was very little solder sealing it. Old portable radios (battery) aerials can provide a lot of tubing of various sizes.
Thank you.
Cheers.
Geoff.

ahhh, yeah, that makes sense

I have a stock of ally antenna tubes, offcuts, and brass rod for making up my own to suit..

How long is the port please ? mesuring cylinder off should be a bit more accurate...