Counterwound spring pairs, needle bearings and grease

[Hsing-ee]

Early BSA and Feinwerkbau 300 rifles are alleged to have been fitted with TWO short mainsprings wound in opposite directions so that on tripping the trigger no disturbing 'torque reaction' would occur.

If this is true, did it actually make any difference?

I have heard tell that 'tunas' in the 1990s also fitted flat needle bearings to the front-end of the spring to allow slipping in a rotational sense rather than allow the spring to twist the rifle one way or another.

I usually polish the ends of the spring till they shine like a new penny, mostly because of being a bit anxious, but partly because with a piece of 600 grit oxide paper, some oil and a flat surface it only takes five minutes so why not? I clean and grease the spring lightly and I have never noticed any torque reaction. Is this because the rifle is much heavier than the spring I wonder? Elseways how do the riders of BMW and Moto Guzzi shaft-drive motorbicycles (that should please Paddy_SP) stay on when they change gear?

Is this torque thing a myth? I have a feeling that even if it is true then a couple of dollops of grease, elbow and moly, will cure it.

What are your thoughts gentlemen? T.R.Robb is selling two-part springs even to this day...

[Garvin]

I've no idea whether they have any scientifically proveable effect, but knowing the Walther LGV Spezial has counterwound springs helps explain away the lack of felt recoil. Maybe it's actually down to the rifle's overall weight/low power? But if I didn't know there were two springs inside busily counteracting twist, would I find it a bit "torquey"?

[Anchorman]

If a spring does rotate on trigger release if cannot have much effect on the accuracy as the Prosport is designed so that the piston can rotate inside the compression cylinder on trigger release due to the annular sear

Dave

[edbear2]

I have BSA's with twin oval wound and twin flat wound springs, as fitted originally, and as available in the present day from J.K. etc. The 43.5 inch guns in .177 were fitted with twin springs, but the large 45.5 inch .22 "sporting" and Military both had large singles...that said, I have a pair of BSA opposite wound springs for a 45 inch gun with factory stamps (all genuine BSA spings had the pylarm mark stamped at the end, and their advertising at the time urged the use of genuine spares).

On firing, the twin springs (especially when flat wound) seem to give a softer recoil imho, on two guns with fairly similar M.V. ...but unless you poundage rated like for like to be exact, this is not really scientific. I normally polish and square the ends of all springs, and either polish the bearing area on the trigger block, or fit a delrin seat on anything old I take apart as a matter of course.

I have gone the full Monty on one oldie I have, and it is as smooth as a TX to cock and shoot....more recoil obviously because of the lighter weight, but silent and smooth.......but back to the O.P., I suppose a light hold and close observation of a gun trying out the two different power plants in succession would be the way to see for sure

[DJS]

I have a number of different springs for my Diana 52, there is a noticable difference in the firing cycle depending on which way the spring is wound. I found it more comfortable to shoot if the rifle rotated anticlockwise. This is around 21 ft/lb though, I don't think you would notice the rotation at 12 ft/lb.
Also my Moto Guzzi 1000 had a big torque reaction. You could use it to lean into a corner quickly and to bring it up out of a corner using the throttle. If you used it the wrong way though it could get you into trouble
Daz

[air-tech]

Here's a sceptical point of view:

Coil springs work by applying TORSIONAL forces to the wire. Yes the spring itself works under compression, but the actual springiness comes from application of torsion to the wire.

The only way to have rotation of a spring when being compressed or released is if either: The wire length changes; the diameter of the spring changes.

Potentially, the wire length could change, and probably does, when torsion is applied *I would imagine* that there is a small amount of shortening of the wire.

As for the diameter of the spring changing, I see nothing other than either a side effect of the above, or else (does not/should not apply) where the diameter to be changed as a result of an outside force.

*I suspect* that the shortening of the wire upon compression will be very small. The angular rotation of one end of a spring typically used in an air rifle must also be small. 20 degrees anyone?

Certainly, taking into consideration the mass of the spring, it's total ROTATIONAL movement, compare to the mass of something like the piston and it's movement, and also the dampening mass of the rest of the gun, sorry, but I don't really buy into feeling this effect.

Not only, but here's something else. If the spring is NOT allowed to rotate, i.e. it is secured at BOTH ends then you have a closed system and as far as I can tell there can be no reaction at all! Of course there should also be no reaction if the spring were perfectly free - but considering the forces, this latter is far more difficult to achieve than making sure it does not move at all.

In reality I would not give this a second thought. The Cardews, applying scientific analysis to all aspects of airguns and tuning, in fact also dismissed this matter as being anything of concern.

Out of curiosity, I did my best to find info online about this, and came up with very, very little.

Here's the best I could find: http://www.eng-tips.com/viewthread.c...=162484&page=5

As an aside, it is common for spring preload on some coilover units to be adjustable via a threaded spring perch, i.e. where the spring sits, you can best see this on full suspension mountain bikes, the only thing that stops the adjustment from changing is the friction at the thread caused by the spring compression, there are no lockrings whatsoever.

If there was any major rotation of the spring, applying any major force, then this spring perch would lose it's adjustment in no time at all. On my bike fitted as per the pic - never ever is there any change in adjustment at all.

http://www.avalanchedownhillracing.c.../fox_dhx50.jpg

[Hsing-ee]

I believe you can feel the torsional effect of the pellet engaging in the rifling and trying to twist the barrel in the opposite direction in a few very lightweight single stroke pneumatics like the Gamo Compact. Perhaps that is what people are feeling when they fire their rifles with a very light hold? Or this is really purely imaginary ....