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I'm curious for the collective wisdom and experience regarding clockwork springs on rotary valves.

Direct real world experiences in particular are appreciated.. I have none.

They are also referred to as 'constant force springs' and in theory I would imagine they would provide a more consistent resistance and possibly a better tactile feel? I've also read that many clockwork spring rotors could easily have the tension adjusted which seems like a pretty useful feature.

Is there an engineering reason that torsion springs have become the standard? Are torsion springs genuinely better or just cheaper and easier to use in manufacturing?

joh_tuba wrote:I've also read that many clockwork spring rotors could easily have the tension adjusted which seems like a pretty useful feature.

All the rotors at hand around here are clock spring, it has been years since I had a normal modern rotary tuba, just because that's what you get with the cheap junk I pick up! So I'm not really the one to comment on subtle differences if there are any, but on that adjustability point ...

The springs I've seen adjusted were actually on an alto horn. He basically unwound the spring, a quarter turn at a time, by rotating the square spindle it's attached to. One quarter turn took it from a little too stiff for its owner's liking, to just barely strong enough to turn the valves - it was a coarse adjustment, and could have been a little tricky for someone who didn't know which parts to hold on to while doing it. My impression from this is that commonly found clock spring rotors can be adjusted, but the ease and usefulness of this feature could be a disappointment. Now Cerveny's high end clock spring rotors come with adjusters, and that's a whole different deal.

Mine have tended to be kind of noisy, which as you have read in the other threads on this matter is about the linkage and in principle has nothing to do with the clock springs. If the clock springs you get come with those linkages, though ...

I've owned, played, and repaired both clocksprings and torsion springs. Some of the clockspring mechanisms come with adjusters but unless they are in very good condition... are pretty useless.

Yes... clocksprings from an engineering perspective are referred to as 'constant velocity springs'. I've never heard of them called constant FORCE springs but I suppose that could be construed to mean the same thing.

IF clockspring mechanisms are in good shape, I prefer them over regular torsion springs. Knowing how to work on them helps me understand what they will and won't do. I think the force required to make them work throughout the whole range of motion is more consistent. Hence the name of 'constant velocity (or force) springs'.

On the other hand, torsion springs are more easily understood by most folks. After all... they are visible and one can clearly see what they are doing.

Either type of spring can be what I refer to as 'spring bound'... meaning that it is wound too tightly. In the case of clocksprings... the spring itself is wound so tightly that it actually rubs against itself when the lever is pressed down. In the case of torsion springs... the spring wraps tighter around the lever spindle as the paddle is pressed and creates friction.

In the case of either spring, there needs to be the proper length of flat spring or round wire to get the smooth action that most of us like.

There have been entire chapters in engineering books dedicated to spring dynamics.

http://www.centuryspring.com/?utm_sourc ... MgodFVAAVA

I could be completely wrong about the 'constant force' nomenclature. Google seemed to suggest that they were one and the same type of spring.

http://www.vulcanspring.com/

That link seems to imply that there are lots of variations on the clockwork spring style with varying properties.

Personally, I think the old clocksprings & 'S'-links are very classy looking. I have a couple old tubas with clocksprings (Tinker is working on a set now ). The other tuba has better-condition clocksprings & linkage and they are pretty fast, smooth and quiet. There was a slight 'clank', but that was mostly due to the old hardened neoprene bumpers. I replaced them with silicone bumpers months ago (after cleaning the rotors) and they are much quieter now.

As long as the clocksprings & linkage are in decent condition (and well oiled), and you make sure everything is tight and have good bumpers, they should be very fast & quiet

My purpose starting this thread was to identify if there was a practical, theoretical, tactile, or engineering reason why one might prefer clockwork over torsion springs.

I am *extremely* picky about my valve action and have invested a lot of thought, time and energy into getting the action on my horns to be stellar. Folks that have played my horns always comment on it.

In the pursuit of theoretically perfect tactile feedback I've found that removing any and all slop from the linkage, firm bumpers so that there is a clear top and bottom to the stroke, careful consideration of the length of lever arms, and the geometry of the linkage to allow for the most efficient transfer of force, all contribute to a crisp direct valve stroke.

The remaining potential variable for improvement is strength and consistency of spring tension.

Related thought:
Has anyone experimented with using rare earth magnets in place of springs? Thoughts?

joh_tuba wrote:Related thought:
Has anyone experimented with using rare earth magnets in place of springs? Thoughts?

I like the idea, but as conventionally applied, they're quite non-linear, and have the potential to bring mechanical wristwatches to a stop.

jsmn4vu wrote:

joh_tuba wrote:Related thought:
Has anyone experimented with using rare earth magnets in place of springs? Thoughts?

I like the idea, but as conventionally applied, they're quite non-linear, and have the potential to bring mechanical wristwatches to a stop.

calling The Tinkererererer....

joh_tuba wrote:.... Related thought:
Has anyone experimented with using rare earth magnets in place of springs? Thoughts?

My short answer is 'YES'. I have done extensive work toward eliminating springs from piston valves. It's not as easy as one might think because magnetic forces diminishes quickly with distance. About the only way I've found to 'smooth out' the peak is to use a rod magnet operating inside a ring magnet.

Think of it in terms of using one large flat spring in place of a torsion spring, coil spring, or constant velocity spring.