Rotary Valve Spring Engineering Thoughts

[joh_tuba]

Those of you that have more of an engineering background than myself..

Other than convenience, is there any engineering reason why it is preferable to have torsion springs located at the lever mechanism RATHER than at the valve itself?

IF a torsion spring were located on the stop arm the force would be located closer to where we actually want it applied. Also, it would potentially allow more flexibility in the lever arm geometry. In addition, I could imagine an easy way to adjust tension without changing springs.

Is this a fools errand? An actual potential place of improvement? A solution looking for a problem?

Thanks!

[emcallaway]

I suspect that the spring being located close to the fingers gives the spring more leverage to work with, but I'm not entirely certain.

I think that I saw that KiltieTuba was selling a couple of rotors with the spring mechanism built in. Perhaps he can comment?

[Rick Denney]

There are probably right ways to attempt it that have never been tried.

But it would also transmit the full force of the spring on all those lightweight linkages between the valve and the finger, and whatever mushiness offered by those linkages would be felt even more directly than they are now.

If you want a useful fool's errand, figure out how to put accurate, easily adjustible stops where the springs are, so that the stop force isn't transmitted through the linkages. Without having to resist those fources, linkages would be easier to make absolutely smooth in operation. And I suspect the action would improve, too.

Rick "moving the springs or stops won't fix poor linkages, of course" Denney

[Dan Schultz]

Torsion springs are often referred to as 'constant velocity' springs. So are clock-springs. The nature of the multiple spirals evens out the force that's required. The force to move a compression or extension spring increases dramatically as the spring is deformed.

As one poster already mentioned... having the spring on the lever gives the user better mechanical advantage.

[joh_tuba]

You guys rock!

All excellent points. The point about mechanical advantage in particular makes a LOT of sense.

[Rick Denney]

I might be the only person on the planet that liked Miraphone's presto linkage, but I thought it was a cool concept they gave up on way too soon

They gave up on it when the white plastic started shrinking and cracking.

Rick "whose Miraphone originally came with those things--now long and happily gone" Denney

[Lars Trawen]

One very important reason not to have the springs close to the valves is the rapidly increased wear on the linkage joints that will appear.
The joints will in that case also transfer the force of the springs.
Today's solution doesn't do that, only the movement forces.