Rotor/Piston - science question

[Lukowicz]

Hi all,

Background:
- On Monday my studio had the chance to test some horns out by Wessex, both Prokofiev and Kaiser. One is piston, one is rotor. (both great horns by the way)
- This sparked conversation about ease of valve depression, valve throw, and more specifically the speed on the valve coming back up.

Theory:
- If we know the speed of the piston/rotor, we can literally determine how fast of passage we are capable of playing from the mechanical limitation of the upstroke.

Question:
- Has anyone calculated the differences in piston springs and rotor springs from a FORCE standpoint on the upstroke? Example: a piston has XXX force in the spring to return the piston back to "up" position. A rotor has YYY force to spin it back into place.
- Has anyone calculated the differences in piston springs and rotor springs from a SPEED standpoint on the upstroke? Example: a piston travels XX.XX MM/HR to return the piston back to "up" position. A rotor travels XX.XX MM/HR to spin it back into place.
- I know there are different springs strengths and people swap out different models, so just a manufacturer provided spring, from whatever company is fine.

Just looking for data, not opinions on what valve spring I should use in my 4th valve, but not my 3rd valve

Thanks
Tom

[windshieldbug]

one factor possibly not considered:

(not 100% truth, but a-great-deal true...)
Top-action piston springs must defy both friction and gravity, whereas front-action piston springs must only defy friction.

[pittbassdaddy]

On the Theory, the downstroke of the valve and the time it takes for an audible note to be produced would have to be considered as well.

To model the theory as originally proposed:
It should be fairly simple to create a mathematical model for piston valves because of the linear motion.
One would have to account for the weight of the moving assembly (vector), surface area of the piston, coefficient of friction between the piston and valve casing (and the change to it provided by lubrication such as valve oil), the stroke of the valve, the amount of force that the spring provides, and the spring rate. Knowing all of these parameters, one could then calculate the amount of time the return stroke would take.

For rotary valves, the math would become much more complex due to all of the different angular vectors that would need to be calculated and a significantly larger number detailed measurements would have to be taken.

If just looking for data on one specific instrument versus another specific instrument, some sort of test rig could be assembled using equipment that can calculate the time it takes an object (valve button or paddle) to travel a specified distance. Most universities that offer engineering or physics degrees should have the equipment needed.

Hope that helps!

[Three Valves]

I was about to say, one CAN formulate all the surface area, distance measurements and tension variables.

Or, just time it!!

And when you find out which one is faster, I suspect you will also discover that either is more than adequate to play anything up to a 16th note which is only as fast as most of us can play anyway, even with an instrument capable of playing up to a 64th...

[timothy42b]

I would test it using this:

https://www.youtube.com/watch?v=lXdxPpvlHGQ" target="_blank

[Lukowicz]

Thanks so far for the thoughts...

we aren't concerned with the downstroke, because downstroke is controlled by how fast/hard the player can move his finger down. Whereas the upstroke is mechanical, and the valve doesn't always stay attached to the finger when you lift up your finger...if you move your finger up fast.

[Three Valves]

I have my wife tie my fingers down to the spatulas. That way I get a more speedy upstroke. Now my lips can’t keep up with my fingers!!

Which makes sense, because I frequently speak more quickly than I can think...

[Three Valves]

I could try lighter buttons and shafts, but my shoe stringed fingers are working out just fine, thank you!!

[MaryAnn]

I have no intelligent input but have noticed that the "faster is better" note players tend to play pistons.

No one is allowed to tie my fingers to any type of spatula, in or out of the kitchen.

[Three Valves]

I have no intelligent input...

You show remarkable restraint.

Me??

Well, we all know what is coming next, don’t we??

Science!!

https://youtu.be/-FIMvSp01C8" target="_blank