Hydraulic cylinder force conversion to torque at knob
Hydraulic cylinder force conversion to torque at knob
(OP)
I am designing a manually adjustable master cylinder that will adjust the amount of spring compression "preload" for a coil-over-damper setup for our product. This is done by pushing hydraulic fluid from the master cylinder through a hydraulic hose to a hydraulic "ram". The ram will extend or contract through a range to acquire the desired preload.
The range of preload force required is between 90lbs - 300lbs.
Where I need a little help is determining how to calculate the torque at the knob when compressing the spring at predetermined locations.
knowns:
1. force @ ram = force @ cylinder (let's make it 350 lbs)
2. pressure at each component is determined by the area of each component.
3. thread pitch = 1/2"-10 (ACME)
4. radius of knob = 1.5"
5. coefficient of friction (stainless on stainless ACME)= 0.16
I am struggling on how to incorporate the mechanical advantage from the thread pitch into the calculations. I understand that a coarser pitch = harder / finer pitch = easier action at the knob.
My desire is to tweak design parameters to get a reasonable action at the handle.
The range of preload force required is between 90lbs - 300lbs.
Where I need a little help is determining how to calculate the torque at the knob when compressing the spring at predetermined locations.
knowns:
1. force @ ram = force @ cylinder (let's make it 350 lbs)
2. pressure at each component is determined by the area of each component.
3. thread pitch = 1/2"-10 (ACME)
4. radius of knob = 1.5"
5. coefficient of friction (stainless on stainless ACME)= 0.16
I am struggling on how to incorporate the mechanical advantage from the thread pitch into the calculations. I understand that a coarser pitch = harder / finer pitch = easier action at the knob.
My desire is to tweak design parameters to get a reasonable action at the handle.





RE: Hydraulic cylinder force conversion to torque at knob
You can get a rough estimate of the torque from using the formula's for bolt fastening a rough and ready formula is
T= 0.2*D*F
where F = axial force ie in your case the spring
D = diameter of fastener
0.2 = friction coefficient for unlubricated threads
For a more accurate figure taking thread pitch into account etc you can use this formula from this site:-
ht
here is one for power screws too:-
h
desertfox
RE: Hydraulic cylinder force conversion to torque at knob
at a glance - the links look very helpful.
i'll dig into it and and hopefully glean the info i need.