gear studing torque gain question

[thezetecman]

Say I use a piece of 16mm studding with a 1mm pitch.

So 1 full turn would move the studding 1 mm.

I tighten the nut with a 300mm spanner with a force of say 30Nm

Does that mean i get a clamping force of:

3.14 X 300 X 2 (max circumference of drive) to 1mm of movement -->1884 : 1

56520Nm or equivalent to a load of 56 00kg??? less losses and stretch etc
or do I multiply by 0.3?

 

[Bluechip]

Hi Zetecman

Here's one, you'll have to convert the dimensions, this is in imperial.

http://www.engineersedge.com/torque.htm

Dave

 

[scoop]

I think that in an ideal world without friction or other mechanical losses you could work this problem out,but owing to all the variables involved such as the materials used for the studding and the nut the size of the contact area between the nut and the surface it sits against and the use of any lubricants,as well as the stretch you mention then it can only probably be found accurately by the use of a physical test with a strain gauge.Probably not the easiest way to do but it will give you an accurate answer.I seem to remember doing similar problems in physics lessons at college many years ago and I think most of the equations for forces using inclined planes used a few sines and cosines in them relative to the pitch of the thread(or the angle of the slope in this case)so your equation may need a bit of tweaking.
Sorry for writing all this and being of no help at all to you other than wishing good luck to you in solving the problem.

best regards Steve C.

 

[Kermit]

http://www.engineersedge.com/motors/lead_screw_drive_system.htm

Edit: I've just spent a few minutes trying to actually "use" that equation found in the link. ??? I'm no physicists and I'm sure very few of you guys are either.


Uh, anyway, that's not needed here I'm pretty sure. This is simply force multiplication by changing the distance over which the force acts. You move say 10 inches at the end of the wrench and the screw/gear turns and moves the load say 1 inch.

This would multiply (ideally) your load by a factor of ten. Small loses of friction and lost motion being ignored. Substitute a torque wrench for your hand wrench and you could easily calculate a nice round number ball park figure that would give you a fairly accurate idea of the forces involved. They will be very big. You listed an 1884:1 ratio

Without using the the tensile strenghts of the metals involved and calculating friction, and so on and so on. That'll be close enough? Those only come into play in a real significant way if you've used grease or put a large amount of 'tightness' on the nut.

Kermit