My purpose is to design a manual knob which when rotates clockwise or anti-clock wise it moves a vertical rod (which carries the load) up or down, and when the knob stops the rod should stay as it's carrying the load. I understand that ball screw drivers are not suitable with hand fed machines, any help??
I think we need a few definitions of the system for the plans
What is the length of the rod motion
What is the accuracy of the rod motion
What is loading power of the rod
Should this system be self-locking
Should system be linear to control
etc...
The length of the rod is about 20 cm.
The accuracy of the rod is not really important (not high).
I don't really understand what do you mean by the loading power, but if you mean the weight of the load it's won't be greater than 0.75 KG.
How could be the system self-locking??
It's linear.
Self-retaining gear behaviour is achieved (possibly not reliably without an additional friction element) above a specific gear ratio. But I guess, a high gear ratio is unsuitable for your application (too many turns for a small movement). An explicite locking mechanism is most likely necessary.
Are you envisioning one rotation of the knob moves the full length of the shaft, or could be it require partial or multiple turns? Does the movement of the rod have to be proportional to the rotation of the knob? Does it have to be purely mechanical, or could it be motorized?
Are you envisioning one rotation of the knob moves the full length of the shaft, or could be it require partial or multiple turns? Does the movement of the rod have to be proportional to the rotation of the knob? Does it have to be purely mechanical, or could it be motorized?
It require multiple turns, that would be better ofcourse. The movement of the rod should be proportional to the knob sure. It has to be purely mechanical to reduce the cost.
No restrictions on the knob and the rod movement or space limitations. I am designing a device carrying fan in upside down position and I would like to use this knob to increase and decrease the distance between this fan and the upper side of the target.
Nice ideas guys thanks so much, but the fan in my case should not rotate but moves in z direction only and may be I need to add another direction which is y direction movement with another knob so what do you think?? I found a device which may be uses the same idea but with another application, I think it's using a worm gear!!!