This is not my main field, so I am hoping that someone here will be able to help me out with this.
I'm working (in my spare time) on a metering structure for small astronomical telescopes (16" diameter main mirrors and less), and I have come to the conclusion that using fine-pitch worm gears will give the kind of precision adjustment that I would like to have in the assembly. I have looked at some of the references for gear design cited in previous messages in the group like Dudley for one.
I note that Buckingham and Ryffel in "Design of Worm and Spiral Gears" state that fine-pitch standard screw threads can be used for the worm. Based on that, I am considering using 1/4" - 56 thread (Machinery's Handbook does list this as a standard thread size) for the worm. For the worm gear, I am thinking of using a 60-degree circular arc with a six-inch radius. I would also like to have the gear "single-enveloping". As a worst-case scenario, I believe that the torque at the gear threads will be approximately 450-in lbs; however, the gear will only have to bear this load while the adjustment is made. After the adjustment is made, there will be a clamping mechanism holding the shaft that will bear this torque.
I am looking to have as minial a weight for the finished structure as possible, therefore, I'm thinking that 7075-T7351 for the gear could possibly be used, however, since the worm will have much less mass, I have yet to decide what to use but I am thinking maybe the same material, or maybe grade 2 Titanium.
Given all that background, my main question is is it possible to make the gear using currently available gear making methods?
What would be the ideal thickness for the gear based on using a 1/4" dia worm?
Is there a better choice of material than 7075, if so, what?
Thanks in advance.
Best Regards,
Matthew Zenkar
I'm working (in my spare time) on a metering structure for small astronomical telescopes (16" diameter main mirrors and less), and I have come to the conclusion that using fine-pitch worm gears will give the kind of precision adjustment that I would like to have in the assembly. I have looked at some of the references for gear design cited in previous messages in the group like Dudley for one.
I note that Buckingham and Ryffel in "Design of Worm and Spiral Gears" state that fine-pitch standard screw threads can be used for the worm. Based on that, I am considering using 1/4" - 56 thread (Machinery's Handbook does list this as a standard thread size) for the worm. For the worm gear, I am thinking of using a 60-degree circular arc with a six-inch radius. I would also like to have the gear "single-enveloping". As a worst-case scenario, I believe that the torque at the gear threads will be approximately 450-in lbs; however, the gear will only have to bear this load while the adjustment is made. After the adjustment is made, there will be a clamping mechanism holding the shaft that will bear this torque.
I am looking to have as minial a weight for the finished structure as possible, therefore, I'm thinking that 7075-T7351 for the gear could possibly be used, however, since the worm will have much less mass, I have yet to decide what to use but I am thinking maybe the same material, or maybe grade 2 Titanium.
Given all that background, my main question is is it possible to make the gear using currently available gear making methods?
What would be the ideal thickness for the gear based on using a 1/4" dia worm?
Is there a better choice of material than 7075, if so, what?
Thanks in advance.
Best Regards,
Matthew Zenkar