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How to mount worm wheel to the shaft without clutch?

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#1 vipinpsharma

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Posted 23 June 2019 - 08:59 PM

 Hi,

 

I have a 2.5" diameter RA shaft. Based on my torque requirements and telescope size, I figured I will be needing a 15" worm wheel RA drive setup. I found this link on eBay (looks like Ed Byers product) but this doesn't seem to have any clutch available. 

 

I was thinking of turning down a few inches length of the 2.5" shaft to 2" which takes care of the bore requirements of the worm wheel. However, I am not sure of the mounting of the worm wheel on the shaft. How will the worm wheel hold on to the shaft with no slippage of any kind? It is probably a very basic question but I have no experience in these areas.

 

Does the ad on eBay assume that the buyer will have the needed clutch which can latch on to the those mounting holes seen on the worm wheel? 

 

Thanks for your inputs in advance.

 

Vipin



#2 555aaa

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Posted 23 June 2019 - 11:29 PM

I think you'll have to fabricate or find a clutch if you want one. The Byers clutch is very simple, it's just a spring-loaded pressure plate that pushes on some plastic material, but it does require a larger bore than what you have there. On my large geared mount, I don't use clutches. The Paramounts I think are also clutchless, and the 1970's vintage Boller & Chivens mounts used a pivoting worm block to partially disengage the worm or balancing.

 

It's a pretty simple machining process to bore out that central hole. It can be done pretty accurately in a good shop, and even if it's not perfect, it can be shimmed to be perfect.

 

 

PS those threaded holes aren't used by the clutch. They are used in the fabrication process AFAIK.

 

see this example:

 

https://www.ebay.com...675.c100623.m-1



#3 photoracer18

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Posted 24 June 2019 - 08:40 PM

Its the clutch hub that mounts to the axis shaft not the worm wheel. See the one titled GEM project with Byers Drives #2 and #25. The hole in the center of the worm wheel has to be bigger than the circle of the 6 clutch bolt holes in the clutch plates. Otherwise you have to pull the worm off the big gear to move it when not tracking and also create a hub for the worm gear.


Edited by photoracer18, 24 June 2019 - 08:45 PM.



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