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1974 Cave Mount Worm Drive Problems

Started by mboessen, 09/09/2015 04:59PM
Posted 09/09/2015 04:59PM Opening Post
Hi, All:

I have built a 16" Newt and placed it on an old 1974 Cave equatorial mount. Apologies to any old Cave enthusiasts, but the ring and worm on this thing are total junk. If you mesh them properly and hook a 1/2" cordless drill on the drive shaft and spin the thing there are 2 terrible spots, including one place about 8 teeth long that will flat out stall the drill. I need a new ring and worm for this thing. Can anyone give me any guidance?

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mboessen's attachment for post 59703
Posted 09/09/2015 06:12PM #1
Hi Michael! Is your scope well-balanced in all orientations? I had (the same?) make and model mount with a 12.5 Astrola on it that I did a LOT of refurb on. I got it for near nothing ($1800) about 35 years ago and put another $3000 into it. The drive was indeed junky: very COARSE pitch on the gears and terrible tracking even with perfect polar align. Dec tangent arm same problem - poorly designed and hopeless backlash. Anyway, I replaced the RA with a Byers 11 3/8 Sidereal and drove that thru a freq box and replaced the Dec with a tangent arm of my own design and build. Those I automated thru the SBIG ST4 tracker that had just come out. Long story short: Tracking went from frustrating to perfect! I tracked on off-axis star at 2200mm and it just locked on like a bulldog for hours on end! Imaging at 1900mm with no smear at all. Back then film was still king so continuous exposure times were 2-4 hours! Your scope: If you are determined to keep it Stock - would need to have the gears worked/lapped? and it still won't work very well. If it's function you want --- replacing the RA drive and tangent arm would make sense. PS The RA and Dec bearings were excellent on mine - silky smooth and true. I never touched them - hope that's true of yours. Good luck with your project! Tom Dey

29-inch Dob in a dome
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Posted 09/10/2015 06:17AM #2
I believe all those early Cave mounts used Boston Gears. These are still readily available.
Keith Parizek