I am rebuilding a Coulter 13.1 Dob. I have purchased bearings and adjuster plates from a 15 inch Discovery scope and building a new rocker box. Discovery 15" have 180' cutout for the altitude bearings and it looks like the Teflon pads are 120' apart. Should I stay with the 180' cutout or go with 130' or so? Does 120' apart on the bearings sound about right or should they be less? I hope to loose at least 50# in this rebuild. I will be out under the stars tonight, first time in over two months. I will check in tomorrow afternoon.
Dob Altitude Bearings
Started by jumpingjackflash1960, 09/27/2008 05:25PM
Posted 09/27/2008 05:25PM
| Edited 09/27/2008 05:28PM
Opening Post
Posted 09/27/2008 08:18PM
#1
Dale--
The angle at which the altitude pads are set depends a lot on the diameter of the bearings. As the alt pads get closer, balance becomes more critical, and altitude motion requires less force. On the flip side, closer alt pads slightly reduce the weight of the rocker. (But what really reduces the weight of the rocker is large diameter bearings.) I've got the alt pads centered at 60 degrees on my 10", and that works fine, because they are 15" diameter. I think the spacing is something similar on my 16", but with 32" diameter. I don't think I'd want anything less on either (well, I could reduce the spacing on the 16"). That angle on the pads would allow the bearings to be cut to 150 degrees. I left the bearings on the 10" at 180, and trimmed the ones on the 16" a bit. So that does allow you to save on weight. You can also remove a lot of material from the interior of the alt bearings without sacrificing stability. I do not recommend semicircular rings though--too bouncy. I built my 16" that way and later added a cross brace. Every little bit helps, and in removing material from the bearings, you're not affecting the balance much at all. If you're going to a truss scope, you can easily drop 50 pounds on this guy.
George
The angle at which the altitude pads are set depends a lot on the diameter of the bearings. As the alt pads get closer, balance becomes more critical, and altitude motion requires less force. On the flip side, closer alt pads slightly reduce the weight of the rocker. (But what really reduces the weight of the rocker is large diameter bearings.) I've got the alt pads centered at 60 degrees on my 10", and that works fine, because they are 15" diameter. I think the spacing is something similar on my 16", but with 32" diameter. I don't think I'd want anything less on either (well, I could reduce the spacing on the 16"). That angle on the pads would allow the bearings to be cut to 150 degrees. I left the bearings on the 10" at 180, and trimmed the ones on the 16" a bit. So that does allow you to save on weight. You can also remove a lot of material from the interior of the alt bearings without sacrificing stability. I do not recommend semicircular rings though--too bouncy. I built my 16" that way and later added a cross brace. Every little bit helps, and in removing material from the bearings, you're not affecting the balance much at all. If you're going to a truss scope, you can easily drop 50 pounds on this guy.
George
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George Golitzin
Funding Member
