Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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My latest scope needs a new eq platform because of the high CG. I'm almost done with this one except for some sanding, varnishing and bolting down the motors but so far it's cost only $29.5. That doesn't count the maple plywood I already had, ball bearings I had and some screws and leveling feet I need to get yet. It'll be done before the scope!
2 motors from Apogee @ $4 each
2 3 inch Newport SS rods @ $6.60 each
maple from Home Depot $8.30
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Ed Jones
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rmcpb
Carpal Tunnel
Reged: 11/16/04
Posts: 1606
Loc: Blue Mountains, NSW, Australia
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Ed,
What is the layout on the bottom board?
Looking good 
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Rob Browne
8" & 13" Dobs
Equatorial Platform
Couple of Panoptics and a handful of BO/TMBs
9x60 binocs
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The bear
scholastic sledgehammer
Reged: 02/11/08
Posts: 824
Loc: rushville, indiana
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yes ed enlighten us to your good owrk this would be ideal for a poor child like me.
doc
might have the motors already hehe
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Longitude -85.42786 Latitude 39.59153
"current build 6 inch F6.5 "Little Toe"
"if all else fails use duct tape "works for me"
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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Here is the bottom board. The 1/15 rpm motors from Apogee are CCW so they must go behind the north bearing. I drilled our the smaller tapped hole on th post to 4 mm to match the motor shafts on a lathe. The SS posts from Newport are 1/2 inch so the radius of the north bearing is 23.93. The CG above the middle of the board is 17.6 inches. Total height 4.25 in. If you want I can start another thread on how I made it.
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Ed Jones
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The bear
scholastic sledgehammer
Reged: 02/11/08
Posts: 824
Loc: rushville, indiana
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yes please this would be very informative and excellent instructional to us all.
doc
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Longitude -85.42786 Latitude 39.59153
"current build 6 inch F6.5 "Little Toe"
"if all else fails use duct tape "works for me"
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Jason D
Post Laureate
Reged: 10/21/06
Posts: 3301
Loc: California
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How well does it perform?
Jason
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XT10 classic with premium optics
Tri-knob CR2 with compression rings
Round Table Platform
4.5" StarBlast
6" StarBlast6
TV EPs
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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As you see it isn't finished yet but it's almost exactly like my first platform (which tracks great)except that I'm not going to knurl the Newport posts. I don't think it'll be necessary. I can always knurl it later if need be.
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Ed Jones
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
Loc: Courtice, Ontario
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Quote:
If you want I can start another thread on how I made it.
Isn't this that thread? And yes I'd like to see all the details too, namely how you setup to cut a VNS with such a tight tolerance for the radius!
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Ryan
Antares 200mm f/6 Dob & 130mm f/5 Travel Dob.
Projects on the go...
- a couple 80mm SS refractors on the back burner.
- a few small mirrors awaiting polishing
- 260mm f/7.15 mirror... still polishing
Member of DRAA
 My house.
 DRAACO
Edited by Biff (05/25/08 10:16 PM)
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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OK well I'll start from this thread.
My latitude is 39.25 degrees and my rocker box is 18 inches square so I started with a platform 19 inches wide and long.. Shown below is the cross section layout. The south bearing is 11.91 inches radius spaced 18 inches from the north bearing. The mid platform CG is 17.6 inches from the platform but my computation for the scope CG is 14 inches, 3.6 inches lower but I don’t think it’s a problem at all.
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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I cut two boards with a 50.75 degree bevel about 4.5 inches X 20 inches. On the back side I tacked a ¼ inch scrap piece of plywood and measured from about where the tape is to a 23.93 inch arc from each side. I drilled a hole for a finishing nail to pivot on at that point
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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On my table saw I bolted a ¾ inch piece of wood with my finishing nail pivot a little more than 24 inches from the blade. The blade was tipped at 50.75 degrees and lowered all the way down. I raised the blade a 1/16 of an inch at a time and swung the board into the blade slowly pivoting on the nail. I raised it another 1/16 th and repeated. Eventually the blade was above the board and it was roughed out. I then switched to a sanding disk and continued, moving the part a small distance into the disk each time until the radius was 23.93 at the midpoint. This makes beautiful smooth bearings (and I have fun doing this as well).
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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I made a trapezoid board 19 in. long by 16 in . on one side and 19 in. on the other. I drew a mid-line perpendicular to the middle of the small side (on the bottom).
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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I glued a block with a 50.75 deg. angle on the mid line for support.
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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The south bearing comes out pointed so finding the mid-point is easy. I align the midpoint with the mid-line and glue and screw it together.
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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With a square set to intersect the curve on the north bearing near the edge, I mark both sides then find the mid-point.
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Ed Jones
Edited by Ed Jones (05/25/08 11:53 PM)
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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I made an obtuse triangle to support the back, lined up the mid-point and glued and screwed it together as before. A support block on the other side would have been easier.
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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I glued a 1.5 X 4.5 inch piece of maple to the inside of two 24 X 2.5 inch pieces. This is for mounting the motor. I drilled a ½ inch hole in two pieces of teflon and cut them into for bearings. 2 cross-pieces of maple were glued for strength. (I taped the posts and bearings in place temporarily to figure out where the cross pieces should go.)
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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3 pieces of maple were cut to hold the bearings. The rear bearing block was easy, the other two were compound angles and it took a number of tries cutting pieces on a band saw to get the angles right so that the ball bearings races ran flat to the bearings. These little pieces were the trickiest part of the project.
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Ed Jones
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1415
Loc: Sin-sin-atti
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The rest is sanding, varnishing, screwing the teflon and motors down, wiring etc.
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Ed Jones
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ZachK
professor emeritus
Reged: 08/21/05
Posts: 709
Loc: Israel
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Thank you, I was planning something exactly like that and I think you gave me what I need to get going. I need to figure out how to do this without a table saw though. I have a jigsaw and a router.
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Zach Kessin
Ariel Israel
Meade ETX 127 Mak-Cass
15x70 Celestron Skymaster Binoculars
Sinar F 4x5 view camera
Rolliflex Camera 80mm F2.8
Pentax K-1000 Camera 35,50 and 60--300mm zoom
4 kids
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