Edmund 6" early grey Pier
Posted 28 March 2014 - 02:47 PM
Posted 28 March 2014 - 05:53 PM
Posted 29 March 2014 - 12:28 PM
Going back I have to modify one very important claim. THE WING NUT ON THE MAIN ALT BOLT DOES NOT WORK IN PRACTICE. It seemed fine in the shop but just won't allow sufficient clamping force with field work. Either use a lever on it, with a wrench on the bolt or put a nut back on it and use two wrenches. The same goes for the DSC 4.25" thread.
The balancing act:
The weight with the side bar goes on first. The second weight goes on the side bar. The side bar should be in line with the OTA. The basic set up is shown in the picture.
The bolted OTA can not be shifted to balance rotation around the DEC shaft. The bolted position of the OTA is initially tail heavy. Sliding the second weight on the side bar allows DEC shaft balancing. The entire double weight assembly as a single unit allows balancing around the RA shaft rotation. At least in theory. The second weight makes the scope front heavy even when all the way back as in the picture. The fix would be to rotate the entire weight doublet on the DEC shaft so the second weight is positioned closer to the rear. This creates a non dynamic system meaning the RA shaft is balanced in one position but not others. It looks nice in the house.
The fix for use is to ignore the side bar and put both weights on the DEC shaft. Put your 'average' eyepiece in the focuser and balance the DEC rotation with some kind of clip on the OTA end, or other moveable weight. Magnets won't work since it's aluminum. You will find very little weight needed if at all, with the eyepiece installed. I find I don't need to bother with an OTA weight, with an eyepiece installed, it's close enough for the clamp without concern.
- Bomber Bob likes this
Posted 29 March 2014 - 01:21 PM
Been a while since you updated this Neil. Is the project finished?
Yeah, what's it to ya?
I went through my pictures and have nothing left. Documentation and presentation just isn't for me.
The teflon strips went in as previously suggested, by rolling them tightly and letting them 'snap' into the shaft grooves with grease. This delighted me, thanks guys.
The plastic pointers popped onto their machined recess' tight and didn't need adhesive. The pointers go on perpendicular to the housings (so you can see them in use). I typically oil the Bakelite setting circles with machine oil and let them sit overnight, then wipe dry. The setting circles go on with a flat rubber ring on each side, and intall the shaft. I preload the shaft with the stop collar so there is no end play and a slight feel in rotation. I installed a nylon washer between the stop collar and housings. Both shaft lock knobs were very lightly rounded then polished on the ends. SuperLube on shafts and bearing surfaces, AND on the lock knob contact areas.
I can't think of anything else particular for the basic mount. Ask questions.
Posted 29 March 2014 - 01:54 PM
The SSC and 4.25" DSC are the same cell in principle. The picture is the DSC since details are hidden behind the larger mounting plate of the SSC. The springs are held centered on the mirror plate by slipping over a nut I put on the base of each collimating bolt with LockTite blue. The mounting plate end of the spring is held centered by the black caps previously described (arrow is touching one). All exterior cap nuts are SS. I placed small washers (visible) between the collimation adjusting nuts and mounting plate.
Posted 29 March 2014 - 02:12 PM
- Bomber Bob likes this
Posted 29 March 2014 - 02:50 PM
The newer focusers have different machining in the housing to accomodate felt. The older ones have the draw tube ride directly in the housing bore. I have yet to find a slop problem in any of them, counting about 12 I've done. The original straight slot set screws that hold the secondary shaft were replaced with a philips SS. The repacements were a bit long and cut down with a dremel.
The splined focuser pinion shaft has a rubber washer on each end, between the knob and focuser body. Pre load is set by squeezing the knobs together as the knob set screws are tightened.
Most of the draw tubes were not blackened inside so I cleaned them and put in a squirt of Rustoleum Cammo Black. The drawtubes, rack, housing bore, and pinion shaft got a very light wipe of SupeLube. After several full travels of the draw tube, I wiped off any exposable redisdue from the tube. NO GREASE ON THE FELT VERSIONS.
NOTE the two bolts and cap nuts in the lower left corner. This was a swap. The original focuser mounting bolts were #8X32. I replaced them with #10X24 and it made a nice difference. The focuser housing and tube holes are oversized for #8. This left the focusers sloppy for mounting room, and the exterior tooth lock washers often slipped cockeyed into the tube holes. The #10 fit much nicer all around. The focuser never had any restriction in room for the secondary shaft with the larger bolts. The larger bolts are philips which are much more friendly than the original straight slot.
- Bomber Bob likes this
Posted 29 March 2014 - 03:03 PM
If some one wants to do a blow out on the finders, feel free to inject it into this thread.
That's it for this thread. Questions welcome.
Posted 18 July 2017 - 06:14 PM
Just bringing this forward so I don't have to go looking for it. Have one of these arriving tomorrow and it will need work. Very nice effort. Thanks for all the detail.
Posted 18 July 2017 - 06:27 PM
Great stuff, but oh I cannot deal with that manner of secondary support. Newts need proper spiders. I hated that stalk back in the day!
Posted 19 July 2017 - 05:51 PM
I've tried tight rolling the strip with no luck. I probably didn't roll it tight enough and admit to being leary of kinking it. I could also use a tackier drag grease under the strip and stick to the SuperLube outside. I'll try it again with some dry runs.
I hate the Edmund staps. For starters, the staps on one of these and on my 8" are just ugly. The factory set looks like a garage job with parts from the hardware store. The massive 8" is even more amature looking. I also don't like the way they hold the tube, or should I say Don't hold the tube. No protection from the saddle contact, not easy to rotate the tube, not easy to field adjust the balance, only hold well in a verticle position if the OTA is being pressed hard into the metal to metal saddle contact, ugly, and a few other derogatory descriptions.
Honestly, the same goes partly for Edmund's red tubes on the pier that use the strap. Here's a picture of my completely restored one. The straps are replacement but original material and brand new thanks to Amicus S. Thanks Fred. They would NOT be considered user friendly by general concensus though you can learn some tricks to the trade through consistant use. The tensioning system on these is unique and interesting but the engineering concept of strapping the OTA doesn't cut it for me.
One 6" Grey was strapped, the other was bolted. Same for the Palomar JR's, one is strapped and one bolted, and ohhhhh to be honest, a third JR is on the vintage look wood tripod that Edmund produced for a short run. I'll eventually TAKE THE STRAP OFF the 6" when I find a good replacement ring system. The one strap is split but perfectly usable and it will go into the bag of original parts and stay with the scope.
I'm delaying this finish build today for the sake of paint. I've decided to do both scopes. I intended to do my keeper eventually and the other one could use a coat - it is just time. Yeoww, talk about variations in shades of grey. These old Edmund grey fine wrinkle finishes tend to fade and age into more variations of color than anything I've seen. From reddish to blueish to silvery grey, I've seen it all and often different parts on the same scope. A friend of mine restored his Edmund 6" here, including painting. We laid out a variety of tones to try and determine the best all around match. After painting and comparing again, the verdict is in. Rust-Oleum Painter's Touch, 2X Ultra Cover, Paint+Primer, "SATIN GRANITE".
A guy near me has one of the red tube 4" models on Craigslist for $85. No eyepieces but it looks like everything else is in pretty good shape. If it wasn't for the Cave Cass, and the Carton and Sears refractor projects I have I might have been interested.