· Get a Cloudy Nights T-Shirt · Submit a Review / Article Click here if you are having trouble logging into the forums Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User You are not logged in. [Login] Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> Classic Telescopes Previous   Index   Next   Threaded   Pages: 1 | 2 | 3 | 4 | (show all) Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Servicing a Vintage Sears / Tasco 3" EQ Mount       #2336527 - 04/18/08 04:46 PM Attachment (313 downloads) Edit   Reply   Quote Quick Reply   PAGE 1 Many who spend time hear in the Classic Telescope Forum have or may have in the future a Sears or Tasco 3” scope. The mounts can appear intimidating to take apart, clean, re-grease and re-assemble. There are a few traps to be avoided so the purpose of this thread is to give the reader a visual “how-to” restore one of these mounts and get at least 40 more years of use out of it! There are some minor differences between the the Sears and the Tasco but nothing critical. The mount that I am servicing here is a Sears. I also have a Tasco mount so I’ll try to post some pictures tomorrow to show the differences. I’d like everyone to weigh in on this thread. Let me know if you’ve encountered something different or if I don’t have something correct. If there is a good response I may consider turning this into an article for CN. I want to hear your thoughts and experiences! I have used some generic terms to describe many of the parts. If someone has a different name for a part, please state so. The best name for a part is one that everyone can quickly understand. Here’s a picture of my newly acquired Sears mount that is dirty, crusty and is currently non-operational due to dried out grease inside the mount: Edited by Preston Smith (04/18/08 06:02 PM) Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336528 - 04/18/08 04:47 PM Attachment (246 downloads) Edit   Reply   Quote Quick Reply   PAGE 2 For me, the best place to start is the clamshell. Remove the felt and remove the nut (counterclockwise). The clamshell hole is also threaded so you will have to rotate the clamshell counterclockwise or the declination shaft (clockwise) until the shaft separates from the clamshell. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336530 - 04/18/08 04:48 PM Attachment (190 downloads) Edit   Reply   Quote Quick Reply   PAGE 3 Be sure to capture the small bronze bushing plate that is under the clamshell and put it in a small cup or muffin tray so you don’t lose it. Hard to replace…. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336531 - 04/18/08 04:49 PM Attachment (169 downloads) Edit   Reply   Quote Quick Reply   PAGE 4 There, three easy pieces. I would recommend that you leave the base on the mount at this time as it will greatly stabilize your operation. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336533 - 04/18/08 04:50 PM Attachment (189 downloads) Edit   Reply   Quote Quick Reply   PAGE 5 Why five screws? Weird, huh? But once you remove the cover you will see why. The four screws in the blue circles hold the cover plate on. The screw in the yellow box actually screws into the Right Ascension friction ring (or brake) inside the mount. The levered knob inside the yellow box is used to push the chisel tipped brass spreader into the friction ring (and expand it against the sides of the mount). To take this apart, first remove the screw and knob inside the yellow boxes. That way you won’t pull everything apart when you take the cover off. Then take out the four screws in the blue rings. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336538 - 04/18/08 04:53 PM Attachment (182 downloads) Edit   Reply   Quote Quick Reply   PAGE 6 OK! Now you can see inside. Remove the gaskets and the small chisel-tipped brass spreader. Don’t lose this! Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336539 - 04/18/08 04:54 PM Attachment (156 downloads) Edit   Reply   Quote Quick Reply   PAGE 7 Remove the friction ring and lift the Right Ascension Yoke off of the mount. A beautiful brass worm gear is now visible (the teeth are on the inside. You CANNOT slide the worm gear out at this time – don’t even try it! Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336540 - 04/18/08 04:55 PM Attachment (181 downloads) Edit   Reply   Quote Quick Reply   PAGE 8 OK, HERE IS THE TRICKY PART!!!!!!! The bearings (bushings) for the worm are NOT screwed in! I know, I know, there are two holes on each side of the bearings. You would naturally think that you need to unscrew them to get the worm out of the assembly. NOPE! BEFORE YOU EVEN REMOVE THEM! Either take a photo or sketch the location of the holes on each side. It is VERY important to do this. Why……(I knew you would ask)…see the next frame. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336542 - 04/18/08 04:56 PM Attachment (150 downloads) Edit   Reply   Quote Quick Reply   PAGE 9 Because the bearings are ECCENTRIC! Yep, take a look below. I’ve taken a picture of the outside and the inside of the bearings. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336543 - 04/18/08 04:57 PM Attachment (139 downloads) Edit   Reply   Quote Quick Reply   PAGE 10 There are four SETSCREWS that hold the bearings in place. This picture clearly reveals the dark dirty secret. Without this, you would be trying IN VAIN to get the bearings out!! (I know…..boy do I know!) This picture is truly worth a thousand words! Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336545 - 04/18/08 04:58 PM Attachment (121 downloads) Edit   Reply   Quote Quick Reply   PAGE 11 After you loosen the setscrews, slightly rotate the eccentric bearings to lower the worm down – away from the brass worm gear. Then you can slide the worm gear out of the yoke and look at all of that shiny brass (and old, crusty grease). Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336549 - 04/18/08 04:59 PM Attachment (149 downloads) Edit   Reply   Quote Quick Reply   PAGE 12 Clean everything up and then let’s start to re-assemble. Here’s a BIG tip. If this is the first time your mount has been disassembled since it left the factory then you have an easy guide to reassemble the bearings. Look for the indentations that the set screws made and you can easily realign the bearings to lift the worm up against the worm gear (once again). However, if the mount has been disassembled many times then there will probably be multiple indentations. THAT is why you need to take a photo or sketch the original orientation of the holes in the bearings so you can easily realign everything. If you don’t do this, it will definitely take you some time (the voice of experience has warned you). You may have to SLIGHTLY rotate the bearings just a few degrees from the original position to get the worm up against the worm gear. Be prepared to do this several times as you position the bearings and tighten the setscrews. Ideally, the worm will move very easy and there will be no play in the big worm gear when you turn the worm clockwise and then counterclockwise. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336551 - 04/18/08 05:00 PM Attachment (119 downloads) Edit   Reply   Quote Quick Reply   PAGE 13 While you are making final adjustments, I strongly recommend attaching the slow motion knob and cable. It’s a lot easier to turn the worm this way. Besides, your fingers will probably be too greasy to turn the shaft! Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336558 - 04/18/08 05:02 PM Attachment (130 downloads) Edit   Reply   Quote Quick Reply   PAGE 14 There, all greased up and the friction ring has been re-installed. You can either place the chisel-tipped brass spreader into the indentation at this time or wait until you have placed the cover on and drop it through the hole in the cover. I prefer to put in at this time so I can be assured that the spreader’s chisel end is firmly seated into the friction ring. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336562 - 04/18/08 05:02 PM Attachment (135 downloads) Edit   Reply   Quote Quick Reply   PAGE 15 OK, put the cover back on. Your first screw should be the one that goes through the cover and threads into the hole on the friction ring. Next, gently reinstall the levered knob on the opposite end so that the brass spreader stays in place. Just turn this knob until it seats the spreader against the friction ring. If you make it tight you will not be able to move the cover to line up with the holes for the remaining screws. Now move the cover back and forth until the remaining four holes line up with the threaded holes inside the mount. Then install the remaining screws. How tight do you make these screws? Not at all. I recommend just seating them initially and move the mount back and forth to see how much friction there is. Ideally, you do not want any slop or wiggle in-line with the axis but smooth movement around the axis so keep “tweaking” (tightening/loosening) the screws as you go. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336563 - 04/18/08 05:03 PM Attachment (137 downloads) Edit   Reply   Quote Quick Reply   PAGE 16 I took this picture so you can see the dried grease and how it was “caked” on to the bearing surfaces. Yuck! Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336565 - 04/18/08 05:04 PM Attachment (119 downloads) Edit   Reply   Quote Quick Reply   PAGE 17 As you remove the declination gear to clean it, I would recommend slapping a little bit of new grease to let is slide out easier. I would also connect the slow motion knob and cable to easily remove the gear once you have removed the nut and threaded bearing to save your fingers from doing a lot of hard, slow work. Post Extras:       Preston Smith The Travel Scope Guy Reged: 04/24/05 Loc: Eureka, Pa Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336568 - 04/18/08 05:05 PM Attachment (159 downloads) Edit   Reply   Quote Quick Reply   PAGE 18 So here it is - the serviced mount! Not necessarily pristine as there are still a few (minor) scratches but this baby is now 100% operational – and will probably be for the next 40 years! Post Extras:       mikey cee Postmaster Reged: 01/18/07 Loc: bellevue ne. Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: Preston Smith]       #2336690 - 04/18/08 06:13 PM Edit   Reply   Quote Quick Reply   Preston....Nice job! How much would you charge for this service? You probably could make few bucks here! Seriously tho' I got as far as the set screws and loosened them up quite a bit. But couldn't figure out the conical bearing hiding inside the casting. I thought maybe there was a groove that the set screws seated into. I knew you couldn't tighten the underneath pair 'cause that jammed the worm into the worm gear so tight that the cables wanted to "kink". After "enough" fiddle fartin' around I found the perfect pressure spot as I gingerly rotated the cables and tightened the bottom set screws. I then just snugged up the side set screws knowing they just might be for centering or alignment purposes instead of for preassure. Mine works so smoothly because my grease was just gummy and not "baked" hard. So I think not much will be gained for me to persue this again! I should get the "Fearless Fosdick" award tho' for tackling this thing before you did! Mike Post Extras:       Littlegreenman Carpal Tunnel Reged: 05/09/05 Loc: Southern California Re: Servicing a Sears or Tasco 3" Equatorial Mount [Re: mikey cee]       #2337462 - 04/19/08 12:17 AM Edit   Reply   Quote Quick Reply   Yes, how much would you charge. Not for lack of screwdriver skills, (I did a few years in machine shops, even a bicycle assembly factory) but I'm just lazy! I just got a Tasco version in that has a lot of slop and needs to be re-adjusted or rebuilt. Thank you very much! Littlegreenman Post Extras:       Pages: 1 | 2 | 3 | 4 | (show all) Previous   Index   Next   Threaded   Extra information 17 registered and 16 anonymous users are browsing this forum. 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