Jump to content


Photo

A 1972 Cave 8" f/4.5 RFT Lightweight Deluxe

  • Please log in to reply
92 replies to this topic

#51 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 03 March 2013 - 11:42 PM

Meanwhile, restoration continues... Mostly stripping off the old paint, applying primer and putting on the new coat of either "Instrument Gray" or Black Wrinkle Finish. It's a lot of work to do this - Aircraft grade paint stripper, sometimes two times, sanding off rust and blotches of paint, refinishing the Dec and RA shafts, and just the time it takes to apply a good coat of paint that will last a while is definitely a trial of patience. On the table are most of the major mount parts that have been reconditioned over the past 3 weeks. Once they have cured completely (a minimum of 1 week) then I'll start to put it back together. Can't wait!

Attached Files



#52 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 03 March 2013 - 11:58 PM

Another shot of the staging area for the mount and rotating rings before assembly. The Wrinkled Black application has been the most challenging - unless done right, the wrinkles come out uneven and I start over again - stripping, priming and spraying it on once more. It takes a good 12 hours for the wrinkle paint to fully cure. I do each piece individually...

Attached Files



#53 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 04 March 2013 - 12:01 AM

There are quite of few fasteners - nuts, washers, bolts and so on that put the scope together. I found it much easier to measure and inventory every one of them and put that info into an excel spreadsheet. I then place the order for those fasteners and when they get delivered, inventory them again, checking off each one on the spreadsheet and labeling each ziplock bag for which the fasteners are intended for.

Attached Files



#54 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 04 March 2013 - 12:19 AM

Although the tube was already in very good shape to begin with, it still needed refinishing to match up with the fresh paint job of the rest of the scope. The fiberglass tube is waterproof, so with that in mind, after cleaning it up with some 409, I commenced to lightly wet sand by hand it with 600 and 1500 grit sandpaper, to smooth out any blemishes. This also helps subdue the spider cracks that tend to happen on the finder ring and mirror cell mount holes when they get bumped or tightened up too hard. Later, rubbing compound and a coat of wax will finish it off to a lustrous finish.

Wet sanding with such fine grades only takes off microns from the surface and does not intrude upon the coating enough to make a difference.

Any deeper gouges left are part of the assembly and covered up by the original parts that were there. In this photo, that would be the focuser edges, spider washers and finder base.

Attached Files



#55 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 04 March 2013 - 12:28 AM

The inside of the tube was weathered with dust and grime and even after washing it, there was still a dull flat black that would not be acceptable for contrast performance. So, I coated it with Krylon Ultra Flat Black. But before applying the paint, I used blue painter's tape to cover up all the holes so that the black paint would not seep onto the white finish from the inside. It turned out to be overkill after I finished, but better to be cautious than loose time in the restore.

This tube is so short - only 38" long, that I was able to reach inside it with the rattle can of paint and get a good coating all the way up and down. The ends of the tube were not hit with paint very well, but that doesn't matter since they will be covered up by the aluminum end rings.

Attached Files



#56 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 08 March 2013 - 12:49 AM

The mount and tube are shown in this photo. First, the front end of the mount is complete. The RA and Dec Shafts have been refinished and shined up, along with the Dec Circle and its pointer. The Tube has been finished with a rubbing compound and wax. The Inner Rotating Rings have been reinstalled on the tube.

Attached Files



#57 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 08 March 2013 - 12:57 AM

The Inner Rotating Rings can be a bear to reinstall if the orientation is not noted before taking the scope apart beforehand. On this scope, I made pencil marks, small punch marks on the inside of the rings and even paper and pencil notes for the correct position of the rings as well as which ring was the upper and which was the lower on the tube when I took the scope apart. This is absolutely essential to do because the drill holes on the Inner Rings to the Tube are not perfectly 90-degrees apart; the rings only go back on one way.

So, after letting the wrinkle paint cure for a week, I slide the rings back on, used tooth picks to hold and verify that all the holes line up before fastening them back on.

It is important to be gentle with the fasteners and not force anything - because the tube is 40 years old and it can easily be spider-cracked if anything is forced against it!

Attached Files



#58 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 08 March 2013 - 01:01 AM

The old tube still has some damage that we just have to live with - here is the worse of it where one of the finder rings mounts to the tube...

Attached Files



#59 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 08 March 2013 - 01:07 AM

When reassembling the scope, after painting, it's very important to clean out all the old threaded holes before putting things back together. Not only new paint, but any kind of crud can interfere with installation of new fasteners and a smooth calibrated elbow torque amount during reassembly. Here is a tap (3/8 - 24) being run through one of the Outer Rotating Ring Adjustment Holes before it is attached to the already installed Inner Rotating Rings...

Attached Files



#60 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:02 PM

When putting the Outer Rotating Rings back on, I try to evenly space the adjustment so the gap between the outer and inner rings are about the same all the way around and so that there is a smooth, but not too loose amount of tension when rotating the outer rings. Later, when performing celestial alignment the first time on the mount, there is a method to follow that will use these set screws to put the optical axis perpendicular to the Dec Shaft.

Attached Files



#61 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:05 PM

Once both Outer Rings are installed, the 3 spacer rods are then installed to complete the Rotating Rings.

Attached Files



#62 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:15 PM

Here's how I get the Tube Ring to Cradle Studs nice and tight without marring them up. This method also works great during disassembly too.

Attached Files



#63 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:27 PM

Next, I cut strips of cork and punch a hole in the middle for the studs to fit through. The strips are longer than needed and trimmed to fit after the OTA is installed. I used contact cement to adhere them to the cradle. The Cave 8" f/7 Lightweight Deluxe was like that new from the factory, so I have been doing this method for all my restores.

Attached Files



#64 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:31 PM

Cave Clock Drives have been covered quite a bit here on CN, so here's the assembled drive for this scope. The original power cord and plug was in good shape, so I reused it.

Attached Files



#65 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:35 PM

I used all new brass fasteners for the Dec Shaft Lock Knob. 1/4-20 Brass Threaded Rod was cut to size and beveled on the end. This was a problem when I was removing this piece because somebody had put so much force on it that the tip had mushroomed and was difficult to remove. The Dec Shaft Lock Knob must be removed before the Dec Shaft Housing Bolt to the RA Shaft can be accessed...

Attached Files



#66 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:40 PM

Finally, the OTA is placed on the mount. The excess cork on the cradle is trimmed to fit. The Clock Drive Housing, polished setting circles, counterweights and collar rings are all installed. All that's left is to install the Mirror and Mirror Cell, Secondary, Focuser, Finder and End Rings!

Attached Files



#67 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:44 PM

Another view. I kinda like this hybrid transitional period color scheme :) The contrast between Wrinkle Black, Gray and White with a little Brass, Stainless and Black Oil Finish Alloy Steel fasteners makes the whole thing look nice :)

Attached Files



#68 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:54 PM

The Mirror Cell was refinished with flat black and new cork along with new stainless fasteners. I kept the original thread teflon adjusters since they were in good shape and I didn't have any extra material laying around to make new ones!

Attached Files



#69 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 09:57 PM

Next, the Mirror is carefully mounted in its cell...

Attached Files



#70 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 18 March 2013 - 10:02 PM

And Then, I went Camping! This time, I didn't bring any scopes for observing, But did see the comet with binoculars one night while at Picacho Peak State Park.

Attached Files



#71 dgreyson

dgreyson

    Viking 1

  • *****
  • Posts: 805
  • Joined: 06 Nov 2012
  • Loc: South Carolina

Posted 18 March 2013 - 11:06 PM

It's coming along great. I definitely needed a tap and die set, a lot of my threads were in bad shape when I got it.

#72 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 19 March 2013 - 09:53 AM

RonE500 mentioned in his 8" Edmunds Restoration thread that he used cleaning taps and dies. I never knew they made specialized taps and dies for that purpose. I do have a good set of popular sizes from #4 to 1/2" in coarse and fine thread though. They do get expensive for the larger sizes.

#73 dgreyson

dgreyson

    Viking 1

  • *****
  • Posts: 805
  • Joined: 06 Nov 2012
  • Loc: South Carolina

Posted 19 March 2013 - 10:19 AM

Most of the Cleaning Taps I've seen were designed to clean and or re-thread damaged or jammed pipe threads. Taps also come as bottoming Taps for threading holes that do not go thru , and Plug which are best for thru holes and Taper, the most common style, to start the thread square with the surface .

I just use the common taper ones to do everything and usually can just drill the blind hole slightly deeper to get enough thread to hold.

#74 gelkin

gelkin

    Apollo

  • *****
  • Posts: 1272
  • Joined: 22 Sep 2010
  • Loc: Western, MD.

Posted 19 March 2013 - 02:19 PM

Dan that looks superb. :bow: Excellent work as always. I'm kind of liking that color selection too. :lol: Love your circles especially.

Attached Files



#75 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3312
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 22 March 2013 - 05:51 PM

Thanks Gerald :)

On your 8" Lightweight Deluxe - is that a factory tangent arm? How do you keep the Dec Circle from hitting the Pier?






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics