Criterion Dynascope RV-6 Project: "Dead Motor, No Shaft!"

Recall from the first post in this series that the person I purchased this old scope from kept the pier, including the RA motor, outside in the rain and snow for the better part of thirty years and that, while loading the pier into my car, a significant flow of water came streaming from the motor box.

Needless to say the original Synchron 6-RPH motor, irreparably damaged with corrosion, would not make the slightest peep when plugged in to power.

I was clearly going to need to find a replacement motor and after Googling around a bit I determined that the exact model was still being sold from Herbach and Rademan, a company specializing in electro-mechanical and scientific supplies.

At first, I thought this would be a simple swap-out, "out with the old, in with the new" type of replacement but after comparing the motor I received from H&R to the old corroded Synchron, I realized that I would have a problem connecting the new motor to the worm gear of the clock-drive.

The shaft on the new motor was too long and didn't have any ability to make the connection with the worm gear which appeared to use a simple "tongue and groove" type of fitting.

After Googling some more, I discovered the excellent Criterion Dynascope Yahoo user group which, aside from being an great resource for Dynascope related issues, lead me to contact Ken Poshedly, an extremely nice and helpful group member who had solved this problem already and was happy to help others.

During his Dynascope restoration, Ken had a fitting made by a machinist that could be fastened onto the shaft of a new Synchron motor to make the connection to the worm gear.

Lucky for me, Ken didn't just have one fitting made, he had many (I believe he said something like 50 or 100) and he was selling them at cost (... just a couple of bucks) to anyone that needed them and, even more lucky for me, he still had a couple left.

I sent Ken my order and he sent me back two of the shaft fittings along with a hex tool for tightening the fitting onto the shaft and some great installation instructions he had printed up.

Sadly though, after tightening Ken's fitting onto the new Sychron motor shaft and attempting to reassemble the motor-worm mechanism, I discovered that the diameter of the fitting was slightly too big to fit inside the worm gear housing... there must have been some slight differences in my RV-6 and Ken's... drat!

Further still, the mini hex nut used to hold the fitting onto the shaft was sticking out from the side of the fitting even after being fully tightened further exacerbating the diameter issue.

Finally, the shaft, particularly with the fitting installed, was just too long to fit correctly when reassembled.

What to do?

After some time pondering this major set-back, it occurred to me that I might seek the help of a local clock repair shop... surely they would have the skill and the tools to deal with such an issue.

Lucky for me it was recommended that I bring my troubles to Jim Peghiny of the "Clock and Watch Shop" in the Auburndale section of Newton MA. 
 
Jim is not only a great guy, but a true expert and craftsman with over 30 years of experience repainting intricate clocks and watches.
  
He took an immediate interest in my project and was fully acquainted with Synchron motors (... apparently they are routinely used in some clocks) an even knew a thing or two about Criterion so I handed over all the crucial parts (new motor, old motor, shaft fittings, worm gear) and upon leaving his shop, I had the distinct feeling that my problems were solved.

A few days later Jim called to tell me that the fitting was now the correct diameter and that he would like to shorten the shaft to make it the correct size as well as glue (with some sort of epoxy) the fitting to the shaft instead of using the hex bolt.

I was elated!... I had just assumed that Jim was going to get the diameter of the fitting right but now he was going to whole route, making the complete mechanism correct end-to-end.

Of course, I quickly gave him the go-ahead and he said I would be able to pick it up the next day.

Well, when I got to Jim's shop I could see that he took great care in getting the mechanism right as he had fully assembled the pieces and even hooked up the motor to test how it functioned powered.

The mechanism was now perfect and it cost just $15 for Jim's work. 

In this day and age for that much work, care and attention to detail to cost just $15 seems undervalued to say the least so I thanked Jim and assured him that I would be bringing all my future clock, watch and telescope repairs to his shop.

Heading back home, I had the distinct feeling that I had just overcome the last show-stopper of this project.

The clock-drive needed reassembly and a new cork clutch but that was minor by comparison to the other issues I had encountered.

The optical tube assembly needed some serious cleaning and some repair (as we will soon see) but overall I did not anticipate any seriously problematic issues...

"It's all smooth sailing from here on out!" I thought.

Next up: "Clock Drive and Cork Clutch!"

Best to all,
BBG

Criterion Dynascope RV-6 Project: "Tap! Tap! Taping the Assembly!"

When we last left off I had just received the components back from the powder coater and, thrilled with the results, was excitedly readying to re-assemble the pier.

Recall though that in preparation for the new finish, I was forced to separate the saddle from the declination axis thereby permanently breaking the original factory friction connection between the two parts.

By this point, I had resigned to "re-attach" the two parts through the use of a hex-and-die tap... in fact, I planned to make three taps through the saddle head and oriented triangularly around the declination shaft so that the three inserted hex bolts would hold the two parts together firmly.

I say "resigned" because a cursory search on the web had me at least slightly concerned for the fragility of the aluminum saddle as it appeared not too uncommon for them to turn up broken.

But, be that as it may, there appeared to be no other way to re-establish the connection so off I went to the hardware store for a minimal "tap-and-die" set and a can of WD-40.

Without much of a plan, I began tapping the saddle settling on creating three taps that would together form sort of a triangle around the declination shaft.

Each tap went very well with a small depression mark setting the position for a pilot hole then followed by the thread cutting process all with the help of liberal amounts of WD-40.

The aluminum was quite soft and proved very easy to drill and tap and before you know it, I had three nicely threaded holes but now for the moment of truth... would the hex bolts hold firm to the declination shaft when tightened.
    

After tightening all three hex bolts I was happy (and very relieved/satisfied) to find that the connection was VERY firm with little possibility of slippage.

Now with the saddle issue finally resolved, I decided to continue assembling the main pier components with the goal of reaching the point at which I could begin to address the next "show stopper" issue... the corroded motor drive!

First, I reattached the "lunar lander" feet using new (but identical) stainless steel hardware and a slight modification from the original design, custom fitted washer-like pads (placed in-between the lander foot and the pier) made from a firm but compressible rubber-like material I had lying around (see below).

I simply cut rectangular pieces the same size as the side of the lander foot that meets the pier so that the washer would completely separate the two pieces but made sure that no rubber washer would show around the edges.

With the washers in place, I felt confident to REALLY tighten the feet to the pier without any marring the fancy powder coat finish and in no time the feet were all attached and I was ready to move on to the pier head.

Without much delay I was able to re-attach the pier head to the pier with the original hex bolts, the RA axis holder to the head with the original latitude bolt, the RA axis itself along with the RA setting circle and setting circle pointer, the DEC axis and finally the saddle with the three custom hex bolts.

Finally, during the re-finishing process the original green felt (... or what was left of it) that lined the optical tube assembly mounting rings had to be removed and now, needed to be replaced.

I ordered a nice, perfectly sized and self-adhesive felt in an identical shade of green from an Amazon store while the components were away being refinished and now I was ready to apply it to the mounting rings.

Applying the felt tape to the rings was as easy as measure, cut and stick though while it adhered reasonably well to both sides (clean aluminum and powder coated), it may need a more permanent adhesive at some point to ensure that it stays put.  

    
Now with the pier mostly re-assembled and such small details as the mounting ring felt complete, its time to move on to the next major hurdle in the restoration of this RV-6... the motor drive.

A sorry sight it is that motor drive... recall that it sat in water routinely for about 30 years so the motor and cork clutch were shot while the fasteners were corroded and the worm gear and wheel were all gunked-up.

Restoring the motor drive will bring some major complications for sure but for now I was happy with the results so far and even more enthusiastic about completing the whole project.  

  
Next up: "Dead Motor, No Shaft!"

Best to all,
BBG

Criterion Dynascope RV-6 Project: "Naval Jelly and Elbow Grease"

With the scope disassembled, it was easy to see that removing the rust that had built up over the many years of direct weather exposure was not going to be an easy task.

Worse yet, the majority of the original paint job was a loss as well with brittle flaking and loose chips falling free at just the slightest touch.

I needed a safe product (and procedure) that could simultaneously remove rust and all other debris from each part leaving me with, more or less, a clean surface ready for a fresh coat of paint.

Enter... Zud, Naval Jelly, steel wool and lots of hard scrubbing!

My grandfather, who was an expert at these type of things (guru of grease, Grainger-aholic, wholesaler extraordinaire), had first recommended Naval Jelly to me when I was just a teen and I have been using it ever since.

It is a strong and safe phosphoric acid based pink jelly that you apply to a surface and let sit for a while before scrubbing off to reveal a new, rust free look.

Better yet, it tends to eat through just about anything including old paint, dirt and other grime making it perfect for the sort of application where you are not trying to spare any of the original surface.

Before and in-between coats of Naval Jelly I decided to scrub each parts surface vigorously with Zud, a Bon Ami-like, heavy duty powder cleanser, in order to remove any obviously loose debris.

In order to facilitate the de-rusting/stripping process, I secured and old box that I used to contain all the mount parts once they were covered in jelly.

This made it easy to cleanly transport the parts around and worked to keep my workspace clean of the arrant blobs of jelly that tend to drip from the surfaces as they "cure".

Though most parts of the clock drive and setting circles are made of aluminum and brass, the hardware is not and corroded right along with the rest of the mount leaving nasty stains on many of the rust proof surfaces as well as resulting in the seizing of some set screws.

Covering these parts with ample amounts of Naval Jelly I sought to remove whatever stains and grime had infected them as well as free up any stuck hardware.

A typical aluminum pan worked to contain these parts as they were being jellied and, as with the box of mount parts, kept the work area clean.

Each coat of jelly was given roughly 24 hours to "cure" after which time I coated each part with Zud and scrubbed until the jelly was no more and all lose material was removed.

I used steel wool to scrub the mount parts but a typical scrub-top cleaning sponge for the clock drive parts so as not to mar the surface of parts that would not eventually be painted.

On several occasions I actually scrapped away the debris from the mount parts using a screwdriver as these surfaces needed some serious attention and would inevitably be completely painted so there was no fear of them being marred by scratching.

After a few of iterations of this process the surfaces of most parts began to look very clean and paintable but there was still a serious issue.

Some rust was simply out of reach of the jelly and my scrubbing.

The entire inside of the pier, for example, was covered in rust yet it was virtually impossible to cover it with jelly much less scrape it clean after the jelly had done its work.

Further, there was rust in nooks and crannies that were equally unreachable... I began to realize that, while the Naval Jelly approach worked to remove most of the rust that was easily accessible from the surface, I needed another approach if I wanted to really rid this mount of all rust.

Next up: "Evaporating the Way"

Criterion Dynascope RV-6 Project: "Disassembly and Decisions"

After getting the scope home and performing a deeper inspection of the various components, it was obvious that this project was going to require a complete overhaul.

Rust had infected virtually every oxidizable surface including all hardware, the whole interior and exterior of the pier, and both axes with particularly bad pitting and corrosion covering the declination axis and its various collars.

Worse yet, the declination axis was actually frozen in place, apparently corroded so badly that it refused to rotate in its housing.

It was clear that the only way to approach this project was to completely disassemble the scope down to independent parts, remove the rust, scour away the grime and lose paint, replace hardware that was too far gone, and completely repaint and re-assemble.

After making a quick run to the hardware store for a few hex keys, some cleanser and an ample supply of naval jelly, I started the disassembly working first on the clock-drive then the axes and then the pier.

Most hardware was still functional coming lose after a little work but a few screws, namely the ones holding the mount head to the top of the pier and the various collars to the declination axis, refused to budge.

Rather than stripping the hex screws, I decided to leave these troublesome parts alone and then revisit them again after a few courses of naval jelly had removed most of the rust that was preventing them from turning as they should.

The declination axis was a bit more concerning though as I could not tell if what was causing it to seize was a lot of corrosion inside the declination "T" housing or if there was just a little near the edges but with this too, I resolved to delay my concern until I had removed as much rust as I could.

The clock-drive looked surprisingly clean given that it had been submerged in water on and off for better than two decades but the motor was clearly suspicious with corrosion coming from the location of the power lines.

It seemed pretty likely that the motor was dead, a fact that I confirmed later after its removal, but the other parts all looked to be in pretty good shape with some minor rusting on the hardware and serious grime (possibly old grease) on the worm gear.

I took care to take many pictures along the way in order to document the proper placement and location of all parts as well as placing all small parts in the cells of an empty egg carton with each cell clearly labeled in order to identify the main component that they were associated too.

With the clock-drive removed, the RA axis slipped out from its housing still connected to the frozen declination axis which, for the time being, I would treat as one single troublesome part.

Removing the large hex bolt that held the mount head to the pier took some doing as it was firmly rusted in place but a slight jerky back and forth movement of the hex key eventually worked to break this bond.

After removing the "lunar lander" feet from the pier, and removing all other lose hardware from all parts, the initial disassembly was complete.

Next up: "Naval Jelly and Elbow Grease"

Criterion Dynascope RV-6 Project: "In the Beginning"

“Every new beginning comes from some other beginning's end.”  - Seneca

For the inaugural project of "This Old Scope" (TOS) I choose (for better or for worse) to attempt to rehabilitate a recklessly abused old classic Criterion Dynascope RV-6 that I found while perusing the listings at craigslist.

But first... I should mention a bit about myself.

I've been involved in amateur astronomy for nearly 30 years with my most active and focused period occurring when I was a teen during the 1980s.

From the outset I had at least as much interest in the telescope itself as I had for the typical amateur activities of observation, sketching, astrophotography and the like.

Whenever I would get my hands on the latest copy of Astronomy or Sky and Telescope magazines, I would immediately spend a good hour pining over the ads, the equipment reviews and the do it yourself projects before cracking into the general astronomy related articles.

Soon, I found myself with a subscription to "Telescope Making Magazine" plus the entire series of back issues, a copy of Richard Berry's "Build Your Own Telescope" and a 50 gallon drum in the basement for grinding my own mirror.

That said, I still have a tremendous amount to learn about mirror making, telescope construction and restoration so now that I'm a settled family man I'd like to revisit my love of the telescope by taking on a series of projects that I will fully document and chronicle here at TOS.

Hopefully in the process I will be able to rekindle my love of the telescope while producing a stream of useful DIY information for anyone with similar interests.

Now back to the project at hand!

As you can see from the photo above, this scope is a sad case indeed.

The man I bought it from was an interesting case too... In his late 40s as best as I could judge, I couldn't help but feel a tad bit melancholy as he recounted how his father had bought him the scope years ago and how he had left the mount out in the rain and snow year after year while always being sure to keep the optical tube assembly indoors.

Here was a classic scope... no... THE classic scope... a six inch Criterion Dynascope being treated like a cheap throwaway import.

Back when this scope was purchased (somewhere around 1972 - 1973), the standard RV-6 model cost roughly $325 which, adjusted for inflation, is about $1,598 in 2010 dollars... a notable investment in a special gift likely given under special circumstances.

Things sure don't always work out as one plans and this man's father had likely never anticipated such a lowly road for this fine instrument... but such is life.

After a few more pleasantries, I paid him the $100 he was asking for the scope and he offered to help me load it into my car.

As we wrestled with getting the mount into the back seat I suddenly noticed a significant stream of water flowing from the clock drive chamber... we locked eyes... "Not a good sign" he said self-consciously.

I reassured him that it was fine, I had anticipated the worst and if the clock drive didn't work, I would simply add it to the list of things that needed attention in order to restore the scope.

We shook hands and off I drove.

Next up: "Disassembly and Decisions"

Best to all,
BBG