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Meade AR6 focuser rebuild

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#1 tag1260

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Posted 10 October 2019 - 07:59 PM

OK. Picked up an old Meade AR6 at a good price but the focuser is pretty sad. Anyone ever been able to rebuild one and make it usable?  What did you do as I keep going backwards with this darn thing.

 

 

I now remember why I put Moonlites on everything!!!!



#2 markb

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Posted 10 October 2019 - 10:33 PM

Likely the easiest and best solution is to replace it.

I believe AgenaAstro has a very nicely finished and well made backplate that is made to fit your tube (I modified one to finish my much larger 7in tube on my 6in A Jaegers). It matches one or more of their great focusers. Great people to deal with and very responsive to questions

The other alternative is to improve the current focuser. You did not specify what made it sad but I will assume your issues are functional not cosmetic. If cosmetic, replace it as above.

If functional, I will assume it has a Synta style knock off of the Vixen cast body design, not one of the spiffy newer excellent billet machined focusers that ship on many Chinese sourced products these days. I had the Celestron version long long ago, and that's what mine had AFAIK.

If so, look on CN for tips on adjustments of the setscrews and pinion gear 'box' screws and fine tune the adjustments. Make sure the pinion shaft is true and not bent.

But what transformed my Synta focuser I used on my first 6in Jaegers refractor (f8), was ordering UHMW 3M tape, 3 micron IIRC, and cutting strips to just cover the internal support rails inside the focuser housing. The 5 micron is too thick. The tape has to end just before the ends of the rails.

The 'teflon' strip opposite the rails was made of a poorly chosen material that was not slick, so I put the UHMW tape on that as well.

The UHMW tape is awesomely slick, and reasonably durable. PM me if you have trouble finding it, or finding the correct thickness.

It ended up transformed, and was significantly smoother than my ex-Vixen140NA focuser of essentially the same, but better executed design.

The Vixen got the same treatment and is buttery smooth now, better than the very good Synta. It focuses my shorttube Jaeger's refractor.

And buy the Orion Accufocuser. Best possible investment for focusing ease on these refractors.

Well, after the UHMW, that is is.

Edited by markb, 10 October 2019 - 10:38 PM.

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#3 tag1260

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Posted 10 October 2019 - 11:09 PM

Yes, appearance doesn't matter to me but functionality does and that's where mine is sad. I'm seeing all kinds of 5 mil but not any 3 mil anywhere. I'll try again in the morning to see if anyone has it. Thanks



#4 markb

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Posted 11 October 2019 - 07:47 AM

I recall looking at many, many listings as well.

 

Short answer:

 

Tapecase 423-3 UHMW tape, 3 mil UHMW, 2 mil adhesive (as far as I have been able to determine)

 

https://www.amazon.c...e?ie=UTF8&psc=1

 

Long answer:

 

I started thinking about Teflon but it flows under pressure, so no good.

 

A CN post suggested UHMW polyethelene.

 

Complicating matters was the way the descriptions are structured, as the tape is so thin, the adhesive backer starts to make up a significant percentage of the overall thickness!

 

I eventually used the 3M data pages for information on what was available, and how thick the backers and UHMW portion could be expected to be. Adhesive backers run 2-3 mils IIRC. The thinnest 3M product, 5421, was about 7 mils overall. Too thick, as it turned out.

 

https://multimedia.3...TDS 2016_R3.pdf

 

I ended up not trying the 3M tapes due to cost and unfriendly form factors, and they would not have worked anyway.

 

I looked for well reviewed tapes with specifications, and the Tapecase products fit. The sidebar mentions nylon, but they are UHMW PE tapes.

 

Note that the product numbers are similar to the 3M products but are definitely different, the final digit on the Tapcase, but not the 3M, relates to the UHMW layer thickness.

 

From my purchase history, I bought the 5 mil overall, 423-3, 3 mil UHMW + 2 mil adhesive backer,

 

https://www.amazon.c...e?ie=UTF8&psc=1

 

I first tried the Tapecase 423-5 tape but it was too thick. Amazing the difference .002" can make.

 

I have 'slicked' 2 Vixen focusers (apparently pulled for upgrades) and 3 Syntas. Very, very happy with the improvement!

 

The upgrade takes under 5 minutes after the first one. You need 3 strips, 2 for aluminum and 1 for the mystery plastic at the top (particularly important on the Synta, the factory plastic is nearly useless). I trimmed them to exactly match the width of the rails.

 

I cleaned the rails of all grease with acetone and/or lacquer thinner (HD, Lowes, or paint store metal can type), throughly.

 

I have not needed any lube or graphite, this stuff is slick!

 

The adhesive backer has adhered well, no shifting seen.

 

Expect to experiment.

 

You may take a couple of tries to get the correct lengths for the rails, and gluing them straight on a single try. I did not try to restick anything. IIRC I ran the tape nearly to the ep end of the rails, and slightly past the objective end, folding and sticking the excess on the rail end. No issues so far on that. It was a juggle to align the tape with the rail given my giant fingers, but I think a tweezers helped, as did starting at the ep end and making the final stick at the objective end, with extra tape to hold onto, trimmed when finished.

 

Be sure to loosen all the setscrews as you will need the clearance to reinstall the focuser tube. After some experimentation you will figure out the appropriate torque for the setscrews when done. I found that my final adjustment was always for the top two, near the focus lock screw.

 

I keep using this tape, and the thicker 423-5 for a wide range of uses, scope and non-scope. Which reminds me, I have to add a strip to restore smooth unfolding to my convertible top on the car.

 

I have not had to re-do any focusers, but at less than 10 minutes for the procedure, not an issue.


Edited by markb, 11 October 2019 - 07:48 AM.

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