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Mr. Edmund gets a Drive

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#51 DAVIDG

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Posted 10 May 2013 - 01:45 PM

Check that you have the single ball bearing still in place that puts pressure on the cam. It is located under the metal strip on the side of the drive. It sounds like it is missing or might have a flat spot worn in it.

- Dave



#52 john gabriel

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Posted 10 May 2013 - 03:46 PM

Thank you Dave. I did have that apart for cleaning, inspection, and lube when I rescued the scope. I will check again, but the ball bearing looked fine / unworn at the time. The wiggle in the cam pin seems to be as much at the lower end of the housing as at the upper end where the ball is, but I will recheck the ball for wear anyway.

I have no idea if the timing adjust was actually used by prior, original, owner, but in other areas it's apparent that he did not lube the mount. I obviously need to take it apart again and inspect the pin tolerance in the housing more closely.

I just wondered if others who use these had noticed the lash as common / design issue and what, if anything, people had done to reduce the problem

#53 tim53

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Posted 10 May 2013 - 04:09 PM

I don't think the Meade Newtonians ever had driven RA circles either


I think the RA circle on my 645 turns with the clock. It's loosely friction fit so that you can reset it.


The pointers are on the dec casting, so they're driven, but the RA circle is on the RA casting and doesn't move except when you turn it manually. If it were driven, it would move with the pointers. Since it doesn't, you have to reset the circle before you leave one object and move to the new target. A driven RA circle only needs setting once at the beginning of an observing run.

-Tim.

#54 rdandrea

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Posted 10 May 2013 - 04:12 PM

the RA circle is on the RA casting and doesn't move except when you turn it manually



Tim, I'll go out to the garage to check it out one of these days.

#55 john gabriel

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Posted 10 May 2013 - 04:36 PM

With this Edmund drive, I put a nice RA circle at the outer end of the polar axis, on the inner clutch plate no less, and will be mounting the pointers (vernier index) to the drive gear. This allows the RA to remain constant while tracking / viewing and then change when slewing to another object.

#56 actionhac

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Posted 10 May 2013 - 07:32 PM

Let me know if this is readable. If not I can send by email.

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#57 actionhac

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Posted 10 May 2013 - 07:41 PM

Dave I have a inverter 12VDC to 115V I use, and most of the time I plug into house current from where I observe on my driveway. Its not the best situation observing from a giant slab of concrete heat sink but otherwise I have hardly any level lawn. I really want to do something about this soon.
John have you checked the gear lash for play? if you have the eccentric slo-motion pin pinched without play try taking up any play in the gear lash. It doesn't seem possible the slo-motion shaft would be worn in the housing since it gets used so little but it should be tight in the housing. Your idea of sleeving the housing would be what I would do before making a new shaft with eccentric pin. If it isn't too bad you can have the shaft plated to increase its diameter.

Robert

#58 DAVIDG

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Posted 10 May 2013 - 09:38 PM

Robert,
Many thanks for posting the design of the setting circle adapter. I found a few sentences and a drawing of it in All About Telescopes as well. I'll see if I can machine the parts up for my mount.

- Dave

#59 actionhac

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Posted 11 May 2013 - 06:34 PM

I was rooting around in the Edscorp box again today.
This is a brand new 1/4" focal length Ramsden eyepiece. Instructions is Rev. 6/75.

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#60 actionhac

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Posted 11 May 2013 - 06:43 PM

Here are a pair of Ramsden, 1/4" focal length and 1/2"fl.
The 1/4" has a problem. I will need to take it apart and look for a flipped element. The tiny little elements in a short fl eyepiece is a very rewarding challenge to take apart and reassemble and not have a coronary.
Notice these do not have the focal length stamped on top, older or newer, anyone know?

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#61 actionhac

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Posted 11 May 2013 - 06:50 PM

Edmund eyepieces are different. The whole eyepiece is one machined piece of aluminum and the only removable part is the lens retainer inside as shown on the left. You unscrew it and that is it to get the guts out. When you screw the retainer back in you do it ever so carefully by hand just to the point when you can no longer hear any rattle from the elements.

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#62 amicus sidera

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Posted 11 May 2013 - 11:24 PM

Its not the best situation observing from a giant slab of concrete heat sink but otherwise I have hardly any level lawn.


Robert, you might find that soaking that concrete pad with water just before sunset cools it off pretty quick, and really improves ground seeing. I sometimes observe over concrete, and give it a good soaking with a hose once the pad is in the shade just prior to dusk; it's a very effective way to cool off such a surface rapidly.

Following your posts here with much interest; excellent work!

Fred

#63 actionhac

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Posted 12 May 2013 - 12:13 AM

Thats not a bad idea Fred! I'm going to try it. It will also reduce the pollen and dust around my scope wetting down the slab.
I can move to the lawn, its not difficult leveling a tripod. It is a royal pain though to level a pier so I'm just a creature of habit and stick to the slab.
I'll try soaking it down. Its not something I'll need to do everytime, only when its a very hot day and I predict a colder night.

Robert

#64 amicus sidera

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Posted 12 May 2013 - 08:17 AM

Hope it works well for you, Robert; the only caveat being that this method is naturally less effective in humid conditions, as it relies upon evaporation to accomplish cooling.

Fred

#65 john gabriel

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Posted 12 May 2013 - 08:14 PM

Robert, thank you for your suggestions sources of lash in the polar axis lash. I had it apart again yesterday, and:
1. The lash at thrust bearing, worm, and drive gear are zero - that's been adjusted pretty closely.
2. There is no visible wear on ball bearing, and leaf spring supporting the cam pin is plenty stiff.
3. Lash at the outer end of cam pin inside of its housing seems to be half the problem, even though as you say this should have little wear. It does have some wiggle, and I have those two posts on either side of the cam pin as snug against the cam as I can get them.
4. The other half of the lash problem is obviously coming from slop in the fit of polar axis in its casting. The teflon sleeve on the lower end of polar axis is cracked and probably should be replaced with a "new" one or some shim / sleeve of same thickness

I see no real advantage to the minimal "slo-mo" control. Seems it would be better if the tangent and its worm support were solidly fixed to the RA housing without the cam pin arrangement entrained. In any case, I've found I can live with the lash, as long as I remember to push the scope "eastward" to the target I want to track. :grin:

#66 actionhac

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Posted 12 May 2013 - 11:34 PM

Look at this drive and the added screw to tighten the slo-mo shaft housing:
http://www.ebay.com/...ric-Clock-Dr...
If your play is 1/2 the polar shaft bushing and 1/2 the slo-mo housing, at least you have identified the source of the problem and can live with it the way it is. The older mounts used bronze bushings and you could knurl the bushing OD and when you put it back in the housing the bushing ID would tighten. Not much you can do with the Teflon. I suppose you could try hand knurling the outside of the bushing.
The added screw above really isn't a bad idea, to tighten up the play in the slo-mo shaft housing. I'd rather not drill a hole in my housing though. Unless I'm mis understanding the real intention of the screw, it may be a lock I guess.

Robert

#67 john gabriel

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Posted 14 May 2013 - 12:45 AM

Thank you, Robert. If I want that thing tight, I'm gonna have to tinker with it some. It seems that a good fit on polar shaft would have been better than the teflon thing, but as they say, "It is what it is". It's a good solid mount, and it does track well if I come into the target object from the right direction to take up the lash when starting to track. :)

#68 actionhac

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Posted 15 May 2013 - 12:58 AM

Pacific Instruments:
http://geogdata.csun...nst/pacinst.pdf
made a great 1" drive. And it will work on a Edmund 1" mount.
Adaptable to most telescopes. Easy to work on and also sports a driven setting circle.
You see these for sale from time to time. Pacific Instruments is stamped into the drive so most of the time the seller knows who made it and will advertise it as a Pacific Instruments clock drive.
Here I have one on a larger 1.5" Edmund mount. Edmund reduced the polar shaft to 1" for the drive.

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#69 john gabriel

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Posted 15 May 2013 - 05:16 PM

Hi Robert - not sure what you imply there - is it out of production meaning I have to find it used? That's a nice looking set of circles going with it, especially if still being sold new.
John

I see from a little looking and reading that these are no longer being made - at least those by Pacific Instruments.

#70 actionhac

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Posted 15 May 2013 - 05:36 PM

Hi John.
I thought I would post a picture of something besides a Edmund drive to show everyone that other drives will fit.
Pacific Instruments is no longer in business but its good gear and quite common on the used market. I particularly like the 1" mount also.
Here is another Pacific Instruments drive on a Cave mounting. Someone spent some time to get this to work since it required a pretty fancy adapter attached to the bottom of the polar shaft housing.

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#71 wfj

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Posted 15 May 2013 - 08:28 PM

Robert,

I've also seen Meade drives on Astrola's. Here's a Jaegers mount with an Edmund drive.

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#72 actionhac

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Posted 15 May 2013 - 08:55 PM

I love the red knobs on Jaegers stuff!
Your drive has the rare automatic RA circle kit installed we were just talking about earlier.

Robert

#73 actionhac

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Posted 15 May 2013 - 10:20 PM

I decided to take a closer look in the catalogs for the driven RA circle kit.
It's in the catalog! just no picture, so I failed to see it!
Well right there under my nose, catalog #671 (1966) it is a new item for this catalog:

"NEW! CLOCK-DRIVEN RIGHT ASCENSION CIRCLE Mounts directly on clock drives to provide sidereal time and eliminate calculation of star positions. Stays true to moving star pattern without your having to correct it. Black phenolic circle with pointer and mounting hardware. No. 60,569 $9.00 Ppd.".

Robert

#74 actionhac

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Posted 15 May 2013 - 11:11 PM

Here is the far-out cover.

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#75 wfj

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Posted 16 May 2013 - 03:38 PM

Your drive has the rare automatic RA circle kit installed we were just talking about earlier.

Hmm. You're right Robert - its right in front of me. I guess I'd better pay more attention in class :)

Now I guess I'd better find those setting circles and pointer ... where to look in the 40+ year pile of astro stuff ....

Thanks for noticing!






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