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Equipment Discussions >> Mounts

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Jesus Munoz]
      #5869486 - 05/18/13 02:45 PM

It is an encoder that measures pe on the axis and corrects for it in real time via guide port. A bit expensive bit rhe price has come down a bit.

Edit: TDM is short for Telescope Drive Master


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Hilmi]
      #5870678 - 05/19/13 02:56 AM

I just placed my order for 2 gearboxes from RS Components. They expect the gearboxes to arrive in 10 days time. Local custom is for shops to over promise and under deliver, so I will assume they will take 2 weeks to deliver. I have also ordered a pinion puller and some brass tubing from eBay. One ships from the US and the other from UK so I guess the US shipment will be late due to the new postal security checks. So overall I think I will have everything needed to upgrade the gearboxes in 3 weeks time. I'll see how it goes from there.

I'm not sure how I will ream the pinion as my Dremel Bits are metric. I have a Dremel press attachment, so I should be able to drill straight down, but I'm not sure how to secure the gear so it doesn't slide or rotate without damaging it. I guess one way to do that would be to make a hole on a piece of wood to place the gear in. I guess the hole should be a tight fit but not so tight as to damage the gear teeth.


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: JSeay86]
      #5870835 - 05/19/13 07:43 AM

Quote:

Finally, I installed a small stainless steel shim between the M2.5 mounting screws and the screw slot on the new high torque motors. The other option is to drill and tap the gearboxes to accommodate 4-40 screws like those used with the stock Losmandy gearboxes. I chose the shims instead to avoid opening up the gearboxes to drill and tap.




I'm a bit confused about this step, especially when I looked at some online directions that said the following about the same step.
Quote:

As the new screws are slightly undersized, put a wrap or two of tape around them where they fit through the motor housing.
The motor is in a very slightly different position, so only tighten the gearbox cover screws after you have fitted the motor.




So I figure a picture is worth a thousand words. What exactly is it you are talking about? I'd like to understand before I place my order for the screws.


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Geo.
Carpal Tunnel
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Reged: 10/01/08

Loc: Upstate NY
Re: Ovision upgrade new [Re: orlyandico]
      #5870978 - 05/19/13 09:33 AM

Quote:

2) the motor gearbox contributes significant PE; we know on the CGEM it can be as high as 25" p-p (can be more than the worm fundamental) but for good-quality Japanese gearboxes the gearbox PE would be around 5" p-p




Orly, any idea of what reduction Celestron is using for the CGEM?


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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: Ovision upgrade new [Re: Geo.]
      #5871307 - 05/19/13 12:41 PM

Hi George, do you mean the gearhead reduction? it's 57.xxxx (some weird irrational ratio) in the Igarashi gearbox.

Hilmi - do not try to ream out the holes with your dremel drill press!!!!!! get someone with a LATHE to do the reaming for you.

Trust me, I tried reaming out the 5mm holes in my AP600's spur gears to 6mm myself. The holes came out not perfectly square and it increased the periodic error. I had to buy new spur gears from AP (good thing they still sell parts for a 25-year old mount!)


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: orlyandico]
      #5871340 - 05/19/13 01:02 PM

1 mm of reaming is a lot to. I was going to attempt 0.2 mm. The bit should self center if done 0.1mm at a time. I have had very little success finding a high precision machine shop in Oman. All the shops I found deal with heavy industrial equipment. I once paid $500 to get a pier plate adapter made and they got it all incorrect even though I gave them cad blue prints.

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JSeay86
sage


Reged: 04/26/09

Loc: Tulsa, OK
Re: Ovision upgrade new [Re: Hilmi]
      #5872704 - 05/19/13 10:27 PM

Orlandico is right, do not use the Dremel tool to ream out the pinion. Luckily I work with an experienced machinist that helped me out a bit with this. I used a low melting point alloy, and made a small casting with the pinion gear in the middle. This conforms to the gear teeth and holds the pinion gear during the reaming process. Then, I reamed out the pinion with a 0.125" straight reamer. You are only reaming out 0.175 mm. This was done on a mill, and I rotated the spindle slowly by hand, and lubricated the bit with a little 3 in 1 oil.

I will get a picture of the spacers that I used for the M2.5 screws. This was my alternate to the tape mentioned above, and it will hold everything square.

Tomorrow I will take some pictures of everything and post with more details.

Edited by JSeay86 (05/19/13 10:32 PM)


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: Ovision upgrade new [Re: JSeay86]
      #5872814 - 05/19/13 11:23 PM

Hilmi, maybe you can pay someone to do the reaming-out for you.

I know the bit will "probably self-center" but if it doesn't... or it's not precise... you'll lose whatever benefits you hoped to gain from the Maclellan gearbox. We're talking about 1" to 2" levels of precision here.

EDIT: please see my post in your other thread. I would be more comfortable with that route (hand-ream the hole with an actual reamer, of the correct diameter).


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JSeay86
sage


Reged: 04/26/09

Loc: Tulsa, OK
Re: Ovision upgrade new [Re: orlyandico]
      #5874465 - 05/20/13 07:09 PM

Alright, finally got around to taking some images.

As mentioned above, there are several things that you need to do for the McLennan gearbox conversion, and the details below correspond to a McLennan conversion using the new Losmandy high torque servo motors. The McLennan gearboxes that I ordered can be found HERE. Ok, the primary steps are as follows:

1. Ream out the pinion gear that comes with the McLennan gearbox so that it fits the output shaft of the new high torque servos. The ID bore of the supplied pinion is 3.0 mm, and the output shaft of the high torque servos is 0.125" (3.175mm). Here I used a 0.125" diameter straight reamer bit. Do this step on either a mill or lathe, and take care to keep the bit square to the pinion bore, as orlyandico stated, and take care not to damage the teeth of the pinion gear!. This step is the trickiest.

Once this is done, install the pinions onto the motors using the pinion spacer tool supplied with the McLennan gearbox (0.9mm spacing), and Loctite. After doing some research, I chose to use Loctite 680. Install and let dry for 24+ hours.

2. Enlarge the mounting holes on the new McLennan gearboxes (the holes for mounting the gearbox to the mount body), so that they fit over the threaded rods that stick out on the G11 mount. I used a 3.95 mm diameter drill bit here.

3. The output shaft of the new McLennan gearboxes is a different size than the stock Losmandy gearbox, so you can either use the existing Oldham style motor couplings with some slight modifications, or you can order new couplers that fit the new shaft.

You can use your stock Oldham couplers, and follow the steps listed HERE, OR you can order Ruland style couplers to replace the Oldhams, OR you can order new Oldham style couplers that fit the new shaft. I chose the last option, and here are the part numbers you need to order from the Ruland website:

-2 each of Part #: OD8/13-AT
-2 each of Part #: MOST13-4-A
-2 each of Part #: OST8-4-A

Once assembled, these will fit both the 4mm output shaft of the McLennan gearbox and also the 0.25" shaft of the worm gear, and the complete couplers have roughly the same exterior dimensions (length and OD) as the original Oldham couplers from Losmandy.

4. Elongate the mounting holes on the stock gearbox covers to accomodate the slightly different mounting location of the motors.

5. The motor mounting holes in the McLennan gearboxes are m2.5 thread, and the stock Losmandy gearboxes are threaded for 4-40 screws. 4-40 screws are supplied with the new high torque servos. Here you have 2 options:

a. Drill and tap the McLennan gearboxes to 4-40 thread. If you choose this option then it would be best to remove the plate on the gearbox that you are needing to tap. This will prevent you from getting any small pieces of metal & shavings (from the drilling/tapping process) inside the gearbox housing.

b. Don't tap the new gearboxes, leave as M2.5 thread. Order M2.5 x 16mm screws to mount the gearboxes. Then, you will need some sort of shim to fit between the M2.5 screws and the mounting screw holes on the high torque servos (which are meant for 4-40 screws) to keep everything tight, as the M2.5 screws will just fit loosely in the mounting holes because their OD is too small. I would not just use tape, I chose to order some stainless steel spacers here that were close to the finished size I needed. Part numbers below for screws and spacers from McMaster Carr.

- 92321A014 (stainless steel unthreaded spacers)
- 92290A065 (SS Socket head cap screw, M2.5 x 16mm, 0.45mm pitch)

The ID bore of the spacers will have to be very slightly enlarged with a drill bit to fit the screws. Also, the OD will have to be turned down very slightly to fit snugly into the mounting holes on the high torque servos. I intentionally ordered the length oversized here, so that you can mount the spacers into a drill bit chuck for these modifications. For turning down the OD, I mounted the spacer in a drill bit chuck and spun it against some fine grit sandpaper. Finally, you will need to take the length down on the spacer to fit properly in the mounting holes on the servo motor.

Here is an image of the mounting holes on the high torque servo motors without spacers:



and here is an image of the mounting holes with spacers installed:



The M2.5 screws fit tightly into the spacers to keep everything square, and the spacers fit snugly into the mounting holes on the motor.

Edited by JSeay86 (05/20/13 07:22 PM)


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JSeay86
sage


Reged: 04/26/09

Loc: Tulsa, OK
Re: Ovision upgrade new [Re: JSeay86]
      #5874476 - 05/20/13 07:12 PM

Please let me know if anything is unclear from the post above, there is a lot of info buried in there. Here is an image of the new gearboxes installed on the mount. I am awaiting my Loctite to arrive in the mail so that I can install the pinions (local hardware stores didn't have the right kind). It will arrive tomorrow, and I should have everything bolted on and ready to test on Wednesday night. I'll report back.



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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: JSeay86]
      #5874980 - 05/20/13 11:45 PM

Clear as can possibly be. I think the simpler option would be to get the gearbox rethreaded though. Making those spacers sounds complicated if you dont have access to a lathe machine

I appreciate the work you have done with that write up


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GeHe
super member


Reged: 08/06/11

Loc: Germany
Re: Ovision upgrade new [Re: Jesus Munoz]
      #5877400 - 05/22/13 03:45 AM

hi hilmi ,
i have the ovision-worm in my Losmandy g11 , additionally , since this week wit TDM , see the graf in this treat :

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5875889/page...


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade [Re: GeHe]
      #5877416 - 05/22/13 04:26 AM

Those are very nice results. I will keep you posted once my gear arrives.

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Hilmi]
      #5885034 - 05/26/13 02:41 AM

9 Days after the Package was shipped from Ovision in France and the Colissimo web page is saying "Your parcel is getting ready to leave the country of origin" This update was on the 23rd and no update since then. So I am assuming my Ovision worm has still not left France. I am proud to say that I no longer consider my countries Postal service the worst in the world, looks like the French have outdone us!

Edit: I retract the above statement, we still hold the position of worst postal service in the world. I called the post office and the package has finally arrived. Perfect timing too as I wanted to do this upgrade before I went camping next weekend.

Edited by Hilmi (05/26/13 03:17 AM)


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Hilmi]
      #5885131 - 05/26/13 05:43 AM

Got the package and started installing it during lunch break, didn't finish the job as I am supposed to meet somebody in the office soon. Here are my observations so far.

-The worm gear was packaged in an inflated nylon bag which was then covered in foam peanuts which was then in a small box which was then covered in more foam peanuts then the outer box. Although the outer box was crushed, the interior box was in perfect condition. Packaging gets 10/10 for protecting such a delicate item.

-If you have the OPWB installed in both axis as some people have done, you will need to get hold of some screws and parts to install the new worm block. This is due to the fact that the new worm block does not fit into the OPWB cradle. It also requires some parts from the standard worm block, those parts being the cover and the Oldham Coupler.

-The Ruland coupler that comes with the OPWB will not work with the Ovision worm block, there isnt enough space between the gear box and the worm block. You need to move the Ruland Coupler to the Dec axis and take the Oldham coupler from the Dec axis and install it on the RA with the Ovision worm and worm block.

-The worm seems to be very well machined and it moves very smoothly on the bearings when turned by hand. I also found it much easier to pop into place than the OPWB. On the downside, for some reason, I found it very fiddly to get the screws into the screw hole when I tried to screw it on. I can't explain why that is the case.

Further info coming soon as I finish the install. Will probably post PE figures tonight or tomorrow night.


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Hilmi]
      #5885876 - 05/26/13 04:54 PM

OK, the first run I did of PEMPro reported a Peak to Peak PE of 3.75 Arc Sec. I suspect something is wrong though because my first worm period looked funny. I must have bumped into the mount. I am rerunning it now to validate. The curve generated from the first run looks very smooth. I'll post the second one once I have finished collecting the data. I'll keep you posted.

And before anybody asks. I did run the calibration wizard, twice just to be sure. Anyway, by the end of this second run I will know for sure


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Hilmi]
      #5885909 - 05/26/13 05:15 PM Attachment (24 downloads)

OK, here is my second test. This is unbelievable for me. The mount PE has gone down to less than 30% its original PE! I cant wait to see what I will end up with once I also install the gearboxes.

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Hilmi]
      #5885936 - 05/26/13 05:26 PM Attachment (21 downloads)

And here is the tracking with PEC training. I am also now taking a single exposure of 240 Seconds (1 worm period) unguided. After I post that I am off to sleep and I will be dreaming of unguided imaging

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Ovision upgrade new [Re: Hilmi]
      #5885958 - 05/26/13 05:45 PM Attachment (29 downloads)

OK, here is a test image, screen capture at 1:1 scale. The image scale is 0.6 Arcsec per pixel. Still not perfectly round, but I believe this level of star roundness is perfectly serviceable. It might even be due to collimation. I'll be testing that tomorrow.

I wonder if the gearbox upgrade (once it finally arrives) will get rid of the residual oval shape of the stars. If the mount continues to behave like this then I no longer have any regrets buying the G11 other than the time wasted troubleshooting.


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: Ovision upgrade new [Re: Hilmi]
      #5885974 - 05/26/13 05:56 PM

Nice improvement Hilmi!

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