Are these Pittman motors good for 24" f/4 #question


Bill
 

I'm beginning to put this motor drive stuff together after a long time off.  10 years ago I had bought a pair of Pittman GM9236C534-R2 servos 5.9:1 ratio, other markings are 321084-001 Rev B, 30.3 VDC, and a date code of 12-13-97.
I want to start off with just basic tracking for the 24" f/4, I do enjoy the manual hunting but definitely want tracking.  I'm sure I'll end up using the goto eventually, but are these motors sufficient for use with the Servo I?

Other than that, I don't really know how to hook these motors up to my alt & az bearings.  Make JBWeld gears or use a cable drive or something else?  Any tips to get me started would really be appreciated.
Thanks!


James Roe
 

I can't give you a definitive answer, but I've been running a pair of smallish Pittman motors on a 32" f/4 for some time.  It is fully go-to.  Slews horizon to horizon in about 3 minutes (I think).  Properly geared down of course.

Jim Roe


Don W
 

Hi Bill,
The 9000 series servos are bigger than the 8000 series that SiTech sells.  They will work well with SiTech Servo 1.  The SiTech controllers can operate up to 24 volts, which is actually about 28 volts limit (two fully charged 12 volt batteries).  The markings on your servos indicate the windings can work at 30 VDC.  However you "Can" run these on 12 to 15 volts, they just would have less torque, but would probably be well strong enough for your mount.

The 5.9:1 gear ratio needs to have enough additional gearing to get good tracking - total gear ratio to give around 10 million tics/rev.  Your servos have 5.9 x 2000 = about 11,800 tic/rev.  So you need 10 million / 11800 = 847 or more "teeth" if you use a main gear.  A 360 tooth main gear would have 11800 x 360 = 4.25 million.  This is still "too low" but a cog belt drive with 2:1 ratio or a bit more would work fine.  Ideal would be a 360 tooth main gear and a 2.4:1 belt drive from the servo output shaft.

Don W


Bill G
 

I do not know your system, but, it sounds much like what I dd
I bought a bare-bones Losmandy AZ8 and approched both Losmandy and Siderel Technoloigies
My oserving is purely visual, with occassionl side trips to my smart phone .

I needed timing gears and timing belts, a motor conroler, and moter mounts.

All of the components (except the motor mounts) came from SiTech, SC-1or SCii. I have SC-1 dual servo controller

The result is an Alt/AZ mount of typical losamndy quality with tucked in motors, belt drive on both axes and encoders on both shafts . Both motors have an encoder. For'Slew n' Track the motor encoders are used, for'Drag n Track' the shaft encocers are used. On any given night I may Use NexusDSC, SiTechEXE, Cart du Ciel or SkySaffari.

99%  made in the usa, %Australia, if you so choose. 

Once assembled, tuned and aligned on the NCP you are good to go, quietly and accurately

Customer support is excellant and the control box  is bulletproof.

BG
 


-------- Original message --------
From: "Bill via groups.io" <astronutski@...>
Date: 7/22/21 9:41 PM (GMT-05:00)
To: Sitechservo@groups.io
Subject: [Sitechservo] Are these Pittman motors good for 24" f/4 #question

I'm beginning to put this motor drive stuff together after a long time off.  10 years ago I had bought a pair of Pittman GM9236C534-R2 servos 5.9:1 ratio, other markings are 321084-001 Rev B, 30.3 VDC, and a date code of 12-13-97.
I want to start off with just basic tracking for the 24" f/4, I do enjoy the manual hunting but definitely want tracking.  I'm sure I'll end up using the goto eventually, but are these motors sufficient for use with the Servo I?

Other than that, I don't really know how to hook these motors up to my alt & az bearings.  Make JBWeld gears or use a cable drive or something else?  Any tips to get me started would really be appreciated.
Thanks!


Bill
 

Do you have any pictures you can share?  This sounds great. Privately or here?


Bill
 

Wow thank you Don. It’s going to take me a few weeks to digest this LOL. I’m sure there will be follow up questions but I am impressed with your knowledge 😁


Bill
 

Thanks Jim. Can you clutch these things?  I jump all over the sky so I’d like to just grab and point then let the tracking kick in. 


James Roe
 



On Fri, Jul 23, 2021 at 7:48 AM Bill via groups.io <astronutski=yahoo.com@groups.io> wrote:
Thanks Jim. Can you clutch these things?  I jump all over the sky so I’d like to just grab and point then let the tracking kick in. 
_._,_._,_

I don't see any reason why you can't clutch them.  On the other hand you will lose your sync with the sky.  I used this system with a GEM C-14 and moved all over the sky (with a script) as many as 50+ times a night chasing variable stars.

Jim


Bill
 

So do I understand this correctly?  If I have encoders on the Alt and Az axes (in addition to the encoders on the Pittman motors) then I could just drag the scope anywhere and those Alt/Az encoders would track where I am even though the servo's would be slipping?


Bill G
 

The shaft encoders are for manual drag/track, the motor encoders are ignored. The motor encoders are for slew/track, the shaft encoders are ignored. It's one or the other. The servo's are not slipping, the clutches are in drag/track mode. In slew/track, the servo's move the scope by hand pad or planetarium software. Manually pushing the scope in slew/track mode will lose the alignment.

That's how it works with my AZ8. I use a NexusDSC in drag/track and Cartes du Ciel in slew/track modes, most of the time.


-------- Original message --------
From: "Bill via groups.io" <astronutski@...>
Date: 7/23/21 7:57 PM (GMT-05:00)
To: Sitechservo@groups.io
Subject: Re: [Sitechservo] Are these Pittman motors good for 24" f/4 #question

So do I understand this correctly?  If I have encoders on the Alt and Az axes (in addition to the encoders on the Pittman motors) then I could just drag the scope anywhere and those Alt/Az encoders would track where I am even though the servo's would be slipping?


Bill
 

OK Don, thanks again.  I understand what you're saying.  So you would recommend running this at 24v with the motors I do have as opposed to 12v, is that correct?
Also, I'm clueless where to find these gear reducers and belt drive parts.  Do you have any recommendations?  I'll be fine once I have a pile of parts, installing/retrofitting them would be the easy part (I think) for me, but all the calculating for reduction and sources for the parts would be my weak point.  As discussed with Bill below, I really want to do the drag & track as I do enjoy the hunt.  I'm sure eventually I would enjoy the slew-to/goto/tracking.
Thank you!


Bill G
 

I meant to ad that I run my SiTech on 18vDC (battery) and have had no power problems. On twelve volts (Battery) the voltage would drop below the minimum the controller needs from time to time (because I didn't charge the batteries). I don't run anything on 120 with an adapter or with cigarette lighter plugs. If you can, make some Anderson Power Poles to replace the lighter plugs and alligator clips where ever possible.

The toothed belts and pulleys are available from the SiTech  store. My belt drives ar 2:1 (one 16 tooth pulley and one 32 tooth pully. The 16 tooth is on the motor shaft, the 32 tooth one feeds the OldHam coupler/worm assembly. The motor mounts were a 'cut and fit' project with thin plywood and finishing up with 3/16" aluminum from Amazon.

Pictures have been problematic for me both here and on CN. Hopefully my descriptions are helpful.  

BG


-------- Original message --------
From: "Bill via groups.io" <astronutski@...>
Date: 7/24/21 11:38 AM (GMT-05:00)
To: Sitechservo@groups.io
Subject: Re: [Sitechservo] Are these Pittman motors good for 24" f/4 #question

OK Don, thanks again.  I understand what you're saying.  So you would recommend running this at 24v with the motors I do have as opposed to 12v, is that correct?
Also, I'm clueless where to find these gear reducers and belt drive parts.  Do you have any recommendations?  I'll be fine once I have a pile of parts, installing/retrofitting them would be the easy part (I think) for me, but all the calculating for reduction and sources for the parts would be my weak point.  As discussed with Bill below, I really want to do the drag & track as I do enjoy the hunt.  I'm sure eventually I would enjoy the slew-to/goto/tracking.
Thank you!


Don W
 

Hi Bill,
As Bill G mentioned, Sidereal technologies sells cog belts and pulleys.  Also you can get almost anyhting mechanical from McMaster-Carr at

https://www.mcmaster.com/

Running SiTech at 12 volts with you motors would have much reduced torque - meaning they could stall under load forcing the controller to stop and go "Blinky".  Running at 18 to 24 volts would be better.  You can do that with batteries, or with a power supply.  You can also do thet from a 12 volt battery using a voltage adjuster (cheap from China) like:

https://www.amazon.com/DROK-Converter-5-3V-32V-Regulator-Transformer/dp/B078Q1624B/ref=pd_day0_6/147-1409160-0139766?pd_rd_w=KgyMf&pf_rd_p=8ca997d7-1ea0-4c8f-9e14-a6d756b83e30&pf_rd_r=MAP5S7PYTK285YTGYXJR&pd_rd_r=36e8bf64-ff90-45f4-bdd7-6facc639d5a1&pd_rd_wg=SdmMZ&pd_rd_i=B078Q1624B&psc=1

I use one of these to power my SiTech at 15 volts.  Note as Bill G said, SiTech runs OK at 12 volts, but if the voltage sags below 12 volts, SiTech will stop.

Don W


David N.
 

Bill,

Here is a build blog of my recent project: https://www.cloudynights.com/topic/743577-rebuilding-my-50-cent-20-inch-string-telescope/#entry10704656

Should help you visualize and understand the path ahead for you, including fixing mistakes and trying different solutions.  I'm currently getting good results in Drag/Track mode and struggling to get accurate go-to's. 

Good Luck........David