Connect gearbox and confing help #configuration #mount


 

Hello to everyone
I made a handmade carrier, but I couldn't find a suitable gear system for it and an idea came to my mind.
I look forward to your help in this matter.
With worm gear and without counter gear to Ra and dec shaft.
If I connect a geared motor directly
What should I write instead of the gear numbers in the config file?
thanks
 


Khalid Baheyeldin
 

On Sun, Jul 18, 2021 at 01:38 AM, sami wrote:
What should I write instead of the gear numbers in the config file?
If you do not have PEC (most people don't) then you can multiply GR1 X GR2,
and put only one value in the spreadsheet, and the other as 1.

For example, for a direct drive Losmandy G11, GR2 is 360 (because the worm
gear has 360 teeth), and GR1 is 1 since there is no other gear reduction.

If, hypothetically, someone uses a motor with a 5:1 gearbox, then GR1 will
be 5 in this case.

If the only gear reduction is in the gearbox, then put this in GR2, and let
GR1 = 1.


Robert Benward
 

Sami,
From the mechanical perspective, what to use depends on your drive configuration. 

Are you planning on a direct drive (shafts inline)?  If so, then GR2 would be 1.  If you use a stepper motor with a planetary reduction built in, then GR2 = the planetary ratio. You should incorporate a flexible shaft coupling.

If you have the have the shafts parallel, i.e. not inline, then you need gears or belts.  May users choose belts, as they are less critical in alignment and spacing.  If you use gears or belts, then GR2 would equal the motor gearbox x belt ratio.  E.G. a 15:1 planetary plus a 3:1 belt, GR2 would be 15x3=45.  GR1 is the main worm/worm wheel ratio.  Note that you can have a 1:1 belt ratio, it does not have to be a reduction.  Retrofitting existing mounts might have a gear system already implemented.

Most choose the 6mm wide belt with a GT2 profile (the shape of the teeth).  You can find these belts and pulleys on Amazon.  Pay attention to the shaft diameters.  Typically, the motor shafts are metric, 5,6, or 8mm.  As for the mount,  Losmandy uses inch, so you are looking at 1/4" worm shaft.  Other mounts made in China or Japan would use metric.  You can find the smaller belt pulley in metric and the larger in inches (6.35mm=1/4").

Hope this helps.
Bob


Johnnie Pattison
 

I asked a similar question about gearing this past week and received a different answer. 100:1 Planetary motor with 20 tooth pulley -> 100 tooth pulley attached to the shaft. GR1 = 100 GR2 = 5. According to this description, it would be 100 x 5 for GR2. Very confused.


On Sun, Jul 18, 2021, 10:29 AM Robert Benward via groups.io <rbenward=verizon.net@groups.io> wrote:
Sami,
From the mechanical perspective, what to use depends on your drive configuration. 

Are you planning on a direct drive (shafts inline)?  If so, then GR2 would be 1.  If you use a stepper motor with a planetary reduction built in, then GR2 = the planetary ratio. You should incorporate a flexible shaft coupling.

If you have the have the shafts parallel, i.e. not inline, then you need gears or belts.  May users choose belts, as they are less critical in alignment and spacing.  If you use gears or belts, then GR2 would equal the motor gearbox x belt ratio.  E.G. a 15:1 planetary plus a 3:1 belt, GR2 would be 15x3=45.  GR1 is the main worm/worm wheel ratio.  Note that you can have a 1:1 belt ratio, it does not have to be a reduction.  Retrofitting existing mounts might have a gear system already implemented.

Most choose the 6mm wide belt with a GT2 profile (the shape of the teeth).  You can find these belts and pulleys on Amazon.  Pay attention to the shaft diameters.  Typically, the motor shafts are metric, 5,6, or 8mm.  As for the mount,  Losmandy uses inch, so you are looking at 1/4" worm shaft.  Other mounts made in China or Japan would use metric.  You can find the smaller belt pulley in metric and the larger in inches (6.35mm=1/4").

Hope this helps.
Bob


Khalid Baheyeldin
 

On Sun, Jul 18, 2021 at 01:08 PM, Johnnie Pattison wrote:
I asked a similar question about gearing this past week and received a different answer. 100:1 Planetary motor with 20 tooth pulley -> 100 tooth pulley attached to the shaft. GR1 = 100 GR2 = 5. According to this description, it would be 100 x 5 for GR2. Very confused.
The gearboxes in stepper motors are already named after ratios.
So your planetary is 100:1, hence GR1 = 100.
The pulleys are named by number of teeth, so you have to calculate the ratio yourself.
100T to 20T = 100/20 = 5, so GR2 = 5 in your case.


Johnnie Pattison
 

Thank you


On Sun, Jul 18, 2021, 11:17 AM Khalid Baheyeldin <kbahey@...> wrote:
On Sun, Jul 18, 2021 at 01:08 PM, Johnnie Pattison wrote:
I asked a similar question about gearing this past week and received a different answer. 100:1 Planetary motor with 20 tooth pulley -> 100 tooth pulley attached to the shaft. GR1 = 100 GR2 = 5. According to this description, it would be 100 x 5 for GR2. Very confused.
The gearboxes in stepper motors are already named after ratios.
So your planetary is 100:1, hence GR1 = 100.
The pulleys are named by number of teeth, so you have to calculate the ratio yourself.
100T to 20T = 100/20 = 5, so GR2 = 5 in your case.


 

exactly what I want to do is make a reducation like in this video and connect it directly to the RA shaft without gearing up 


 

https://www.youtube.com/watch?v=Dmi01grPYCI


 

https://www.youtube.com/watch?v=6pDPNkWU2vo
to make a gearbox like this link and connect it directly to the shaft to make it work without any gears in between.
because it's too expensive to get gears where I am 
That's what I think of him.


Khalid Baheyeldin
 

Sami,

Roman Hujer, the designer of this portable mount, already has the calculations in this link

https://www.thingiverse.com/thing:2748281


 

The telescope I'm going to use is heavy, so it needs to provide about 40 kg of torque.
 


 

pictured
pictured
I'm doing the same transporter, but it's bigger, so I'm trying to make it work with a direct shaft connection because it doesn't have the right gear. 
 
 


 

Khalid Baheyeldin
              // Axis1 is for RA/Az
#define StepsPerDegreeAxis1  12288.0  // calculated as    :  stepper_steps * micro_steps * gear_reduction1 * (gear_reduction2/360)
             // NEMA17 + PLANET   :  200  * 16  * 27/20   *  1024/360   = 12288.0
             // Axis2 is for Dec/Alt
#define StepsPerDegreeAxis2  12288.0   // calculated as    :  stepper_steps * micro_steps * gear_reduction1 * (gear_reduction2/360)
             // NEMA17 + PLANET  :   200  * 16   * 27/20  * 1024/360    = 12288.0                                     
             // PEC, number of steps for a complete worm rotation (in RA), StepsPerDegreeAxis1*360)/gear_reduction2.  Ignored on Alt/Azm mounts.
#define StepsPerWormRotationAxis1 4320L   
             //  NEMA17 + PLANET  : (12288*360)/1024 = 4320

Can I copy it and paste it into the configuration?


Khalid Baheyeldin
 

This code snippet is from an old version of OnStep. It does not apply, as is, to 4.x.

And you can use those values only if your hardware is identical to what Roman Hujer designed.

Now I am not sure what you are trying to do. The picture you posted is not Roman's portable telescope.

Please try again to explain in detail what you are trying to do.
Specifically, what is the motion transfer from the motor to the axis, and all gear reduction in between.

Use Google Translate if you need to.


 

Khalid Baheyeldin
Let me put it this way:
I'm doing the same project as the picture I took above.
since I could not find a gear system accordingly,
I want to run it directly by powering the ra and dec shaft,
I've decided to do the same with Roman Hujer's planetary system.
for this, I will write about how and where to write the desired rate of the required gearbox in the configuration file.
I hope it's more understandable.
I wrote it using translation.
 


 

Halid Baheyeldin
Let me put it this way:
I'm doing the same project as the picture I took above.
since I could not find a gear system accordingly,
I want to run it directly by powering the ra and dec shaft,
I've decided to do the same with Roman Hujer's planetary system.
how, where, how to rate the required gearbox required in the configuration file for this. I can write.
I hope it's more understandable.
I wrote it using translation.
 


Robert Benward
 

I am reading some of these posts and I think there is some confusion about gear ratios.  Whether you call it GR1 or GR2 is irrelevant.  Most seem to call the final stage GR2, which is what it is called in the Excel spreadsheet (forgive me, I may have reversed them in my previous post). 

The final stage is the worm and the worm wheel (or just worm & wheel), the part that usually comes on your equatorial mount.  The worm wheel is usually 360 teeth, 180 teeth, 144 teeth, and some less that that depending on the size of your mount.  The other gear is the worm, and 1 revolution of the worm advances the worm wheel 1 tooth.  Thus all these ratios are 360:1, 180:1, 144;1. etc...  

The other stage is GR1.  This stage comprises the gear reduction from the motor going to the worm (and everything in between), so if you have a 4:1 belt, that figure is included here.  If your motor has a planetary gear reduction, that value can go in one of two places.  Let say your stepper is a 200 step type, and you have a 100:1 planetary after it.  So the gear train looks like this>  200step/rev motor,  100:1 planetary, 4:1 belt, 360:1 worm & wheel.  You can incorporate the planetary ratio in the steps/rev, so that figure would be 2000steps/rev, and the GR1 would be just the belt, or 4:1.  Or, you can put the planetary (100:1)  with the belt reduction, so the GR1 would be 4:1 x 100:1, or  400:1.  In any case, they are all multiplied together, which is the salient point.  Note, many will combine the planetary ratio with the stepper's # of steps/rev, since they come together as once piece.  What ever works for you, as long as all ratios are included.

What is important when using high planetary ratios (or any high overall reduction ratio), is you generate high RPMs at the stepper. But, there is also an RPM limitation.  These steppers peter out after 1000rpm, and many lose much or all of their torque beyond that.  The other limit is the 60,000steps/deg.  Once you set the desired slew rate, this puts a demand on the processor to generate the required steps over a given period of time.  This is the 60,000 limit.

Many prefer larger size steppers with high torque, which don't need the planetary's torque multiplication benefit.  A favorite is 400step motor with micro-stepping and direct coupling.  The spreadsheet will provide the tracking resolution.

Use the Excel spreadsheet. 

Hope this helps to clear up some confusion.

Bob


Lyle Stephens
 

Wouldn’t a 200 steps per revolution motor with a 100:1 planetary after it result in 20,000 steps per revolution, not 2000?

 

Lyle

 

From: main@onstep.groups.io On Behalf Of Robert Benward via groups.io
Sent: Sunday, July 18, 2021 9:53 PM
To: main@onstep.groups.io
Subject: Re: [onstep] Connect gearbox and confing help #configuration #mount

 

I am reading some of these posts and I think there is some confusion about gear ratios.  Whether you call it GR1 or GR2 is irrelevant.  Most seem to call the final stage GR2, which is what it is called in the Excel spreadsheet (forgive me, I may have reversed them in my previous post). 

The final stage is the worm and the worm wheel (or just worm & wheel), the part that usually comes on your equatorial mount.  The worm wheel is usually 360 teeth, 180 teeth, 144 teeth, and some less that that depending on the size of your mount.  The other gear is the worm, and 1 revolution of the worm advances the worm wheel 1 tooth.  Thus all these ratios are 360:1, 180:1, 144;1. etc...  

The other stage is GR1.  This stage comprises the gear reduction from the motor going to the worm (and everything in between), so if you have a 4:1 belt, that figure is included here.  If your motor has a planetary gear reduction, that value can go in one of two places.  Let say your stepper is a 200 step type, and you have a 100:1 planetary after it.  So the gear train looks like this>  200step/rev motor,  100:1 planetary, 4:1 belt, 360:1 worm & wheel.  You can incorporate the planetary ratio in the steps/rev, so that figure would be 2000steps/rev, and the GR1 would be just the belt, or 4:1.  Or, you can put the planetary (100:1)  with the belt reduction, so the GR1 would be 4:1 x 100:1, or  400:1.  In any case, they are all multiplied together, which is the salient point.  Note, many will combine the planetary ratio with the stepper's # of steps/rev, since they come together as once piece.  What ever works for you, as long as all ratios are included.

What is important when using high planetary ratios (or any high overall reduction ratio), is you generate high RPMs at the stepper. But, there is also an RPM limitation.  These steppers peter out after 1000rpm, and many lose much or all of their torque beyond that.  The other limit is the 60,000steps/deg.  Once you set the desired slew rate, this puts a demand on the processor to generate the required steps over a given period of time.  This is the 60,000 limit.

Many prefer larger size steppers with high torque, which don't need the planetary's torque multiplication benefit.  A favorite is 400step motor with micro-stepping and direct coupling.  The spreadsheet will provide the tracking resolution.

Use the Excel spreadsheet. 

Hope this helps to clear up some confusion.

Bob


Virus-free. www.avg.com


Robert Benward
 

Yes!!  It was late, and I was tired when I replied.  You are 100% right, it should be 20,000, I had a 10:1 planetary in my head because that is what I am pursuing.   Good catch.  But I hope the post cleared up a few things??

Bob


George Cushing
 

And of course there's this approach. 



Worm gears from a Celestron fork mount. 

180 tooth Meade 2080 set:



I have about a half a dozen Meade sets.