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Author Topic: Gear ratios for standard canned steppers  (Read 59 times)

dodgy geezer

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Gear ratios for standard canned steppers
« on: March 01, 2020, 18:32:43 »

Hi,

I have an EQ3-2 mount and a dual hand controller/stepper set for an EQ-4, with a few spare steppers from other mounts. So the RA tracking is slightly out - which is why I am interested in a DIY stepper controller which I can mod to my non-standard setup.  Buying a new EQ3-2 motor set and throwing the EQ4 one away seems to be rather a costly option.

I am assuming that the standard canned stepper/gearbox unit which is sold with most of the EQ mount range is the same set in all cases. It seems to look the same.  What I am guessing is that:

1 - each mount type has a different worm gear ratio.
2 - this worm gear is directly turned by a standard stepper with gearbox, which has the same internal ratio for every range
3 - this stepper is controlled by a handset with a controller programmed differently for each mount type - so the standard motor turns at a slightly different speed which is correct for the final worm gear ratio.

If this is the case, I can happily use the published EQ3-2 worm gear ratios to program the controller. If not, I will need to find out what the ratio is for the stepper gearbox that I have.

Does anyone know if all the canned steppers for the EQ range are indeed a standard motor/gearbox combination?
 
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ecc2000

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Re: Gear ratios for standard canned steppers
« Reply #1 on: March 01, 2020, 18:47:03 »

Hello,

We find all the characteristics of many skywatcher mounts, ratio, angle of stepper motors, even the number of teeth for gears on the internet!

On Youtube there is also a lot of information!

For stepper motors in principle the angles used are 7.5 and 1.8 !

You can keep your original motors, the main thing is to remove all the gears, and to mount pulleys (GT2) with belts to remove the maximum play in the reduction.

Pierre
« Last Edit: March 01, 2020, 18:50:46 by ecc2000 »
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dodgy geezer

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Re: Gear ratios for standard canned steppers
« Reply #2 on: March 01, 2020, 22:21:42 »

You can keep your original motors, the main thing is to remove all the gears, and to mount pulleys (GT2) with belts to remove the maximum play in the reduction.


I wanted to keep the original motors AND their attached gearboxes, but I wanted to know if these motor/gearbox units, sold for several different EQ mounts, are all standard items with the same gear ratio. That information seems to be hard to find on the Web.

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TCWORLD

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Re: Gear ratios for standard canned steppers
« Reply #3 on: March 01, 2020, 22:39:48 »

Hi,

You can use the exting motors and gearboxes.

There are two different variants of the EQ3-2 out there, the ratios for both of which can be found here: https://www.astroeq.co.uk/tutorials.php?link=ratios

Both of the two configurations are saved as templates in the config utility - on the configuration page you can select the open button and chose one of the two EQ3-2 options.

It's worth trying those first - part of me thinks the reason there are two different EQ3-2 options that I've come across is that one of them uses EQ4 motors as both look the same.

If those don't work, let me know.

Kind Regards,
Tom.
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Tom Carpenter (AstroEQ)

dodgy geezer

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Re: Gear ratios for standard canned steppers
« Reply #4 on: March 02, 2020, 16:03:07 »

Thanks for the rapid response! 

I see that as well as giving rations for the mount worm gear you also give ratios for the stepper motor gears. This answers my question to some extent - it shows that many of the EQ stepper RA motor gear boxes are the same at 120:1 -  the two EQ3 versions and the EQ5, and presumably the EQ2 and the EQ4... 

It is odd to find the Dec motor/gear ration so different. You would think that they could use the same hardware to get the benefit of mass purchase, and then alter speeds inside the controller, where it's only a software load needed.

So I can probably swap motors across different mounts to a certain extent, but I must be careful to only use RA motors for RA, and not Dec...
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