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[cuivenion]

Hi, I'm wanting convert my EQ5 to a direct drive, bypassing the worm and using a timing belt to drive the worm gears. I'm a bit of a layman in these matters so any help would be great. Here are things I'm getting stuck on.

- Are there any timing belts that would fit the teeth on the worm gears of the EQ5?

- As far as I'm aware the lower the gear ratio the better for the motor, it doesn't have to spin as fast and it can produce more torque. So  I'm thinking of a timing pully like this:

http://www.beltingonline.com/72-tooth-xl-pulley-al72xl037-5215

With the correct gear and teeth of course.

How does this sound? Any help would be very appreciated.

[TCWORLD]

You're going to end up with an incredibly low gear ratio. The EQ5 worm gear has 144 teeth. If you connect it directly to a motor with a 72T pulley, you'll end up with a total gear ratio of only 2:1!

AstroEQ won't support a ratio that low. Theoretically you need a minimum of 80:1 but that low would give you a resolution of only 2.5 arcseconds per microstep. Practically a minimum total gear ratio of 200:1 is required.

[cuivenion]

Ah, I see. Thanks for the reply, would you have any suggestions on how to go about this. I'm mainly thinking of bypassing the worm entirely. That way there would be zero backlash and the mount would be a lot more accurate.

I don't doubt you're right but I'm wondering how I achieve the suggested ratio if I'm connecting to the worm gear directly.

[TCWORLD]

Short of going for as low tooth count as possible pulley for the motor, and using a motor with a low backlash planetary gearbox, I don't see how it's possible. You would need a gearbox of around 50:1 or higher, and then a pulley of at least 19 teeth.

[cuivenion]

Looks like it might be a lot harder than I first thought, I'll get back to trying to get the backlash out of my dec axis.