Gt2 pulley non-standard bore

[g-rex]

I'm currently converting an old (black) Heq5 to Onstep. It's pretty much done and awaiting testing.

My main issue has been getting a pulley wheel to fit due to the worm shaft being 9mm and pulleys only available with a bore of 8mm or 10mm.

I've initially put a 10mm on and shimmed it but it's not perfect and I'd much prefer a proper fit.

 

Long shot but I wondered if anybody knew of a supplier who may sell a 9mm wheel or have the tools to bore out a 8mm?

 

Thanks.

 

Edited January 14, 2023 by g-rex

[Dr_Ju_ju]

you may find something here https://www.beltingonline.com/timing-pulleys-bars-c-272/

[AstroKeith]

9mm is going to be a special.

A simple job for anyone with a lathe to drill out an 8 to a 9. 5 minute job.

Now to just find someone with a lathe!

[newbie alert]

Beltingonline had a reprofile service 

[Peter Drew]

I have a lathe and could do this.     🙂

[malc-c]

Have a read of this old post  Some links may be broken as it's over a decade old and the forum has since been updated.  -  You may also run into ratio issues as the gearing isn't as simple as 4:1 or 5:1 so you will need to run the mount from a PC using EQMOD with custom gear ratio setting

[skybadger]

4 hours ago, AstroKeith said:

9mm is going to be a special.

A simple job for anyone with a lathe to drill out an 8 to a 9. 5 minute job.

Now to just find someone with a lathe!

I'm not too far away, could face and bore it. 

[michael8554]

You could drill out a 8mm with a 9mm drill bit.

But on a lathe would be better, so that the hole can be drilled absolutely concentric..

Michael

[g-rex]

Thanks for the replies and ideas. Appreciate the offers but turns out someone I know has a lathe so he's going to sort them for me 🙂

malc-c the ratio is 5 to 1 (60 tooth and 12 tooth) Its going to be running on Onstep so it's just a case of re-flashing the chip with the correct number of steps. Onstep have a calculator for this and it worked ace when I went from eq3-2 to eq5. I think the Rowan mod is 5.2 to 1 so it's pretty close. 

 

Thanks again 👍

 

[malc-c]

5 hours ago, g-rex said:

Thanks for the replies and ideas. Appreciate the offers but turns out someone I know has a lathe so he's going to sort them for me 🙂

malc-c the ratio is 5 to 1 (60 tooth and 12 tooth) Its going to be running on Onstep so it's just a case of re-flashing the chip with the correct number of steps. Onstep have a calculator for this and it worked ace when I went from eq3-2 to eq5. I think the Rowan mod is 5.2 to 1 so it's pretty close. 

 

Thanks again 👍

 

That's OK... just wanted to confirm you weren't expecting it to work with any handset which uses the stock 9:47 ratio.

I would advise you to have any modifications done using a lathe and or mill.  Part of the problem I had was getting the pulley to fit the shaft of the motor and remain concentric, and given the design of the pulleys it's easy to get it wrong.  The alternative is to have something like the Rowan kit and machine it from a solid piece of ali.

[markse68]

Yea best to use a 4 jaw chuck and dial gauge off a shaft that’s a good fit in the existing bore- not a 3 jaw or you’re almost guaranteed eccentricity 

Mark

Edited January 15, 2023 by markse68

[kbrown]

Not sure how much torque is required in this application so this might not be suitable: I have successfully modelled (FreeCAD + Gears add-on) and 3D printed timing pinions and pulleys. I always used helicoil style thread inserts for the grub screws. Can't tighten them too much as it's easy to break or deform them by doing so.

Edited January 16, 2023 by kbrown

[malc-c]

23 hours ago, kbrown said:

Not sure how much torque is required in this application so this might not be suitable: I have successfully modelled (FreeCAD + Gears add-on) and 3D printed timing pinions and pulleys. I always used helicoil style thread inserts for the grub screws. Can't tighten them too much as it's easy to break or deform them by doing so.

Not sure of the initial torque required to get the scope moving, but it's enough to separate the flange of an ali pulley once it's been bored out as there is very little material left.

 

I'm not an expert in 3D printing, but if the material is hard enough this could be an option as the pulley would be made from one single piece, much the same way as the motor pulleys in an Rowan kit

[Lucas1807]

Hello out of curiosity do you know if this mount works with asiair. The original not modded version. Thanks