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HEQ-5 Pro Rowan Belt Mod issue


Penguin

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I have a possible issue when fitting the Rowan Belt mod to my early HEQ-5 Pro and I wonder if anyone can advise:

It's an early mount, as evidenced by the silver setting circles and the fact that the motor fixing plate only has one grub screw for the middle cog.

The issue is that the RA axis motor spindle is significantly narrower than the hole in the sprocket. There is nearly a millimetre of play there (see the attached video clip). The Dec one was nice and snug so I assume it is not supposed to be like this.

Should I crack on regardless? I can tighten it up with the grub-screws obviously be then it will be off centre and that can't be right! The spindle is 4mm diameter and the hole in the sprocket is 4.9mm (see the attached photos) and I don't know which is at fault. I have emailed Rother Valley Optics who supplied the kit in the hopes that the sprocket is faulty and they can just post out a new one.

20220403_164830.jpg

20220403_164939.jpg

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The shafts on both motors on my HEQ5 are 5mm so the pulley would seem to be machined correctly.  So either early machines had different motor fitted to the RA drive, or someone in the past changed the motor and got one with a 4mm shaft.

My advice would be to drop Dave at Rowan engineering a line, link or include the video and ask how much they will charge to machine a new RA pulley with a 4mm bore rather than the normal 5mm

Edited by malc-c
missed W in rowan
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18 hours ago, david_taurus83 said:

What measurement was the Dec axis?

I didn't measure the Dec axis at the time but I'm pretty sure it had a thin part at the top that the gear was on, then a shoulder and then a thick part, so the thick part was probably 4.9. I'm thinking that mine may have been the one where SkyWatcher ran out of the old stock of motors and moved to the new ones, hence why mine has one of each.

I've sent the motor back to Rother Valley and they will pass it on to Rowan who say they will machine up a part to make it all fit, FOC. So top marks to both companies for customer support.

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That is a great solution. 
 

I would have been happy to pay for a machined part and Rowan doing that free of charge is great. 

I did the belt mod several weeks ago and with the great advice from @Padraic M, adjusting the DEC backlash made a huge difference in my mount reducing the DEC backlash from 3000ms to <200ms measured by PHD2. I will tackle the RA worm soon.

Excellent mount performance so far. 
Best of luck and keep us informed.

Jim

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Fantastic customer service from both companies.

Afraid to say that I started all this when I modified my HEQ5 to belt drive in 2011.... Only I had to use off the shelf pulleys, and using a 4:1 ratio it was only suitable for computer control using EQMOD.  Dave at Rowan Engineering then took the concept of the kit I made up a step further and CNC's a one piece motor pulley that maintained the factory ratio so it could be used with a handset.   The main advantage of a 4:1 ratio is a more regular PEC, but other than that having a belt driven mount is so much more smother and quieter than the geared system.  It also takes out one more item that causes backlash.

It's really humbling to hear that they have agreed to make a part to fit the motor you have, and at no cost.  Keep us posted how things go on

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