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HEQ5 belt conversion - issue


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I have a HEQ5 rowan belt conversion which has been in situ for a few years, although not heavily used. However, my guiding has not been particularly good and so I removed the cover to check the belts. I have noticed that the RA belt is buckled and when running actually catches on the teeth of the belt running in the opposite direction, which can clearly been seen in the photograph.

Has anyone else encountered this and what did they do to resolve it?

Thanks
Adrian

 

20200410_113929.jpg

Edited by microbe
typo
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You'll need to get a replacement belt, and some Allen keys.

It looks like the motor has been pivoted around the bottom right bolt (which is a motor plate bolt), but I'm not sure how the motor plate is held in place as it looks like there are neoprene washers holding it in place, which could well have moved over the years, especially if the mount wasn't balanced, putting a lot more strain on the axis..

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With some clear nights beckoning try slackening the screws and moving the motor and the mounting plate on the slots to tighten the belt and move the shaft over to get the belt to clear. You might get it to run ok while waiting for a new belt to arrive

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You can increase the clearance of the belt so the belt teeth don't touch by loosening bolts 'A' and moving the motor plate downwards a bit and re-tighten 
Then loosen bolts 'B' and move the motor upwards to tension the belt.

You are looking to increase the distance between the idler roller and the motor 9T pulley.

BeltDamage.png

Edited by 1parsec
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15 hours ago, 1parsec said:

You can increase the clearance of the belt so the belt teeth don't touch by loosening bolts 'A' and moving the motor plate downwards a bit and re-tighten 
Then loosen bolts 'B' and move the motor upwards to tension the belt.

You are looking to increase the distance between the idler roller and the motor 9T pulley.

BeltDamage.png

Many thanks for everyones advice and I have also ordered a replacement belt from Rowan Astronomy

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5 hours ago, Waldemar said:

just have the belt run at the other side of the tension wheel, or choose a shorter belt

Unfortunately the next belt in a shorter length that's available is 160mm long. This is too short to fit. 😪
Going the other side of the idler roller reduces the belt wrap to about 1/2 the number of teeth than standard.  This might introduce tracking problems from tooth engagement.
When the positions of the motor and motor plate are adjusted the belt doesn't come in contact any way. 👍

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2 hours ago, Dr_Ju_ju said:

This mob will make you one up, to whatever length....  http://beltingonline.co.uk/    you will need to supply width, tooth spacing & length.....

Not sure if they can do a custom length in Synchfroflex T2.5 ?   Would be quite expensive if they do???   
The standard 177.5mm length is the correct length any way 👍

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Do they use plastic belts in that kit ?

When I was developing the concept of a belt drive conversion of the HEQ5  ( https://stargazerslounge.com/topic/121114-heq5-experiments-with-belt-drive/ )  I used reinforced MXL pitch rubber timing  belts (from Beltingonline :) ) and they are still going strong - no signs of stretching or perrishing  after 9 years in the observatory.   

Might be worth looking at getting alternatives if the belts in Rowans kits degrade after a few years !

Replacement from Rowan is priced at £4.95.  The belts I used cost me less than £3 plus postage for the pair back in 2011, so I would guess  even with inflation rubber belts may be cheaper.

I never used any idle wheel in my design, but then I opted for a 4:1 ratio as I use EQMod to control the scope.  Dave at Rowans machined the small gear to give the same ratio as the original gear drive so the hand set could be used, and added the idle wheel to increase the amount of belt in contact with the teeth on the smaller pulley.  Maybe it's the constant inward and then outward flexing that has caused the belt to fail ?

Hope you get it sorted soon.

 

 

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30 minutes ago, malc-c said:

Do they use plastic belts in that kit ?

Hi Malc,

The kit uses Synchroflex belts which have steel wire tension members and polyurethane rubber which are good down to -30C and up to 80C.   Damage is usually due to excessive tension.

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Dave, apologies, it looked "plasticy" from the image.  Thanks for clarifying the construction.  Would it be possible to apply enough tension to cause the stretching, unless something was used between the mount and motor to exert the tension, but even then I would have though steel reinforced belts would be up to that ?

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