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Belt tensioner for iEQ45

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#1 Phillip Easton

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Posted 31 October 2012 - 10:00 AM

So decided to try Paul's belt tensioner outlined here:
http://www.flickr.co...ts/721576310...

Not having the tools to make components I decided to try and source parts to make my own. So this is what I have come up with:

1/4" Aluminum Screw Posts

MR695-ZZ Radial Bearing 5 x 13 x 4mm

PTFE Flat Washer, USA Made, #8 Screw Size, 7/16" OD, 0.19...

Figure I will need to reduce the thickness of the heads on the post and screw but that should be easy to sand down. Bracket will be a thin piece of aluminum I have laying around. Plan to make the hole in the bracket wide enough to get the screw through but not the post. This way the screw and post will tighten down on it to keep the assembly from moving. May make it so I can adjust up and down to control the tension.

So asking for feedback or comments on the design or possibly alternative parts.

Handy chart for inch to mm conversion.

Cheers!

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#2 Midnight Dan

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Posted 31 October 2012 - 10:17 AM

From your drawing, it looks like you have to thin the "bracket" to allow room for the screw that holds on the post.

I'm wondering if you could find a shoulder bolt to use instead of the post. Then you could leave the bracket full thickness, thread the hole in it, and screw the shoulder bolt into the bracket.

Here's some options on shoulder bolts. They even make some with a thin head to start with. Might be something here you can use:
http://www.mcmaster....r-bolts/=jylfrt

-Dan

#3 Wembley2000

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Posted 31 October 2012 - 10:34 AM

The bearings need to be no larger than 10mm outside diameter. If they are larger the plastic cover will rub or not fit at all.

Paul has since updated the bearing to 6x10x3mm

Paul's brackets have some rake back to them also to help center the roller to the belt.

#4 Phillip Easton

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Posted 31 October 2012 - 11:13 AM

Dan,

I like the idea of the shoulder bolt but not sure how to make it so I can adjust the bearing up and down to adjust the tension.

Just realized I would probably be better off putting the bracket on the outside like Paul did in his. So I have updated the diagram.

Wembley,

Agreed, my idea was to keep the whole assembly under 10 mm wide so it doesn't rub on the outside of the cover. The bearing is 4mm wide and 13mm tall. Are you saying this is too tall to fit under the bracket/top of the cover? It looked to me there would be enough clearance.

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#5 Astronewb

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Posted 31 October 2012 - 11:30 AM

Phil, I have revised my tensioner, now on Version 2, thanks to feedback from Brian and others. I have stiffened the bracket to prevent it from bending and provide increased clearance for the cover.

Here are some pics if it will help:

[img]http://farm9.staticflickr.com/8187/8141975656_025a9a...
V2 Angle View by Astronewb2011, on Flickr

[img]http://farm9.staticflickr.com/8184/8141945351_e72d4e...
Tensioner V2 Side View by Astronewb2011, on Flickr

You can see the rake needed for clearance and position.

Cheers

Paul

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#6 mgwhittle

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Posted 31 October 2012 - 12:19 PM

I wish you would just make some and offer them for sale.

#7 Astronewb

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Posted 31 October 2012 - 12:52 PM

I wish you would just make some and offer them for sale.

Wish I may...wish I might..? PM me, I have a few V2's available.

Paul

#8 mgwhittle

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Posted 31 October 2012 - 05:27 PM

I wish you would just make some and offer them for sale.

Wish I may...wish I might..? PM me, I have a few V2's available.

Paul


Done!

#9 Moromete

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Posted 11 August 2013 - 02:08 PM

Why was the belt tensioner necessary for IEQ45?

#10 Moromete

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Posted 12 August 2013 - 01:21 AM

Will the AZ-EQ6 need 2 belt tensioners too? Why?

#11 timmbottoni

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Posted 12 August 2013 - 06:17 PM

Cool invention. Does it help with Periodic Error?

Timm

#12 EFT

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Posted 12 August 2013 - 07:09 PM

Will the AZ-EQ6 need 2 belt tensioners too? Why?


I don't think so. The motor position is easily adjusted in the AZ-EQ6 so that the tension can be easily increased or decreased so I don't think a tensioner will be necessary.

#13 Moromete

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Posted 13 August 2013 - 01:08 AM

Ed I see your point, but I still think 2 spring loaded belt tensioners should have been inside the AZ-EQ6 because the user doesn't know exactly when the belts come loose or even start to slip and the motors have to be moved to tension again the belts as you said but you don't know when you need to do it.

The belt related problems present in iEQ45 I suppose will be present in AZ-EQ6 too because I don't have much trust in the quality/durability of those belts considering the "cut costs" desease present everywhere now.

A spring loaded belt tensioner for each belt would have been the perfect simple cure in real time for this and increased PE without warning.

I suppose a German manufacturer of such a mount would have payed more attention to such design details considering the AZ-EQ6 is not a cheap product these days.

Ed, maybe your future hypertuning kit for AZ-EQ6 should contain those 2 spring loaded belt tensioners.

#14 EFT

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Posted 13 August 2013 - 09:51 AM

Ed I see your point, but I still think 2 spring loaded belt tensioners should have been inside the AZ-EQ6 because the user doesn't know exactly when the belts come loose or even start to slip and the motors have to be moved to tension again the belts as you said but you don't know when you need to do it.

The belt related problems present in iEQ45 I suppose will be present in AZ-EQ6 too because I don't have much trust in the quality/durability of those belts considering the "cut costs" desease present everywhere now.

A spring loaded belt tensioner for each belt would have been the perfect simple cure in real time for this and increased PE without warning.

I suppose a German manufacturer of such a mount would have payed more attention to such design details considering the AZ-EQ6 is not a cheap product these days.

Ed, maybe your future hypertuning kit for AZ-EQ6 should contain those 2 spring loaded belt tensioners.


That's a good point regarding the user's ability to know when tensioning might be needed. At this point, I'm not too worried about the belt stretching, but only time will tell whether this will be a problem or not.

#15 Astronewb

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Posted 15 August 2013 - 09:23 AM

Why was the belt tensioner necessary for IEQ45?


It wasn't necessary, but it was a good way to reduce backlash inherent in the belt due to 'droop' between the two pulleys.

One side of the belt is always going to have more slack than the other when the pulleys are a fixed distance, especially after use when the belt stretches a bit.

The result is easily seen on the iEQ45 (and similar mounts) with the housing cover removed so you can see both pulleys.

Marking the pulleys with a felt tipped marker and then slewing in RA left and right will show the delay in the worm pulley before it starts to turn when changing the direction of the slew.

It's not a huge deal for visual, but for imaging, eliminating the delay (backlash) results in faster calibration in PHD when clearing DEC backlash and reduces correction movements when guiding.

For those that like to tinker, here's my final configuration of the tensioner:

Posted Image
4. V5 Angle by Astronewb2011, on Flickr

This mod works on early iEQ45s, iOptron is going to offer a fine toothed pulley and belt with their worm upgrade kit, and may be installing it on the current 2013 iEQ45. That fine pitched belt is extremely stiff, and may not need a tensioner at all?

Hope the info helps,

Paul

#16 biz

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Posted 15 August 2013 - 05:58 PM

Why was the belt tensioner necessary for IEQ45?


It wasn't necessary, but it was a good way to reduce backlash inherent in the belt due to 'droop' between the two pulleys.

One side of the belt is always going to have more slack than the other when the pulleys are a fixed distance, especially after use when the belt stretches a bit.

The result is easily seen on the iEQ45 (and similar mounts) with the housing cover removed so you can see both pulleys.

Marking the pulleys with a felt tipped marker and then slewing in RA left and right will show the delay in the worm pulley before it starts to turn when changing the direction of the slew.

It's not a huge deal for visual, but for imaging, eliminating the delay (backlash) results in faster calibration in PHD when clearing DEC backlash and reduces correction movements when guiding.

For those that like to tinker, here's my final configuration of the tensioner:

Posted Image
4. V5 Angle by Astronewb2011, on Flickr

This mod works on early iEQ45s, iOptron is going to offer a fine toothed pulley and belt with their worm upgrade kit, and may be installing it on the current 2013 iEQ45. That fine pitched belt is extremely stiff, and may not need a tensioner at all?

Hope the info helps,

Paul

Hi Paul.
Good job, I like it.
That's good news about the stiffer belt and as you say your neat little device may not be needed. Time will tell on that one.
cheers
Graham.






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