Telescope Reviews: Belt tensioner for iEQ45

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Phillip Easton
super member

Reged: 12/24/10

Loc: DFW

Belt tensioner for iEQ45
#5497582 - 10/31/12 11:00 AM Attachment (14 downloads)

So decided to try Paul's belt tensioner outlined here:
http://www.flickr.com/photos/astronewb2011/sets/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!

Post Extras:

Midnight Dan
Postmaster

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...

Re: Belt tensioner for iEQ45 new

[Re: Phillip Easton]
#5497600 - 10/31/12 11:17 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.com/#shoulder-bolts/=jylfrt

-Dan

Post Extras:

Wembley2000
super member

Reged: 01/07/12

Loc: NW Ohio

Re: Belt tensioner for iEQ45 new

[Re: Midnight Dan]
#5497626 - 10/31/12 11:34 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.

Edited by Wembley2000 (10/31/12 11:37 AM)

Post Extras:

Phillip Easton
super member

Reged: 12/24/10

Loc: DFW

Re: Belt tensioner for iEQ45 new

[Re: Wembley2000]
#5497667 - 10/31/12 12:13 PM Attachment (6 downloads)

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.

Post Extras:

Astronewb
sage

Reged: 09/19/11

Loc: Connecticut

Re: Belt tensioner for iEQ45 new

[Re: Phillip Easton]
#5497694 - 10/31/12 12:30 PM Attachment (9 downloads)

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

Post Extras:

mgwhittle
scholastic sledgehammer

Reged: 08/24/11

Loc: Chattanooga, TN

Re: Belt tensioner for iEQ45 new