Best material for dob bearings.

[faulksy]

Just wondering what the best material is for dob bearings with ptfe pads. My bearings are painted with hammerite.  But I know some use formica ?

What do you use and any links.

And what do you use to bond it.? 

Impact adhesive maybe.

Thanks

[johninderby]

EbonyStar laminate was the best for bearings but now discontinued unfortunately. A laminate with a pebbly surface is best and this seems to be the best one currently available.

F1782 Stardust Quarry

https://www.blackheathproducts.co.uk/products/lam/formica/f1782/

Trying to find offcuts can be difficult though. 

Edited March 7, 2022 by johninderby

[Mr Spock]

I'd be interested to know the same. Despite my Dob having roller bearings on the az I'd like to change. The reason being the bearing is only half the size of the base and so there is a lot of wobble in them. Having more stiction isn't an issue as eventually I'll be using an EQ platform.

[PeterStudz]

I used 2mm textured ABS sheet running on PTFE pads for my AZ bearing. I fixed it down using small countersunk screws (no glueing). The idea was that I could easily remove it and try other materials. But it worked so well I didn’t bother. Smooth and virtually no stiction. The sheet is like this…

https://www.ebay.co.uk/itm/ABS-Plastic-Sheet-2mm-600mm-x-500mm-Textured-Black-/124165920352?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l6249&mkrid=710-127635-2958-0

Surprisingly (well, for me) the Alt bearing I settled on uses PTFE pads running against  PTFE tape. I tried all sorts of things instead of the tape but in the end simple PTFE tape was the best. Maybe that’s because the tape does have small dimples. 

PS - this was for an 8 inch Dob

Edited March 7, 2022 by PeterStudz

[NGC 1502]

Some time ago a local clubmate of mine bought the appropriate laminate from David Lukehurst. David is well known to those into premium Dobs.

It’s probably a good idea to contact David and ask if he can still help.

[RobinH]

I used an Ikea chopping board. It was one of their thick white ones, the size is only abot A4 size but thats enough for smaller dobs. Very cheap.

[NGC 1502]

6 hours ago, RobinH said:

I used an Ikea chopping board. It was one of their thick white ones, the size is only abot A4 size but thats enough for smaller dobs. Very cheap.

I’ve experimented myself with all sorts of materials for Dob bearings, some have worked well some not. So if the Ikea chopping board works that’s great, whatever the theory may say.

Both my OO UK Dob mounts use aluminium altitude rings running on Teflon, instead of the traditional pebbly laminate on Teflon, that works well too.

[200pman]

Why not make some manual controls for it.

[RobinH]

The chopping board has a bobbely surface and works well with teflon pads. Its only useful for the azimuth as its just a flat plate. Perhaps it could be bent with heat to suit the edge of semicircular alt runners. I find gluing formica strip difficult and had it come unglued after a few months..

[NGC 1502]

On 09/03/2022 at 19:07, RobinH said:

The chopping board has a bobbely surface and works well with teflon pads. Its only useful for the azimuth as its just a flat plate. Perhaps it could be bent with heat to suit the edge of semicircular alt runners. I find gluing formica strip difficult and had it come unglued after a few months..

 

Indeed the bobbly surface is relevant, just like the traditional recommendations.  My OO UK Dob altitude bearings are aluminium coated with a hard paint that dries bobbly on the edges that contact the Teflon.

If trying to glue formica strips, best is a contact cement.  The ends can be positioned on the upper side in the area that never comes in contact with the Teflon pads. Secure with small round headed screws after drilling holes.

[NGC 1502]

On 09/03/2022 at 16:44, 200pman said:

Why not make some manual controls for it.

Yes that can be done.  If you’re into DIY it’s not too hard to figure out.  If like myself you have stacks of stuff that “could come in handy for something” then a rummage around can be fun.

[PeterStudz]

As for contact/impact adhesive. I’ve tried a few types but keep coming back to good old Evo-Stik. Get it in a tin (a few sizes available), like my well used example, rather than a tube. Can do large surfaces, spread with a foam brush or thin piece of plastic or ply. I haven’t tired it on Formica but it should work. Creates a very flexible bond. I’ve used it to bond foam mat for dew shields and if you attempt to pull it apart the foam will split instead of the join. 

[Louis D]

Rick Singmaster of Starmaster Telescopes preferred using teflon pads riding on FRP (Fiberglass Reinforced Plastic) wall board (or glass board) for the azimuth bearings.

[PeterStudz]

2 hours ago, Louis D said:

Rick Singmaster of Starmaster Telescopes preferred using teflon pads riding on FRP (Fiberglass Reinforced Plastic) wall board (or glass board) for the azimuth bearings.

Yes, I saw that. Although I couldn’t find anything quite like that in the UK. If there’s a place to buy these here I’d be interested.

[PeterStudz]

This thread made me revisit this interesting article…

https://skyinspector.co.uk/wp-content/uploads/2020/07/SandT-1999-10-Improving-Dobsonian-Motion.pdf

I’d seen it about 10 months ago when building my base but at the time couldn’t work out exactly what “Teflon sheet” is. The article is from 1999. However, looking at it now it’s obvious. It’s basically PTFE sheet often used for heat presses and is now easily available and cheap eg…

https://www.amazon.co.uk/dp/B07H55M1ZR/ref=cm_sw_r_cp_api_glt_i_YKDS2EN8M1ZV20EK3HG5?_encoding=UTF8&psc=1

Moreover, I might have already used something virtually identical without realising. I experimented with PTFE tape on my Alt bearing and found it good. The construction of PTFE tape sounds very similar to this sheet. It also has a dimpled surface. I’ve attached a closeup picture of the bearing/tape that I used. 

I’m going to order some of this sheet to see what it’s like and do a few experiments myself. 

[lguise]

Peter, I’m interested to know how you got on with the Teflon sheet?

Linton

[fwm891]

I use anodised aluminium strip from b&q against PTFE blocks. Bends easily and can be glued or screwed in position.

[Chriske]

I use PLA printed bearings in combination with felt these days, not for very large and heavy scopes of course.

[Mr Spock]

I went down the expensive route and bought one of these 

[fwm891]

3 hours ago, Mr Spock said:

I went down the expensive route and bought one of these 

I have one of these under my 16 inch Dob (450mm OD).

[Swoop1]

if texture is important, would offcuts of plastic packing strap work?

[NGC 1502]

15 hours ago, Swoop1 said:

if texture is important, would offcuts of plastic packing strap work?

 

Experimentation is key.  I’ve seen plastic packing strap with a crisscross pattern embossed, that could work so best to try it and find out👍

[PeterStudz]

On 17/04/2022 at 11:31, lguise said:

Peter, I’m interested to know how you got on with the Teflon sheet?

Linton

Hi Linton,

I’ve got some but been a little busy. But will let you know how I get on.

[faulksy]

i emailed David lukehurst today to see what he uses and can he supply some.

i will let you know the outcome 👍

[faulksy]

On 07/03/2022 at 19:46, NGC 1502 said:

Some time ago a local clubmate of mine bought the appropriate laminate from David Lukehurst. David is well known to those into premium Dobs.

It’s probably a good idea to contact David and ask if he can still help.

i contacted david. he supplied me with 3000mm x 40mm for my alt bearings and a square piece 600mm x 600mm for my azy bearing for £40 inc postage

what a awsome dude

fitting it all today 🤣

Edited May 8, 2022 by faulksy