Roller bearings vs. teflon pads for Dobs...

[emadmoussa]

I only used roller bearings with my Dobs, and now I have a very well priced Orion Dobsonian ...but it uses teflon pads instead. I'm not sure what to expect.

I hear a lot of members upgrading to lazy susan bearings, so I'm thinking there must be something about the teflon pads that forces some members to ''upgrade''. I wonder what the pros and cons of this?

Thanks!

[Moonshane]

teflon needs (or works better with) a textured surface on the bearing. most skywatcher/synta dobs that have teflon pads have a smooth surface and this creates stiction hence the change.

if I bought a synta dob, I'd be covering the bottom of the rocker box with a textured laminate and expect it to be perfectly smooth. I suspect lazy susans will work well until the mechanism clogs with grit etc which I'd expect it to after a year or so. I have no evidence for this though.

[ChrisLX200]

I think roller/ball bearings are 'too much of a good thing' in the friction reduction department. Any slight imbalance and the scope won't stay where it's put. Teflon adds a little bit a of stiction so it resists initial movement a little bit but then glides nicely. It's not just the Teflon though - it is what the Teflon runs on that makes the difference. A knobbly bit of worktop surface (wahtever you call it - I forget) provides just the right balance of stiction and friction.

ChrisH

[faulksy]

if its a orion optics it will be fine, as shane says you need the textured finish for the teflon to work properly, yours will be like mine the ground board will have a hamerite coating, same on the alt

[emadmoussa]

Sorry, forgot to mention it's the Orion XX series scope. The base looks quite smooth to me, not sure what kind of surface sandwiched in the bottom section.

Erm...if Teflon pad driven bases are slightly sticky, then wouldn't that be a pain when the scope is pointed  at zenith? I mean, vertical steering will be awkward...

[Moonshane]

not really. with teflon and the textured bearing you get no lag between pushing and moving

with a well made bearing there should be no overshoot, no sticking on first push and no blowing round in the wind. it should start smoothly, move smoothly and stay where you put it.

[8kids]

I spent many hours fiddling with bearings  and lazy susans. What do I have now........back to good old Teflon pads, much less trouble.

[John]

I've used both types and prefer teflon pads too. I found the bearings in the lazy susan type arrangements were just a little bit too free running and there was a little roughness to the motion that I could see reflected in the eyepiece at high power. You need some friction in dob bearings - enough to hold the scope on target even with a decently large eyepiece but you also want a smooth release and motion when you want to move the thing. Decently implemented teflon pads achieve this best I think.

[emadmoussa]

Do Teflon pads wear off over time?

[Moonshane]

after the initial bedding in not really.

even if they do, just cut them off and glue on some more.

[emadmoussa]

Aha, thanks Shane.

[Myopicus]

I have read a post on SGL (by Ptarmigan or Avocet i think - definitely a bird name) about Dob mods, whereby a lazy susan was fitted and then the teflon/ptfe pads were then shimmed up to just touch the contacting surface, giving silky smooth rotation with I guess enough 'stiction' (a term i've only ever heard applied to mountain bike suspension forks - but I know exactly what you mean).

I wish I could find the thread, it made good use of a water butt stand to raise the Dob to standing height, too.

[purdo]

These may be the threads you are looking for:

Equipment - Discussions - Mounts - Tall Water Butt Stand - 12.4.14

Beginners - Getting Started Help & Advice - Firstlight SW200P Dob - 25.5.14

I cannot link the threads as I am using a Kindle.

[michaeldurban]

This Az. movement is an ongoing problem..and discussion..and experience..

I have a SW dob and absolutely hated (I say Hated!) the teflon

pads...even after cleaning, ebony star(-ish) materials, cut out milk

jugs (my wife : "why are we using so much milk !), cd's, LP's and many

other home made remedies...nothing worked (for me..)

So..I decided on Lazy Susie...

Never looked back..

A lot of people moan and complain about that it moves too freely and such..

I just tighten the centerbolt and voila...

If you ask me...LS is the way..

but like I've said..different experiences for different people..

[michaeldurban]

just bolt the LS onto the bottom base plate...

No need to secure the rockerbox onto the LS..

(the centerbolt and weight of the scope will keep it securely in place)

hehe..as you can see in the second pic..I also used teflon furniture sliders..

pfff...

[Avocette]

I have read a post on SGL (by Ptarmigan or Avocet i think - definitely a bird name) about Dob mods, whereby a lazy susan was fitted and then the teflon/ptfe pads were then shimmed up to just touch the contacting surface, giving silky smooth rotation with I guess enough 'stiction' (a term i've only ever heard applied to mountain bike suspension forks - but I know exactly what you mean).

I wish I could find the thread, it made good use of a water butt stand to raise the Dob to standing height, too.

A little further up the Dob learning curve and a few inches larger in aperture and I modified my 300p Flextube to teflon:-

http://stargazerslounge.com/topic/211776-300p-dob-goodbye-lazy-susan-hello-control/

[John]

I reckon that, like many things, individual preferences for the way in which a dobsonian moves around the mount axis vary. Once you have used the scope for a while you get a feel for it and, if it doesn't suit you in it's "native" form, modifications are possible to change that 

So it's not really one v's the other but finding out which suits you best.

[astronymonkey]

I use both teflon and the lazy susan both together on my scope and find this combo works well if the teflon is of the correct thickness.

ive never had a problem with lazy susan and if it is sandwitched between two smooth discs of metal I find the friction level to be ideal.

I agree with the point about finding the feel for a scope, its like getting a new car and the brakes and steering feel different but after a few drives you get used to it.

cheers

[ollypenrice]

Do Teflon pads wear off over time?

Mine haven't. My 20 inch has been in service here for about ten years. I do run an intensive maintenance programme, though. About once every five years I remember to look into it and then forget about it.

Trust John Dobson. He had an incredibly elegant idea. Those who followed did lots of homework. You want the static and the moving friction to be as close to identical as possible so you don't jerk and overshoot. Virgin Teflon, textured formica and Turtle Wax. If you want a worse result, deviate from this.

Olly