Teflon (and alternatives)

[eqcradle]

I don't seem to be able to source teflon locally (Canberra), but a guy at one of the local shops suggested that UHMWPE (ultra high mol. wt. polyethylene) was similar and actually had better characteristics in terms of not sticking when you move it. I'm just wondering whether anyone here has used it and can vouch for it. I also recall seeing a post somewhere that suggested using one of those white plastic chopping boards instead. My Googling suggests that good chef's chopping blocks might be UHMWPE, but I don't think the the Woolies version would be.

My intended use is slightly different to how it would be used in a Dob's bearings. I'm trying to devise a sort of thrust bearing to dampen a bit of wobble in one of my alternative EQ platform ideas. I'm wondering whether a couple of circular pieces of teflon sandwiched between 2 bits of wood with a bolt through the middle to control the friction would work...

CL

[Ian Robinson]

Try a company called Specialised Plastics in Lambton in NSW , I recently bought some plastic (tubes and sheet , not Telfon , but PVC) for my thesis project from them and I believe that they carry or can get most types and profiles of plastic and they'll precision laser cut it to size too.

If you want their phone number , I have their business card handy somewhere in my study and can dig it out.

I was looking a building 16" dob several years ago and bought some precut Telfon and might be able to locate it too (it'll be stashed in my garage somewhere and probably pretty dusty) if you strike out with them. I even bought some Ebony Black sheet too , which was , like the teflon , never used .
Maybe I should put that stuff onto Ebay ? I don't often come here so an email is best if you want more info.


Got it from CrazyEd in the USA.

[MrB (Simon)]

www.eplas.com.au


That link is to the contact page, none in ACT but one in Sydney. Up top of that page is a link to Teflon (PTFE)
I've dealt with E-Plas before (in Perth, just walked in) they had no problems selling small amounts, if you're lucky they'll have scrap/offcuts there somewhere.

[eqcradle]

Thanks for the pointers to those companies guys (and the offer to rummage through your garage Ian). BTW, I found the address for Specialised Plastics:
http://www.specialisedwholesale.com.au/site/index.cfm

I'll probably go with the real deal and order a couple of small sheets of teflon from one of them.

I'd still be interested to hear people's view on the UHMWPE though.

Cheers,
Chris

[sheeny (Al)]

UHMWPE does not have the same characteristics as teflon. Teflon has a lower coefficient of friction, but the beauty of Teflon really is that the static and dynamic coefficients of friction are the same. UHMWPE is like almost all other materials in that the static coefficient of friction is higher than the dynamic. This means that when you push a UHMWPE bearing, you have to push a little harder to start it than to keep it going, and as you release pressure the static coefficient of friction will absorb some of the last small amount of push - so the scope stops and then springs back slightly. Not what you want for a dob/scope.

Teflon will give a smooth movement right to the end with no spring back.

Having said that, however, UHMWPE and Ebony are among the best alternatives to Teflon if you can't source any Teflon, or Teflon proves to be too pricey! But there is no doubt teflon is the best!

Al.

[Suzy_A]

Originally Posted by eqcradle

I don't seem to be able to source teflon locally (Canberra),

No Teflon in Canberra?

Why not try a politician?

There are lots of very slick ones around and nothing seems to stick to them...

[rmcpb (Rob)]

Susan, Susan, Susan. What a lack of respect for our elected leaders who are a shining example to the rest of us in this country

[Andrew C]

Absolutely agree with these comments.

DotMAR EPP is also a good professional source of teflon in a wide range of profiles including tubing.

Andrew

Originally Posted by sheeny

UHMWPE does not have the same characteristics as teflon. Teflon has a lower coefficient of friction, but the beauty of Teflon really is that the static and dynamic coefficients of friction are the same. UHMWPE is like almost all other materials in that the static coefficient of friction is higher than the dynamic. This means that when you push a UHMWPE bearing, you have to push a little harder to start it than to keep it going, and as you release pressure the static coefficient of friction will absorb some of the last small amount of push - so the scope stops and then springs back slightly. Not what you want for a dob/scope.

Teflon will give a smooth movement right to the end with no spring back.

Having said that, however, UHMWPE and Ebony are among the best alternatives to Teflon if you can't source any Teflon, or Teflon proves to be too pricey! But there is no doubt teflon is the best!

Al.