graphite bushes/bearings ?

I have obtained drawings for a low temperature stirling engine, which specifies graphite to be use for certain bushes and bearings. Would carbon motor brushes be a likely source of material or is there a plastic which could be used as an alternative ? If none of the above, where could I obtain suitable pieces of graphite?

Be careful if using motor brushes. Many of them incorporate copper powder to improve the conductivity.

You could try **LINK** for or http://www.olmec.co.uk/graphite_blocks.htm graphite rod.

Russell.

Edited By Russell Eberhardt on 21/02/2016 12:02:19

Anthony Knights:

You could consider Nylatron, graphite impregnated nylon available from eg Direct Plastics.

Noggin End sell graphite in small amounts

Noggin End stock graphite **LINK**

Rod

Check out the EDM (spark erosion) suppliers for graphite. Where are you based ? a few suppliers here in the Midlands.

Does it specify a grade of graphite on the drawing ?

If you post the block dimensions required & any grade info I'll see if I can find a suitable offcut at work (graphite machining specialists - many tonnes of various different grades on site !).

Nigel B.

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Nigel,

You could end-up as everyone's best friend !!

Seriously: It might be worth striking a deal with your employer.

MichaelG.

Looking at a commercial LTD it seems to use a grade that will more or less take a polish. I'd guess that means very dense and very fine grained but there is little information about.

It would be logical for Noggin End to stock the correct on but he mentions other uses for it.

It's about on ebay in rod form as well but no info on grade.

John

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Thank you gentlemen. As usual, prompt and useful advice. No grade specified, but there are 3 parts to make which would probably only need 25mm of 10mm rod, which was why I asked about motor brushes. Noggin End looks good so I'll be giving them a try.

Edited By Anthony Knights on 21/02/2016 17:53:01

Seriously: It might be worth striking a deal with your employer

I would clear anything with the boss first - not worth risking the job for a bit of graphite !

In the past he has been amenable to requests for small bits / offcuts, but larger amounts of more expensive grades would most likely be chargeable. In the past also it has not been worthwhile commercially to raise invoices etc. for very small orders, but he has recently installed a credit card machine specifically to cater for small online orders of "standard" machined graphite parts like studs, nuts & bolts, so supply of smaller quanties of "raw material" should also be possible now.

As above, let me have a bit more info & I'll see what I can do.

Nigel B.

I managed to pick up graphite rod from large Arc Lights at a car boot sale a while back.

Martin P

When I was running EDM machines here in the Midlands I bought off two companies. Erodex and Graphite Technologies. There are other suppliers but these where local to work.

I would also vouch for this, very durable

Michael W

www.graphitestore.com will have everything you need.

Also, graphite rods sold on eBay for use by jewellers stirring pots of melted gold or silver etc.

I have some graphite impregnated PTFE/ Teflon, I use it for the bushes on displacer rods in hot air engines.

One design of LTD that I'v seen uses pointed ends on the crankshaft bearing on blocks of graphite, I think the suggestion was to use motor brushes for this motor.

Are you going to use a diaphragm, or a piston, if the latter a bit of graphite for the piston would be good, and a glass cylinder, best cylinder a glass medical syringe.

Ian S C

"Be careful if using motor brushes. Many of them incorporate copper powder to improve the conductivity."

So how will this affect operation in this application?

Regards Ian.

Well, if i might hazard a guess, best case scenario it's for a push fit bushing which sits as dead as a door nail, not harming or upsetting anything or anyone else around it. Now worst case scenario it's for a moving part like a piston that might, on the worst of all the worst days becomes a conduit for electric shock?

Other than that, it might just be a handy to know piece of info, i ne'er knew that before now, i thought a carbon brush meant exactly that.

Michael W

Edited By Michael Walters on 22/02/2016 10:08:53

Michael W Seeing that both carbon and copper are conductors How would a moving part make any difference How would there be any chance of electric shock ?