Engineering plastics: - Delrin??

The black is better than the red. :-) In technical plastics, black is often a sign of added MoS2. But it needn't be that way.

Something with PTFE.

Can you use ready built DU-bushings?

Nick

Nylatron GSM, possibly ? That's got molybdenum disulphide in it. Not very high temperature, though, and it looks like it might creep under continous pressure.

I've bought it from Engineering & Design Plastics of Cambridge.

-adrian

ISTR it does absorb some water, though not as much as plain nylon.

Vesconite might be better if water resistance is important

They do a prompt service from South Africa if you pay by credit card. Last time I bought some I tried their agent in the Netherlands thinking it would be quicker or cheaper. It was neither, plus they wanted payment by euro cheque.

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Forget Nylon, go straight for Acetal (Delrin is Acetal, but DuPonts trade name).

Acetal has the lowest CoF of any unmodified engineering polymer, and pound for pound is one of the stiffest unfilled polymers you can get. Doesn't absorb moisture, but like all polymers will change sizes minutely with temperature, but then it is also a little bit compliant so this really shouldn't matter much. Acetal has an inherently harder surface than Nylon due to its high level of crystallinity.

Nylon can absorb up to 5-7% of its weight in moisture under saturated conditions but will lose it again under dry conditions. This causes quite an apparent physical growth and shrinkage on the parts. On the other hand, Nylon is more impact resistant than Acetal, especially when it has absorbed moisture which provides a step change in toughness. Dry Nylon becomes quite brittle.

Plenty of Acetal (Delrin) on e-bay. Go for the black stuff rather than the natural (white) as this is inherently more UV stable as the pigment is predominantly carbon black.

The "Red Stuff"could have been anything from High Density Polythene to Nylon to ABS to Polypropylene.

Peter

Thanks to all answers in the group Black stuff up to now.

Nick please explain DU to me, is it a trade name?

Adrian

No, this is a type of bushing. Cheap like ????. Just google for "DU bushing" to get overwhelmed.

Nick

No it's Depleted Uranium, keep clear of it

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-- Regards,

John Stevenson Nottingham, England.

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They looks like outer steel lines oilites.

Thanks for the info.

Adrian

I thought it was something to do with taking the piss...

Regards, Tony

Made by Glacier; sintered bronze on a steel backing (like a big end shell), and the bronze bit is impregnated with PTFE. Used dry. Very impressive low friction, low wear, long life. No connection with Glacier, I just used to use them on friction and wear test rigs. I can't remember offhand but they probably also have a better PV factor (pressure multiplied by speed) even than expensive Vespel because the bronze conducts the frictional heat away.

Thanks for the information.

I think I will go for the black engineering plastic initially as I see two advantages for me.

1) I can machine to size and fit and even include end packing pieces.

2) As the stuff is slightly elastic and deformable it will not transfer shocks as easily. How true this later part is time will tell.

Many thanks again

Adrian

If you're talking about suspension in cars, the plastic of choice for bushings is urethane, comes in a red colour.

Tom

Hi Tom;

Not quite cars but a Gokart and I used up all my red stuff that i thought was Delrin on the stub axle shaffs and at the bottom of the sterring shaft.

so I started to ask the group what seems to be best now.

The red stuff I have had for some 12 years and could not really remenber its origin except from an autojumble.

Looking at doing swinging arm suspension at some point so looking what might be best then and I suppose still be general purpose!

Cheers

Adrian