plastic in place of sae 660 bronze?

[motorworks]

Hi
I am hoping someone may be able to help
I have a shaft on the end of a roller that is 100 mm
in diameter and I need a bearing/pillow block to fit it.
The problem is the area where the bearing goes is
8" wide by 8" high by 4" thick.
I have been throught most of the books and all are
too big.

Fairly heavy load,slow turning,near salt water and sea mud.
(sea wall roller on the back of a deep sea dragger)

We are now using SAE 660 bushings* in split blocks, but only getting 4-6 months out of the bushings

** Wondering if some type of PLASTIC would work**

*bushing are 100 mm x 120mm x 95mm

take care
eddie

http://www.geocities.com/motorworksnf/123

 

[patprimmer]

Have you tried Teflon (PTFE) or bronze filled Teflon or polyurethane.

Nylon, Acetal, Polyester or UHMWPE or Xlinked PE could all work depending on load and speed and lubrication/cooling.

Fairly heavy and slow turning is no where near a good enough description to hazard a decent guess.

You should be able to buy any of the above as rod or block form big enough to machine your bearings, some with things like silicone oil or Teflon or carbon fibre or Kevlar pup or graphite powder or molybdenum di sulphide powder or bronze powder or some combination of whatever works for the particuar plastic.

If the pressure and speed is high enough to melt some plastics, you will need a higher melting point plastic.

If they pound out, you will need a better creep resistance and tensile strength.

If they are cut up by grit, you will need a softer tougher polymer.

How many do you need, if there are commercial volumes (like 100s at a time) there might be better methods of production, like a small run in an existing pipe fitting mould or having a mould made. Moulds are very expensive, but parts from it will be cheaper.



Regards

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[plastx]

Pat's right about needing more info to narrow the field. Bronze filled PTFE would be a good start though the heavy load may cold flow even the filled PTFE's. Best bet is to contact a distributor who has a range of materials and can supply small quantities of materials in rod/tube form and can give recommendations.

Try TriStar

http://www.tstar.com/default.asp

or Professional Plastics

http://www.professionalplastics.com/

 

[Pud]

Try PEEK (PolyEtherEtherKetone) - if that does not work you are probably out of plastics to choose from.

Here is a random site off a Google search for "PEEK Machined parts" Halfway down is mention of a bearing grade. Plenty of hits.

I have assumed you are in the USA:

http://tinyurl.com/5td5hd

Cheers

Harry

 

[patprimmer]

Pud

The link says he is in Canada.

I keep discounting PEEK on a cost basis, even though I sold it for ICI back when. Do you still even remember ICI.

For an application like this it is a valid consideration as material cost is probably a very small portion of the total bearing replacement cost.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Pud]

My abject grovelling apologies for assuming USA! How can I recompense? Will sackcloth and ashes for a month be ok?

For these sort of postings I always assume "one off" as the op does not state otherwise, and "the back of a deep sea dragger" implies low volume (e.g 1)

After my posting above I did some searching and 2" is about the biggest diameter available in PEEK. Looks like a segmented bearing with a retainer cage might do the job.

Attached is a TIFF file of such cage. (I think!)

Cheers

Harry

 

[Pud]

Oops, TIFF file attached...

H

 

[patprimmer]

You could also cut 4" circles from the thickest plate or sheet you can find, then stack them side by side to get the width required.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.