Which plastic? A technical properties discussion

[Chris]

I don't really understand the various properties of plastics, but I guess there is wear, heat, friction, machinability, durability, flexibility etc etc.

I want some plastic block or thick sheet that I can shape to make a catch plate for my wheel carrier. So it want so to be low friction, but good wear. I have been looking at websites and my eyes are beginning to cross. There are plastics I have never heard of. So I thought I'd be lazy and put the question out there. What is a good universal sort of material that would be good for this. There are plenty of suppliers and it doesn't seem to expensive. I'd like a block about 15 mm deep by about 100 x 50 or something like that. It may be that a sample will be good enough. These are usually only about £2.50.

Got to crack on with it as I am at the fabrication stage of the wheel carrier already! Spindle is ready to go in.

Chris

 

[Gary Stockton]

pop Rob a PM to perk his attention - that's his game ....

 

[Jon Wildsmith]

Delrin or Acetal is good stuff and you can get it in black.

 

[Andrew Prince]

Chris, high density polyethylene (HDPE) or polypropylene (PP) will probably do that job just fine. (plastic cutting board)
I could probably bore you to tears on plastics (but will save you that pleasure).

If you want something a bit tougher - polymethyl methacrylate (perspex) or polyurethane will give you something more robust. Something in-between would be ABS (acrylonitrile butadiene styrene) but I seem to recall that it might not have good UV resistance - don't quote me on that though.

I can't really picture what this catch-plate is for? Shock-absorbing or providing strength to the carrier structure? Something else?

Cheers,

 

[Chris]

It's the striker plate where the arm of the carrier will stop. It has to allow for droop, flex in the chassis, being on a hill etc when you shut the carrier. Metal on metal is not so good as both sides will wear. If one half is ramped plastic then the carrier will lift and lock into place in the same place each time. This will wear faster (if at all) than the steel and can be replaced in due course. It won't rattle as much either if it's metal on plastic.

Makee da sense?

Chris

 

[Andrew Prince]

So something absorbant (in a shock sense) and cheap would be good/ideal? Get a PP cutting board and be done with it

Acetal (polyoxymethylene) is probably 20x the price and is an engineering plastic, so you're getting into a different realm with lots of options but none offering anything extra for your application IMHO. The cheapest option of all might be a slice of sidewall from a retired tyre

Cheers,

 

[Chris]

No, it's not a shock absorber. It's just the catch / guide plate that guides the arm of the carrier to it's final position. I need it thicker than a chopping board as I have to machine it. Probably 20 mm to start with or something like that.

The anti-bang bit is sorted.

I think that you and Jon have probably narrowed it enough for me. I just couldn't face researching ALL of those plastics.


Chris

 

[Andrew Prince]

Probably 20 mm to start with or something like that.

Chopping board cut in half and glued together? Depends how cheap and simple you want to be.
Thinking about it, nylon sheet might be a good option too - halfway between PP and POM price-wise and very tough (think of the frame of a Glock)

 

[Chris]

Glock? Never owned one and never wanted one. Soulless piece of crap. Not like my stainless Beratta 92 FS. Ahh, a thing of beauty.

I'm not gluing bloody bread boards together. Blimey, probably cost more than just buying a sheet to start with!

I could make the steel part and cover it with plastic, but frankly that's just messing around.

Chris

 

[Rob]

My knowledge of plastic is limited to engineering plastics, specifically POM (Delrin or Acetal) composites. If you want me to recommend a good self lubricating plastic I would say PTFE filled POM. Nylon is hygroscopic, meaning it will expand as it absorbs water.

 

[Paul_Humphreys]

I know nothing about plastics, but when I asked I was told polyethylene was the best. The man who told me this works with it every day and made me the bit .

Paul

 

[Chris]

Plenty of suppliers on line - Derlin looks like what I am after, but whilst not that cheap, it's the postage that's the killer. I'm not paying nearly £10 postage for a piece 100 x 100. It's nuts.

I need to find somewhere local. Or maybe just get some aluminium block.


Chris

 

[Andrew Prince]

I need to find somewhere local.

I'm sure even Tesco in Chesterfield has PP cutting boards

 

[Chris]

That's just the sort of help I need.

Chris

 

[Jon Wildsmith]

is this no good Chris?

 

[Chris]

Damn and can you believe that I searched Eblag this very morn and didn't get any thing sensible on Delrin except some stupid Star Wars figure. Whatever Star Wars is

Damn, I'm all over that! And it's only down the road.

Chris

 

[Chris5-7chev]

Chris, Nylotron would suit your application perfectly IMO so how bigga peice do you need? and of course would be FOC
Chris S.

 

[Chris]

Well I have ordered some of that just now, but I'd love anything else to work with matey.

You should be coming up to Holymoorside this Sunday. There's another 80 coming already! One step closer to taking over the World.

Getting much better with that machinery too. Ordered one or two little extra bits here and there making life easier, but still need to get the levelling feet sorted.


Kettle always on.

Chris

 

[Chris5-7chev]

Sorry Chris made a spilling mastake meant to say Nylatron, will dig out some offcuts this week. C.S

 

[Chris]

Thanks mate. Need some bits and bobs to play with.

Made a really neat mock up of the sort of thing I need today, but in steel. Really got that miller working well now. Less flex in the quill / nose with this new collet holder system. Also picked up a MT3 - B15 x 12mm adaptor for the Jacob's chuck Jon. No more falling out!

You can do so much, it's just a question of realizing what all of those things are!!