delrin bushings: are they brittle?

6Speed

Ordered up a set of delrin bushings and needed to cut off some of the length because they wouldn't slide all the way into my narrowed beam. When I went to put the bushing into the vice with a towel wrapped around it (so it would hold still while I cut), I barely put any pressure on the bushing and it cracked. Are they that brittle or did I get a bad set?
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'57 Beetle

drscope · Posted: Mon Jan 23, 2012 12:19 pm Post subject:

Delrin is a much more brittle material then urethane.

Urethane is a TERRIBLE material for this application. It can't handle the grease and UV light also takes a toll on it.

The best material is probably UHMW, but you are going to have to make your own.
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Mother Nature is a Mean Evil Bitch!

6Speed · Posted: Mon Jan 23, 2012 12:55 pm Post subject:

So if oem bearings aren't an option (beam was cut from ends) then Delrin is the best to go with?
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'57 Beetle

drscope · Posted: Mon Jan 23, 2012 1:35 pm Post subject:

Delrin is better then urethane.

But if you still have 1 good delrin bushing to work with, why not order a stick of UHMW from McMaster-Carr and take it along with your good delrin bushing down to the local machinist. Have him whittle out a set.

It may cost a little more, but it will last a life time and then some.
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Mother Nature is a Mean Evil Bitch!

6Speed · Posted: Mon Jan 23, 2012 3:48 pm Post subject:

That's a pretty cool idea. Do you know what size I need to order?
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'57 Beetle

Keith · Posted: Mon Jan 23, 2012 4:44 pm Post subject:

sovereignsamba · Banned Joined: March 06, 2004 Posts: 2845

just get a good beam Rolling Eyes

drscope · Posted: Mon Jan 23, 2012 6:31 pm Post subject:

Measure the fattest OD of your delrin bushing and then order the size you need or the next size up.

http://www.mcmaster.com/#standard-uhmw-polyethylene-rods/=fxr4ix

This is GREAT material for any sort of suspension bushing. It's what we use on all our race cars.

On a street car it will transmit more road noise into the cabin when used in some applications.
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Mother Nature is a Mean Evil Bitch!

Ace · Samba Member Joined: July 07, 2003 Posts: 1903

Just a note about using delrin in this application. Delrin isn't compatable with petroleum products IE most grease. It will cause it to swell and crack. From the sounds of things, yours were new when you tried to cut them though.

oldmanmark · Posted: Tue Feb 07, 2012 11:50 pm Post subject:

when i rebuilt the beam on the 63 i used delrin. i put a light coat of white lithium on one. a bit stubborn going into beam. i dont remember which one. havent driven car since then. if grease makes them swell and crack sounds like i should take it apart and clean it off ?.

Ace · Samba Member Joined: July 07, 2003 Posts: 1903

Id find out if the grease is hydrocarbon based. Lithium based may be ok depending on the grease itself.

Here is a chart on reactivity with different chemicals.

http://www.omsdive.com/delrin_chem_chart.html

You will see under grease the effect is rated at "severe". Lithium Cloride shows a resistance of excellent.

oldmanmark · Posted: Wed Feb 08, 2012 12:01 pm Post subject:

ACE thanks. ill read the ingredients of the white lith. i used and look into it. i sure dont want to take a rebuilt beam apart just to clean it off.

Ace · Samba Member Joined: July 07, 2003 Posts: 1903

Once it comes in contact, it only absorbs over time an changes the chemical composure of the delrin. You can wash it with soap and water if you get some grease on them but once it is absorbed, it is ruined.

Ace · Samba Member Joined: July 07, 2003 Posts: 1903

Actually, it is resistant to hydrocarbons. It is the tricloraethelynes that get to it. Many delrin datasheets are available through dupont if anyone is curious.

oldmanmark · Posted: Thu Feb 09, 2012 1:26 am Post subject:

i wont get to it till weekend. keeping fingers crossed. i think i bought the tub from the autozone. if white litth. its compatible then i could leave alone Ace? or be safe than sorry. i rebuilt beam over year ago. lots time to soak in.

Ace · Samba Member Joined: July 07, 2003 Posts: 1903

My experience ws with plastic products which delrin is a form of. It made something that was rigid and usually unbreakable just chip away easily with your fingers. Try flexing it where the stock grease seal used to be as that should be the outer lip of the delrin bushing. If it breaks off alarmingly easy, you know what happened.

drscope · Posted: Thu Feb 09, 2012 2:05 pm Post subject:

Some of the nice things about UHMW is that it isn't damaged by solvents, grease or fuels.

And it is a lubricious material meaning it doesn't need lubricant to be slippery.

Urethane and delrin have to have lubrication in order for parts to move freely and smoothly on their surface. But both urethane and delrin are suceptable to deterioration from grease and oils.
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Mother Nature is a Mean Evil Bitch!


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