At 12:24 am 7/18/97 -0700, you wrote:
> The car is long since gone. I machined the Delrin bushings to
>match the metal incased rubber bushing that I had removed. I punched
>out the inner sleve from the rubber ones, removed all of the vulcanized
>rubber off of them, turned them down just a hair to give a very smooth
>uniform fit, and then polished them. So in the end, the Delrin was a
>press fit into the A-arm, the center steel tube was a snug greesed fit
>in to the Delrin and would be then be locked in place when the Nuts were
>tightened up against the steel tube. When the swing arm moved, the
>Delrin bushing moved with it slipping on the polished steel center tube
>with greese. I did it this way because I didn't want any wera in the
>A-arm journal, and figured that replacing the Delrin or the tube would
>much easier to do.
> It seemed to handle better, but did give a firmer ride, and
>provided more feedback through the wheel, since there was little to
>absorb normal shock. Delrin is fairly soft to begin with so it handled
>the larger loads by flexing around the steel inner tube. Since it very
>reliliant, it never seem to lose its shape. It worked fine until the
>engine melted #3 piston and the car was parked at that time and sold
>several years later having never seen the road again while I owned
> Thats what I did, at least as I remember it from almost 20 years
That is what I would do if I had a large enough diameter Delrin stock.
The piece I have is 1" dia. and therefore too small. I read about acetal
plastic in my Machine Design Materials reference. It states that Delrin
is Dupont's brand name . Sounded like the best thing since buttermilk.
The acetal can handle much higher heat than rubber without problems.
The melting temperature was specified at 350 to 425 F.
I just tried a sample in my oven and it melted at 375. The molten plastic
was still fairly viscous. A little thinner than silly putty. After cooling,
the glob appears to be undamaged except for some air bubbles as inclusions.
I think I will attempt to fill an old bushing/sleeve with molten acetal
and see how it turns out. Will have to build a jig to hold everything
in alignment while in the oven.
Jim Barrett Tiger II 351C and others