"Pirateer guy" Dan@ wrote in message
...
On Sat, 21 Mar 2009 20:16:36 -0400, "Ed Huntress"
wrote:


"Pirateer guy" Dan@ wrote in message
...
I need to make a part out of rubber. The part is obsolete and cannot
be purchased. I have one, but it has shrunk over the years and is now
loose and it leaks water.
The part is an isolation ring for a boat engine mount. It sits between
two pieces of aluminum and is compressed by the two pieces.
This allows some movement between the engine and the engine mount and
it also seals out the water.

I am thinking that I can use the existing part to make a mold to build
a new part out of urethane. I can add bulk to the existing part to
make up for the shrinkage.
Problem is, all I can find on the web is urethane for making the mold
not the part. Does anyone have any insight into how I can do this?
Fairly complex part, but I have one to make the mold from.
The link is to a parts manual that shows this part. It is on page 14,
of 20 and it is Item Number 8. It is OMC part number 322214or OMC
393162. same part.
Thanks everyone
Dan

I don't have the specific reference, but casting-grade polyurethane rubber
for making gaskets and such is, or was, available in three different
durometers that correspond to a wide range of gasket types. I can be cast
in
Plaster of Paris, so it's very easy to work with. It's been used for
decades
to make reproduction parts for old cars.

Maybe someone else can help you with a link.

--
Ed Huntress


Thanks Ed, that's exactly the direction I was trying to go. It looks
like www.smooth-on.com probably has the stuff I'm looking for.
Now I have to call them and start asking lots of questions.
I'm thinking Shore A 90 durometer?
Maybe someone here that has already done this will chime in and push
me in the right direction.
Dan


The stuff I was trying to think of is Devcon Flexane. I don't know if it's
still available.

Using it is covered in a good little book that I have around here somewhere,
_How to Cast Small Metal and Rubber Parts_, by William Cannon. If you're
patient, you can read it for free on Amazon. d8-)

According to the book, a car-door weatherstrip is around Shore A 30. A car
tire is around 50 - 60, and the cover of a golf ball is approximately 95.
Flexane is available (or was) in Shore A 80 and 94, with an additive that
will let you mix any *softer* degree of hardness.

I hope it's still available. It's great stuff. I've used it, but not for 20
years or so.

--
Ed Huntress