Casting a new rubber spindle end cover for rthe starter motor on a 74 TR6.

This rubber cap was hard, brittle, and part of the lip had broken away:




I was able to fill in the missing areas and some cracks with Bondo:




I filled the interior of the cap with vaseline with a steel nut embedded.  this was to keep the cap from trying to float in the liquid plaster.  I made a dam of a piece of 2" PVC, and sealed it with clay to a scrap piece of aluminum.  Then sprayed everythoing with Pam as a release agent.




Then poured in ordinary Plaster of Paris.




An hour later, I had an exterior mold for the cap.  I lost a little of the sharp edge of the mold while removing the pattern, but illed it in with bondo.




Next, I machined a piece to form the inner cavity of the cap.  The cap had to have a groove in the inner circumference.  This groove fits around the edge of a push nut that goes on the starter armature spindle.





Here is the arrangement to hold the core part of the mold in the right relationship to the exterior part.  The Urethane resin I used sets in about 24 hours.




The new part is on the left in each picture.  The thicker wall in the new part is intentional.  




Here is the part installed on the starter: