to those following along - here is an update
I got the one sample type of Igus plasitc bushing. I thought the press fit was going to be too tight but they pressed in with about 100 pounds force. The clearance on the shaft is about 0.003". They feel is pretty slippery compared to the 660 cast bronze. The Igus website mentions that it is fine to run on a mild steel shaft so maybe no need to chrome harden. I have another model of Igus coming, thinner flange and for higher temperatures but shorter 15mm instead of 20mm.
I want to consider "inventing" a seal to keep brake dust out of the bushings (at least one side), all bright ideas welcome. Included are a few pictures to explain. The seal material could be a number of things e.g. : brass, galv. metal washer, leather, felt, lip seal with a way to attach or ? other ideas. It looks like the only way to attach is using something like JB Weld.
closeup where seal invention would go - 2 places
Thanks for any ideas.
diagram of seal invention location
shows Igus bushings installed
