1972 Sturmey Archer Dynohub overhaul
Hello everybody, I've enjoyed reading the forums for a while, but this is my first posting.
I'm currently in the middle of overhauling a 1972 SA Dynohub that came my way, and I have a question for anyone with experience working on these hubs. I've done plenty of overhauls on other types of hubs, but this is my first time working with a generator hub.
The issue I'd like advice on is the presence of rust inside the hub shell. It mostly seems to be surface rust, as a rag and penetrating oil takes it right off, revealing shiny chrome underneath. Where the rust concerns me more is in the gap between the armature and the magnet. I realize that there should be some magnetic resistance when rotating the armature inside the magnet, but it feels like the rust may be adding some gritty resistance. Since I do not have a keeper ring (and I assume that they're about as rare as unicorns), I'd like to avoid separating the armature and magnet to clean off the rust. Would the armature be harmed in any way by dropping a modest amount of penetrating oil into the gap to dissolve the rust?