Rainbow D4 / D4SE Lower Fan Spacer

R2679B is the lower fan spacer in the Rainbow D4 and D4SE motor stack — the piece that sets the running clearance between the lower fan stage and what sits against it on the shaft.

It does nothing visible until it is wrong. A spacer crushed on removal, or a stack rebuilt without it, lets the lower stage sit out of position: the fan can contact its neighbour, which grinds or scrapes under load, or it runs off true and the motor wastes effort turning a fan that is no longer square to the shaft.

Fit it in sequence during a motor rebuild. If you already have the stack apart, lay the spacers out in the order they came off — the upper and lower spacers are not interchangeable, and the two are easy to confuse once they are both sitting on the bench.