
Carbon brushes (in N-gauge motors especially) have tiny springs! The springs are so small that once lost they are lost forever - and none of the usual remedies really work: having hands and motor in a plastic bag is too restricting to allow the fine fiddling, and doing the job over a box lid is no help if the pinging action of the tweezers sends the thing half way across the room! (DAMHIK!)
Solution: don't use tweezers - slide the spring onto a sewing needle. Complete control, and no pinging.
