I am posting here since many folding bikes have internal geared hub and I got no help in the bicycle mechanics forum. I am looking for someone who has worked on a Sachs 3 x 7 hubs to answer a question about re-assembling one of these hubs. I have an extra flat washer that does not show up in any schematics I have found for the hub. If anyone comes forward as having some knowledge / experience, they can either reply to my post in mechanics or let me know and I can post more details in this forum.