A while ago I bought a Sidewinder for Brompton:
that allows you to roll the folded bike laterally like a suitcase. In an add-on product for Brompton rack, that an average buyer must be able to mount, there had been some compromises. Thus the parallel movement of the folded bike had to be compromised with one of the original wheels moved to serve the lateral motion. The rear add-on wheel had to stick out very far to the side to prevent the rear rack from scraping against the ground. The original Eazy Wheels get beaten up quickly when only 2 of them support the bike in lateral movement.
Frustrated a bit by the imperfections in SideWinder I made one from scratch, retaining only the original idea, getting back the use of 4 wheels for longitudinal motion and using Bikegang skate wheels for lateral. I repositioned the wheels so that the rack stays parallel to the ground in lateral motion. This allowed me to put my lock bag on the nondrive side. (With the original SideWinder it rubbed against the ground on the nondrive side.) The nondrive location of the bag allows for the bike with the new lateral arrangement to be pulled up the stairs like a suitcase. The photos show bikes with the original (black) and remodeled (green) SideWinder (no original SideWinder parts are used in the latter though).
