I don't remember who posted the Atlas with that rim, but it's in the "what is it" section somewhere. They probably were used on Karts too. What I showed was a Peerless rearend from a mower used on a trike. It has the band brake drum bolted to the sprocket too. Atlas made mowers and minis, and the Karts they were used on may have been made by a mower builder too. One way of keeping their costs down would be to use parts already available, rather than tooling up to make their own.