Don't know if these are wheelchair (don't look like anything I've seen on a chair) of from a "racing trike" or else. Part of a stock obtained long ago from a retired framebuilder.

Look like they'd be ideal for a bike trailer. Pram hubs perhaps?

If so, that was a corpulent tyke... If it was a trike, I'd expect there to be some way to couple to the drive mechanism. I think they were for a wheelchair or the fat baby pram.

Maybe for a hot dog cart or a reverse trike?