I had seen the helium cars before, but never really noticed the trucks were outside clasp. I've actually got two different versions of the outside clasp trucks; the CBC / B&LE that have the "turned down" hanger ends, and what I'm calling the Vulcan clasp type that I use for my D&RGW 70 ton offset cars ( and Kennecott Utah Copper ore cars...) I think the latter would be pretty close for at least one of the plain bearing classes in that handy PDF in the other thread.
Vs.
I haven't played much with adding a lot of finer detail to the trucks, as I'm at the limit of the printer resin in this HO scale size, and the resin isn't as strong or forgiving as acetal. The journals on these truckframes are already somewhat large as I needed that size to keep enough material around the axle point cone, so they definitely come across as chunky.
