People should remember that even O-72 which equals a 36 inch radius curve is very sharp for model railroading. My HO club uses a minimum radius of 40 inches which is equivalent to O-80. Most home HO layouts use a minimum radius of between 30 and 40 inches on their mainlines. Almost no one in HO uses an O-36 (18 inch radius) curve. NH Joe
Wellll... In comparisons between O3R and HO track the ol' 'radius' and 'diameter' sometimes gets lost.
O-72 (diameter) in O3R parlance is actually 18" radius in HO. (O-72 O diameter=36" HO diameter=18" HO radius)
Ergo, a 40" HO radius standard would end up being O-160...40" HO radius=80" HO diameter= O-160 O diameter. That's a 14' square table just for a circle of track. Club layouts, indeed! I know it's more than my basement would accommodate! It'd be AWESOME, though, ...indeed!!
Yeah, that ol' O-72 ain't as wide a "wide" radius as is advertised in many O3R publications/catalogs...all things considered. It's interesting that many HO manufacturers list "24" minimum radius required" on their equipment package...like full-size passenger cars. That would be O-96 in O3R. Not many O3R mfrs require that for their full 21" passenger cars....even though they'd look much better running on a minimum curve of that dimension.
Then, there's N scale...
Ah, the constraints we've bought into to play in this 3-rail world!
KD