A quick list of On30 gauge minimum radii by locomotive and rolling stock type.
Most manufacturers only warranty operation on 18″ radius or more.
But, I’ve taken almost anything down to 10″ radius.
Some with little modification, others with substantial redesign.
Athearn HO Scale Locos/On30 Donors – (Recommend 18” for all equipment)
SW1200 switcher 18” (15” with lots of adjustments)
SW1500 switcher 18” (15” with lots of adjustments)
Bachmann On30 – (Recommend 18” for all equipment)
2-6-0 Mogul 18” 12”
0-4-0 Porter 12” 6”
0-4-2 Porter (7” with adjustments) 15” 9”
0-4-0 Davenport Gas-Mechanical 12” 6”
2 truck Class A Shay 18” 15”
2 truck Class B Climax 18” 12”
Closed Street Car 15” 3”
2-8-0 Baldwin Outside Frame Consolidation 22” 18” possible (12” with lots of adjustments)
Railtruck 18” (10” with lots of adjustments)
2-4-4 Forney Inside/Outside frame 22” (18” with adjustments)
4-4-0 American Steam Locomotive 18” (15” with adjustments)
2-6-6-2 Mallet 22” 18”
4-6-0 Ten-Wheeler 22” (18” with adjustments)
Railbus + Trailer 18” 18”
Bachmann HO Scale Locos/On30 Donors – (Recommend 18” for all equipment)
50 ton Class B Climax mechanism 18” (15” to 12” with lots of adjustments)
70 ton 3-truck Class C Shay 18” (15” to 12” with lots of adjustments)
0-6-0T SaddleTank #8181x 18” (7” with adjustments, lots of rear overhang)
HO SCALE Hi-Railer #46207 18” (7” with adjustments)
School Bus #46211 18” (10” with adjustments)
4-6-0 locomotive (52” drivers) #84901 18” (10” with adjustments)
4-6-0 locomotive (63” drivers) #84902 18” 15”
CURRENT “Phase 3” 44 tonner, central motor 18” (15” with adjustments)
45ton siderod diesel, central motor 12” (10” with adjustments)
4 wheel Ballast vehicle 9” 7”
Brill Trolley 18” 7”
Freight/Passenger Cars
Bachmann (Recommend 18” for all equipment)
Flatcar 18” 12”
Gondola 18” 12”
Boxcar 18” 12”
Stockcar 18” 12”
Tankcar 18” 12”
Passenger Coach 18” 12”
Combine 18” 12”
Baggage Car 18” 12”
Caboose 18” 12”
V Dump cars 15” 10”
Wood Side Dump cars 15” 10”
Log Skeleton cars 18” 12”
Boulder Valley Models – (Since Closed)
SC1/2 Pedestal Flats 6” 6”
501 thru 508 “Shorty Cars” 9” 9”
511 thru 513 “16-foot cars” 15” 10”
521 thru 524 “16-foot cars” 15” 10”
551 thru 555 “15-foot skeleton log cars” 12” 12”
561 thru 564 “15 foot hopper” 15” 12”
601 thru 606 “20-foot cars” 15” 15”
607 thru 609 “20 foot cars” 15” 15”
611 thru 616 “20-foot cars” 15” 15”
617 thru 619 “20 foot cars” 15” 15”
621 thru 626 “20 foot cars” 15” 15”
631 thru 633 “20 foot cars” 15” 15”
Chivers
Shorty cars 15” 6”
14’ Caboose 15” 6”