I recently acquired some rolling stock of the tinplate prewar A.C. Gilbert O gauge. Since I have not acquired an engine, I haven't placed the cars on the track - until today. I was surprised to find that the trucks - billed as O gauge - are very loose with no contact between the rails and the flanges. They will work on O gauge track, but with a lot of "wobble" as they roll. I was wondering why these loose-fitting trucks were not more carefully designed.
DFD26... no contact between the rails and the flanges...
Which is what 12" to the foot scale trains are designed to do also.
The wheel treads are tapered("fast angle") on 4' 8.5" gauge trains so the flanges do not contact the rails, and the cars roll down the middle of the tracks. The flanges do contact, sometimes, obviously, to keep the cars on the track if they get off center.
Rob
Thanks Rob. That helps!
The simplest analysis of the behavior of railroad trucks predicts that they will oscillate from side to side ("hunt"). I had the opportunity to observe this behavior years ago on the Cass Railroad in West Virginia. Riding in (on?) a converted flat car, I could see through the chinks in the floor, the truck endlessly shifting from side to side as the train moved. I have also noticed the rear truck on some of my "fast-angle" toy-train cabooses waddling as the train moved away from me.
The equations also predict that, if the coning of the wheels is reversed, that is, with the smaller diameter closest to the flange, the wheels, rather than moving back and forth and only briefly kissing the rail, will lock up to one rail or the other and stay there. This seems to be why wheels are strictly condemned when they wear into a reversed cone.
I have read that the need for some clearance between the flanges and the rails is the explanation for the odd number used as the dimension of standard-gauge prototype track, that is, 4 feet 8.5 inches. Supposedly, Stephenson first laid his track to 4 feet 8 inches (possibly dictated by a center-to-center spacing of 5 feet for 4-inch thick wheels) before discovering that he needed some wiggle room. He elected to modify the track rather than the train.
The analysis of railroad wheel behavior can get very complicated very quickly, as this Wikipedia article shows: http://en.wikipedia.org/wiki/Hunting_oscillation
Bob Nelson
Thank you, Bob, very much for taking the time to provide this information. Compared to my Lionel equipment, the "wobble" of which I spoke was more pronounced with the Amercian Flyer O gauge than what I am used to. I have really enjoyed learning about prototype operation alongside of modeling.
You didn't mention the condition of the equipment. I have a fair amount of O gauge Flyer including A.C. Gilbert 3/16" equipment and the trucks don't hunt any more than my post war Lionel or MPC equipment. I have seen trucks with a lot of wear, particularly with the wheels loose on the axles or with a slight bend to the separate axle, which do exhibit the kind of behavior you describe.
Yes, since I've gotten my first prewar Lionel and Flyer I see what you are talking about. The prewar trucks seem to have a somewhat looser gauge compared to my postwar Lionel and Marx trains. Could be due to the loose fit of the wheels on the axles.
So far there have been no derailments, even going through switches. But then my layout uses only old Marx all metal switches. Don't know how these cars would do on modern switches.
Since you haven't had this kind of problem, that bears a closer look at my gear. Admittedly, I purchased the rolling stock well used. I think I have my weekend project "cut out for me". Thanks!
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