Is there a chart or speadsheet available that shows which Accumate truck is the correct one to use with a particular Atlas car? For example, I think that the Atlas 90 ton hopper utilizes the #22056 70 ton roller bearing truck which includes the coupler. Also, while I see some differences between the 40 ton, 70 ton and 100 ton trucks such as the type of bearings, journal covers, the number of springs and the shape of the part that bears down on the springs, I cannot tell what the difference is between the #22051 friction bearing truck and the #22076 40 ton friction bearing truck. All of my rolling stock that has Atlas friction bearing trucks seem to have a truck most similar to the #22051 truck.
The Accumate images are at N Scale Supply: See the following link: http://www.nscalesupply.com/ATL/ATL-Trucks.html I,ve compared what I see there to my own models.
You're thinking Atlas trucks with Accumate couplers. IIRC, Accumate doesn't make trucks for rolling stock, they only make couplers. That model ATL-22071would look good under the 90-ton hoppers, as well as any 100-ton grain hoppers you may have. Personally, I don't see any difference between the two trucks either, so I would imagine you could get away with using either one on, say, any 40-foot boxcar. But I'm not too much of a rivet-counter, so take that for what it's worth. Perhaps a little detail, and the price, is all I can see different. Both would look good on older equipment. On the newer stuff, you're better off going with roller-bearing trucks.
Atlas have also used different truck on the same model, e.g. the 90 ton hoppers have been earlier delivered with Bettendorf trucks and Rapido couplers, newer runs had Roller Bearing trucks and Accumates. I don't know whether this was related to some prototype or just due to availability. The biggest difference is the Atlas 100-ton truck with the 36" wheels, it really makes cars look different. I even use this in exchange to MTL trucks...
The 90-ton hoppers were probably built with friction bearing trucks and converted to roller bearings later. In the case of the model, maybe it is just availability.
Bingo... the 90T hopper was tooled when true (5' 10" axle wheelbase and 36" wheels) 100T trucks weren't around in N scale... so Atlas used a 70T truck. Even today, they still have to use a 70T truck for them, as a correct 100T truck won't fit.
Thanks guys for all your replies but I still don't know what the difference is between Atlas friction bearing trucks #22051 and #22076? The friction bearing trucks on older Atlas cars with the Rapido couplers and four digit stock numbers appear slightly different than those on the cars with Rapido couplers and five digit stock numbers. The part of the bolster resting on top of the springs of the older cars seems to have two small square sections as compared to the same piece on the newer but still old cars which seems to have one rectangular piece. What I can't tell is which truck # is which. Normally I'm not such a "rivet counter" type, but my curiosity has gotten the better of me!
The difference is in who made the prototype. Although when N-scalers usually speak of trucks the name "Bettendorf" comes to mind but they were only one of number of manufacturers who make trucks, which is why the trucks are different. The #22076 truck is accurate for a National C1 truck, while the #22051 is accurate for a Bettendorf truck.
