So here's a pic of the 1937 AAR and Modified AAR cars.
You can see on the one at the top, the floor has been milled out for those two center cross-bearers on the under body piece. Both kits have the same under body piece. You can see how on the lower shell, the center would be lifted off floor causing a bow to the center sill.
Jason
Jason,
From my information InterMountain has correctly modeled the the two underframes.
On the original AAR 1937 box car the cross-bearers were flush with the wood flooring and "Z" floor stringers span was from the body bolsters to the cross-bearers with separate stringers between the cross-bearers. For the modified AAR box car the floor design changed and the floor stringers span was from body bolster to body bolster and now the cross-bearers dipped to allow passage of the stringers.
Looking at two assembled models that I have, I can see that the cross-bearers on the underframe for the original AAR 1937 box car is flush with the floor and explains why there is a gap in the stringers whereas on the modified AAR box car the stringers have no gaps and both the cross-bearers and cross-ties rest under the floor stringers.
The two underframe parts should be different and if they are not that could be the problem. If the cross-bearers do show from the side that could be an assembly problem. The tops of the cross-bearers and cross ties should touch the flooring where they fasten to the side sills.
Bob Witt
P.S. The earliest production runs for the AAR 1937 box car only should have a single stringer on either side of the center sill. InterMountain did get that wrong. By early 1940s there were two floor stringers on each side of the center sill.
