Crossmember spacing

[Whiskymack]

Building a model of this RS700L. It appears to have an auxilliary transmission visible just back from the diesel tanks and in cab shots clearly show 2 sticks.

I have an RS700 brochure whith a photo of an aux. case mounted between two standard Mack crossmembers but if I mount the casing in the position in the photo posted it places the rearmost of those crossmembers very close to the next one. I could move the next crossmember further back but it looks to me like the spacing of the camelback trunnion crossmember and the next crossmember forward of it is a standard dimension.

On a full sized truck, what would be more likely, Keeping the standard dimension between trunnion crossmember and the next one forward and just have two crossmembers very close together or reducing the distance between trunnion crossmember and tne next one forward to create more even spacing?

[Vladislav]

I never noted any special distancing between the trunnion stand and a crossmember to the front of it. More looks like Mack put them relatively even. And in many cases it even looks to me as they put those crossmembers anyway they wanted with just no logic.  Some trucks have a prop shaft intermediate support installed on that next to the front crossmember but some alsao have it on the 2nd to the front one. 

[Whiskymack]

I've just managed to answer my own question. I found another picture where I can just make out the bolt patterns on the frame rails and I can see two sets of 6 bolts close together so they must have put the two crossmembers very close together. I think there is a similar thing going on under the back of the cab on some of the Western R's, including the 1st gen Superliner. There's a cab mount crossmember which is a kind of curved bar and immediately behind it there is a standard crossmember with the forward edge of the flange cut away so it butts up directly against the cab mount. I don't know if there was a standard dimension between the rear trunnion and the crossmember to the front of it but that crossmember always seems to be in more or less the same place as far as I can see. There must be some science to it. I'd have thought someone would have calculated where the stresses were going to occur. By the way, The cab looks fantastic, Vlad. I cant't believe how much work has gone into that. It's a work of art!