Murdoch17, on 02 January 2013 - 04:42 PM, said:
@ Daedalus304: Yes, a LDD file showing the placement of the BBB wheels would be most helpful! Thanks for offering to do it!
Hey! I put together a somewhat comprehensive LXF file for you, using some stand-in BBB medium wheels. Turns out the technic pulleys are right about spot on with the real BBB wheels! Just to be on the safe side, I included two methods of spacing them close together with different offset styles, and I also included a couple basic structures that I tested with real bricks and real BBB Med Drivers to make sure they work. Building in 6 wide is going to leave you with a rather high looking running board, but as the wheels are also exactly 1 brick thick you can build outside them if you so wish. I also included two other structures highlighting the odd build clearances needed with one version of the wheel offset. I hope you find this file helpful!
As you can see, to fit them in the 8-stud wheelbase you need to have your center axle offset from the other two, because of the flanged drivers. Flanged drivers are tricky, but easier to build with when they are on an offset (Offset axles are in green bricks, red bricks are not) because you can build more tightly around them. My Baldwin Mallet engine uses this form of spacing, but it worked well because that engine has no running board the there is some tight piston spacing.
For your tank engine I'd suggest you use the 9-stud wheelbase (The top one). This makes your flanged drivers on "friendly" spacings which are easier to deal with and build around - as so:
With just a mild amount of recolouring you should be able to use the frames from the LXF on your actual engine, as these substitute wheels are extremely close to the real BBB drivers in physical dimensions. I hope this was the information you were looking for, if I missed anything helpful please let me know.