1/16 Scale FrankenDiff

[ddmckee54]

OK, progress has been made - but it's been a LOT like doing the Hokey-Pokey. This is my current progress:


From right to left we have the following:
1 - This is the cover for the locknut, The screws that hold this on will simulate the lug-nuts.
2 - This is the first version of the duals as described in Post #22. It didn't fit!
3 - This is the version that attempted to fix the issues from Post #22, it mostly worked. I tweaked the bores in the 3D CAD model by hand and realized this will be a royal PITA on a more complicated model - more on this later.
4 - This is my better idea, it ALMOST worked - more on this later also.
5 - Which you can't see, is bolted onto the other end of the axle and fixes the problem with #4.

This is the later. A couple of days ago I started a thread on another forum about slicer issues - with internal bores and pockets not being dimensionally accurate when scaled, here's the link:https://www.homemodelenginemachinist...-issues.36499/

I use Simplify3D for my slicer and I have always had to oversize the holes if I wanted things to fit together. It sounds like Cura has the same problem. I know from the diff housings that when I use S3D to scale the model to 103%, the external dimensions are within 1/4mm of the 120mm desired width of the housing - which is close enough. All of the internal bores and pockets measured too small though. The really confusing thing was that they were all too small by about same amount. They were all about 97% of the desired size. I got to wondering how the slicer was handling the internal bores and pockets when scaling, and if this was the problem with undersized holes all along. So, like Ford, I had a better idea. I took the task of scaling the part oversize, to allow for shrinkage, away from the slicer and gave it to the CAD program - which I reasoned was better equipped to handle the task. I reset the bores and pockets to their original values and scaled the part to 103% before I exported it to the STL file. #4 is the result, and it almost worked. Remember Major problem #2 from the above post? Yup, I do-ded it again. I didn't allow for any clearance Clarence! The 12mm hex driver would have been a press fit, and that's not good. I fixed the clearance issue and that resulted in #5.

Having wheels on both sides does tell me that I need to go back to the drawing board though. I currently measure about 200mm across the wheels and axle, I need to be at about 185mm. Now the question is where can I lose that 7.5mm on each side?

I added this image, to show that #5 exists and to show the gap between the duals. I think the gap looks about right. But I could shave a couple mm out of the gap, it's about 4mm-ish now. I could easily modify the wheel offsets 5mm and it wouldn't be too noticeable. I've got 100mm between the wheels now and the Bruder frame rails are 80mm outside to outside, so that leaves me a 10mm gap between the tires and the frame rail. If I move the wheels in 5mm that still leaves a 5mm gap, which should be enough for spring shackles and other odds and ends. I'll also have to move the angled transitions on the axle housings in 5mm, to give me a place to mount the springs, but that I'll fix when I re-do the pocket dimensions for the scaling fix.