1/16 Scale FrankenDiff

[ddmckee54]

Zabco:

I went with Alibre for a couple of reasons, you can get a perpetual license, and you can get an off-line version of that license - one that doesn't need to phone-home every 30 days. I refuse to rent a cad package, and I also refuse to let somebody else hold my files hostage. I pulled the trigger on the Alibre purchase this morning, only had 4 days left on the trial. I've REALLY got to learn Best Practices, and actually use them, instead of just poking and prodding at it like I have been.

I printed out a prototype of the front half of the diff to see how things fit. Let's just say that my measurements were apparently less than accurate. Or at least my 3D model is less than accurate. I guess I got some 'slpainin to do to it. Over the weekend I hope to get to the point where the WPL guts will fit between the front and rear halves of the diff.

I left side to side clearance for fit of the pinion to ring gear, as well as front to back clearance for the pinion to ring gear. I figured I'd print a prototype and let the diff find its' happy spot, then measure how much I needed to adjust the model.

I've definitely got a problem with the diff carrier bearing fit - they don't. Looks like I measured the bearing ID and OD, then drew the 3D model using the ID dimension instead of the OD.

Then I've got this STUFF in the middle of the axle itself, that I can't for the life of me figure out WHY it's there. On both axles there a hole with a very short pin inserted in it, imagine a 6mm long pin through a 5mm axle and you've got the picture. I'd include a picture, but that axle is at home and I'm NOT. There's a plastic collar that slips over the pin and retains it, but the pin also limits how close the outboard edge of the collar can get to the diff carrier. Just outboard of that junk is a plain bushing, yup - a bushing. There are bulkheads on both sides of the bushing fixing it in place. The inboard bulkhead also does a very rough job of limiting the side to side position of the diff assembly by limiting how far outboard that plastic collar can move.

I can't think of ANY good reasons why the crap is there. The best explanation I can think of is that WPL uses this assembly in other differentials and it's needed in that other application. We all know that WPL uses bits and pieces from this model and that, slaps them together, and calls them a new model. In the next round of design I'm going to chuck all that crap in the middle of the axle into the trash-can and see if anything breaks. I've still got bearings supporting the diff carrier and bearings on the outboard ends of the axles. That's all that most full-size cars and light trucks have. If it's good enough for them it's good enough for me.

It's supposed to be rainy Saturday night and Sunday, we'll see what I can get done on the Frankendiff.