[ddmckee54]

I spent most of the day yesterday fighting with Alibre locking up. I'm trying to do the final 3D design for the powered steer diff parts. The design I showed a couple of posts ago was quickly thrown together to see if I could even make it work. NOW I need to cross the I's and dot the T's so that it will all work together, and that means accurately modeling all the individual parts. That's actually a good thing as I found a couple of gotchya's while doing it.

One of those gotchya's was determining how much I needed to shrink/stretch the ends of the diff front and rear housings to accommodate the single front wheel instead of the dual rear wheels, and still maintain the same wheel track. It turns out I needed to take 13.5mm off each side. I know that doesn't make sense that I need to move the end of the diff housing inboard when going from duals to singles, but I spent a couple hours convincing myself that moving things 13.5mm inboard was actually right.

The second gotchya was when I realized that the screws holding what I'm calling the diff pivot in place (that's the part where the steer axle pivots in order to steer) would be hitting the outboard bearing - that would not be good. So I had to change the design of the diff pivot, it's now about 6mm longer. THIS change interfered with the outboard screws holding the front and rear diff halves together. Since the diff pivot slides over the ends of the front and rear diff halves holding them together, those screws aren't really needed any more. Problem solved, but I did have to change the 3D models for both halves to reflect this.

The third gotchya is what does the length of the brass tubing splice need to be? My modified rear axle measures 147mm from end to end. My modified axles were 70mm nominal in length, so that means the spider gears were occupying 7mm of space in the middle. My 3D printed non-powered front axle needs to be 172mm from end to end. If I subtract the 7mm for the spider gears, and divide by 2, the stack-up for my front axle length should be 82.5mm? (Why do I feel like Rodney Dangerfield in "Back to School" right now?)

Plus I realized that there's nothing keeping the outboard bearings of the steer axle from sliding outwards. On the rear axles the hex driver holds the bearing in place, on the front axle there's nothing but air in that location. Oh well, that's a problem for future me to solve.

Don