Friction sucks or actually heat+friction sucks. The differential with printed parts only has worked pretty good so far but as other parts in the drivetrain have gotten more durable the more stress is put on the differential.
My biggest problem has been the Axle shafts “digging” in to the diff casing due to the heat and friction.
I don’t really want to incorporate “non-printed” or “non-standard” parts, but I have made some 0.15mm thick lasercut washers to put on the inside and outside as seen on the pictures. More testing to be done.
As a sidetrack I have started to design a new diff or rather new gears in the diff to even out the pressure of the gears. More on that later, first priority is to make this work somewhat ok.
I did wonder about that, if the gears had the possibility to to melt onto the diff casing, also the little square in cup that mates with the gear has snapped off for me (but that was ABS). What’s the best filament you’ve found for printing them?
I´m printing the “Axleshafts” in Polycarbonate now and they haven´t broken yet. Gears in ABS and as for the casing i´m testing both Nylon and PC. But maybe with the washer the casing can be in ABS…
Normally they put something like 10k silicone diff oil into the differentials to reduce the amount of “spin out”. Incidentally that might also help with the longevity. Center diffs normally have 10k-30k or even thicker for bashing 50k-200k
I’m not quite sure how oil tight the diff is though, it should normally have recesses for the rubber O rings with a metal washer on top to prevent rubbing the housing. Coat those washers and rings with marine grease and it might be ok for 10K diff oil and thicker.
@Daniel_Noree I really like the idea of 3d printing as much of the car as possible. What I think would be amazing would be if we could design the car to use more than one differential. That way people could choose if they wanted a printed diff or off the shelf one. Just a thought.
