QMRD3

I've had the rover put together twice, and experienced challenges both times. In all cases I haven't put a single motor on yet.

In the above picture, the rover has its weight on the wheels for the first time, but with plastic axles that deteriorated quickly. The differential failed under this static load after about two weeks time, due to the creep of PLA under high stress. The differential holds the body level, so the forward weight of the body is held up via the differential. I have adjusted the body pivot point to minimize this static load, but it is surprisingly easy to "load up" the differential. Given the length of all of the moment arms, this force can get significant rather easily.

All of the axles are now aluminum hex bar, and the differential mechanism has been strengthened (via print settings, not geometry). The differential may need to be redesigned so a one piece hex bar can be used, instead of having the joint in the middle. 

The left-hand main rocker broke recently, so both rockers need to be reprinted with more perimeters. The "diff links" (curvey parts that hook the rocker to the long hex bar of the diff) also need to be printed again. It is difficult to get the diff links to both flex and be strong enough. If they can flex a little, it can help reduce the high loads on the differential itself (the hex bar also flexes a lot, which is great). 

Unfortunately I didn't get pictures of the whole rover before the rocker broke (I was rolling it outside to wash it and take pictures at the time). The quick clamps have been replaced with a better "steering lockout" system until the steering motors can be installed (may be quite a while, I hope to use tank steering at first for powered driving). Hopefully I can get my "fresh wash" picture before the end of the summer. 

The front wheels are on! I need to get all the wheels on and locked in the straight-ahead position because I will be using tank steering at first. I'm eventually going to modify Roger's Ackerman control method from Sawppy, but my motor strategy is different so it will take some time.

Also with the rockers set up, before I mounted the wheels, I tested the articulation. In my opinion this needs some work and may be the weakest part of the whole contraption. We'll see how it works when everything is on the ground under it's own weight. 

Here is another shot with the front wheels on: