It walked! At Burning Man! It didn't make it to the DMV, or even out of Kidsville, but I am so happy that it walked at all, and on the playa at that.
Here is a video of it's first steps, ever, on the playa:
Thank you, everyone here, who helped me figure out the technical details. I didn't, and still don't, really know what I am doing. But with you guys help I was able to get the machine this far.
LeChat, it was wonderful to meet you and your wife. I'm glad we randomly met. Thank you again for your help here, and perspective on playa-- that it can take two years to make a vehicle that does more than go around the block, three years to get out to the trash fence. And Sail Man, thanks again for helping get this thing back in the trailer-- you are truly stronger than four hippies!
I think, with some more time in the garage, this machine is likely to make it past the Esplanade next year.
But first it is going to rest, in storage, for a couple months. The month long mad rush to finish it in time, of late late nights and waking up early in the morning to do it all over again, got a little crazy even by my standards of live-eating-and-breathing the projects I do, and I need a little vacation from being a mad scientist for a while.
The main problems are:
- It needs feet. Though I love the foot prints it made, it was sometimes punching through the crust of the playa and sinking 4 or 5" into the playa (!).
- Sinking into the playa increased the loads on the crankshaft, because the legs would touch the ground before they had stopped moving forward, so the weight of the machine was taken sideways on the crankshaft support arms, which caused a weld on a crank shaft support arm to tear off. Just making the legs required 544 one inch long aluminum welds, so I thought I was pretty good at TIG welding aluminum by the end of this. I have the stack of dimes look, at least. But I am not. The weld that tore had no penetration and was just filler rod laid onto the surfaceâ€¦ I need to reinforce the crank shaft support arms with brackets that are riveted or bolted on. And then reinforce them again with some sideways tubing, for good measure.
- The nylon bearings I used in the leg joints have too much play in them. The legs were sometimes able to rub against each other, even with 2" of separation. I am going to try replacing the nylon bearings with bronze bearings, which are much tighter. And if that doesn't work, I will have to go back to making clevises to make a set that will take a larger hip axle (if I move up from 3/8" rod to 3/4" or 1" rod, which will allow less movement in the leg joints).
- Idler pulleys on the chain, so that we don't have to make the chain as tight as it was to keep it from skipping. This will work, right?
- Optical encoders on the motors, so that the motor controller will keep the left and right side at the same RPM. Currently, the motors are given a voltage and allowed to vary their RPM slightly as the torque requirements change, which means the machine yaws slightly when one side needs slightly more torque.