B9 Electronics: The Inside Story Part 3 – Leg, Hip & Waist

OK, fair warning now… the further we go up, the more complicated the electronics become… sort of…Again, this is what I did. There are several ways to “skin a cat” and this is one of them……
My hip section moves up and down to simulate a power failure from a power pack pull out as well as to bow to pick things up, address royalty, etc. The motor to rotate the torso is also located in the hip section. This is a departure from Mike Joyce’s replica robot where the waist rotation motor is actualy inside the torso. The motors used for both the hip and waist rotation is the Dewert 24v motors. Each one is controlled by a Vantec RET 411P single motor controller. These plug in to the RC receiver. I fused each RET 411p to protect it from any overload or spike from the batteries, etc. The manual for the RET 411P is located on the Vantec web site at http://www.vantec.com/retman98d.pdf. It is a very straight forward wiring procedure where the positive and negative leads of the motor are connected to the white and gray wires of the vantec controller. The black and orange wires go to the positive and negative leads of the battery. Note where the switch goes. I will use one of the switches inside of the programming bay to control hip and waist rotation. By switching them off I could save on battery power consumption and also serve as a safety control mechanism if I wanted to limit movement of my robot.

Waist Plate, Donut and support rings

Building a fully mobile robot has some challenges that static robot builders do not usually have to deal with. For example, the donut (a fiberglass ring that sits between the torso and the waist plate) has to be able to withstand the impact of bumps and jolts of a greater magnitude and for longer periods of time than a stationary robot or it will split or crack. In addition, my donut is connected to the torso and will disconect at the waist plate. I have designed my robot to disconnect from the lower portion of the donut to the waist plate by a twist lock method. I have seen other builders make the donut secured on the waist plate and the torso seperates from the upper part of the donut via screws from the inside of the torso via the side vents. What I have below are a few pictures of the underside of the donut. Look carefully at the grooved “twist lock slots” on the donut.

To handle this situation, James (my machinist) came up with a way to insert a large delrin ring inside the donut that would mate with the delrin twist lock plates to provide compression support to prevent the donut from being crushed. Standard aluminum spacers would not provide adequate/contiguous support for the donut. I would of made a titanium donut If weight and cost wasn’t an issue.

B9 going on a diet!

After I had the realization that my B9 was becoming a porker I decided to put him on a diet. A drastic diet!! I had James (my machinist) lighten the entire endoskeleton. Every rail, plate and bar was lightened. Every nut that could be removed was removed and threaded into the structure that could support it. Below are the before and after pictures of my “aluminum liposuction procedures”. It is beautiful isnt it?! Too bad it will be covered up with silicon rubber.

Weighing In

OK, what you see before you is the complete lower assembly (well I have my side plates off currently) of my B9. I am very proud of this. It was a lot of work (and money) to get to this point. But like the man said, a B9 is never truly finished until I say it is (ahem…or maybe the wife has a say in it???) Anyhow, I decided to put him on a scale. WOW … what a surprise! From the waist down he was 300 lbs. For comparison, Mike Joyce’s entire replica robot weighs in at approximately 275. That presents a huge problem for me.
With a projected weight of my robot now at over 400 lbs the current motors will not perform very well so that means I need to redesign the drive section with more powerful motors and that means just 1 thing ……. you guessed it, bigger; more powerful motors need bigger or more batteries. So I am changing the electrical system from a 12V system to a 24V system.
I will also have to redo the drive section and try to lighten all metal surfaces as much as possible. This will not be cheap….