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….

The Hip Bone is connected to the Tread Bone

Well, this is my first version of my moveable hip design. It is based on the design that is on the B9 website by Mike Joyce. The plans on the site did not have a lot of detail needed for a machinist to take it and run, so I had to modify it. My machinist did an outstanding job. His name is James VanReenen and he is the owner of the North Dallas CNC machine shop. He does outstanding work and he is a fan as well (which really helps in doing this stuff).
Most of the drill hole sizes were not listed so he had to figure them out. In addition, the existing plans do not work with the current tread section offered by Eric Johnson so I made the following modifications: Foot mounting side supports that fit inside the tread section to hold the legs had to be made shorter and the holes for the wheels were in different locations. The leg stance width had to be made narrower, and the original plans had wood as the top and bottom plates for the hip. I changed those to aluminum to make it a bit stronger to withstand impact of a mobile robot for RC use.
With these modifications, Mike’s design now works with Eric Johnsons tread section and Will Huff’s rubber pants, legs and knees. For specific details and new drawings just send me an email and I will forward them to you.
One additional safety note, my tread section is all Steel. I have a soil sampler, motor drive units and batteries and power supplies in and just above the tread section so my CG is kept very low.
If you have aluminum tread sections I would seriously look at getting steel ones. If you want to stick with aluminum then I would rethink my design and probably use reinforced or extruded pvc and wood for the hip plates and legs. Remember, you want to keep the CG low and that means keeping the weight down the higher you go.