Leg Cart Progress

Well, we just wrapped up our second class session. We kept lecture time pretty short – we only did a brief introductory presentation on steel weldments (which you can check out here) and reviewed a couple of homework assignments from the first class – and then spent most of the class on (a) prepping the controls team to work with the upcoming Leg Cart simulation and (b) coordinating the mechanical team’s build progress. James or Dan will post some simulation videos soon, but in the meantime I thought I’d show off some of the mechanical work.

To get started, let’s review the hardware we bought before class, starting with…

One of the sets of decisions we made as instructors early on was deciding on the powerplant. We needed something that provided sufficient power to provide hydraulic fluid for a 1-2 ton robot, that was (a) robust, (b) relatively affordable, and (c) as off-the-shelf as possible. We decided to rip the hydraulic powerplant out of a forklift (specifically, a Toyota FGC-45 from 1991) and repurpose it. The net result is that we have a 135 horsepower, propane-powered powerplant that produces upwards of 35 gallons per minute of hydraulic fluid at 2,500 psi. The fact that it’s propane fired means the robot can operate for brief periods indoors, and also means that we can swap industrial-grade fuel tanks good for 6 hours of runtime without having to custom build or fill any of the fuel system components.

So that’s what we have – what we’re working on now is making the Leg Cart, our prototype hydraulics platform. The idea here is to make a platform on “rails” (i.e., only able to move in one dimension) that has a single leg and a hydraulic powerplant on board (we’re borrowing the pump from our full system and running it off of a giant electric motor). This will be the students’ introduction to hydraulic systems, so we’re building something small (relative to the final system – the cart will still be 600 pounds…) at first so we can screw up and figure out what we’re doing. Without further ado, here’s the progress we made on the cart chassis in the past week:

Spark and Mac have been working hard at it for the past week or two – good work guys! Next up, we have the base weldment for the arm pivot:

Adam and Andy teamed up to work on this over the past week. Unfortunately, some material was backordered, but we’ll be resolving that shortly.

Joel, Joe, Mike and Jona are all working on parts that are heavy on machining and low on welding, so we’ll see updates from them a bit later on in the process.

That’s it for now. Keep an eye out for an update on simulations!

-Gui