Shane's R2 Build Log
For the same reason I went with metal legs, I also opted for metal feet. My foot shells are made from steel and come from WorrParts. I believe these foot shells are based on the JAG versions, having undergone little to no changes over the years. These things are HEFTY. With these, I'll definitely not be concerned with bumping into things.
All of the WorrParts footshells are welded and sanded. They come with all of aluminum detail pieces for the sides of the feet with the exception of the half-moon pieces. They also don't come with nuts to attach the detail pieces. For that, I needed to pick up some 4-40 nuts (I couldn't find Nyloc. :-( )
Because steel starts rusting pretty much immediately on contact with oxygen and water, the feet also come drenched in oil. This means they needed to be cleaned up and primed right away.
Foot Strips and Knurled Hose Fittings
I'm using a set of aluminum foot strips and knurled hose fittings from Bob Considine. The strips are chamfered to produce a nice, smooth join with the foot shell. They're perfectly fine. The KHFs I'm not so sure sure about. I could be wrong, but they seem to have been cast. They don't look machined. They also kind of leave a powdery aluminum dusting on my hands every time I touch them. This may go away the more they're handled. But if I'm not satisfied with them when it comes time to attach them to the footshells, I may go in search of others.
The KHF require 5/8-18 nuts, which is a finer thread than you'll find at Home Depot or Lowes (at least I couldn't find it). I ended up having to special order the nuts from BoltDepot.com.
Continuing along with the metal foot theme, I picked up a set of CSR aluminum half-moons from club member Bob Considine. I honestly don't know if there's a difference between CSR and CSL half-moons. Even with CSL, different designs depending on which movie R2 you're trying build. Given the foot shells are both CSL and CSR compatible, I figured what the heck.
The half moons are machined from 6061 aluminum and come with a complete set of hex screws/washers to mount them to the side panels on the feet..
Center Foot Wheel Assembly
Casters have historically been the go-to for the center foot wheel. The problem with casters, though, is that sometimes that they don't always move so smoothly. Try to push a caster 90 degrees off its current axis and you can be in for a fight, as anyone who's pushed a shopping cart will know.
Modern astromech builds have begun adopting the omni wheel from VEX Robotics. These wheels have rubber rollers around the wheel's edge that can move perpendicular to the wheel's primary axis. This allows for smooth movement in any direction with minimal fuss. This is the route I ultimately wanted to go.
I considered building my own wheel assembly for a set of VEX wheels. But club member Kevin Holme already created a really nice solution and was selling it to other members. So instead of burning a lot of time and money experimenting with different wheel assemblies of my own, I picked up one of Kevin's.
Ths VEX wheel assembly from Kevin Holme comes with all the goods - 4 4" VEX omni wheels, 4 flanged bearings (0.375in x 1.125in x 0.313in), a wheel mounting bracket made from 1/8" aluminum, a ton of 10mm flat washers for wheel spacers, and the bracket and bolts for mounting the wheels to the spacer. It also comes with a piece of 1.25" square aluminum bar with 1/8" thick walls that's intended to be used as a spacer between the wheel assembly and the foot shell. Apart from the square bar, the whole thing comes preassembled.
When you play with the foot assembly for the first time, you instantly appreciate the awesomeness of the VEX omni wheels. These things can move in any direction with none of the awkward resistance a caster might sometimes give when it needs to turn. Also, they're a lot of fun to roll around on the floor. It's obvious why these are becoming increasingly popular among builders, despite the extra expense.
Warp Drive (Foot Drives)
Doug Bickert's Warp Drive system is simply awesome! Each drive assembly features an AmpFlow E30-150 motor, a 1.5" wide 4" diameter Colson Wheel, a 3.25" VEX Pro Omni Wheel (for the caster), a mounting bracket, a chain (#35, 3/8 pitch - the same used on go-carts) and matching wheel sprocket (19 teeth, 2:1 ratio). The motors can run on 12v or 24v setups. They only pull 17 amps at max power under no load and have a 125 amp stall current. They can also be used with pretty much any of the popular motor controllers in use by club members today.
I'll be using these with a Sabertooth 2x32.
I'm cheating a little bit on my CS:L build and using a set of aluminum CS:R battery boxes. Matt McCormick was offering these to the group and they were too nice to pass up. The boxes are built to the CS:R ANH spec. The ports for the knurled host fittings come pre-drilled. The back of the boxes are removable using two screws. And Matt even cut out the motor ports.
All that's left for me to do is drill/tap the holes for attaching the boxes to the footshells, and then attaching the battery harnesses and KHFs.
These four, somewhat hollow, battery harnesses came from WorrParts. They're made out of aluminum and come with the T-connectors already installed with steel pins. The bottom pieces don't come pre-attached, nor does they come with any mechanism to attach them (some folks use a dab of glue or silicon for this purpose).