California Science Center

Today was R2 Builders day at the California Science Center, which is currently hosting the "Star Wars: Where Science Meets Imagination" exhibit.

As usual, Mike's R2 was the star of the show, making the rounds and regaling the crowd.




Mike gave a talk about R2 building and the R2 Builders Club. He talked about his R2 on stage, and showed various parts (including my drivetrain). William Miyamoto and Guy Vardaman also said a few words.



There we also the cool props at the exhibit, including Luke's landspeeder, the rebel blockade runner Tantive IV, and the Jawa's sandcrawler, among many, many more.





And of course, a Lucasfilm R2-D2 prop was there.



Afterward, we visited one of the R2 mailboxes and took some pictures. All in all, a fun day!

More Center Foot Work, Started Working on Drivetrain Chain

Tonight I continued where I left off on the center foot.

I trimmed the channel sides a little lower.



I started working on the layer that the casters will attach to.



I cut a pair of 1/2" pieces of plywood to size, and glued them together. These will be trimmed to match the angled profile of the foot shell.




Finally, I wrapped up with an attempt to separate the chain so that I can get pieces of the correct length. My chain tool turned out to be a piece of junk, so all I did was make an oily mess. I found a better chain tool in my bag of tricks, so I may be able to continue working on this without having to go out and buy one.



Saturday: The California Science Center Star Wars exhibit, featuring... R2 Builders!

Worked on Center Foot

Not a whole lot of progress tonight.

I am deviating slightly from the original design of the center foot. I'm going to sink the sides that form the channel into the the base, rather than use supports. This allows me to stack two layers of 1/2" plywood above the casters without having the foot wind up being too tall.

First I made a couple of parallel dado cuts, 1/4" deep and 1" apart.



Then I trimmed the base to size. At least I hope I did, I'm a little worried I may have overdone it on the trim, but I'm still working on fitting it into the shell.



I also widened the channel gap in the right foot shell, so the tip of the ankle can fit through now.

Like I said, not much progress.

Installed Drivetrain Bushings, Filed Foot Shell Channels to Match Drivetrain Depth, Dremeled Drivetrain

Some bushings that I ordered from McMaster-Carr arrived today. These are the 1/2"->3/8" reducers that I need for the ankle bolts. I lightly tapped them in with a hammer, and now they have a nice, snug fit.



Next, I filed the bottom of the channel slots in the outer PVC foot shells to match the depth of the drivetrain. When I first filed these down, I intentionally left a little bit of slop on them, until the drivetrain was ready. Tonight I finished the job.



I found that I will need to widen the channel gap on the right foot shell about 1/16". The tip of the ankle isn't quite fitting through.

I also had to hack on the drivetrain itself tonight with the Dremel. The door frames slightly touched the drivetrain from the inside, so I removed a small amount of material to resolve that.

Drilled Holes for Motor Mounts, Prepped Foot Strips, Finished Door Holders, Attached Door Details

Tonight I drilled the holes in the main bar of the drivetrain to attach the motor mounts. Four holes on each main bar, 0.266" in diameter and countersunk.



The drivetrain is getting closer. I still need to file some flat spots on the axles for set screws on the gears and wheels, and I need to hack on the shaft adapters a little bit to get them to fit snugly on the motors. Then the shaft adapters need to be pinned to the shafts. And the chain needs to be attached, of course.



I also cleaned the aluminum strips that go on the front and back of each of the feet. Here's a tip: If parts arrive taped together, do yourself a favor and don't wait a year or more to take the tape off.



Next, I finished installing the foot shell doors by nailing in small strips of PVC onto each of the bottom door holders.



Now all I need to do when I want the doors to come off is pivot the strips of PVC.



After gagging on acetone fumes earlier, I was ready to gag on PVC glue fumes. I glued down the various details that go on the doors of the outer foot shells.



And that was a wrap for this evening.

Main Batteries Arrive, Attached Foot Shell Doors, Marked Main Bar for Drilling

Today, the batteries I ordered from ragebattery.com arrived. I ordered a total of eight 6-volt, 12 amp-hour batteries. My foot and dome motors will run off of 24 volts, so those will be wired in series. The sound system runs off of 12 volts. (The dome electronics run separately off of four D cells.)

I ordered enough batteries to have a spare set when needed. The 6-volt package is reasonably small and inexpensive.



I finally installed the foot shell doors tonight.

First, I taped the doors in place, as centered as I could get them.



Next, I glued down little squares of PVC. The squares on top have rectangles that extend above them. They are fixed behind the top door frame. The bottom squares will have similar rectangles on them too, but those rectangles will pivot on a nail. That way the doors can lock and unlock from behind, by reaching underneath and pivoting them. The doors then slide out from the bottom.

There are also a couple of small strips on the diagonal sides, to help center the doors left-to-right. All Mike's idea.




I wrapped up tonight's work by marking the main bar for drilling, where the motor mounts will be held in with screws. Hopefully I'll drill those tomorrow, and then all the cutting and drilling on the drivetrain will be done! Unless I find a problem, that is.

Ground Down Wheel Hubs, Drilled Ankle Drivetrain Holes, Drilled Shaft Adapters, Cut Battery Boxes

Today I went back to Mike's, where good things always happen.

I showed Mike the very tight fit of the wheels in the wheel housings. Mike took the wheels to the bench grinder to help get them to fit much better. Mike ground down the first one, I did the other three. After the wheels were shaved, we added lubricant. Now the wheels spin nice and free in the wheel housing.

The grinder makes neat sparks.




I had been paralyzed with fear on making one of the last cuts to the drivetrain, the hole for the ankle bolt that attaches the drivetrain to the tip of the leg. I wasn't sure how best to drill this hole. Should the channels be cut separately? Together? How to position them?

In the end, we drilled both channels as they would be mounted in the drivetrain. We drilled slowly and were able to successfully drill straight holes, 1/2" in diameter. I plan to use a 1/2"-to-3/8" bushing, and a 3/8" bolt in the hole.



We also drilled some more shaft adapters, using the 3/4" steel rod I had cut this past week.



Last on the agenda was cutting out a square from each of the battery boxes, for maintenance purposes. This square will be on the inboard side of the battery boxes, and will be held in by a screw in each corner.

Mike used his super-human Dremel abilities to cut very straight lines with the small saw blade attachment. The first battery box gave Mike a pretty good coating of PVC dust.



He managed to avoid a second coating when he cut the other battery box.



The drivetrains are almost done. I just need to drill and countersink the four holes in each main bar for the motor mounts, and I need to assemble the chain.



Thanks for the two millionth time, Mike. The finish line is drawing closer, I won't be bothering you for help that much longer.

Recut Top of Center Foot, Mounted Half Moons

A big thank you to Matthew Henricks, who generously donated some 1/2" high quality plywood for the rebuild of my center foot.

The bad news is that I had to junk my center foot made from poplar, the good news is that today's recut of the center foot from Matthew's plywood went extremely fast, as I was able to use the poplar center foot pieces to guide the plywood cuts.



Like last week's version, this version seems to have turned out pretty good. The fit is just about right. Note that I still need to build up the bottom of the foot to accept the caster wheels.




Next, I returned to the foot shells. Today I mounted the half moons onto the doors.

I started by placing all the parts on the foot shell doors. The outer foot shell doors have a few details on them, while the center foot shell doors just have the resin half moon pieces.

I traced each item, and then removed everything except the half moon, and taped it down in place.




I placed another half moon on the drill press table, so that when I set the door upside down with its half moon taped underneath it, the back of the door would be perpendicular to the drill bit. I marked a location on the back of the door dead-center, and two more marks one inch to the left and right, for the three #4 1/2" screws that will hold the half moons onto each door.



The doors seem to be holding the half moons just great!



I had intentions of getting the door holders installed today, but that didn't happen. One of these days it will though.

Finished Adding Foot Shell Reinforcements

This morning I sanded smooth the Bondo I applied last night. Barring any future mistakes that require repair, the foot shells are done being filled and sanded. (I reserve the right to even out the seam between the door and the shell via filling and/or sanding as needed.)

I finished gluing in the last of the foot shell reinforcements. Each of the outer shells got a pair of thin strips of PVC to help reinforce the bottom strips on the front and back of the shells.



I removed the temporary feet from my droid in anticipation of being able to install the drivetrain on the outer feet. I plan to recut the center foot tomorrow from high quality plywood that Matthew Henricks is making available to me.

It looks like R2 parked in a bad neighborhood.

Received Battery Chargers, More Drivetrain Assembly, Finished Footshell Filling

Today I received the battery chargers for the main batteries that will power my droid. I'm still waiting on the actual batteries, they should arrive soon. The charger I received a couple of days ago is for the remote control transmitter and receiver batteries.



I did some more assembly work on the drivetrain tonight. I needed to see how everything fit together before I drill the final few holes.



I think (and hope) that I'm just about done with the foot shell finishing work. I filled the last of the small voids in a small edge of each of the outer shells with Bondo.

As a reminder, a large portion of the inboard side of these outer foot shells will be completely cut out and removed to allow the drivetrain to pass through, into the battery boxes (which will also need to be cut). Thus, I did not bother finishing that area of the foot shells to perfection.

Tomorrow I'll sand, and then I think the foot shell finishing is complete. Yes, I still need to attach the doors. I'll get to that eventually...

Installed Bearings, Wheels on Drivetrain

I spent most of the evening in the garage tonight, fitting the bearings into the holes that were drilled into the wheel housings yesterday. The bearings are slightly tapered, enough that they didn't quite fit through the holes. I used the drill press with the drum sander to sand the edge off the bearing. I let the bearing spin at a slow, constant rate against the sanding drum, in order to get an even sanding all the way around.



Once the bearings were all pressed into the holes, it was another chore to get the wheels in there. It is a very tight fit. I had to sand down the inboard side of the bearings to get everything to fit, and it is under stress. I may go back and sand some more, to relieve some of the stress.

The axles went in without too much fuss, it's just a matter of aligning everything perfectly.



I wrapped up tonight's work by screwing the channel down in place and installing some of the gears, to see how it all fit together. I think everything is still looking good.



I still need to drill four holes in each main bar to hold the motor mounts, and I need to drill holes in the channel for the ankle bolts. At that point, the main part of the drivetrain will be done, and all I will need to do is install the chain. I also still need to install the doors on the foot shells.