2006 - what actually happened

    More photos of RoboShaw's 2006 adventures

RoboShaw received a lot of improvements before Burning Man 2006. As usual for me with these sorts of projects, things kind of got a little out of control, and RoboShaw ended up with some pretty significant updates.  Highlights included:

• A 50Amp Nippon Denso car alternator with built-in regulator. I machined a custom pulley to fit behind the torque converter; this worked like a charm. It turns out that the control algorithm in the regulator is pretty aggresssive; if the battery is at all low (eg below 13 volts), the regulator attempts to pump 30 amps into the battery to charge it in a hurry. While this does an admirable job of keeping a car's battery charged during stop and go drive, RoboShaw's 6 hp engine just doesn't have the torque at low rpm to keep the alternator turning. I would have been better off with a smaller pulley on the engine, probably. In any case, to work around this problem w/o disassembling the alternator and providing an external regulator, I added a 1 ohm power resistor in between the alternator and the battery. This resistor was wired so that a switch could short it out. I used this to start the engine, and it allowed to to rev the engine before engaging the alternator fully when charging low batteries. A bit crude, but very workable for a high-touch rig like RoboShaw. A truly clean solution would sense engine rpm and react automatically; I may replace the switch in the future with a 2N3055 power transistor since the power dissipation isn't too bad.
• Voltage and amp gauges; the amp gage is right next to the engine since the majority of the power generated goes to the headlights and battery charging; the voltage gauge is back where the driver can see it. Both are illuminated.
• Completely rebuilt drive train; I was able to get rid of the stock Comet torque converter frame and substitute flangette bearings to hold the driven element of the converter. A better design for the chain idler also made adjusting chain tension much simpler.
• Single push-pull rod steering. This got rid of all the difficulties with the steering binding under load. I did upgrade the Heim joints to 5/8" in size and upped the push-pull "rod" to 3/4" pipe to prevent excessive flexing, and the plain bearings were replaced with left-over 1" pillow block bearings.
  
• Paint - RoboShow was decked out in desert cammo. I sprayed this pretty easily with two cans of Rustoleum textured paint - smoke and desert sand colors. This worked very well, and this paint is quite tough. This would look nice on a bicycle as well. The drive unit itself was painted flat black.
• Sound system - I ended up going overboard here; I used a 70 W RMS/channel "Gothic" stereo car amplifier driving 6x9 Pioneer speakers in boxes suspended above the rider's heads. A 30G ipod carried in my pocket provide ample tunes for cruisng the playa. This set up worked very well; more than loud enough, the marked directionality of the Pioneers meant that folks ahead of us could easily hear us 50+ yards away. I can recommend this combo as quite resistant to abuse and much fun - listening to The Offspring or Rammstein while driving across the playa surrounded by flaming propane effects was a real highlight.
• Lighting - Since RoboShaw was now packing an alternator, I replaced the single marginal headlight with dual driving lights. This really helped out on the playa late at night. I also added several more CCF lights in a more intense blue color. A set of red CCF tubes mounted to the rear avoided any problems with our rear-aspect visibility.
  
• RoboShaw's head - last year we used a variety of hats to decorate RoboShaw's head; this year I hammered out some aluminum plates to fit the quadrants of his skull and drilled them for LEDs in those little plastic clips; I wired 12 sets of 6 LEDs in series with one blinking unit in each set; the 72 blinking LEDs made RoboShaw very noticable at night. The 2 intense ultra-bright red LED "eyes" were left in place from last year.

So how well did all this work out?

Things that worked:

• Steering.  No trouble at all, and never a hint of problems.  I'm still considering replacing the trailer hub that forms RoboShaw's steering axis with dual pillow blocks to reduce canting loads.
• Sound.  Clean sound, plenty loud, and easily controlled.  I just need to do a better job of selecting tracks for the IPod; with my Solaris desktop supporting gtkpod I no longer need to get my son to handle this task.
• Paint.
  
• Alternator & gauges.  Lots of juice, and I knew what was happening.

Things that still need some love:

• I forgot the chain oil in Menlo Park; the #35 drive chain ran largely dry all week and wore out the sprockets.  They had already taken a beating the year before, when they received daily oiling.  I think an automatic chain oiler is in order; I can do this w/ a simple 12V solenoid valve, small oil tank, and a needle valve to regulate flow.  I'll use some of that new canola-based chain saw bar oil - it's bio-degradable so having a total loss oiling system won't make me feel like such a environmental hooligan. Constructing a complete enclosure for the chain seems like a lot more work than it's worth.
  
• Lighting durability was a problem, and additional visibility of the long front assembly wouldn't hurt..  Unlike the first year, the playa was heavily rutted in spots and this caused more vibration than last year.  In addition, some of the CCF tubes were damaged during reassembly, and the new head assembly's resonant frequency was clearly lower than last year's resulting in more vibration on the front tubes.  As a result we lost a total of 5 CCF tubes by the end.  I'm replacing the ones that were damaged accidentally, and will improve the vibration isolation on all the CCF tubes not on the engine.  For the engine, I think I will go to all LED lighting, and the long frame section will get lit with 120V LED Christmas lights - 4 watts for the whole string!  I think I also need to solder the wires on the LEDs in RoboShaw's head; two of the 12 strings stopped working by the end.
  
• Upon return and disassembly of RoboShaw, the rear wheel bearings were found to be worn out.  This wasn't terribly surprising - RoboShaw often carries substantially greater loads than the 300 lb nominal rating of each wheel and the playa isn't exactly kind to unshielded bearings running with intermittant lubrication.  After some searching, I found precision bearings that are a press fit into the existing wheel hubs on an airless wheelbarrow wheel vendors website.
  
• The rough ride on the playa got old, and the added weight of the speakers mounted above the rider's heads made the sunshade assembly shake more than I liked.  To work around these problems, I'm adding an additional bolt-on brace to between the seat assembly and the long frame piece.  This should greatly stiffen up the assembly, but for the ride quality we're going to larger tires at lower pressure.  Schwable makes some wide low pressure tires ("Big Apple") that fit RoboShaw's rims, and the increased volume should help soak up more bumps w/o the risk of tube pinching.  Changing tires is also a lot less work than adding suspension :-).
• I was jealous of all the art cars that had fire to play with... so I'm adding some propane flares to RoboShaw.  These will need to be on a tall mast to meet mutant vehicle (and common sense) safety considerations.  By putting them on the engine, I can keep the propane and fire well away from the riders and the flammable sunshade.  Perhaps I can control the valves using a low pass filter from the audo track and have the flames act as a bass beat.