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
RoboShaw ended up with some pretty significant updates.
- 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?
Robotshaw once again did lots of miles - something around 100, I think
- cruising around the playa during the week of Burning Man 2006. I gave
rides to people from all over, including Switzerland, Ireland and
Germany. RoboShaw even pulled another mutant vehicle - 700+lbs on
small wheels - back to its camp when their drive sprocket packed it
in. I particularly liked ferrying folks until 4:00 am Burn Night
to the sounds of Sugar Magnolia and other Dead tracks. I did make
some notes of things I liked, and things that still need work; these
will guide the efforts for 2007.
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
- 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.
- Alternator & gauges. Lots of juice, and I knew
what was happening.
Things that still need some
- 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
- 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.