This page, as usual, is decidedly temporary and is for info only. The first section illustrates the
use of the funrise brand toy tank tracks to increase the dimensions of a typical robotic platform.
The second section shows a couple of views of a strictly mechanical piece of whimsy I started
on one Sunday afternoon. It is designed to run around inside 8" sewer pipe and associated
fittings.

Funrise Tread based Platform

Funrise is the parent company of Tonka, their prestige line. The Funrise brand name appears on
cheaper toys including a tank which KB and KMart both sell, sometimes on sale for $8. I used
the treads from this toy tank in the following skid steer platform.

There are drive motors both front and rear on both sides.  A fifth motor rotates the range-finder
and the larger blue cube at the rear is a compass.

As can be seen, the underside is reasonably smooth with good even ground clearance making
the platform reasonably immune to even long pile carpets. The blue box at the bottom of the
picture is, in fact, two rotation sensors back to back. They are the odometers. You may just be
able to pick out numbers written on the motor casings. These are rpm values as measured at
9.00 volts. By using 4 matched motors, the mechanical accuracy is very good. It runs straight
for many feet even of carpet or polished wood flooring. You can very occasionally hear the
RCX code correcting the left right counts.

This close up shows how nicely the treads mount over standard pulleys. There are four on each
axle. From this view, you can also judge the ground clearance.

Sewer Rat

Well, its one way to use up all those small tyred wheels and 24 tooth crown gears!

There are two symmetrical drives each of which can haul many times its own weight up vertical 8" pipe.
There are 4 fixed center wheels which serve to keep the device away from the apex of elbow joints.
The other wheels are in two sets of 4. Each set of 4 has it's own drive motor. Each wheel is spring
loaded outward to grip the inside of the pipe. The drive to each wheel is via pulleys to provide torque
slip, as there is no room to put any kind of true differential in this size package, its completely full!
The center section is the "payload", which in this case is the battery box. The giant universal joints are
made out of those 4x4 round bricks with technic holes in the edge, which I think come from a Star Wars
set.

This picture tells the story, or should I say, shows some large non-Lego parts :) The pipe is 8" sewer.
I bought it new, don't worry. The device will make it around that bend! And orientation doesn't matter,
it goes at the same slow speed up, down or sideways. Debugging this piece of mechanics was hard. It
did used to get stuck half way round the bend and it's quite difficult to get it out! The people in the local
hardware store gave me some odd looks when I enquired about the possibility of ordering transparent
sewer pipe and fittings!

Please email me at barnes@sensors.com if you need any more information.