Servo - January 2014

drive wheels are also recessed so that the drive pulleys all line up correctly.

An Oilite bush is used where the 1/2" shafts of the motors pass through the chassis rails. This adds support to the shaft and means we do not need another bearing on the outer side of the wheel. I don't like to support shafts on the outer side as these bearings and their mountings would be very vulnerable to damage in a fight.

CheepShot 3.0 and Xhilarating impaX each had the same Achilles heel: If the nose of the bot was lifted — even a short distance — off the ground, the rear wheels would also lose contact and the bots would be pushed around too easily.

Trilobite’s design got around that by ensuring the rear wheels are far enough back to always remain in contact with the ground. The diameter of the motors used in the new design are much bigger relative to the wheel size ( 3" wheels and 2" motors as opposed to the two 1/4" wheels with 1" motors) so that any vertical rear wall in the chassis means that even a 14° angle would result in the (Figure 8).

That is not acceptable, so I needed to find a solution. That solution came in the form of two 3/4" diameter 1/4" wall thickness aluminum tubing. I could machine a section of the tubing to leave a curved wall (Figure 9) that can be screwed to the end of the main chassis rails (Figure 10). The bot will now have traction no matter how high the front end is pushed up.

A 1/8" thick 7075 aluminum base plate is secured in place by Plastite screws; a similar thickness is used to make a front bulkhead (Figure 11). The latter is attached using medium Nutstrip and 10-24 machine screws. The top panel is the same as the bottom, and 3/8" UHMW side armor panels protect the wheels (Figure 12).

A 5/8" case hardened steel shaft is bored out to lighten it (I did this with success in the weapon drive shaft of Surgical Strike) and is used as the hinge pin for the wedges. The shaft will be retained in position with a couple of cotter pins.

A scaled up version of Trilobite’s "drum killer" wedge is made up of a titanium backplate, 7075 aluminum hinge brackets, and a UHMW "nose" (Figure 13). A Team Whyachi MS05 power switch is added to the interior (Figure 14).

If space and weight are tight, the much smaller Fingertech Robotics power switch likely has a sufficient current rating for a couple of Mini-EVs or RS-775s.