Servo - July 2012

FIGURE 8. Attachment for Mr. Croup.

FIGURE 9. Damage from Ripto.

attachment. A large dustpan type scoop would have been useful to help control an RC toy based bot, Chobham, which defeated Trilobite in a judge’s decision. I will also replace the 7075 aluminum in the plain wedge with titanium, since it suffered a lot of damage (Figure 9) in its fights against Ripto.

BUILD REP RT:

Siafu: an Army of Ants – Part 2

In Part 1 of this series, I outlined the design process I went through to establish the basic layout of my new drum Ant kit. In Part 2, I will detail the design of the drive motor mounts, the hubs and wheels, the drum and its mountings, and the design of the front wedge profile.

The new motors are similar to the larger ones used in my Weta and Trilobite Beetleweight kits. They have a cylindrical gearbox and a motor no larger in diameter than the gearbox. There are two M2 tapped holes in the front of the gearbox — again similar to the larger motors.

FIGURE 1. Ant motor plus mounting plate.

● by Pete Smith

I designed a flat plate that could be mounted onto the front of the motor (Figure 1). The first plates I made were 0.030” thick aluminum but while these worked, I found that 2 mm long screws were a little too short and 3 mm ones were a little too long and interfered with the mechanism inside the gearbox. A thicker 0.060” plate allows the 3 mm screws to secure the plate without damaging the internal gears. Four holes sized for #2 screws provide a method to secure the gearbox to its place in the chassis.

In the past, I have used Dave’s hubs and Lite Flite wheels (Figure 2)

FIGURE 2. Dave’s hub.

in my small bots. These have worked well. They are light and resistant to damage, but I have found that the Loctite® required to secure the outside washer can make it hard to remove, plus access to the motor mounting screws is difficult without removing it. This can be a problem in a competition if a wheel or motor is damaged and needs to be replaced. A different Loctite may help, but I decided to try out another design of the wheel and hub in the Ant.