Servo - March 2011

out of the chuck between operations. The part is remounted in the chuck using the blade boss for these topside operations, so strict accuracy is not maintained. If you do need high accuracy and have to move the part between operations, then a four jaw chuck and careful setup is required.

I fitted the blade to the hub using Grade 8 hex head screws (Figure 10). The hex heads are a little more likely to get damaged in combat, but will be much easier to replace if they do as you can usually get a pair of Vise-Grip pliers to get a solid grip on even a badly damaged head. Socket head screws often have the hex sockets damaged and can be a pain to get out in a hurry.

The new blade and boss were tested at the Franklin Museum event in Oct ‘ 10 and proved to work well. I would get the next set of blades a little harder perhaps, but it’s always a balancing act between being too hard and breaking, and too soft and bending/blunting. I might also try a longer and thinner blade to give a little extra reach. SV

PARTS IS PARTS: Mtr niks Viper

● by James Baker

The Mtroniks Viper series of boat speed controllers have been used in many of my robots in the past. Made in Great Britain, these controllers offer full forward and reverse functions, one touch calibration, and advanced failsafe functions. They also have a built-in battery elimination circuit and motor stall protection.

There are a lot of speed controllers available for sub-featherweight robots (under 30 lbs) from lots of different manufacturers, and all have their advantages and disadvantages. For one specific application, I consider the Mtroniks Viper to be unrivaled. One of the areas of robot combat I am involved in is providing the opportunity for the paying public to come and drive identical robots in combat against each other. This “arrive and drive” attraction features robots specifically designed to fight only each other, in a quick assembly combat arena. This controlled combat format allows the robots to be optimized for long run times, quick battery changes, exciting battles, and reliable operation in any kind of weather. Yes, you read that right, these robots often run in the rain.

My smallest arrive and drive robots weigh under two lbs and use a pair of Viper15 speed controllers

The first prototype medevil class robot.

(which are 100% waterproof) coupled with silicone covered motors, and a single sealed 7. 2 volt 3,000 mAh NiMH battery. The 15 amps rating of these controllers is more than enough to run these fast little machines without ever breaking a sweat — even in heavy rain. I have actually given demonstrations to potential customers where I have run one of these robots in a bath full of water. These robots actually float, but do regularly submerge completely when they crash into other objects. This rather extreme demonstration serves