MicroRAX

MicroRAX is a miniature version of the popular t-slot aluminum extrusion framing system available from suppliers such as 80/20 and Faztek. Using special brackets and hardware you can quickly and easily create joints and mount components to these extrusions creating a very strong, aesthetically appealing, and reconfigurable assembly. The standard sized extrusions have long been used in manufacturing environments but they're also very popular for constructing large robot frames especially for the FIRST high school competition and other similar projects.

Before MicroRAX the smallest t-slot extrusions available were 1" X 1" which is far too big and heavy for most smaller-scale hobby robotics projects. MicroRAX extrusions however measure 10mm X 10mm which makes them perfect for many smaller robot projects. Currently there is a very limited amount of hardware and brackets available for these extrusions but that will soon change as MicroRAX grows in popularity and other suppliers begin to offer their own compatible parts. Lynxmotion is one supplier who has plans to offer their own custom brackets that will open the door to many more applications such as the ability to mount motors, servos, and interface with their popular Servo Erector Set.

This page provides a basic look at the various projects I've created that utilize MicroRAX. Some of these images show robots I'm working on and some show simple experiments I've created to see what can be done with MicroRAX extrusions. I intend to add more pictures to this page over time and eventually hope to add step by step instructions on how to accomplish more advanced functions with MicroRAX.



Mecanum-Wheel Robot Test Bed



Early Linear Motion Experiment



Rack & Pinion Linear Motion

This is a rack and pinion linear motion system I created using a micro-size servo hacked for continuous rotation. The servo is currently mounted to a Lynxmotion rotational base with double-sided tape but will eventually be mounted inside the base. The rack and servo gear were purchased from Servocity.



Tractive Force Measurement Apparatus

This is an experimental test device I built to measure the tractive force output of individual robot wheels or a compete robot. The device was built using MicroRAX miniature extruded aluminum T-slot and uses an 11lb load cell and LCD readout scavenged from a $20 digital scale bought on eBAY. The way the device works is the wheel or robot is placed on the "trolley" which can roll forward and backwards following guides. When the robot is turned on or the wheel starts turning, the trolley is pushed against the load cell which is rigidly mounted to the main frame. The force output is then displayed on the LCD screen.


For testing individual wheels the fixture shown in the above image was constructed. This is mounted to the main frame but can swivel to adjust the application force on the wheel. A small gearmotor is mounted to the underside of the swing arm and this drives the wheel. During testing weight would be added to the top of the swing arm to provide additional down pressure simulating the weight of the robot itself. These tests were performed to select the wheel with the best coefficient of friction and thus tractive force.

This test apparatus was quickly assembled in a few hours and could benefit from numerous improvements to make it a much more accurate measurement tool. First, it would be very useful if the applied load could be recorded so that the data could be plotted and closely analyzed. Right now the user can only see the force output in real-time which misses out on transient performance.

Secondly, the gearmotor used is powered directly from a battery pack and is switched on or off only. Ideally the motor would be controlled from a power supply to ensure the voltage and current is similar between tests and not effected by battery drain. Also the motor output speed should be monitored with an encoder and controllable by the user.


More to come...