Summer Mecanum Drive
After seeing many successsfully implemented mecanum drivetrains throughout the Velocity Vortex season, we decided that we should try and not only build a drivetrain using mecanum wheels but also program it. We began by simply replacing the stealth wheels that were on one of the old programming bots and used that to test the basics and to get the programming working. After seeing varying degrees of success, we decided that we should also actually build a drivetrain ourselves so that we could not only practice building a drivetrain (since we only had one member of the build team that had experience buildind a drivetrain before) as well as further testing of the limits of the mecanum system.
We began with two possible ideas. The first was to make a frame out of REV Extrusion, and the other was to make a drivetrain similar to the Andymark Tilerunner using wood and other parts we already had. Because we did not have enough REV to build the frame we designed we decided to go with the "wooden Tilerunner" since we had plenty of wood, and wood is significantly cheaper than REV.
We begun the design process with the wheels. Because of the way that the mecanum wheels operate we knew they would have to go in a square. After determining the location of the wheels, we begun the process of deciding where the motors should go.
some entirely indecipherable whiteboard sketches
These sketches were later condensed into the diagram below.
We decided that the top left design would be the best to start for a number of reasons. First off, it is the most compact, leaving us plenty of room in the center of the bot for other mechanism and electronics. In addition, the motors that power the drivetrain generally have a great amount of stress, and mounting them through holes in the wood gave us an easy way to help support them so they dont bend. We initially planned on having the motor shaft sink into the wood so that it was supported on both sides and wouldn't bend, but we forgot to take that into account while deciding how far sideways the motors would be placed.
Next we made a CAD of our wooden walls so we had a better idea of what we were actually working with, which also gave us an easy way to cut out our wood on the CNC Router, leaving no room for Human error.
An isometric view as well as the dimensions of the inside wall
An isometric view as well as the dimensions of the outside wall