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ExMod The experimental module development platform
2. Wheel Mounting
Submitted by Asellith on February 4, 2010 - 9:20pm.
Wheel and Sensor Mounting
The frame is designed to be experimental. Nothing is permanent and can be moved where needed. The wheels are about the only important part that cannot be moved. As I mentioned earlier I mounted the servos in Aluminum U channel. However servos don't get you very far without wheels. I found a tutorial on mounting the omniwheels to the servos here: http://www.acroname.com/robotics/info/ideas/omnimod/omni_mod.html
However I didn't like the design so I modified it slightly. I didn't use the finishing washer. I just used a standard locking washer. Also I tried the nylon bolts but found them lacking in stability and strength so I upgraded them to steel bolts. These work great and have not failed me yet.
A big issue was finding a round servo horn. I finally had to break down and buy a bag of miscellaneous servo horns from two different hobby stores in two different states. Hobbytown USA sells them but I couldn't find them for much cheaper individually online. This way I have a few extra horn types for other projects.
The servo horn screw didn't fit through the T-nut so I had to put it under the T-nut and bolt that down before I screwed it into the servo. A bit of a pain but the added benefit that you can't loose the screws. That was the hard part the rest is done by threading the other T-nut onto the bolt and screwing the bolt into the servo horn's nut. Don't forget the lock washer to keep things tight. Remember the idea is not to tighten it down as tight as possible but to secure the omniwheel to the servo. Watch you don't get over excited and damage your wheels.