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Critter, Stage 2

May 28, 2010 01:24

I will soon start constructing the new version of the critter. Right now I am in the R&D phase. I have the following goals for this version:

More useful drive system. I'll be using a 2-wheel differential drive (instead of 4) with one or possibly two casters. Due to my inability to locate a suitable gearhead motor/wheel/encoder combination that is also reasonably priced, I will likely construct a gearbox, which will be a royal pain, but will solve most of my problems.

A sonar & IR rangefinder boom that will be fixed to a servo and able to construct a map of the local area and localize itself within it.

Constructed out of more permanant materials. No wood this time. :)

A more rugged frame and better collision avoidance/detection.

Ability to dock to recharge SOMEHOW.

More efficient power supply for the onboard electronics.

In addition, I will design the frame to be less topheavy, so the batteries sit as low as possible. I'm also designing this to be able to handle impacts gracefully, although I'm hopeful that impacts can be all but avoided.

The issues I'm currently researching are as follows:

Searching for a GOOD gearbox construction tutorial. I understand the mechanics of building one, and I'm confident I can do it, but I'm not sure if I can do it well, and I'd rather have a minimal number of false starts. I would consider using a prebuilt gearbox that satisfies all of my needs. However, keep in mind, this robot will weigh up to 15 pounds when completed, so anything developed for a mini robot (which is what most of the available stuff is), isn't going to work. I'm also not building something as big as a battlebot, so most of what's available for those applications isn't going to work either. It's also far too expensive.

Searching for a good supplier of gears. Something with a lot of selection and cheap. I'm going with nylon gears for this stage of the project. Also going to need motors, wheels and shafts, although when I'm not worrying about how to integrate a gearbox and encoder, I have many more options available. The wheels I have on the critter now are nice and would probably work if I bought some more of them. They're 4" in diameter and made of solid hard rubber. However, I'm going to need to find some wheel hubs that have some method of attaching the wheel to the shaft without using superglue or a cold welding compound like I used on the current critter.

I need a material to build the frame out of that is VERY sturdy, but also light, and preferably not metal, at least not entirely. Some type of thick plexiglass would be ideal, provided a 10-12" span can support 15 pounds of weight without warping.

For all of the materials, I would LIKE to be able to find a reasonably local supplier (DFW area). Not absolutely necessary, but it would make my life easier when I'm not entirely sure of what I need.