Thursday, May 24, 2012

Details and Diagrams of MicroFork

As far as I can tell there are only a few major modules to MiroFork. Here they are:

  • Drive Module - Applies force to the ground so MicroFork can move.
  • Tool Fixture - securely attaches a tool to MicroFork and moves that tool relative to MicroFork.
  • Power Module - Feeds other components with energy. This is a PowerCube.
  • Control Module - Allows the behavior of other components to be controlled by the driver.
  • Tool Module - One of many possible machines that attach to MicroFork (eg, snowplow, tiller, etc.)
  • Passenger Module (optional) - Allows the Driver to ride on MicroFork.
In the spirit of hypermodularity, each of these modules should define interfaces such that they can easily be swapped out. This modularity is somewhat expensive. It requires additional materials and manufacturing as compared to an integrated tool. For long lived, versatile tools it's worth it.

Here are my vague ideas on these components and interfaces. I've already posted a little on the drive unit. I now consider those thoughts largely irrelevant. The drive unit can be implemented in lots of ways depending on the requirements. I'm reluctant to make MicroFork a skid steer because I want it to be useful on a suburban lawn (so no skid marks). I'm leaning toward a lawn tractor type design-- 4 wheels, two steerable, two powered by a differential transmission which is in turn powered by a hydraulic motor. This is complex, but would be manageable with salvaged parts. This isn't a good long term OSE solution but would work for me personally in the short run.

The Tool Fixture is the core of MicroFork. All other components attach to it. I'm like my forklift style manipulator because I imagine it to be simple to build and sufficiently flexible for MicroFork type work.

Time for the pictures! To the left is a the forklift based tool fixture. The green plate would support multiple attachment schemes. The two important ones are Bobcat quick disconnect, and 3 point hitch (like the one on my Dad's John Deer tractor-- probably class 2). A big feature of this design is ease of dis-assembly. The pins holding together the pivots can be removed to collapse the whole thing. Having multiple brown members of different lengths, allows the angle of the green plate relative to the ground to be changed. 

Next is the interface design between the Drive Module and the Tool Fixture. This is a simple 'drop and pin' arrangement. It doesn't allow for any movement, but is very general and should be (I'm guessing here) very strong. So long as the fixture and the drive module have correctly spaced joiners, it won't matter how they do their job (tracks, or skid, or articulated steering).

I still don't know how the other modules fit in. There may be problems with balance, strength, and alignment. I don't even know how a real forklift operates (I'm hoping to take a long look at one sometime soon.)

Ideally, if the interfaces were well defined/designed the different components of MicroFork could be implemented in parallel-- good job team WikiSpeed.

I was contacted by Graham who will be making a MicroFork this summer. I'm hoping to be able to help with the design if not the construction.