Bulldozer Review

From Open Source Ecology
Jump to: navigation, search

See CAD file - [1]

Overview: Currently, we are working with the non-symmetric drive configuration on the MicroTrac, as that allows for the narrow wheel base of interest using the exising Modular Wheel Units. This means that these are already available, and require no fabrication but only using modules already available within the set. This is chosen because the 15,000 in lb motor is surplus, at $280 each, but it does not have a coupling mechanism that would allow the Modular Wheel Unit to be any shorter. A more specialized motor would be useful, but those are approximately 5x more expensive, so not feasible from the cost perspective.

The first question is, thus - can we find a suitable high torque hydraulic motor that allows for significant shortening of the Modular Wheel Unit, to allow for a narrow wheel base that allows for symmetric track mounting in the high-trac configuration of the existing microtrac? If not, we need to build our own hydraulic motors, which is a 2 year or longer program.

If we accept the existing Modular Wheel Unit, then the question is how to optimize the existing design:

  1. Reduce the height of the machine while using the structural power cube, such that the machine can be used in the Microtrac walk-behind configuration
  2. Harden the tracks for long life of sprockets, rollers, and all moving parts so that the track design meets or exceeds industry standard longevity
  3. Verify all the set screw and collar strategy to assure that aggressive turning will not make the shafts split. Requires calculations to determine maximum allowable weights and forces, and pressure relief requirements, to allow for simple collars, clamp collars, and set screws to be used, to allow modularity and interchangeability of the drive system.

More Detail

More specifically, we uncovered many specific points that need to be verified and improved from the Bulldozer_Roadmap:

  1. Clamp collars for idlers - field performance and slippage? Requires SME review, calculations, and field data.
  2. Clamp collars for drive sprocket - what is the torque limit for the clamp collar in practice? Needs data collection and field verification.
  3. A way to remove bolting conflicts and bolt heads protruding on surfaces that can be used for attaching other modules. Feasibility of partial XYZ bolting on corners to remove bolt heads is one strategy. Bolt conflicts were catastrophic in the August build - in that they forced a limited range of attachment possibilities.
  4. Cab bolt conflicts did not allow solid mounting of cab on Power Cube. Better mounting with improved tipping balance should be explored.
  5. Series hydraulic system only was functional in the initial build - because 2 separate 1 spool valves downstream of one another function as a series circuit for the 2 wheel motors.
  6. Little space remains currently for putting on aggressive treads - due to interference with Power Cube
  7. Machine height is almost too large for MicroTrac. This does call for a smaller width of the base once we are capable of building our own hydraulic wheel motors. Currently, the wheel motors are a stopgap measure using off-shelf parts.
  8. Longevity of metal tracks needs to be verified - right now they are mild steel
  9. All together, track pieces and other parts should be cut with CNC torch table.
  10. Initial proposal is to master the bulldozer platform as a series of consecutive steps, with strategically determined functionality and price point.