LifeTrac Design Challenge

The LifeTrac open source Tractor is our weak link in the OSE Christmas Gift to the World for 2011. As we prepare to publish the Civilization Starter Kit DVD v0.01, we will include a Beta release of Prototype IV of LifeTrac, and Full Product Release of The Liberator open source CEB press, Soil Pulverizer, and Power Cube. We have gone trough 3 prototypes of LifeTrac at Factor e Farm, and we need to go to Prototype IV to address the outstanding wheel drive issues and loader balance corrections.

On the wheel drive, we are now working on quick release wheels –  where a cam mechanism and 1-2 bolts allow you to take off entire wheel assemblies on LifeTrac – in under 5 minutes. This is a great step forward on LifeTrac’s direction as the world’s first life-size Lego tractor. We have already shown quick interchange power units,  design-for-disasssembly (bolt-togeter) construction, interchangeability of motors, and quick-connect implements.

The concept design is a monolitic assembly with motor, bearings, and shaft – that can be taken right off the existing frame – by loosening a bolt and releasing a cam lock:

This simplifies the former miunting method. where 3 mounting plates were attached to individual frame members by using 6 bolts:

As we build this, we will use higher-torque, splined shaft motors in Prototype IV to address the failing coupler issue on the former keyed motors.

Moreover, we are addressing weight distribution issues for the LifeTrac loader arms. We are bending them to get the loader closer to the tractor body. We found in field testing that the tractor would begin to tip with  about 1500 lb of load on the front loader. As we now have over 150 3000 lb pallets full of compressed earth bricks, we will need to move them – and we want to do it with LifeTrac IV. Here is modeling of height reach after modification:

To obtain assistance on this problem, we are hosting a Design Challenge for LifeTrac (see problem statement and solution wiki page) by partnering withGrabCAD – a crowd-source, open engineering design platform. I found about GrabCAD through our successful Kickstarter campaign. Hardi Meybaum, GrabCAD CEO, was one our Kickstarter backers. We appear to be on the same page with respect to the potential of open engineering for addressing pressing world issues, so I have much hope in an evolving partnership within the context of rapid development of the GVCS 50 by year-end 2012.

More news on the GrabCAD Design Challenge is forthcoming. This will be our first experiment of true crowd design. The problem is well-defined and simple – but the solution will require some serious engineering to make it practical. As a reward, we are considering admission to our Build Naturally Workshop next year – which we are hosting as part of our Kickstarter reward structure. This includes admission to a one-day Natural Building workshop at Factor e Farm in 2011 + DVD documenting the natural construction with CEB, Straw, and Lumber, including modular house and workshop designs that can be adapted based on our designs. Includes hands-on experience: brick laying with CEBs and square bale insulation; assisting with lumber production with the Dimensional Sawmill, and square bale making with the Baler.

Regarding the solution path for the LifeTrac quick connect wheels – we will prototype the monolithic assembly here, with the splined motors – before the 24th of December – as the parallel design challenge progresses on GrabCAD. Mike Apostol is doing the CAD modeling here, and James Slade will do the build in our new workshop, which is now closed in, while Ian Midgley continues to document.

The working concept is:

  • Bolt with cam around bolt, where cam is locked in by a lever. and tightening the bolt both fixes the lever and pinches the frame tubing
  • Cam has a handle running parallel to the shaft when unlocked, and parallel to frame members when locked. Cam handle is welded directly to cam.
  • A second bolt towards middle of assembly pinches the assembly around tubular frame members
  • A peg (see concept drawing) fixes the assembly in place on the frame. Note that the cam and bolt can be integrated into one, not shown on concept drawing. The second bolt is also not shown in the concept drawing
  • Cam concept (top view, bolt head not shown):

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