Tractor Design Rationale, Product Ecology

LifeTrac is a low-cost, multipurpose open source tractor. It satisfies many of the OSE Core Values OSE_Specifications#GVCS_Specifications.2FCore_Values

1. Open Source. The LifeTrac was designed from the ground up with the intention of making freely available not only the design, but also the education necessary to understand, use, and improve the design.

2. Low Cost. As compared to its commercial equivalent, the LifeTrac is 1/10 the cost to acquire. There are even more dramatic reductions in the cost to own.

3. Do-It-Yourself. Most of the components and sub-assemblies are held together with bolts. If you've got a wrench you've got a tractor.

4. Closed-Loop Manufacturing. Because the materials the LifeTrac is made out of require so little machining, they can be produced by future GVCS machines. No need for exotic materials or fancy injection molding.

5. Industrial Efficiency. The LifeTrac's performance is on par with what is available commercially.

6. Lifetime Design. Unlike what is available commercially, the LifeTrac is designed to function indefinitely. With no one to make money on a locked-in customer there is no reason to design for obsolescence.

7. Robustness. The LifeTrac might be ugly, but it works everywhere and for everyone.

8. Technological Recursion. With a LifeTrac you can begin to accumulate and manipulate the raw materials that you'll make everything else out of. Eventually, another LifeTrac.

9. Local Resources. What good are the resources under your feet if you can't use them? The LifeTrac opens up new avenues for self-sourcing.

10. Replicability. With full documentation of how to source the materials, build the tractor, and use it in the field, the LifeTrac eradicates barriers to entry.

Definition: LifeTrac is a versatile, 4-wheel drive, full-sized, hydraulically-driven, skid-steering tractor of 18-200 hp with optional steel tracks. LifeTrac is intended to be a minimalist but high-performance, lifetime design, design-for-disassembly workhorse and power unit of any land stewardship operation. It features featuring easy serviceability by the user. Its modular nature allows for quick attachment of implements; interchangeability/stackability of multiple power units (Power Cubes) for adopting power level to the task at hand; quick attachment of all hydraulic components via quick-coupling hoses; including quick interchangeability of hydraulic motors for use in other applications. It can be fitted with up to two sets of loader arms. LifeTrac is intended to be used with modern steam engine Power Cube module for fuel flexibility, such that locally-harvested, pelletized biomass crop, such as hay, may be used for fuel. Regarding safety features, LifeTrac replaced the traditional power take-off (PTO) shaft for driving other implements with a detachable hydraulic motor for the same purpose, where this motor may be mounted on the tractor, on the implement, or wherever it is required.

Problem Statement – Industrial tractors are being designed increasingly for planned obsolescence with 10 year lifespans, and the user typically cannot service their own tractor due to complexity of design. Power transmission and engine systems are the dominant failure modes of tractors. Fuel costs are a significant expense of operating a tractor. Capital costs of purchasing tractors typically place their users in debt.

Solution – LifeTrac is designed to be the peoples' tractor. The user is able to service, modify, and produce fuel for the tractor. Gear transmission is replaced with a hydraulic drive train, where quick-connect, flexible hoses are the means of transferring power. Lifetime design (bolt-together construction, modularity) with general purpose parts allows the tractor to be passed down from generation to generation, before its life-cycle is completed as feedstock for the induction furnace. The absolute simplest design facilitates creation of small-scale enterprise for manufacturing these tractors in as little as 3 days of time using a RepLab1 facility. This allows communities to be entirely self-sufficient in their mechanical power infrastructures, while reducing lifetime costs of tractors by a factor of at least 10.

Further Information – Tractor on Wikipedia; skid loader Wikipedia; CADTrac; DIY tractors in post-war Poland

Development Status and Needs – We have completed Prototype I and Prototype II, and have secured an order to fund the building of Prototype III. Prototype I (ref) was an articulated version of the tractor without roll cage, and Prototype II (ref) was an enclosed version with tracks and skid steerin. Prototype II has demonstrated quick-attachment and stackability of power units (ref), as well as interchangeability of wheel motors and control valves via quick-couplers for repurposing in other applications. A complete 3D model of LifeTrac with correct scaling is available (ref). 3D CAD and fabrication drawings are needed. The next steps are fabrication of Prototype III (ref to be blogged), as well as development of toolpath files for producing LifeTrac with CNC torch table assist. Moreover, minor redesign of LifeTrac lends itself to adaptation as a tracked bulldozer – via addition of chain gear reduction to the direct-coupled wheel drive. The next step is CAD drawings addressing outstanding design issues.

Development Brief for LifeTrac Digital Fabrication - Download the LifeTrac Blender file. Then import it into a professional CAD package like Solidworks to generate 2D fabrication drawings, and further, these drawings have to be converted to toolpath (xy) files for a torch table.

The problem requires virtual dismounting the tractor into all of its structural tubing and plates - the components that we will be cut with the torch table. The tubing is 4x4x1/4" mild steel tubing, and the plates are 1/2" mild steel plate plate steel.

The final step is optimizing the cutting strategy based on available stock steel that can fit on a torch table. For example, we can start with a sheet of 1/2" thick steel, not individual plates, for producing all the mounting plates.