After the initial test drive two weeks ago – we have built and tested wheel tracks for LifeTrac Prototype II, the hydrauilically-driven, open source tractor. Now LifeTrac is able to handle extremely rough terrain – which would otherwise halt other wheeled vehicles, including LifeTrac I. LifeTrac II can go over sizable humps and holes in the ground, and riding LifeTrac II is a spectacular experience. Here we show the build, installation, and testing of the tracks on rough terrain:
The addition of tracks makes LifeTrac well-suited for navigating through many of the erosion ditches and rough terrain of Factor e Farm. This is a great relief on practical grounds, as we are now well under way to gaining control over our landscape. Also, there is clear indication that the full traction is a lead into building bulldozers for earthworks.
The wheel tracks are robust, quite satisfactory, and well-worth replicating. They cost $520 in off-shelf parts for both tracks, totaling slightly under 70 feet of chain. Our particular design is designed for 16” truck tires. The test drive proved that the tracks provide the required traction, don’t slip on the wheels, and stay centered on the wheels.
The treads consist of 3/8” chain and 1” rebar, bent with our shop press on a bending jig (download in dxf format):
The rebar pieces are 20” long, and they are welded to the chain every 5th link. Each track has 40 treads, and totals 160 links of chain. These exact numbers happen to work for the exact LifeTrac II design as shown in this Blender design drawing. Note also that there are different types of 3/8” chain – and the type with exactly 9 links per foot is the one we used. This particular chain, in allows enough space between links for the rebar to fit flat on one link for welding (without hitting adjacent links). Chain with smaller links will not allow the rebar to touch only a single link, thereby complicating the welding. Moreover, we welded the chain on the inner side of the rebar – to minimize wear on the tires – by allowing the wheel sides to contact the smooth chain instead of the more rough rebar.
The bending jig works well with an 8.5” wide press foot consisting of a (1”x4”x8.5” steel slab). The rebar bends into shape readily with 20 tons of force. There were defects in 2 of the bent pieces – as the rebar began to crack at the bend. We fixed this by welding, and reducing the speed on the press cylinder by throttling down LifeTrac I, which powered the press.
It took about 30 minutes to cut the rebar for 1 track with an abrasive metal cutoff saw. It took 30 minutes to bend them, and 3 hours to weld. Thus, making one full pair of tracks as above takes one full day. It took another full day to figure everything out – from design, to the build of the rebar bending jig, to streamlining the workflow. Torching the rebar to pieces also works, but it then requires grinding prior to welding.
Overall, tracks are an excellent concept – which we tested first-hand with delight for ourselves, and we recommend them highly. It was plain fun to negotiate the big bump that you saw in the video, like on a roller coaster ride. Moreover, since the contact with the ground is maximized, the operator is in for a very smooth ride as perturbations on the ground do not transfer to the operator. We know that anyone who understands what it means to get stuck in mud or holes or ice will appreciate the access to low-cost tracks, and we are glad to document a working design.he ini