LifeTrac II Build/Wheel Tracks Construction Video Script
LifeTrac Tracks Construction Video Script
The LifeTrac wheel tracks provide all terrain traction including the ability to traverse ditches that are about 2/3 the length of the tracks themselves. They are created from simple materials: treads bent from 1 inch rebar, 3/8" chain with links measuring 2 inches long, and chain links for connecting the ends of the chain.
Fabrication of the tracks requires two custom jigs, one to press the rebar and one for welding the treads to the chain.
The pressing jig is constructed from seven steel members welded together. The bottom member is a piece of upside-down 7/16"x6" u-channel measuring 16-3/4 inches in length. Two 1 inch thick plates that measure 4 inches by 5-3/4" with notches in the top for holding the rebar are welded onto the bottom plate, at an inner distance of 14-3/4 inches apart, creating a U shape. These are supported by a piece 3 x 6 x 1 inch thick welded on the inside to support the U under the pressure of rebar bending. The press foot in the shop press should be 8.5 inches wide.
The tread welding jig is made from 1/2 inch rebar. This jig is made of a frame consisting of 12 slots to hold the rebar while welding on the chain. The jig is 57.5 inches long, 13.5 inches wide, and 2.75 inches high.
The top of the jig consists of two 58 inch runners spaced 13.5 inches apart on center from one another by 24 cross pieces. The cross pieces are cut to 15.5 inches and should be welded to the runners with 1 inch extending on either side beyond the runners. From one end, weld the first 2 cross pieces apart 1 11/16 inches from center to center, and continue to space these pairs 3.25 inches apart down the length of the jig.
The bottom of the tread welding jig is a similar pattern, with the runners spaced 5 inches apart on center by 24 5 inch cross pieces. Repeat the same pattern of spacing the cross pieces as on the top.
The bottom and top of the jig are connected at each end by 2.75 inch high pieces of rebar and in three places evenly spaced in the center of the jig by 3.75 inch vertical pieces.
The first step in fabrication is to cut the 1 inch rebar into treads measuring 20 inches in length. Each track uses 33 rebar treads, so for one tractor you will need to cut 66 treads total. This requires 110 feet of 1 inch rebar.
Using the rebar pressing jig and a 20 ton shop press, bend each of the treads, one at a time.
Now prepare to weld chain to the treads. Each track requires two chains 131 links long. Leave some room on one end of the jig to pile up the track as you move along. Place a tread in each tread holder and lay the chain out on the side of the jig. Weld the chain onto the outside of the rebar, leaving one link free at the very end of each track for linking together, and 3 links in between each tread. Wrap the chain around the tread to hold it in place and weld thoroughly. Make sure the chain stays lined up properly at the end of each tread and does not twist between treads.
When you've finished all of the top welds on each side, flip over the jig and weld the bottom of each link to the treads. Lift the jig up at an angle to better expose the treads you are working on.
Flip the jig back to the first side, lift out the section of track you've just completed, refill the jig with loose treads, and continue to weld the track together until you reach the end of the chain, where you will leave one link free for connection.
Lay out the completed treads on the ground for mounting on the tractor. Line them up with the wheels and drive onto the center of the tracks. Using come-alongs, ratchet the ends of the tracks tightly towards one another. Let out air from the tires and then tighten the track once more until the links are close enough that you can connect them with chain links. Bend the steel pins on the chain links.
This completes the fabrication, assembly, and mounting of the LifeTrac all terrain tracks. For more information on the LifeTrac tractor tracks, visit the Open Source Ecology wiki page.
