Probably one of the greatest perils in owning vintage machinery lies in the eccentricities of former owners. In some cases you can track down the original owner to ascertain the machine's condition. But of the many old machines I have owned, I have never had one unit I could connect to the original owner.
That was the case with the 'Nimble T-6' (see GEM, August 2003), my 1952 International Harvester bulldozer. In that first article, I wrote about modifying the T-6's controls to make it easier for me to operate. That modification worked fine, but the unit had problems with the tracks, which I had yet to confront. Specifically, the left track was good, but the right track was in bad shape: The street grousers were bent and smooth, and the bushings were worn through to the pins.
I made several inquiries to firms that replace pins and bushings, and the best deal was with a firm in Lancaster, Pa. The cost of replacing the pins and bushings would be about $700 - the big problem was getting the track the 150 miles to the repair shop. For the past 70 years my main hobby has been antique machinery and metal working. I have maintained a shop of sorts, equipped with a lathe, drill press, power hacksaw, welding equipment and many sundry tools. I have had occasion to shrink fitted bearings with heat, and I've used heat to loosen tight parts.
Getting to Work
Given these problems, I decided to experiment with rotating the bushings in place in the links - and on the tractor. To do this I made a substantial clamp from some heavy pipe and plate with a boss that would engage the void in the bushing caused by wear. The clamp was held together by 3/8-inch high-strength bolts. I welded a heavy stub of steel to accommodate a 5-foot length of 1-1/4-inch pipe to the clamp.
Somewhere along the line I acquired two propane burners, and I clamped these in position so the flame would impinge the link. I arranged a cable from the pipe attached to the clamp to an overhead pulley, and then to my 14 HP hydrostatic garden tractor. I fired the propane torches, waited two minutes, got on the tractor and after a little slipping the bushing began to turn. The final result was that the bushings rotated about 130 degrees. Unbolting the hot clamp and repeating the process was time-consuming, but the end result was worth it.
The total track length was shortened by 3 inches. We have used the machine with both the loader bucket and the bulldozer blade, and have had no slipping of the chain over the sprocket. Surely someone must have used this process before? There are no doubt many crawlers (some not too old) with worn-through bushings. If a person had to have a machine shop fabricate a clamp, it would still be less expensive and a lot less bothersome than having the pins and bushings renewed.
There is a possibility of heat having a negative effect on the links. According to an official International Harvester Co. publication, the links are drop-forged and heat-treated. This means the links are heated to 2,000 degrees F in several steps for drop-forging, and for the heat-treating the metal is heated to 1,350 degrees F and the cooling timed. I borrowed a high-temperature heat-recording device, and the average heat of the metal in the link was 450 degrees F when the bushing started to turn. This is well below the temperature required to change the properties of the steel.
While my experience seems like a happy ending, the fact still remains that at 87 it is a bit risky for me to be going through the gymnastics of getting on and off the machine.
Contact engine enthusiast Dick Holcombe at: P.O. Box 247, Dushore, PA 18614; e-mail: email@example.com