Allis Chalmers HD20 in Australia

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1953 Allis Chalmers HD20

This photo was generously emailed to me from Australia by Grant Muirhead, where he is in the business of land clearing for agricultural uses in the bush. The 'trailer' is, I believe a trailer mounted ripper (sans tooth in this photo) with a cable lift. The HD20 features a long forgotten Detroit Diesel engine called the 6-110. In keeping with Detroit Diesel convention the first number represents the number of cylinders and the second number represents the cubic inch displacement per cylinder. If the engine were in a "V' configuration there would be a 'V' after the number of cylinders. Anyhow, the most common of the Detroits were the '71' series which were made from the mid 1930's until pollution issues chased them off the market in the 1980's. The 71 series appeared in various configurations from 2 cylinders to 16 cylinders with a very high degree of parts interchangeability. It was eventually more or less 'reamed out' to '92' cubic inches and appeared was popular in that configuration as a truck engine for a while. Detroit Diesel was for many years a subsidiary of General motors who dominated among other things the bus market. These engines (mostly the 71 series) found their way into the back of nearly every city bus in the United States. The engines are very reliable, inexpensive to repair and emitted more noise and soot than anything else on the road primarily because of their 2 cycle design. On the small side Detroit also made a '53' series that appeared in configurations from 2 cylinders to 8 cylinders, and then there was the 6-110. A big motor, but not all that powerful. The whole series was discontinued by Detroit in favor of a 149 series. The 149 has been seen around in a lot of large quarry trucks, generating plants, and particularly in locomotives.

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1953 Allis Chalmers HD20
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HD20
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Bush dozer - Front

The development of the V configurations of the 71 series simply left no place in the market for the 6-110. The 8V-71 was shorter, lighter and more powerful, and the HD20 is about the only thing that I can think of that used the 6-110, though I am sure there were in its day a lot of other machines as well. Even Allis Chalmers who had used Detroit diesels in all their Diesel powered dozers from the beginning of time walked away from Detroit Diesels when they bought Buda and began using Buda engines in all their dozers (and incremented the model number to an HD21.)

This machine had a diesel converter on the back of the engine coupled to a manual transmission. This implies that it used diesel fuel (on its way to the engine) for torque fluid.

Yet a Different HD20 from Australia

Here is another HD20 photo from Australia. I have included it because it shows some classic features of an older dozer not often captured in a photo. Of particular interest here is the blade. This is a cable angle dozer. As was typical of dozers in the early 1950's it features a front driven cable lift mechanism. There is a winch drive off the front of the engine. You can see the rod going forward on the outside of the machine. That would be the blade control lever. It is a 3 position lever--- drop, hold and lift. Typical of these winch controls is a band brake. When you lift the winch winds through the brake band and when you release the 'lift' it goes to neutral and the brake band holds it. Pulling the lever the other way releases the brake and the blade drops. the other thing to notice is that the cable then goes to the top of the radiator and turns into a 4 part line for actually lifting the blade. This slows down the action and provides the lifting power for the heavy blade. Since this is an angle dozer, the 'side skirts' can be disconnected from the C frame and the blade angled manually. Six way hydraulic angle/tilt blades had not been invented yet. The front cable control is a vast improvement, however, over the rear cable control shown on the dozer above. The rear cable control is useful for controlling towed equipment such as a towed cable lift ripper or a scraper but when used to control a blade it is not as nice. The reason is that the rear winches are PTO driven and the PTO is not "live" meaning that the blade won't work when the clutch is released. The front winches will work any time the engine is running. Additionally, of course, if you are relying on a rear cable control and want to use it for a towed piece of equipment, then you have to take the blade off, or chain the blade up in order to have the cable control for the towed equipment. The front cable control is dedicated to the blade solving that problem.

Also notable in this photo is the 'manifold-Muffler' on the engine. Instead of having an exhaust manifold feeding into a muffler as is common with many engines, the muffler and the exhaust manifold are a single unit. I have seen this on other Detroit Diesel models. My Champion Road Grader has one of these and they are really quite effective in managing the noise.

You will also notice in looking at these older dozers that the canopy is different on almost every machine. There is a reason for this. Up until roll over protection became a mandatory safety item, dozers didn't come with a canopy or a cab. They were open air machines and what ever was put on top of them was an 'after market' item. The canopy was built somewhere, all to different styles and for different purposes. Some were just a rain roof, others were brush guards, and some were built sturdy enough to handle a 'roll over accident' though the latter was not the norm.

Oregon with a long history of safety codes, required 'sweeps' on canopies in the early '50's for dozers used in logging. The 'sweep' is the rail angling down from the top of the canopy to the radiator. This is suppose to deflect much of the brush over the top of the machine instead of having it slide down the engine housing and reaching the operator. At that time the other requirement was only a rear mesh screen to stop flying cable from broken rigging from coming in the back.

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