Modeler's Corner

Vintage Stirling,Caterpillar


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This is my tank-cooled version of a vintage Stirling cycle engine from drawings by Jerry Howell.

Some modifications from the original drawings include threading the connecting rods and their mating ends 0-80 UNF to make assembly and adjustment easier. I also threaded the crankshaft pin for the same reason.

To facilitate machining the hot cap from stainless steel, I opted to bore clear through vice, making a blind bore. I then fabricated a head for the hot cap and secured it with six 0-80 UNF Allen head screws. (Tapping 0-80 in stainless is an exercise in patience!)

The heat-retaining shield over the hot cap is my own design. It helps the engine run smoothly with a minimum size flame from the oil can alcohol burner.

This was a fun project built entirely on my old Atlas 10F lathe; no rotary table, no collets and no milling machine, only a milling attachment on the lathe. I machined the main body hexagon shape from round stock using a hex machine nut for indexing to obtain the desired 60-degree angles.

Just goes to prove that you don't necessarily need all the latest and greatest equipment to complete an interesting project.

Ken Hollenbeck
607 Cherrywood Lane
Sister Bay, WI 54234


This all started one morning after some of our members of the Vintage Machinery Club meeting showed a video of their trip to the Caterpillar assembly plant in Illinois. On the video I saw the huge track machine D11R being built up and running.

In my younger years, I had operated bulldozers and was always attracted to the Caterpillar. But usually what I wanted I did not often get. However, after that evening and watching that great machine, just the power, size and good style started me thinking. Maybe I could build a model of this D11. I have built models most of my life: airplanes, boats, cars, old engines, etc.

So I called the local Cat dealer and asked for specifications, wall posters and dimensions, requesting anything I could get to assist me in building a model of this machine.

Tom, one of the sales people said, "No problem, how long do you think this will take?" At this stage, I had no idea.

I?received the materials a couple of days later. After a week or so, I decided on a 1/6-scale, 2 inches to the foot, as it turned out to be quite a large model. As the days rolled on, I finally managed a full-size cardboard pattern of the main body frame, and knew the amount of steel required. So it was off to the steel yard.

I told the man there that I needed steel plate to build a bulldozer. He said they didn't have that much steel and I reassured him it was only a model. I told him I needed half a sheet of 1/4-mild rolled, half a sheet of 1/8 and half sheet of 18-gauge. He said it was about 250 pounds of steel.

So it was back home to start work. At that stage, I was still not too sure where to start. I lit up the gas torch and got into it, cutting around the patterns to form the sides of the main body, then the bottom and both ends. This gave me a frame and body to work with. The main body was then painted and the track gear was just sitting on the grille to be painted, fabricated from strips of 18-gauge, 3/4-inch wide, and five 1/4-inch holes drilled with 1/4-inch rod put through them and welded as a unit.

The bulldozer is powered by two mobility scooter motors, 12-volt DC, with a gear shaft speed of 60 RPM, then into a winch planetary reduction of 5-to-1. I have hexagon output shaft turning 12 RPM, keyed to the final drive sprocket of 25 teeth - equals 24 feet per minute.

The hydraulic cylinders for the blade are from a Mercury stern leg unit, with a small modification to the top worked in just right. The power motor for them is 12-volt DC. Now the ripper is an OMC outboard pump and the hydraulic cylinders I have made from 1-inch hydraulic tube and 1-1/2-inch hex bar for the tops. These were threaded, cut for O-rings and screwed in. They work well, have great power and not an oil leak in sight. That was good!

The exhaust flaps lift as the machine begins to move in either direction, from a small blower under the hood. The lights, including the amber flashing light on top of the cab, are controlled by the operator. There is also a smoker for the exhaust. However, the timing device has given some grief, but it sure is impressive when I've had it working.

The track is cast alloy in two pieces: 86 cleats or plates and then the chain, and the plates are bolted to the chain, just like the real one.

Idlers at each end of the track gear are 6 inches in diameter and also alloy, supported by two ball bearings. Sixteen idlers, which also pivot, are supported by 32 ball bearings, and the total track carrier pivots on the shaft to which the blade supports are connected.

The total control is from an old 6-channel Futaba radio control for model aircraft. By working most days, the project took 12 months to complete and I really did enjoy building it, but everyone enjoys it more with a load of dirt to push around.

This project was completed in January 2006.

Alan Mayo
165 Gear Road
Te Horo RD
Otaki, New Zealand 5581

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