DAT Joyner Engine

This Joyner double acting tandem is comparatively small.

| May/June 1996

  • DAT Joyner Engine

  • Joyner DAT Gas Engine
    Joyner double acting tandem gas engine: 6" bore, 8" stroke, 32" flywheels.
  • DAT Joyner Engine

  • DAT Joyner Engine
  • Joyner DAT Gas Engine
  • DAT Joyner Engine

Box 4, 8250 200 Ave., Bristol, Wisconsin 53104

With this engine, DAT means Double Acting Tandem. The engine collectors that go to Cool spring and take the side trip to Heath Station see the six big Snow DATs. Each are 400 HP with 20" bores, 36" strokes and weigh about 40 tons. These are among the smallest of the DAT's that were made.

What is unique about the Joyner is that it is comparatively small. It has a 6" bore, 8" stroke and 32" flywheels and weighs about 3,200 pounds so it can be trailered to shows.

Now for those who do not know about these engines, the Tandem is that there are two cylinders, one in front of the other. The Double Acting means that it fires in front and in the back of each piston. The connecting rod from the crankshaft goes to a crosshead. A round piston rod from the crosshead goes through a seal at the back of the rear cylinder to the rear piston to the seal in the front of that cylinder to the seal in the rear of the front cylinder to front piston and out the front seal of the front cylinder. This piston rod is hollow so water can be pumped through it to cool the rod and the seals. This water enters at the crosshead. The engine has four combustion chambers with four spark plugs, a four cylinder engine on one piston rod. The usable HP is very low on this engine because there is so much friction to overcome with a crosshead, four seals, eight lobe side shaft, water pump, mechanical lubricator and magneto. Also the 2 Vs' piston rod takes up part of the 6" bore.

The engine was built by Lanson Joyner of Washington, Louisiana, about 1919-20 as a one-of-a-kind prototype to prove his patent on cooling DATs. This patent was granted September 27, 1921. He previously had another patent on a DAT in 1918 when he lived in St. Cloud, Minnesota. I believe that by the time he got his patent, the market for DATs being small, it did not pay for him to get into it. My engine has no plate as to name, serial number or HP. I only have the patent to go by.

I met engine man Don Blousey of Baraboo at a show in 1994. He saw my patent drawing of the Joyner and said he would like a copy to make a model of it. 1 sent him the copies. He came down to see the engine in early 1995 and said he would like to take it up to his shop and restore it.


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