Western Minnesota
Steam Threshers' Reunion

The Western Minnesota Steam Threshers' Reunion, frequently simply called "Rollag," is a great event that every old machinery enthusiast should see at least once in their lifetime. Held on Labor Day weekend every year, it is jam-packed with a huge number of things to see and do. You won't get bored at Rollag!

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This 600 horsepower Snow engine/compressor is 67 feet long and weighs 140 tons. It came out of the oil fields of Northwest Pennsylvania. The unit was used from 1915 to 1971 to compress natural gas for transmission via pipelines to distant users.

With the assistance of several members of the Coolspring Power Museum, some WMSTR volunteers picked up the engine in Pennsylvania in November of 1991. They moved it to Minnesota, built a building and a foundation, erected it, and had it running by the 1998 Labor Day weekend.

The duplex twin cylinder engine has a combustion chamber on both sides of the piston. Its bore is 24-inches and the stroke is 48-inches. The displacement is 39,600 cubic inches. The folks at WMSTR now run it on propane. Running without a load on the compressor, it consumes 17-gallons of fuel per hour.

Two igniters in each combustion chamber ensure positive ignition of the fuel-air mixture. Yes, that adds up to eight igniters, total.

It is believed that this is the largest internal combustion engine on display at any show grounds in the USA.


The 18-foot diameter flywheel weighs 24 tons and turns at 80-90 rpm.


Here is a closer look at the valve operating mechanism.

Look at the size of those valve springs. They are about the same size you'll find under a full-sized pickup truck.

The brochure in front of the valve cage is 8-inches wide. Compare its size to the parts in the picture.


This half-crosshead supports the weight of the piston rod and piston.

Note the water coming out of the blue pipe, just right of the red-painted slipper. The piston rod is water cooled and this is where the coolant is discharged. Without this feature, the packing would burn up from combustion chamber heat.


I call this an "up-side-down" oiler. The drops of oil can be seen rising through the sight glasses, instead of dripping down.

The sight glasses are filled with brake fluid. The oil, being lighter, will float up through the heavier liquid.

This picture was taken through a telephoto lens in dim light, but you can make out the drops of oil in this enlargement


This view shows the compressor portion of the unit. Notice its small size in comparison to the engine.

A lesson can be made from this comparison. It takes a huge amount of energy to compress a gas. Remember this the next time someone tells you how wonderful the yet-to-be "hydrogen economy" will be. Hydrogen is a gas and it will have to be compressed before it enters the distribution system. That enormous amount of compression energy will be wasted, lost, never to be regained, again.


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Revised -- 17/19/07