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UNDER THE BENCH ENGINE

Author Photo
By Errol L. Hahn | Aug 1, 1999

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20188 270th Street, Sigourney, Iowa 52591-8425

The nine inch 35 pound flywheels were being used as trucks for a
larger engine. I thought they deserved better. The crankshaft,
timing gear, valves, connecting rods, and piston are from various
lawn mower engines. The two aluminum connecting rods are welded
together to move the flywheels back from the water hopper. The
cylinder is mechanical tubing 2? inch inside diameter. The head is
1? inch thick steel drilled for valves cut down to the size of a
dime. Valve guides are grease gun pipe. Carburetor is a high
pressure hydraulic fitting. Main bearings are one inch square
bridge support rods with bronze bearings from Case-IH corn head.
The water hopper and base are various pieces of scrap steel. The
fuel tank is box iron from old school bleachers with angle iron bed
rails for ends. Compression was lowered by leaving the piston back
? length of a three inch stroke. Ignition is a buzz coil with
points made of banding steel with brass welding rod inserts for
contacts on Corian kitchen counter top. Corian is also used on cam
gear to activate the points. The governing mechanism is parts from
a tractor governor and automatic transmission parts. The valve
keepers are sweat fitting pipe caps with ? inch washers brazed to
them to keep the valve springs centered.

The engine ‘rocks’ just like the big ones because of a
double dose of counterweights on the flywheels and the lawn mower
crankshaft. The governor mechanism holds the exhaust valve open so
much of the time with the heavy flywheels that the muffler does not
get hot at 250-300 rpm. The cart wheels are from an old feed truck,
and the check valve is buck shot.

An interesting project, maybe because you don’t often see a
scrap heap that runs!

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