The Nash Gas Engine Electric Plant
I recently completed a 1/8th scale model of a 25 hp 2 cylinder Nash gas engine electric plant. Nash engines were produced by the National Meter Co. of NYC and were designed by their head engineer Lewis H. Nash. The engine design era was the late 1890’s when illumination and remote electrical power was becoming popular in America. Nash engines used an L-head valve design with ignitor ignition. The early Nash multi-cylinder engines used troublesome mechanical linkages to trip the ignitors. They soon evolved to an electrical solenoid ignitor tripping device before switching to spark plugs. I chose spark plugs. No sense in creating unnecessary problems. When most engines of the era were still spark governed hit & miss designs, Nash was the first US engine manufacturer to adopt throttle governing which probably explains why they became popular dynamo engines.
In particular, the two cylinder Nash engines were unique among dynamo engines of the era in that they used a 180 degree crankshaft design. This resulted in two power strokes in 180 degrees of crankshaft rotation and then 540 degrees of rotation without a power stroke. This would have caused considerable voltage fluctuations in the speed sensitive poorly regulated dynamo’s of the time. Nash chose to stay with this crankshaft design and installed one oversized 60” flywheel and sometimes two 60” flywheels we assume to minimize cyclic irregular speed variations. This model uses the same flywheel arrangement found on the 25 hp Nash dynamo originally installed in 1906 at the Biltmore Estate in Ashville, NC with one normal size and one oversized 60” flywheel. The original 1906 Nash dynamo stills resides in the Biltmore powerhouse in running condition.
This Nash model engine design uses a 1” bore x 1.13” stroke. Construction is mostly fabricated brass and steel. The camshaft, drive gears, valve operating levers, and adjustable roller cam lobes are exposed, the cylinders and cylinder heads are fully jacketed including the exhaust manifold. Lubrication is by splash and wet oil sump. The compression ratio is 5.5:1. This engine runs on propane using a small self compensating RC carb. A pair of Nash engines from the Coolspring Power Museum provided the necessary detail and dimensions for the model engine and generator design. The engine drawings were done by a good friend and model builder Doug Kelley.
The model dynamo is near identical to the Garwood Electric model dynamo used on a previous project with a few minor improvements. It is actually a 12 pole permanent magnet alternator with the output rectified to DC and regulated at 12v output. It is rated at 3A output at 500 RPM. The meter panel enclosure doubles as an engine cooling system incorporating a computer radiator, expansion tank, and a dynamo powered and thermostatically controlled cooling fan.
This model has been is a very nice running engine from the first start. With or without load, it sounds just like my neighbors John Deere B tractor. The audio comes close, but doesn’t quite capture the unique sound of this little engine.
Jeff
