Yuba Steam Vehicles

Yuba Steam Engines,

All Wheel Drive Tractor, Engine and Boat Motor

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Side view

Bob Harns Driving, Pulling a Compactor

Bob Driving, Pulling a Compactor

Driver's Position

Rear Knee Action Suspension Transverse Leaf Springs

Right Front Engine

Turning to left

Turning a Tight Circle

Disappearing into the sunset

Bob in cross wise position turning front wheels from full left to full right

Excerpt from Lothrop & West's Yuba Steam Vehicles

The Yuba -tractor was built as an experimental, prototype vehicle between about 1946 and 1951 by a small group at Yuba Manufacturing Company, San Francisco and Benicia, California, as a possible successor to the "Ball Tread" crawler tractors manufactured by Yuba in the early teens. The new tractor work started from scratch with ideas and sketches, clay and wood models and machine drawings, one unit of the vehicle at a time, to carry out the special concept of an on-road and off-road, earthmover style tractor on pneumatic tires with four-wheel drive and propelled by steam. (Auxiliaries were powered by a Jeep 4 cylinder engine.) Reliance was placed upon the earlier Doble work, but there were many changes from most past practices. Read more.......

Bob Harns and the Yuba Tractor

Backing in to cross wise position

Coming in to narrow alley at Yuba Benicia plant

Right front engine and right front Kuse action and 90 deg steering rods

Yuba Tractor Rear Elevation

Yuba Tractor Engine

Excerpt from LOTHROP & WEST: A surviving engine from the destroyed tractor has recently (1975) been used for laboratory testing at Steam Power Systems, San Diego, at even higher temperatures and with good results.

Yuba Tractor and Marcus and Athel Lothrop 1951

Marcus and Athel Lothrop driving the Yuba Tractor.

Yuba Boat Motor

Excerpt from LOTHROP & WEST: In addition, a very light, portable, complete plant of about 10 horsepower was built for boat propulsion. This system was about as described (as the Yuba Tractor) except for scale. A battery driven electric motor took the place of the "Jeep” engine. The condensers were under water, as was the steam engine. That had three cylinders in line with an overhead cam shaft. There was a similar valve shifting mechanism with one forward cutoff and one reverse cutoff.

Bob Harns and the Yuba Boat Motor

Boat Steam Engine and Condensers on its Side

Boat Engine Mounting and Intermediate Frame Tank Structure

Yuba Boat Engine Steam Generator and Stack

Engine Held by Polite Workman

Pistons and Connecting Rods

Generator Burner and Control Unit

Generator and Elevation and Control Unit

Yuba Boat Motor Frame and Etc.

Engine Generator and Flex Hose

The All Wheel Drive Tractor


		Lothrop & West, A Discription of "Yuba Steam Vehicles" (paper)



Yuba Boat Motor Excerpt from LOTHROP & WEST: In addition, a very light, portable, complete plant of about 10 horsepower was built for boat propulsion. This system was about as described (as the Yuba Tractor) except for scale. A battery driven electric motor took the place of the "Jeep” engine. The condensers were under water, as was the steam engine. That had three cylinders in line with an overhead cam shaft. There was a similar valve shifting mechanism with one forward cutoff and one reverse cutoff.


Bob Harns and the Yuba Boat Motor		Boat Steam Engine and Condensers on its Side


Boat Engine Mounting and Intermediate Frame Tank Structure		Yuba Boat Engine Steam Generator and Stack

Yuba Steam Engines,

All Wheel Drive Tractor, Engine and Boat Motor

The All Wheel Drive Tractor

Yuba Tractor Engine

Yuba Boat Motor