WHEELED VEHICLES 
197 
leg horizontal boiler su imported on an I-beam frame. Almost 
the entire weight of tlie machine rests on the rear traction wheels, 
each 7^ feet in diameter with a 24-inch tire. The fore part of the 
engine is supported l)y a single 4-foot wheel used for steering. 
Provision is made for the operation of the steering gear both by- 
hand and by power. A single cylinder 11- by 12-inch balanced 
Fig. 58. — A Holt Three-wheeled Traction Engine hauling Sugar Pine Logs. 
California. 
valve engine is placed on top of the boiler, and at 165 
pounds' steam pressure develops 60 horse power. Power is 
transmitted to the traction wheels by chains, and either wheel 
may be driven independently of the other. This is especially 
advantageous in making sharp turns. A radius of 25 feet is 
practicable in operating a train of five cars. 
Water tanks with a capacity of from 400 to 700 gallons are 
carried on the frame directly in front of the boiler. The average 
water requirement per day of ten hours is from 2500 to 3000 
gallons. From 1^ to 3 cords of hardwood fuel, 1 to 2^ tons of 
steam coal or from 200 to 300 gallons of fuel oil are required. 
