26 BULLETIN 300, TJ. S. DEPARTMENT OF AGRICULTURE. 



the ditch, are used to a considerable extent in drainage work. A 

 common form of this type straddles the ditch on cross-beams. The 

 straddle ditchers generally work upstream as do all dry-land exca- 

 vators. 



A machine of this type often used is illustrated in Plate V, figure 1 . 

 It has a 30-foot boom and a 1-yard dipper. The steam power used 

 is obtained through a 2-cylinder, 35-horsepower engine and a vertical 

 boiler. The machine rests on a platform which is mounted on two 

 steel beams, each 29 feet long, that straddle the ditch. It can be 

 mounted on either caterpillar tractors or wheeled trucks. In the 

 latter case, each end of the two beams is supported on a 2-wheeled 

 oscillating truck, the wheels being 2 feet high and 18 inches wide. 

 They run on a wooden track 6 inches thick and 3 feet wide, which is 

 built in 6 sections each 20 feet long. One section of the track on each 

 side is always unoccupied and these are lifted ahead by means of 

 cranes operated by power derived from the engines. This track will 

 support the machine in the softest ground. The excavator will dig 

 12 feet deep and 22 feet wide on firm ground; with an extension to the 

 dipper handle it can dig 18 feet deep. It will deposit the dirt on 

 either side at a distance of 32 feet from the center of the ditch. The 

 dipper will swing over a bank 14 feet high. Where track is used the 

 machine is pulled ahead by a cable from the engine which hooks to 

 the track on both sides; this is done without interrupting the work 

 of excavating. If desired, caterpillar tractors are furnished instead 

 of the wheeled trucks. The front tractors are 4 feet wide by 11 feet 

 long, and the rear tractors are 4 feet wide by 7-J feet long. This exca- 

 vator has been known to dig as high as 1,500 cubic yards in 10 hours 

 in especially favorable material. It has dug through 12 inches of 

 frost. From 7 to 8 men can set up and take down the machine in 

 from 5 to 8 days. 



Another machine of this type is illustrated in Plate V, figure 2. 

 The excavator is made in various sizes; that most commonly used has 

 a 38-foot boom and a 1-yard dipper. Power is supplied by an internal- 

 combustion engine of 25 or 40 horsepower which burns kerosene, 

 gasoline, or distillate oil. The machine rests on a platform which is 

 mounted on two steel beams, whose standard span is 32 feet. Exten- 

 sion axles are provided which permit of a maximum increase of 3 feet 

 in the span. The front axle is mounted on a two-wheeled swiveling 

 truck with cast-steel double-flange wheels. The rear end is carried 

 by two heavy, wide-faced, double-flange steel wheels set loosely on 

 the axle. The shipping weight of this size of dredge, including 

 engine, dipper, and machinery, is approximately 3S,000 pounds. 



Perhaps the cheapest straddle-ditch excavator of the dipper type 

 that is in use is a homemade one which has been used to some extent 



