by Wes Trindal
Editor’s note. A frequent contributor to MVM, Wes Trindal is an ex-private of the, 4th Infantry Division, ETO and an ex-engineer, U.S. Army’s Corps of Engineers, Engineer Research & Development Laboratories (ERDL), Fort Belvoir, Virginia.
We in Major General Raymond (Tubby) Barton’s “Fightin’ Fourth” Infantry (the “Ivy Division”) made darn good use of the enemy’s slit-trenches during our attack. The trenches had been occupied just before by Generalleutnant Hans Schmidt’s old 275th Infantrie division, Wehrmacht, of the German Third Reich. That was on November 30 and December 1, 1944, on a sugarbeet field east of Grosshau. This was in the terrible Hurtgen Forest — the Hurtgenwald — where our 4th Division troops lost more than 4,000 combat infantrymen during 3 months of combat. We were liberating Germany from the Germans!
Oh, how we dog faces wished that our own U.S. Army could have supplied us with instant foxholes and slit-trenches to protect our valuable M1 rifles and ourselves—both are U.S. government property, you know!
Enemy firepower is just not fair. The Wehrmacht exposed us to point-blank fire from Mauser rifles through big flak 88mm guns coming from the edge of the forest. We only had M1 rifles. That’s how I came to appreciate high-speed ditching machines being introduced in our Corps of Engineers equipment.
Engineering A Solution
Fast-forward from 1944 to 1959, 15 years later, to the U.S. Army’s Corps of Engineers (CE) Engineer Research & Development Laboratories (ERDL) in Fort Belvoir, Virginia. The Mechanical Engineering Department had assembled a “Queen Bee,” a prototype entrenching machine. A heavy-duty Gar Wood Industries ditching machine, crawler track mounted, was disassembled and only the ditching machinery portion was bolted onto the back of an earth-moving Euclid 11 cubic yard dump truck with its dump body removed.
In 1959, this clobbered-up beast was the ERDL civilian engineers’ answer that the CE troop needs for a road-worthy ditching machine that could do all manner of jobs. Besides digging trenches, foxholes, artillery emplacements and graves, the ditcher allowed the troops to do a variety of construction tasks, such as dig trenches for buried utility lines and even rapidly fill sandbags.
The fact that the ditcher is self-propelled means that the troops do not need a GI driver, a 5-ton 6x6 truck tractor and a low-boy semitrailer for transporting a normal, crawler-track ditcher around between jobs.
The Ditching Machine is described in MIL-D-52091 (CE). The first MIL-SPEC (1960) was titled, Entrenching Machine, Combat, High Speed. The revised, later issues were titled, Ditching Machine: Diesel Engine Driven; Wheel Mounted, Ladder. The ditchers are in Federal Stock Class, FSC 3805.
The minimum performance requirements were as follows for subsequent buys of entrenching machines, now called ditching machines:
•Dig trenches (ditches) min. 24in (610mm) wide and from 0- to 72in (0- to 1820mm) deep
•Dig at least a min. rate of 20 feet per minute (fpm) (6.1 meters per minute (mpm))
•Excavate earth in straight, curved and zig-zag trench lines; on upgrades of min. 21% and on downgrades of min. 27%; and on both right and left side slopes of min. 17%
•Dig in sand, dirt and in CL-type and ML-type soils; the Unified Soil Classification System is covered in the publication (Technical Memorandum No. 3-357) of the U.S. Waterways Experiment Station, Vicksburg, MS
•Dig in frozen ground down to a min. depth of 12in (305mm)
•Travel on highways, trails and cross-country, and ford water crossings up to min. 36in (915mm) deep
•Provide power transmission systems that provide direct mechanical drive to the rear earthmover (EM) tires, using rear wheel drive, while traveling
•Provide hydrostatic drive means to these rear earthmover tires, while digging
•Equipped with a rear-mounted ladder bucket and vertical digging boom, having both a travel position and a digging position, all with hydraulic controls
•Provide direct mechanical drive to the bucket line during digging
•Equip the digging boom assembly with a reversing side-discharge belt-type spoil conveyor
•Furnish a hydraulic system to include hydraulic controls, reservoirs, pumps, motors, cylinders, lines and filter
The ditchers are intended to be used by Engineer troops under worldwide climatic conditions, as well as in both combat situations and construction jobs.
The 11 cubic yard Euclid dump truck had the body with hoist removed and the chassis-cab modified. The original GM diesel engine, an in-line 2-cycle 6-71 Detroit Diesel, powered the whole machine. Behind the diesel and the original 5-speed clash-box transmission, we added an auxiliary transmission (aux box) to incorporate the ditching machine power take off (PTO), the hydraulic pumps, and the hydraulic-motor rear axle drive for digging speeds. At the rear, the planetary drive axle was moved and mounted solidly to the end of the truck’s main frame rails (no suspension). The original Gar Wood crawler undercarriage was removed to allow mounting the machinery on the chassis-cab.
The performance of our Gar Wood/Euclid Queen Bee was verified by technicians at the Engineer Proving Grounds (EPG) of Fort Belvoir. With that information we prepared and coordinated the MIL-SPEC with the commercial ditcher manufacturers. An Invitation to Bid (IFB) was finally sent to all the ditching machine manufacturers for a fleet of entrenching machines. They were well aware that they would have to engineer a truck-type vehicle under their ditcher machinery in place of their commercial ditcher crawler tracks. That would be an interesting challenge to meet the specs and pass the tests!
Barber-Greene Entrenching Machine
Among the ditching machine firms bidding, Barber-Greene was the lowest bidder. They were awarded the contract in the 1960s. Barber-Greene modified their commercial ditcher and installed it on a special wheeled vehicle which was built by Barber-Greene to comply with MIL-I-52091 specification requirements of minimum performance and components.
The Barber-Greene machines were powered by an International Harvester heavy-duty 6-cylinder and in-line diesels, having 817 cubic inch displacement (CID) or 13 liters. This engine was an industrial type from the Melrose Park (IL) Construction Equipment Division. The mechanical drive included a manual clutch, feeding the Clark transmission, a 5-speed manual type, into a full-torque, PTO aux box and, finally, into the ditcher machinery and Clark planetary rear axle.
The machine rode on front tires of size 14.00-24, 14 ply rating (PR), having traction lug treads, and rear tires of size 21.00-25, 24 PR, having a chevron-grouser, earthmover tread. The straight front axle was a center-pivot type, in lieu of longitudinal leaf springs. This provided more than 4 inches (102mm) of side-to-side articulation. Thus, the frame-mounted rear axle guided the buckets on the digging boom. The hydrostatic drive, used for digging operations, fed the power of the diesel through the aux box to the planetary axle, providing infinitely-variable inching speeds from stationary up through 20fpm (6.1mpm).
The ditcher operator’s station was on the roadside of the machine. To start work, the driver aimed and positioned the ditcher to the beginning of the ditch. Then he set the friction-lock on the steering wheel. The mechanical flip-over steering wheel lock, on the top of the steering wheel, insured that the entrenching machine will not waver from its designated path.
The driver became an operator. He merely moved from his driving seat to his operating seat that faces the control panel. The operator can watch rearward as the lowering digging boom crowds the buckets into the dirt bank, and he could glance forward, from time to time, in order to correct the course with power steering control as the hydrostatic-drive inches the machine along the ditching line.
The ditching boom was lowered and raised hydraulically. The PTO from the aux box powered the ditcher machinery and drive chain that, in turn, drove the bucket line through the sprocket with a spring-loaded safety clutch. This clutch was adjusted to provide full power and yet save breaking the bucket line when the ditcher hit an underground obstruction.
As I remember, this clutch also rapidly engaged and released with jarring pulses. Those powerful break-out forces were imposed on the hung-up bucket. Many times this was enough to dislodge the stubborn rock or other immovable object. The reversible spoils conveyor could discharge dirt to curbside or roadside or load trucks as needed. It, too, was hydraulically-controlled and driven.
The ditching machine was equipped with normal automotive components, making it road-worthy for travel between job sites. It was required to travel up to a minimum of 27mph (43 km/h).
The ditcher, nevertheless, was a piece of construction equipment tailored to the mission of digging holes. She was big , measuring about 30ft (9.1m) long, some 12.5ft (3.8m) high and 8ft (2.4m) wide. It tipped the scales at over 36,000lbs (16,330kg).
The ditcher was equipped with service and blackout lamps in a CE-type 24-volt waterproof military system. The service brakes were straight air type, having non-fading, sintered-iron brake linings in anti-bellmouth, gray-cast-iron drums. With respect to lighting and brake systems, the ditcher fully complied with the former ICC Regulations for heavy trucks.
The driver was provided with a windshield and canvas roof in an otherwise open cab. Speed was more restricted by the giant rear earthmover tires that have an inherent high-speed loping problem rather than by driveline gearing.
The ditcher driver’s seat was of the torsion-spring suspension type to compensate for the lack of spring suspension. A pedestal tractor seat was furnished for the operator.
Unit Rig Entrenching Machine
Unit Rig of Tulsa, Okla., was the lowest bidder on the next contract. The Unit Rig machines furnished the same component parts in their contract as did the previous Barber-Greene machines. The Unit Rig vehicle configurations included the same IH in-line diesel and Clark main transmission, plus an aux box and the Clark planetary rear axle.
Tire sizes and ply ratings were also the same. The Unit Rig ditcher machinery was functionally and mechanically pretty much the same as the previous Barber-Greene ditcher. They, of course, employed their own ditching machinery and installed it all on the frame rails of their own special-built wheeled vehicle.
ERDL Refined Our Ditcher Requirements
In 1969, we researched and published another version of specification MIL-D-52091. That resulted in a new ditching machine configuration for our Corps of Engineer troops. Lessons learned from the previous buys were included in a new set of ditcher requirements.
The utility companies across the U.S. were purchasing special, full AWD, on-off highway work trucks (from American-Coleman, FWD, Oshkosh, Walters and others) to perform construction and maintenance jobs. The utilities had their contractors install cranes, earth-augers and many other work tools on these trucks, so why not the ditchers?
We evaluated the use of these heavy-duty vocational trucks for ditching machines. We consulted users and original equipment manufacturers (OEMs) and then tailored the gathered data to future ditching machine MIL-SPEC requirements.
The bidders could choose the Oshkosh Chief, the FWD Blue Ox or any other similar type of extra-heavy 4x4 utility trucks with the same minimum features. The Combat Engineer troops were in need of more convoy speed and a front-to-rear even distribution of weight when on the highways.
The next generation of ditching machines would better satisfy these needs of our troops. Also, those very costly special-built wheeled vehicles would not be needed from the ditcher firms since these work trucks were available from truck OEMs. Nothing is “off the shelf,” just that production end items are less costly than engineered, scratch-built end items.
Parson-FWD Ditching Machine
The new low bidder on a contract for the new 4x4 ditching machines was the Parsons Division of Koehring Company in Newton, IA. Parson subcontracted with FWD Corporation of Clintonville, WI, for a version of their Blue Ox truck.
The FWD truck was greatly beefed up for ditcher application. This time, the engine that Parson and FWD selected was a Detroit Diesel, the 6V-71T (or 6V-91T) 2-cycle turbo-charged and the transmission was one of the Alison TT (model) power-shift types. The remaining drive train was supplied by FWD, using their heaviest locking inter-axle differential drop box type transfer case. FWD furnished their 50,000lbs (22680kg) with rated planetary axles, steer drive at the front and drive at the rear. The front axle was center-pivot mounted, while the rear was a solid mount.
Whereas the utility trucks were normally equipped with the traction lug, size 18.00-22.5 wide-base single tires, Parson and FWD had to furnish four each, size 16.00-25, tubeless earthmover tires with grouser lug treads. The wide-base tires could not take the static 38,000lbs (17370kg) loading on the rear axle when ditching. Now, with the size 16.00-25 earthmover rear tires, the troublesome loping characteristic of the Barbour Green and Unit Rig machines was corrected.
The road travel powertrain was located high in the frame to allow for the FWD transfer case drop. The digging hydrostatic motor used the transfer case to power all the wheels on the ditcher when digging. The operator’s station was also mounted high on the roadside to insure excellent operator visibility while digging.
The ditcher machinery was the same as was furnished by Parsons’ competitors; the ladder type digging boom and bucket line that is hydraulically raised up for travel and lowered down for digging. The spoils were delivered to the sides via a hydraulic drive conveyor belt.
The military electrical system was updated to more safely comply with the higher speeds (see the CE modified system on Figures No. 07 & No. 08). A set of four service headlamps were configured in quadlamps for high and low beam night driving. The PAR-46, Trade No. 4880, sealed beam units were inserted in flush-mounted buckets, installed in lamp boxes on either side of the engine hood. The upper high beam lamps were aimed high and operate only when the dimmer switch is on high beam. The lower two lamps were aimed for low beam and are in operation all of the time. This system has been used on other CE vehicles, such as crane carriers.
The front and rear service turn signal lamps were sealed lamps with shock isolated 24-volt filaments and were flush-mounted in industry standard 4.5in (114mm) holes. The ditching machine included legal clearance and side marker armored lamps.
The west coast rearview mirrors and spotter mirrors were attached to massive steel mounts. In addition to the swing-away pivots fore and aft brush-loops were included.
The driver’s seat was of the torsion spring type with shock absorbers and seat belts. The side mounted operator’s seat had a backrest and seat belt.
A standardized military hot water heater and defroster was furnished to direct heat to the driver’s and passenger’s feet, as well as to defrost the windshield. The Parson-FWD ditching machine had an enclosed canvas cab.
The fleet of self-propelled wheel-mounted ditching machines served the troops well in the worldwide areas where they were needed and assigned. The problem was that the initial cost was high and the maintenance to operation times were not what they should have been — too many ditchers were deadlined for parts.
ERDL optioned to consider a fleet of low bed, fixed- or tilt-deck machinery trailers with lunette eyes, the same as commercial contractors use with their dump trucks to tow their slow speed and crawler track machinery. We researched the users and the OEMs of lunette-equipped low-bed machinery trailers. We published specification MIL-T-52479, and procured an initial fleet of thirty-eight of them from the Hyster Company in Kewannee, IL.
Now, our troops are able to use any prime mover (M-Series 5-ton dump trucks, medium tractors, hydraulic cranes, rough-terrain forklifts and crawler tractors) that has a strong rear pintle hook. These prime movers can tow 15-ton, tilt-deck, engineer equipment transporters, loaded with front-end scoop loaders, pavers, ditchers, backhoes and other machinery and supplies at highway speeds and even over rough terrain, to any job site and back.
I wonder! I’ll bet our Armed Forces now would like to have a versatile high-speed diesel ditching machine in lieu of a hand-operated shovel to dig their foxholes for them. What do you think?