German Pile Drivers, WWII Tactical and Technical Trends, No. 46, May 1, 1944 (Lone Sentry)

The details as to four German pile drivers are now available. The 50-m/kg pneumatic pile driver (Druckluftramme 50-m/kg), the 200-m/kg pneumatic pile driver, the 450-kg diesel pile driver (Dieselramme 450-kg), and the percussion atomization 500-kg diesel pile driver (Dieselramme 500-kg, Schlagzerstauburg) can all be used in conjunction with the model 39 field pile-driving frame (Feldrammgerüst 39) described in the preceding article. The following summary of information as to these four pile drivers is taken from British sources.

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a. Technical Data

Pneumatic Pneumatic Diesel Diesel

50-m/kg 200-m/kg 450-kg 500-kg
Weight of monkey 121 lb 448 lb 970 lb 1,092 lb
Total weight -- -- 2,123 lb --
Stroke 1 ft 5 3/8 in 3 ft 3 1/2 in 4 ft 7 in (max) 7 ft 2 5/8 in
Striking rate 105 per min 54 per min 56 per min 50 per min (approx)
Cylinder bore 2.5 in 3 9/16 in -- 8 1/4 in
Force per blow 360 ft/lb 1,440 ft/lb -- 8,255 ft/lb
Overall length 2 ft 10 1/2 in 5 ft 1 in (closed) -- 10 ft
Pile diameters 5 7/8 to 9 7/8 in 9 7/8 to 14 1/8 in -- 10 to 18 in
Weight including clamps 176 lb 672 lb -- --

b. Pneumatic 50-m/kg

This driver is suitable for pile driving in the construction of bridges up to 8 tons capacity. For piles up to 8 feet 3 inches in length it can be used on land or on a raft without the pile-driving frame, but for
[Pneumatic Pile Driver]
piles of greater length it must be used in conjunction with the field pile-driving frame (Feldrammgerüst).

(1) Components

The main components are the stationary part, consisting of the piston, piston rod and piston base, the moving weight (monkey) consisting of driving block, cylinder and screw-in cylinder head; the spring-loaded clamping device; the guide for use with the field pile-driving frame (Feldrammgerüst 39).

(2) Description

The driver (50-m/kg) is of the fast-hitting type, and it attains its high rate because the acceleration of the moving portion is due not only to its own weight but also to the compressed air operating downwards on an internal flange at the base of the bore of the cylinder.

Air enters through a coupling (10) (figure 1) on the piston base (8) and passes through the passage into the annular chamber. From there, the air enters through the openings across the slide valve into the chamber above the piston (6) and lifts up the cylinder (5) and driving block (7). At approximately 3/4 stroke the slide valve reverses and cuts off the air supply from the annular chamber. The air above the piston then escapes to atmosphere through the exhaust passages. The monkey then falling under its own weight and the force of the compressed air in the annular chamber, drives in the pile.

Located in the air passage in the base of the piston is an air filter (9) to prevent the entry of sand or dirt into the inside of the cylinder and on to the valve.

(3) Method of Use

The pile is laid out horizontally. The pile driver is lined up with the head of the pile and attached to it by means of the spring-loaded clamps. A bolt is then passed through the two clamps and the foot of the pile driver and the clamps tightened up.

After attaching the air hose, the pile driver and pile are raised by the four erecting rods which are screwed into sockets on the frame, on the base of the pile driver, to which the clamps are attached.

The pile and driver are held vertically by four men, and the driver set in operation. Once the pile is firm, the erecting rods are unscrewed and driving continued.

Two lengths of air hose, 24 ft 7 1/4 in and 49 ft 2 1/2 in are supplied. The shorter length is connected to the driver and the longer one to the compressor.

c. Pneumatic 200-m/kg

This driver is suitable for driving piles in the construction of improvised bridges up to 16 tons in conjunction with the field pile-driving frame either on land or on a raft. It can be operated by an air compressor.

(1) Components

The main components are the stationary part, consisting of the base plate, the piston rod end bearing, the piston base and the piston; the moving portion consisting of the monkey block, the cylinder and screwed-in cylinder cap; the spring- loaded clamps and the guide for use with the field pile-driving frame.

(2) Description

The driver is of the free-falling type. The monkey is lifted up by compressed air, falls freely on to the base plate and gives up its kinetic energy to the pile, after covering a stroke of approximately 1 yard.

Compressed air is admitted through the lubricator in the piston base via the air passage into the bore in the center of the piston rod. Then the air reaches the slide valve, and passes it into the chamber enclosed between the cylinder head cap and the piston. The compressed air lifts up the monkey until the exhaust port connects with the air passage of the valve mechanism; the chamber above the slide valve will then be emptied of air. The compressed air on the under surface of the slide valve forces the valve up and, in so doing, cuts off the further flow of compressed air. The compressed air in the chamber above the piston escapes to atmosphere through the exhaust port.

Owing to its momentum the monkey rises a little further and then falls downwards freely.

Since the piston base is of cruciform construction, the monkey contains corresponding recesses. To prevent the monkey twisting in relation to the piston rod, two keyways are arranged on opposite sides in which the keys slide. The projecting bolts prevent the keys falling out.

There is a fine mesh gauze air-filter in the lubricator body in the air inlet passage, to prevent entry of foreign matter, such as sand or dirt, into the interior of the driver.

The keyways for guiding the monkey are lubricated by use of the grease gun on the grease nipples.

(3) Method of Use

Slide the guide piece on to the foot of the mast. Lift up the driver by means of the winch, fasten it to the guide, and then fix the guide by means of the "U" band stop supplied with the driving frame.

Then fill up the lubricator and grease the keyways by means of the grease gun and nipples. After thoroughly blowing through it, connect up the rubber air hose.

At temperatures below +10° C (50° F), with very moist air, a light oil is poured into the rubber air hose.

The driver is then raised to the top of the mast and again secured by the stop. The pile is then raised by means of the winch and secured to the mast by the pile guide (supplied with the driving frame). The driver is then lowered on to the top of the pile and fixed to it by means of the spring-loaded clamps.

Unlock the pile driver by twisting the exhaust port collar until the locking studs spring into the holes in the collar. Open the air-cock at the compressor, and the pile driver will begin to work.

For transporting the 200-m/kg pile driver, the exhaust port collar must always be turned as far as the stop after pressing in the locking studs so as to fix the monkey, and at the same time protect the piston rod from receiving dirt through the exhaust port.

d. Diesel 450-kg

In conjunction with the field-driving frame this driver is suitable for driving piles in the construction of improvised bridges up to 24 tons capacity.

(1) Components

The main components are the piston with anvil, the monkey, the guide tubes, the headpiece, the fuel tank, the trailer.

(2) Description

The diesel pile driver works on the two-stroke principle, i.e. an explosion takes place on each hitting stroke. The required ignition temperature is reached through the compression of the air trapped between the top of the piston (5) see figure 2, and the monkey (4), by the falling of the latter. Shortly before the monkey strikes the anvil (14), fuel is injected into the compressed air in the combustion chamber and ignites itself and burns. The gases evolved by combustion lift the monkey upwards clear of the piston so that the exhaust gases will blow away.

[German Diesel Pile Driver]

The monkey falls freely under its own weight, and its kinetic energy is used in driving the pile and in compressing the air for the next explosion.

It is important to filter the fuel carefully to avoid choking the nozzle (8) and prematurely obstructing the fuel pump (10).

All moving and striking parts must be well-lubricated. For the piston, the necessary lubricant, good diesel motor oil, is added to the fuel in the proportion of 1 3/4 pints of motor oil to 1 gallon of fuel. All remaining oiling places are lubricated with diesel motor oil.

(3) Method of Use

The pile driver is lifted up off its bogie trolley and fixed to the mast of the driving frame. The clamp securing the monkey on its seating on the anvil is taken off. The fuel tank is fitted and connected to the fuel pump (10) and the tank filled up. The bowden control cable is fitted to the pump and the air in the fuel system released by unscrewing the bleeding screw. The bowden cable control is opened and the pump operating lever (12) depressed several times.

The pile driver is then raised, being secured in position by the "U" band stop, (supplied with the driving frame) the pile placed in position and pile driver lowered.

The cable from the winch is then attached to the monkey of the pile driver by a trigger hook and the monkey raised to the top of the driver. Pulling the trigger with the lanyard allows the monkey to fall and start operating. The stroke is controlled by regulating the amount of fuel injected, by means of the bowden cable.

e. Diesel 500-kg (see figure 3)

This driver operating with either the field pile-driving frame (Feldrammgerüst 39) or the tubular pile-driving frame (Rohrammgerüst) is suitable for driving piles in the construction of improvised bridges. It can be operated either on land or on a raft by one noncommissioned officer and 12 men.

(1) Components

The main components are monkey (piston) with oil reservoir for self-lubrication; cylinder, with fuel tank; base plate and anvil; guide cheek plates; cradle and bogie, and accessories.

(2) Description

The 500-kg diesel pile driver (percussion atomization) operates as a single-acting two-stroke diesel engine, i.e. an explosion and an effective blow on every cycle.

The fuel is atomized in the combustion chamber. The method of operation is as follows:

In falling, the monkey operates the knocker arm of the fuel pump and approximately 0.9 ccm (on setting the fuel pump control lever for heavy blows) is injected, at a pressure of 1.5 atmospheres (22 lb per sq inch) on to
[German Diesel Pile Driver]
the spherical cavity in the top of the anvil. The monkey, the lower end of which is shaped spherically corresponding to the cavity in the anvil, crushes the fuel already injected so that it is atomized and dispersed in the combustion chamber, analogous to hitting a drop of water with a hammer.

The firing temperature results from the compression by the monkey of the air trapped between the monkey and the anvil, which becomes so hot that the finely atomized fuel ignites and burns.

Part of the energy generated by the descent of the monkey goes to drive in the pile and the rest serves to compress the air for combustion.

The gases generated by combustion throw the monkey upwards again. The stroke depends on the amount of fuel burnt. The monkey falls freely under its own weight. The amount of fuel is controlled by the setting of the fuel pump control lever. The exhaust gases pass out through four ports in the cylinder jacket.

The diesel pile driver is comparatively speaking insensitive to differences in energy content of different gas and diesel oils as well as blended fuels, and can thus operate with various fuels. It is important to see that the fuel is well-filtered. The monkey lubricates itself automatically.

(3) Method of Use

First of all, attach the piston-raising trip mechanism to the mast. With the Model 39 field pile-driving frame the raising cable is simply hooked on, but with the tubular pile-driving frame the cable must be attached by means of U-bolt clamps. After that, the pile driver is raised by another cable and attached to the mast by means of the guide plates. The trip mechanism is then lowered to a trip stop on the outside of the cylinder jacket which causes the trip lever to engage a circular groove on the piston through a slot in the cylinder. For transport purposes, the slot is covered up, and there is also a safety screw engaging the same circular groove as the trip mechanism.

Clean fuel is poured into the fuel tank through a filter funnel, and the pipe line to the fuel pump opened by giving three to four turns to the cock spindle on the top of the fuel tank with the square-ended key. The fuel pipe and pump are bled of air by loosening the bleeding screw which must not be taken right out.

The monkey is raised by means of the trip mechanism almost to the top of the cylinder. The piston-lifting eye-bolt is taken out and after the oil reservoir has been filled up, replaced by the self-lubricating plug and valve. Normally motor oil is used for lubrication, but at temperatures under 0° C (32° F) a 1 to 1 mixture of motor oil and petroleum is used.

The fuel pump-control lever is fitted and the fuel pump tested by hand by means of a tommy bar, after first setting the lever to maximum output. The fuel injected during testing is withdrawn from the bottom of the combustion chamber using a hand syringe through a plug in the cylinder wall.

The pile driver is raised to the top of the mast. The pile is placed in position and the driver lowered on to it, and the turnbuckles securing the base plate disconnected.