Soft Recoil System

Soft Recoil System
EDITOR’S NOTE: The following article was prepared by personnel of the Army Weapons Command, Artillery Systems Laboratory, Rock Island Arsenal. Contributors are as follows: Harold R. Lohmann, Gilbert J. Melow, Jr., Robert E. Seamands, and Howard O. Sand.
The strange looking field artillery piece shown above, with its trails on backward, is a 105-mm howitzer that fires its projectile from the out-of-battery position. This weapon is really only a test fixture. It has no wheels, lunette, or fire control; and can be elevated and traversed only within limitations. This system was built to demonstrate and prove the soft recoil principle. Figure 1 depicts a concept of a tactical 105-mm soft recoil FOB weapon.
With its soft recoil cycle, this unique weapon offers a number of significant advantages. The soft recoil principle reduces the recoil force by as much as 70 percent which enables the designer to reduce the weight of a 105-mm weapon by 15 percent and by an even higher figure for larger caliber weapons. The overall weapon length can also be reduced by as much as 30 percent. Because of the shorter cycle time and the easy access to the breech for loading, a significantly faster maximum
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rate of fire is possible. Perhaps the greatest benefit offered by a soft recoil weapon system is the improved stability. It can be emplaced and fired with little or no site preparation or anchoring.

Figure 2 illustrates the operation of the soft recoil cycle. The recoiling parts run forward and build up momentum in the counterrecoil direction. When the weapon is fired, these parts recoil back to (or slightly beyond) the initial position where they are caught by a latch.
This cycle differs from the conventional firing out-of-battery oscillating cycle utilized in automatic weapons because the recoiling parts are seared in the full recoil position and the firing is initiated at various positions from the in-battery position. The various positions depend on the propellant zone used. As shown in figure 2, the complete cycle time is half that of the conventional weapon.
In operation, the recoil mechanism is essentially a pneumatic spring which stores the energy that moves the recoiling parts toward the in-battery position. When the recoiling parts reach the proper forward velocity for the zone to be fired, the weapon is fired and the direction of motion of the recoiling parts is reversed. As the recoiling parts return to the latch position, the energy expended to move them forward is replaced and stored for the next round. An advantage of this type of recoil mechanism is that the recoil cylinder will no longer require a precision
Figure 1. 105-mm soft recoil howitzer.
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CONVENTIONAL WEAPON
FIRE OUT OF BATTERY WEAPON
Figure 2. Recoil comparison.
machined orifice and control rod. The recoil cylinder has a single hydraulic cylinder with piston rod and piston.
TABLE I
WEAPON COMPARISON
Characteristic
M102
Soft Recoil Howitzer
Recoil—Counterrecoil
cycle (sec)
3
1.5
Recoil Force (lbs)
11,000
3,500
Length (in)
258
172
Weight (lbs)
3,300
2,700
Range (meters)
11,500 (w/M-1)
11,500 (w/M-1)
Traverse (deg)
360
360
Elevation (deg)
—5 to +75
—5 to +75
Stakes Required
Maximum
8*
2**
Minimum
4*
0
NOTES: * 4-inch diameter × 24-inch stakes
** 1 ½-inch diameter × 18-inch stakes which would not be required for most firing conditions
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A buffing mechanism is positioned at both ends of the cradle to slow down and stop the recoiling parts should a misfire occur or should the crew attempt to fire a high zone round when the weapon is set for a lower zone.
A comparison of characteristics for the standard 105-mm, M102 Howitzer and the 105-mm Soft Recoil Weapon Concept (Figure 1) is shown in Table I.
Firing tests that were conducted in 1967 have demonstrated the accuracy of the 105-mm soft recoil firing fixture to be comparable with the M102 howitzer. The M102 howitzer and the soft recoil test fixture both use the same cannon. The results of the comparison accuracy tests that were conducted at Aberdeen Proving Ground and Yuma Proving Ground are summarized in Tables II and III.
TABLE II
INDIRECT FIRE ACCURACY
Elev (mils)
PE (r) (M)
PE (d) (mils)
Charge 3
Soft Recoil Howitzer
534
.23
.93
M102
534
.19
.45
Soft Recoil Howitzer
1155
.36
1.20
M102
1155
.63
1.29
Charge 5
Soft Recoil Howitzer
534
.35
.79
M102
534
.28
.59
Soft Recoil Howitzer
1155
.26
.50
M102
1155
.24
1.54
Charge 7
Soft Recoil Howitzer
534
.33
.46
M102
534
.13
.45
Soft Recoil Howitzer
1155
.24
.81
M102
1155
.49
1.14
TABLE III
DIRECT FIRE ACCURACY
Charge 7
Range - 500 Meters
Weapon
Standard Deviation, Mils
Horizontal
Vertical
105-mm Soft Recoil Howitzer
.26
.31
105-mm How M102
.36
.28
105-mm How XM164
.26
.25
105-mm How M101
.26
.25
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Figure 3. 155-mm soft recoil howitzer.
The operational reliability of a soft recoil type weapon depends upon three requirements. First, it must fire at the proper time; that is, when the recoiling parts have reached the correct forward velocity. Second, the propellant must ignite and burn in a predictable and reproducible manner. Third, the latch must function properly every time. The first requirement has been satisfied. The second has been made less stringent with the invention of a device which senses the recoiling parts velocity, automatically actuates the firing lock at the correct velocity and simultaneously shuts off the accelerating force so if there is an ignition delay, the recoiling parts will coast until the charge ignites. This shut-off feature provides a high degree of assurance that the tube will return to the latch position. So far as the third requirement is concerned, the present latch system has never failed when the recoiling parts have returned to the latch.
The 105-mm soft recoil firing fixture was demonstrated to interested artillery personnel at Fort Sill on June 13th and 14th, 1968.
Figure 3 is an artist's sketch of a 155-mm Howitzer concept which incorporates the soft recoil cycle. This weapon would have a maximum range of 14,700 meters and would weigh only 7,200 pounds—5,500 pounds less than the standard weapon. A 155-mm soft recoil design cannot be finalized until the ammunition problem is resolved. Standard 155-mm propellant charges have an unpredictable ignition delay, varying from about 40 milliseconds to more than 80 milliseconds. A reproducible ignition delay, with a small variance, gives the designer no basic problems. A 40-millisecond variance does. First, he must allow up to 2
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feet of extra forward travel to allow for the "coast period" of the recoiling parts when the weapon should have fired but did not. During this period the angle of air will change because of structural deflections. The change will cause a range error. Analysis indicates this error will be unacceptably large at both high and low quadrant elevations. Therefore, ammunition studies have been initiated to reduce the ignition delay variance in 155-mm propelling charges.
Use of the soft recoil cycle to provide increases in range and/or payload and to enhance stability of a field artillery system is another potential of this recoil cycle. A weapon utilizing the soft recoil system would allow great advances in these areas where stability may not be the primary operational objective.
The soft recoil cycle is one of the more promising applied research programs currently being investigated by personnel of the Weapons Command. Perfection of this recoil cycle will provide field artillery design engineers with an important technique for reducing weapon weight while improving weapon mobility, rate of fire and stability.
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LUNAR RELIEF MAP
The Army Map Service (AMS) will help the National Aeronautics and Space Agency to make simulated man-landings on the moon. The area on which they "land" will be a simulated surface being built by the AMS from a high-fidelity lunar relief map made from Orbiter IV and V photography provided by the space agency.
Technicians in the Relief Model Branch at AMS, a U.S. Army Corps of Engineers agency, are building the 22 by 14 foot hand-carved model of the landing site which astronaut trainees will see as they "approach" the "target area."
The model is a part of a Lunar Module Simulator (LMS) to be installed at the Kennedy Space Center to provide flight crew training and orientation on the Apollo landing site designated as II-P-8. Through the use of the LMS, including the crew station, optics, instructor console, compute complex, closed circuit TV and other equipment, astronauts will experience a lunar landing approach without leaving Florida.
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TROOP CARRIER TESTED
Navy and Marine Corps units are testing a new jet-powered armored troop carrier. Developed in the lines of modified landing craft now assigned to Navy riverine unit in Vietnam, the new carrier transports 44 combat-equipped troops behind 3 inches of armorplating.
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