Chrysler and radar: the SCR584 radar-mounted anti-aircraft guns
Radar began with work by Dr. A. Hoyt Taylor and Dr. Leo C. Young, government scientists who noticed that radio signals are reflected from steel buildings. Turning their equipment around to the Potomac, they were able to track ships moving up and down by tracing interference patterns. Their report to the Navy’s Bureau of Engineering, sent in 1922, was received with enthusiasm, and Drs. Taylor and Young continued to experiment for many years, In 1930, they found that they could apply the same principles to aircraft altimeters, measuring the time it took for a radio "ping" sent to the ground to return, greatly aiding in low-visibility flight. Unfortunately, from 1926 to 1930, the reports were made public to everyone; on the lighter side, the British worked independently on this new phenomenon, seeing its potential for discovering invading aircraft (by 1931, American scientists were able to find aircraft fifty miles away). German and Japanese scientists were also working on radar; German physicist Hertz had discovered the reflectivity of radio waves in 1887.
Fast-forwarding through some history, at the dawn of World War II, a British chain of twenty radar stations prevented a major German bombing campaign in 1940; these stations had only been established a year earlier, in 1939. Radar also provided an alert of the attack on Pearl Harbor well in advance of the actual damage; though this was not the first alert (R.C. McCloy on the USS Condor first spotted the planes, but no report was sent to naval headquarters). The Army’s radar spotted the attacking planes nearly an hour before the attack started; had there been a system in place to use the system, and had the alert been immediately sounded, many American lives might have been saved, not to mention much of the Pacific Fleet.
With the start of the war, the government asked Chrysler to collaborate in both production and engineering. This site has some information on other Chrysler military operations, where the company distinguished itself in the economical, yet reliable, production of vehicles and airplane components. To the point, however, Chrysler was specifically asked to design, build, and test radar antenna equipment to be used with 90mm anti-aircraft guns. Working under top-secret security conditions, Chrysler managed to build the project ahead of schedule, and at only 44% of the estimated cost! (The patriotic K.T. Keller did not profiteer, and passed along cost savings.) The system was packaged in a single trailer, while the original system had taken seven full trailers, making it much more usable in the field.
The story began in 1942, when two researchers from the National Defense Research Committee joined K.T. Keller to show preliminary sketches of the radar antenna; K.T. Keller, then president of Chrysler, said that the paraboloid antenna could not only be made of steel, but could be stamped using auto presses; he also criticized the gearing used to turn the dish, which Chrysler was then building for Canada. As a result, the scientists recommended to the Army that Chrysler provide the entire microwave radar antenna system, not just the dish. That was approved, and a team was set up, including VP Herman L. Weckler, VP F.J. Lamborn, and C.W. Hirsch, who was made superintendent of the new division. F.W. Slack was responsible for all radar work done within the engineering offices and labs.
The price then was estimated to be $16,451 per unit; less than the goverment’s estimate or that of prime contractor General Electric, who had predicted around $50,000. The actual cost ended up as $9,386. Chrysler engineers were working under ideal conditions at that time, with the leadership of the Three Musketeers still reigning.
Engineers George Slider and L. P. Smith were assigned to begin the work. By April 29, 1942, they were at MIT, examining what had been done thus far. That work was determined to be unsatisfactory on several counts, including long trains of spur gears, weight, parts non-interchangeability, and inability to achieve close accuracy. A complete re-design was undertaken immediately by Chrysler Engineering staff.
The device had to send out 2,000 10-centimeter microwave radio pulses per second. The particular system produced by Chrysler Corporation was named SCR -584 and was teamed with a-heavy anti-aircraft battery of four 90mm guns, a British-invented IFF (identification, friend or foe) unit; a power source; and an M-9 gun director. The scanning pedestal or antenna mount, officially named Signal Corps Pedestal-MP-61-B, turned at 1,750 revolutions per minute. The plastic-enclosed antenna itself, located at the center of the "dish" beams short wave radio pulses one-millionth of a second in duration at intervals of one twothousandth of a second. The system interprets the return signal and determines direction, speed, altitude, and course of the target. Once locked on, the antenna tracks target evasive moves and synchronizes the guns. The equipment was designed to cope with aircraft speeds up to 700 miles per hour, up to 60,000 feet, at a target distance of not less than eight miles (Stout, p. 28). The secret proximity fuse completed the ensemble, since it was effective if triggered within about seventy feet of the target. Gear train accuracy was fundamental to success.
In a matter of months, the whole technology was accelerated-using the intellect of individuals on both sides of the Atlantic. Radar was truly cutting-edge, state of several arts work, not only sending out unprecedented-power signals, but also collecting the much-weakened return signals. General Electric engineers masterminded the principal electronic features of the apparatus while Chrysler solved pedestal mounting, dish rotation, and transportation aspects of the system.
The paraboloid reflector dish was engineered at Chrysler to be made out of steel, rather than the aluminum used in the experimental model at the Radiation Laboratory. In order to withstand winds of up to 60mph when in operation and not be tipped over in hurricane winds of 100mph, 6,640 half-inch diameter holes were included in the six-foot dish, saving seventy pounds of scarce steel each (Stout, p. 48).
Chrysler was asked to work out the unsolved mechanical problems of gunlaying short-wave radar, and then develop manufacturing machines, tools, processes to achieve quantity production. SCR584 required gearing that would hold to a maximum accumulated backlash of3.375 minutes out of a total 21,600 minutes of measurement. The motor specified turned 3,600 rpm. The dish could turn a maximum of eight times per minute horizontally and less than four times per minute in elevation. Thus reductions were necessary of 472 to 1 and 1,080 to 1 respectively.
So far as was known up to that time, the solution was another Chrysler First: a special planetary-type gear arrangement 2 and 7/16 inches thick and 6 and 7/8 inches in diameter produced a reduction to 120.8 to 1. In turn, this was made to connect with three conventional spur gears with an additional reduction of near 9 to 1, bringing total reduction to 1,080 to 1. The total reduction was completed in a smaller space than the conventional approach of using three spur gears to obtain 8 to 1 reduction. The combination of dual planet gears, in association with a fourth member, a second annulus gear, was unique as far as was known at the time. The parties involved in the project considered this engineering success one of the major contributions to the success of the antenna system.
In addition, the spinner motor required an unlubricated air seal to prevent absorption of short wave impulses by the hollow radio frequency transmission lines. The seal held six pounds of pressure, provided by a small compressor. Friction was minimized by use of Chrysler's Superfinish process, yielding 95 percent optically-flat surfaces on the bellows and seal. The carbon disc (shades of Fluid Drive) between the housing seal and sleeve was also Superfinished.
Pedestal support castings served as dimensional foundations for the whole assembly, and thus were made to extreme accuracy. All wire harnessing was color-coded to distinguish separate circuits, totally interchangeable, machine-tape-bound, and fungus/insect resistant.
Chrysler Engineering designed a special 19 foot, ten-ton semi-trailer that would clear the hatches of Victory ships. By no means were these commercial trailers, since they were much stronger, and were equipped with a series of built-in jacks to achieve accurate leveling. Due to Dodge Main's crowded schedule, the trailers were subcontracted by Dodge to Fruehauf, a well-established manufacturer. Each trailer had to pass a stringent high-pressure water test to prove its tightness against rain.
Dodge first made up six tool-room models and shipped unit one to Chrysler Engineering for accelerated life-testing on December 4, 1942. System two was placed in prime contractor General Electric's hands on December 26, 1942. Two more went to the Antiaircraft Board for preliminary trials by them. Because of the urgent need, Dodge continued to produce while the intensive testing proceeded, completing fifty systems during the testing period.
By August 31, 1943, 610 systems had been shipped. On Columbus Day, 1943, the Army's Signal Corps announced that production would be halted at 1,470 systems plus extras. The leadership had determined that number was sufficient for needs since the Allies had gained control of the air. This quick-moving program found 132 SCR-584s in the UK before Christmas, 1943.
Dodge Division delivered system 1,470 on January 28, 1944, with 628 additional sets going to the U. S. Marine Corps, coast defense, and spares for a total of2,098. Dodge had provided an average often complete systems per day. By mid-April, 1944, the machine tools and special equipment were moved out of Dodge Main's sixth floor, and the space converted to building B-29 engine pump parts. The SCR-584 residual pilot line equipment was moved to a Defense Plant Corporation warehouse in Indiana.
Operational Results Achieved By SCR-584 Radar-Guided Anti-Aircraft Systems In Combat
The SCR-584 achieved outstanding results in every theater of the war. In all cases, use of the equipment to direct the hurling of a deluge of 90mm antiaircraft shells saved Allied lives, both civilian and military. Originally contemplated as a defensive syste1l1, it soon proved vital to numerous offensive opportunities. Among hundreds of important episodes are the following:
Emergency At Italy's Anzio Beach. The initial shipments of SCR-584 systems were sent to North Africa in 1943 for training. When the flawed landing at Anzio in Western Italy turned sour, among the problems was the fact that the enemy successfully jammed the 268 radar. Two complete SCR-584s were rushed into the chaos on February 24, 1944 and dug-in up to their trailer rooftops over night. The next darkness saw twelve Nazi bombers entering beachhead air space only to lose seven aircraft to the 90mm guns directed by SCR-584. Abruptly, air attacks stopped for a week. A single plane appeared, to test the defenses-only to be destroyed. Ten more systems were emplaced that week, and effectively eliminated the air threat to Anzio.
Combating The V-I Flying Bomb. Twenty SCR-584s were assigned to England's Channel coast to reduce the number of V1 Flying Bombs hitting London. The eighty 90mm guns, using the new proximity-fused shells, destroyed hundreds of those weapons, including one August, 1944 Sunday when 97 of 101 were shot out of the sky. Overall, less than 10 percent of V-Is reached their targets.
Normandy: A Close-Run Action. The June 6, 1944 invasion included thirty-nine systems, performing to such deadly purpose as to thwart Luftwaffe attacks on the beaches. Given the extreme risks associated with crossing the Channel and penetrating Hitler's Atlantic Wall, SCR-584 helped provide the edge needed.
Excitement In The Bulge. German forces staged a powerful drive that penetrated the Ardennes Forest area-in 1940, as they outflanked the Maginot Line by an end run, thus forcing France's surrender. What had worked earlier, again seemed attractive to a nearly cornered Nazi High Command, and so it was. As USA forces fought back, to retrieve a tense situation, George Smith Patton's Third Army had to be pulled out of a committed battle, turned ninety degrees North, and launched toward Bastogne, 100 miles distant. Fortunately, SCR-584s were available to this amazing military movement and excellent use was made of them in blocking, containment, counter-attack, and resumption of offensive operations. During the first several days, only SCR-584- controlled tactical aircraft could be used, due to terrible weather conditions.
Radar's Role In Gaining The Eventual Victory
Historians and other writers working in the years following the close of World War II have varied in their positions as to the significance of this or that technological advance. As more information becomes available, through declassification or other sources, honest differences in view are normal. The war at sea differed completely from the Eastern Front in Russia. Many proponents of various air weapons remain staunch in their beliefs that air attack was the decisive factor. Perhaps all might agree that being able to read enemy signals was of decisive advantage in those cases where it could be done. Additionally, perhaps there might be agreement that being able to detect enemy forces in conditions of restricted visibility would be equally valuable.
In weighing radar's overall impact on the victory, consideration is due numerous advances in equipment and methods of use. Operations Research played a role. Massive production of materials and machines was vital. So too, was code-breaking including Ultra/Enigma (the Poles recovered an Enigma machine and managed to get it to the UK), details of which were held secret for decades following the end of the war. Applied use of radar, in all its forms and applications, was certainly the savior of the UK. If she had fallen, the liberation of Europe from Hitler's yoke would have been enormously complicated, and perhaps, impossible.
Dr. I. A. Getting, Aide to Dr. DuBridge, letter to K. T. Keller, October, 1945: "Those of us who have worked so closely with you and your engineers feel particularly sad that the closing of our Laboratory will also mean the end of this close association with you. I can honestly say that nowhere during the past five years have I met with a more efficiently administered engineering laboratory or a finer group of fellows than at the Chrysler Corporation."
Dr. LA. DuBridge, Director, Radiation Laboratory, letter to K. T. Keller, October, 1945: "No company has cooperated with us in a more patriotic and self-effacing way than the Chrysler Corporation. I have been deeply impressed by the efficiency and speed and ability of both your engineering and your manufacturing people. I am certain that the SCR-584 anti-aircraft radars would not have been completed in time or designed with such reliability had not your group played such an important role. "
Chrysler Corporation helped fill critical needs at a turning point for civilization.
— Dr. David George Briant, ashore at The Grey Lady, Latitude: North 33 Degrees, 42 Minutes, I Second; Longitude: West 112 Degrees, 10 Minutes, I Second. (99-06-03)
(Also see this page on the SCR584 system.)