The EBR in Maryland

The_Chieftain: Over the last two articles, we’ve been following the trials and trubilations of the prototype EBR as it was being tested by Armored Board, to see if it made a good substitute for a light tank. Armored Board,  as a recap, said ‘no, but as armored cars go, it’s really not bad at all’.Once Armored Board were done with it, they put it on a train and shipped it to Aberdeen, Maryland, for the Ordnance chaps to have a look at. Once they replaced the two damaged intermediate wheels which came as shipped from Fort Knox, they conducted an ‘accelerated’ program of testing, from 13 June 1951 to 3 July 1951. It may be interesting to consider the French expectations if they shipped spares of those with the vehicle.Being Ordnance, they kept with the methodical natures with which they were familiar, and they started off their report with “Description of Material” (Not “Materiel?”. Interestingly, they kept the same nomenclature as Fort Knox: “French Armored Car.”The French Armored Car (Panhard) was designed to embody a large radius of action, high mobility, maneuverability, adaptability to both road and cross country terrain, and sufficient armor to withstand small arms fire. The Armored Car crew consists of four men: A car commander, a gunner, and one forward and one rearward driver, both of the latter being located in the hull. The vehicle has eight driving wheels, the front and rear wheels being rubber tired, the four intermediate wheels being of tractor type. The end wheels are the main driving wheels for normal road operations. These wheels are equipped with Michelin Metallic Tires (Size F25), which have bullet proof tubes inflated with nitrogen. During cross country operation the intermediate wheels are lowered, thus assisting in driving the vehicle. These wheels are made of metal and equipped with two inch cleats for traction. The four end wheels are suspended by coil springs and hydraulic shock absorbers. The intermediate wheels are raised and lowered hydraulically and incorporate a pneumatic cushion for protection against shock. Steering is accomplished through a rack and pinion and is assisted hydraulically. During road operation the two front wheels (with respect to direction of motion) are the steering wheels and the rear wheels are automatically locked. During cross-country operation when the intermediate hweels are lowered, all four wheels are utilized in steering when traveling either forward or rearward. The vehicle is powered with a 12 cylinder air cooled, pancake type engine, coupled to two four speed transmissions in tandem. The first transmission coupled directly to the engine is considered the cross country gear box, the second being considered the highway gear box. The cross country gear box can be locked into a 1:1 gear ratio for straight through drive to the second gear box. Operation of the vehicle disclosed, however, that better results could be obtained by a combined use of both gear boxes regardless of operating conditions, this giving 16 speeds forward and 16 speeds in reverse. The vehicle is also equipped with a central locking differential and reversing gear, jamming torque divider and side gear cases at each axle. The turret is equipped with a 75mm gun and a coaxial 7.5mm machine gun. It also mounts a 7.5mm machine gun on a pedestal mount. A 7.5mm machine gun is mounted on the front and rear of the hull. Two optional turrets are available for the vehicle, one with a 105mm howitzer, the other with four 20mm anti-aircraft guns. Vision and sighting devices consist of one periscope for observation and one gunner’s telescope. Seven periscopes are provided for the car commander and each driver has one periscope for observation. The vehicle’s armor plate thickness is as follows: Hull Front and rear 40mm Sides 16mm Roof 10mm Floor 20mm Turret Front 40mm Sides 25mm Roof 20mm  And so it started the battery of tests, once photographs were taken and the thing weighed. It crossed a 57” gap, with all eight wheels in use. The vertical wall scaled was 19”, but it stated “The French representatives did not encourage climbing a higher wall and were convinced (in their own minds) that 19” represented the maximum climbing effort of the vehicle”. A slight dig at the French reps there, methinks.Trench crossing didn’t go so well.When negotiating the trench course in the Munson Test Area the two front wheel, constant velocity joint housings failed. The dimensions of the trench course are 25’6” across the top and 59” in depth. The sides slop at an angle of 25 degrees with approximately a 3’ radius at the bottom. It was necessary to lift the Armored Car out of the trench by crane and transport it to the shops for repairs. A study of the failed housings revealed that the left housing had cracked in an old break which had been welded. Distortion of both failed housings, however, indicated too light a construction. Information received from the French representatives was that the housings are to be redesigned with external ribs for strength. New housings were received from France and installed on the vehicle, they were of the same design.The Frame Twister and Washboard courses did only slightly better.Frame Twister: When negotiating this course, operations were carried on with the intermediate wheels in their lowered position with drive on all 8 wheels. Under this condition, the intermediate wheels are hydraulically suspended against shock. When raised they are not. The vehicle satisfactorily crossed the frame twister course, however, when the intermediate wheels rode the crown of the waves, opposite end wheels were off the ground and the vehicle rocked from left to right as it moved forward. The course could not have been traversed with the wheels up, since the wheels would have struck the course and caused damage to their suspension which is not filled with oil when retracted, thus possessing no shock absorbing qualities.Washboard: Operation over the 6” high washboard course was attempted with the intermediate wheels raised. In this position, the intermediate wheels, having only 5 ¾” ground clearance, struck the course. The wheels were lowered to complete the run on the course and the vehicle ride was found to be fair. Inasmuch as the gun is not stabilized, the amount of pitch developed while traversing this course indicated that firing under these conditions would be impracticable for any degree of accuracy.The side slope test at 30 degrees was successfully passed, then onto the Perryman Cross Country Course.Limited operations were conducted on the Perryman Tank Cross Country Course. The vehicle displayed good mobility for a wheeled vehicle. Here again the softness of the suspension was in evidence. Operations were conducted with the intermediate wheels lowered, all wheels driving. When negotiating water holes on the course, a considerable amount of water splashed into the driver’s compartment when the driver’s hatch was open. [There would seem to be a simple fix for this – Chieftain] All operations were conducted with the driver’s hatch open, to obtain the maximum of visibility and ventilation for the driver [Ah]. The built up sections at the top of each right and left side fender, to house the coil spring suspension, limited the field of view of the driver to almost straight ahead. This was a handicap, for the driver had to continuously stretch to pick out obstacles normally obstructed by the fenders.Next, they dragged out an M24 for some comparison tests.Churchville Hill Courses: Satisfactory operations on the hull courses were conducted except for trial run on a 30% eroded grade used for special testing of wheeled and tracked vehicles. On this slope, the Armored Car had considerable difficulty whereas a Light Tank M24 had no difficulty at all. When negotiating this course, it was observed that the intermediate metal wheels with cleats contributed much to the final success of the vehicle in negotiating the slope. It was also observed that control of steering was poor, as the vehicle pivoted on the intermediate wheels. The vehicle had a tendency to slide off its course of travel and follow the ruts, whereas the M24 tank displayed no side slip. After operations, it was observed that the intermediate metal wheels contained several cracks.The report also observes the difficulty in steering mentioned before caused by the reduced weight on the end wheels when the center wheels are taking the load, meaning less force is applied to changing direction. The 20% mud slope test also showed that the M24 posessed “much greater mobility” than the Armored Car, but the Panhard did eventually make it to the top, after considerable wheel slip. On the road, the car got up to 60mph, and on the test bench, the engine managed 187.5hp at 3,800rpm.Then came the fun bit.Turret and Fire Control Tests.The Panhard Armored Car is fitted with an oscillating type turret in which the gun is stationary or fixed with respect to the turret. Gun elevation or depression is obtained by oscillating the complete turret. The turret mounts as a primary weapon the 75mm Puteaux APX cannon which fires all rounds standard to the 75mm gun M3 or M6 (Medium Tank M4, Light tank M24). Coaxially mounted with the main gun is a 7.5mm machine gun. In addition to the turret fire power, 7.5mm machine guns are located in the fore and after drivers’ compartments, and fired by these crew members. A direct sighting telescope of 4.5 magnification is the primary fire control (Final telescope design is to be a 6 power scope with a fixed reticle). The telescope incorporates a central sighting system with ammunition graduations for the APC (2030ft/sec) round and the 7.5mm Machine Gun. Rotation of a range input knob by the gunner indexes a movable firing reticle opposite the appropriate range graduation. Range date is obtained by visual estimation. Secondary fire control or provisions for indirect fire are not supplied. Manual and power traversing and elevation systems are provided for stationary and moving target laying.Accuracy was as follows:A gun camera installed on the 75mm was used to obtain power tracking performance of the traversing and elevating mechanisms.[…] While on the 15 degree side slope, it was observed that the power traversing system would not hold the gun uphill with the traverse controller in the neutral position […] tracking performance was generally acceptable but not superior to US systems. On the side slope, tracking ‘up hill’ was not smooth. Maximum rate of traverse, just over four revolutions per minute. “A free play of approximately 7 degrees exists in the azimuth tracking controller which is disturbing to the gunner”. Maximum elevation, 10 degrees, maximum depression, 12. Yes, the gun depressed more than it elevated.Maintenance was considered to be ‘very little required’, but a coil spring on a corner wheel did need replacement.Anyway, overall conclusions was that the general design and performance of the vehicle was good, but the off-road mobility did not compare to a light tank. Pretty similar to what Ft Knox concluded.Specifically.The tractor type, intermediate wheels, greatly improve mobility during cross-country operation. They are, however, too light in construction and are thus easily damaged when operating over rocky terrain or surfaced roads. Softness of the suspension provides for a comfortable ride. Inasmuch as some of the coil springs had to be replaced prior to this test, indications are that the springs are too weak for continuous off-road operation [The vehicle arrived with a notable lean to the right] Driver compartments are too compact. The gear shift levers located almost under each leg of the driver are inaccessible. Also, because of the location of these levers to either side of the drive, continuous hand changing from steering wheel to shift lever, for both left and right hand is necessary during a shifting operation. Open drive shafts in the driver compartments are located too close to drivers’ legs for safety or comfort. The low seating position of the driver combined with the high fenders with built-up sections for the suspension coil springs, limits the driver’s field of view even with the hatch open, to straight ahead. The small round seats furnished for the crew members in the turret are too small to stand on safely when riding with the hatch open. Likewise, hatch openings should be padded for crew protection. The low height of the pancake type 12 cylinder engine, which allows it to be mounted under the floor of the turret basket is a noteworthy feature. The provision of forward and reverse drive with equal speed ranges and steering control is an outstanding feature of the vehicle’s design. Except for spark plug and generator deficiencies, performance of the Panhard engine was found to be satisfactory as tested on a laboratory test stand. The bullet-proof tire tube design is considered in general to be satisfactory; however, for use on military vehicles not having tractor type wheels as aids to give added traction for cross country or sand operation, these tires are deficient, in that they cannot be deflated for increased floatation. The dispersion accuracy of the 75mm Gun using the APC M61A1 round is considered satisfactory The variation in center of impact experienced at 2,000 yards is not directly related to telescope reticle super-elevation design.[It doesn’t say what it is related to…] Gun “throw off” in both elevation and azimuth is considered to be excessive. Retention of boresight was good. Elevation handwheel effort is excessive Firing shock was not disturbing to crew or turret components. Space requirements provided for gun crew members is limited.So, overall, Aberdeen concluded, rather a lot like Knox, that there were some interesting engineering features, that the fightability of the vehicle was a bit limited (but making it bigger/more fightable may reduce the things that the vehicle gets right), but what was the point of it when you were a country which had light tanks?Looking at it from the benefit of almost seven decades later, it's interesting to consider that this is an armored car produced only six years after WW2, and much of its fundamental design actually pre-dates WW2. Considering the time, it's a heck of a design.