M19 Tank Transporter (1940)
USA (1942-45). (6,554 M20 tractors built)
Born from the
Diamond T family of heavy duty trucks and tractors, the M19 Tank Transporter is one of its main sub-variant, well used in WW2. This was a heavy tank transporter system composed of the 12-ton 6×4 M20 Diamond T model 980 truck and 12-wheel M9 trailer with more than 5,000 produced to carry tanks from the railroad (or a port) to the "last mile" depot before the frontline. The M19 was used by all the Allies in WW2, from Africa to Europe to the Far East. It was superseded in the
M25 "dragon wagon" in 1945 already, but soldiered on in other tasks, in Korea, Far East in British service, and only retired around 1971.
Development
The US Army had no tank transporters prior to 1939 but standard trailers mater to artillery tractors, but was the war progressed, the need arose, especially with a new generation of medium tanks such as the M3 Lee, and M4 Sherman. For this, as early as 1940, the need arose for heavy prime mover for tank transport, from the railway ro the depot, sparing the tank a long run at slow pace to the battlefield. This part of the logistic train was appreciable to reduce the wear and tear of precious combat assets.
For that task, the hard-cab Diamond T 980, from a Company in Chicago already known for its heavy duty utility trucks and long haul trailer tractors, seemed te ideal candidate, when identifed by the British Purchasing Commission, looking to equip the British Army with a vehicle capable of towing its heaviest tanks. The Diamond T Company also had produced military vehicles for the U.S. Army Quartermaster Corps. Its vehicles were already rugged for military operations. They were, once contacted, capable of creating a prototype for the US Army, but incorporating a few slight modifications matching existing British requirements. So an order was soon approved for 200.
The US Army incorporated it under the designation "Diamond T 980, 11 t, hard-cab, 6×4 truck". It was powered by the gargantuan Hercules DFXE diesel rated for 201 hp (150 kW), geared very low, for a massive torque, and towing the maximal theoretical trailer load of 115,000 lb (52 t), comprising the trailer itself. This was more than enough for towing the heaviest tanks in service such as the British Churchill (45 tonnes for the crocodile with trailer) or the late war 38t M4A3E2 "Jumbo". The British for this had the
Scammel tractor.
Design
M20 Tractor
So the The M19 Tank Transporter (US supply catalog designation G159) consisted of the 12ton 6x4 M20 Diamond T Model 980 truck and companion 12 wheel M9 trailer. The Model 980 (factory designation). Called also the "ballasted tractors", these vehicles had indeed a variable solid ballast compartment forward in order to stay stable whatever the trailer load. They had an immense bonnet, and thus, were powered by a 895 cubic inches (14.7 l) naturally aspired Hercules DFXE diesel engine (185 hp, 138 kW), however in other sources it appeared boosted up to 201 bhp (150 kW) at 1,600 rpm. In any case, th maximum torque was up to 685 ft/lbf (929 Nm) at 1150 rpm. It was geared very low so to demonstrate enough torque to pull a trailer up to 115,000 pounds (52,000 kg) as seen above. The engine was chosen by the British, but remained compatible with the US logistic train.
The driveline was composed of two plate dry disk diaphragm spring clutch, driving Fuller four-speed main, and three-speed auxiliary transmissions. The was a "low" first gear, three road gears, the 4th being direct. The auxiliary drive comprised low, direct, and overdrive gears. The lower gear led to choose extra very low gears for extreme off-road use while the direct and overdrive allowed were split, making for six road gears total in addition. There were also spicer driveshafts driving two Timken double-reduction axles. They had a 11.66:1 final drive for the ratio.
The chassis was a classic ladder frame, with three beam axles, leaf springs on front and on the rear tandem, but with locating arms. The wheelbase front the front axle to the rear bogie was 179 in (455 cm). There was a rear frame crossmember and another pintle hitch on the front crossmember for positioning the trailer. They all Budd split rim disc wheels combined with 12.20×20-20" tires, single forward and dual mud/snow compatible at the rear. They used air powered drum brakes were used on all axles and braking could be independent from service brakes. There was a single disk transmission parking brake using four brake pads with a cable clasp mechanism, combined with a 16 in (41 cm) disk behind the auxiliary transmission.
The behind cab Garwood winch had a capacity of 40,000 lb (18,000 kg) and a 300 ft (91 m) steel cable. It was installed on the Model 980 for towing damaged tanks aboard. The Model 981 (1942) swapped this for a winch with 500 ft (150 m) of cable in order for towing loads both in front and rear of the vehicle for full tank recovery, just not only loading.
Early models still had the commercial cab shared by the 4-ton G509 but from August 1943. However, it was changed for the standard open military cab with tarpaulin. The latter was designed to to be assorted with a universal ring mount on top, mounting either a Browning M1919A4 0.3 in LMG or a M1920 0.5 in Heavy Machine gun. Its long butterfly hood had vertical louvers on both sides which differed from the G509.
The short "ballast body" behind the cab had a capacity of 18,000 pounds (8,200 kg) to increase traction on the rear tandem axles. There were also closed tool compartments on both sides and all the material to unstuck the vehicle. There were also two open containers forward a bottom-hinged tailgate and a main aft box holding a spare tire.
M9 Trailer
It also carried the M9 Rogers trailer as tank tractor, the result being known as the M19 tank transporter, perfectly able to carry all variants of the M4 Sherman and derivatives. Some were also delivered to the USSR under Lend-Lease. The Model 981 had front rollers for winch cables. That was the only way to recoignise them. The M9 had tandem rear axles, single front axle on rotating dolly. It had ramps hinged down at the rear end to be deployed, very strong to support a transiting 52t weight. Fomr the winch cable rollers and sheaves the usual way was to pull tanks, unclutched, onto the trailer. Then it was attached and secured by chocks and chains. The trailer itself had some stops to block the tracks from sliding either ways.
The M9 trailer's front axle suspension system had trailing beam assemblies on coil springs. The rear bogie comprised dual tire wheel, none were compatible with the M20 tractor's tires; they were specific. The rear tandem beam assembly was a center pivot type: Its axles were on both ends of the beam. The dual tire wheel on both ends of the axles, comprised a beam on each side to have four wheels per axle line and in all, twenty-four 8.25×15" tires, on demountable rims, two per wheel.
M19 TT specifications |
| Dimensions (L-w-h) | 23 ft 4 in x 8 ft 6 in x 8 ft 5 in (7.11 x 2.59 x 2.57 m) |
| Weight | 26,650 lb (12.09 t) empty, 45,000 lb (20,000 kg) loaded |
| Crew | 2-3 |
| Propulsion | Hercules DFXE 201 hp (150 kW) |
| Transmission | 4 speed × 3 speed auxiliary |
| Suspension | Beam axles on leaf springs |
| Top speed | 23 mph (37 km/h) |
| Max range | 300 mi (480 km) |
M9 trailer specifications |
| Unladen | 22,020 lb (9,990 kg) |
| Laden, max | 112,020 lb (50,810 kg) |
| Dimensions | 29 ft 8 in x 9 ft 6 in x 4 ft 9 in (9.04 x 2.90 x 1.45 m) |
| Suspension | Trailing beams front, center pivot beams, rear, 24 wheels. |
The M19 TT In Action
Production started in 1941 with the first batch shipped to Britain in January 1942 and sent straight to North Africa, notably for transporting the M3 Grant and the M4 Sherman when it was introduced later in 1942. In addition to the tank running its own engine if possible, the winch proved quite useful. Tanks were quickly recovered, often under hostile fire, returned to workshops. If some 5,871 were produced until the summer of 1945 when cancelled, i was used mainly by the British, Canadian, Australian and Neo-Zealanders, Free French, Polish, Czech, in almost every theatre. It seems it was even sent to the USSR under lend-lease: Approximately 295 Diamond M20 trucks paired with the 45-ton M9 Rogers trailers were delivered. However they more rarely sa action in Asia, but under commonwealth forces.
Indeed, the US Army itself soon preferred in Europe the M25 "dragon wagon" tank transporter as soon as it was available. The latter, made by Paccar (Pacific Car & Foundry) could indeed received an armoued cab, it had a tighter turning radius, better traction and lesser rolling resistance. On the M19 it became common practice to carry five 1-short ton (910 kg) concrete blocks routinely on the bed to improve traction. Later M20s were converted to a semi-trailer configuration than trailed cto fix some issues. This also improved fuel economy by almost 50%. However the M19 was appreciated as mechanically reliable but from 1944 it started to be relegated rear areas, supresded on the frontline by the M25.
The British Army by itself absorvbed more than 1,000 M19 systems in this war, and they soldiered on until the early 1950s, before started to be replaced by the Thornycroft Antar, now capable of carrying the new generation of MBTs such as the Centurion, Conqueror, and Chieftain. A fe few remained in use until 1971. Sold off by the Army they were often converted for heavy haulage and recovery by Pickfords and Wynns, filling a lot of roles in the civilian sector. On British roads they soldiered on with heavy lowloaders and fairground trailers, or kept ready for heavy rescue operation ass wreckers. The last ended in private ownership in Britain or the US. Howvever in the US they are a bit forgotten, completely eclipsed by the M25.