Develop a powerful tractor for as many applications as possible, one easy to operate by a single person and based on the proven concept of the Unimog: that was the idea pursued since 1967 by Gustav Krettenauer, agricultural engineer at the Daimler-Benz Gaggenau plant, and his team.
High tractive power at low speed: that was now the most important thing in large-scale farming. Agricultural was going through a period of upheaval at the time. Concentration and mechanization resulted in fewer and fewer farms producing more and more. In addition, to stay ahead of the competition it was necessary to employ manpower and equipment more efficiently than ever before.
The design of the MBtrac was determined from the very start by the following principles: like the Unimog, the tractor had to have four equally large, driven wheels; in the interest of efficiency, as many parts as possible were to be carried over from the Unimog. At a top speed of 25 km/h it had to be possible to engage and disengage the front axle drive and lock the differentials of both axles “on the go”. With the driver’s seat arranged in the middle, most of the weight had to lie on the front axle so that the weight would be distributed evenly when full tractive power was applied. A more powerful hydraulic control system than the one to date was planned to supply the front and rear power lifts. The vehicle was to have two power takeoffs. And instead of a platform it was to have a third mounting area for agricultural implements.
Frame and front axle almost like a truck’s
With light pebble grey paintwork, red wheel rims and fenders, a first MBtrac 65/70 was displayed at the German Agricultural Association (DLG) trade fair in Hanover in 1972. The designation of this first model described the output: the four-cylinder OM 314 engine developed 65 hp according to DIN or 70 SAE hp. The MBtrac fundamentally differed from conventional farm tractors in a number of ways. A flexible, lightweight channel-section frame with welded tubular cross members to which a variety of implements could be mounted replaced the block construction customary since the 1920s, in which the engine block and transmission housing were components of the load-bearing structure. There were mounting areas at the front, at the rear, and behind the cab. The seat console was fitted to the frame members amidships. A rigid rear axle ensured maximum lifting power and precise implement control; furnished with springs and shock absorbers, the front axle made for particular comfort.
Besides that, the closed cab, placed in the middle of the vehicle for minimum vibration, afforded far better working conditions than were the standard in those days in agriculture. Wide, non-slip steps made for convenient entry. The driver sat on an air-sprung seat protected from dust and inclement weather. Even an air conditioner could be had as an optional extra. Clearly arranged, ergonomically designed instruments and controls simplified operation; the central cab provided an excellent view of all mounting areas.
“I can even listen to the radio in the sound-insulated cab of the MBtrac 1300,” said Helmut Schröder from Hedern, who first made acquaintance with the MBtrac when he got stuck in the mud in a conventional all-wheel-drive tractor and was freed by a lighter MBtrac 700. That convinced him, and he soon switched to MBtrac. Hans Peter Mohr from Altenbruch, not far from Cuxhaven, also appreciated the advantages of a closed cab: “Whatever the weather I can work comfortably and protected. In particular – and this is a very crucial point to me – when I kick up a great deal of dust I notice practically nothing of this normally so unpleasant nuisance.”
Favorable response immediately leads to expansion of the range
Eyed suspiciously by the experts, the MBtrac met with great interest among farmers at the 1972 agricultural show. The Gaggenau people took some 350 orders home from the fair, despite the fact that the tractor was not scheduled to go into production until July of the following year. The factory displayed unusual haste in presenting the new product because Klöckner-Humboldt-Deutz also came out with a new tractor called Intrac at the DLG fair. Gaggenau built 520 tractors by the end of 1973; 2,714 units of the first series rolled off the assembly line by the end of 1975.
Spurred by the immediate success, Daimler-Benz presented an even more powerful tractor at the 1974 DLG exhibition. The MBtrac 95/105 was shown with light green paintwork; however, for the time being it remained just a prototype. Instead, beginning in August 1975 the new MBtrac 700, equipped with the 65 hp engine of its predecessor, and the also new MBtrac 800, output 72 hp, were chosen to become the heirs of the original MBtrac 65/70.
Heavy-duty variants arrive in 1976
At SIMA, the biggest French agricultural fair, which took place from 7 to 14 March in Paris, Daimler-Benz already had introduced a heavy-duty MBtrac 1000. At the time the 5675 cubic centimeter six-cylinder OM 352 diesel engine, the power plant in the prototype MBtrac 95/105, still had an output of 95 hp – hence the designation MBtrac 1000. By the time of the DLG show in May in Munich, the engine, its reliability proved in hundreds of thousands of vans, minibuses and Unimog – had its output boosted to 110 hp, and the tractor it powered was now called the MBtrac 1100. The engine obtained its maximum torque of 363 Nm at 1600 rpm. In addition, a turbocharged version with 125 hp and torque of 393 Nm was available and powered the MBtrac 1300.
The Federal Minister of Agriculture, Josef Ertl, personally appeared at the Daimler-Benz stand when the fair opened and praised the innovative concept of the MBtrac, which, as he pointed out, involved significant new investment: “This year’s agricultural trade fair brings an abundance of advanced farming technology. Daimler-Benz makes a sizeable contribution by appreciably extending its tractor range. To create the prerequisites for this it has invested more than 70 million marks in Gaggenau, the factory that builds the Unimog and MBtrac.”
On the outside, the larger engines distinguished the MBtrac 1100 and 1300 as completely new designs from the light MBtrac 700 and 800 series: the four-cylinder had a displacement of 3.8 liters; the six-cylinder engine was a 5.7-liter unit that could not be fitted under the tractor’s hood without modifications. Since there was no room there for a muffler, at the front of the vehicle a thick, black, sheathed exhaust unit poked its finger into the air like the funnel of a locomotive. The upper side of the long hood and the slightly angled radiator grille also were painted black.
Low soil pressure, high ground clearance
The MBtrac was designed so that 60 percent of its dead weight rested on the front axle and 40 percent on the rear axle. The result was that under load, i.e., with implements mounted at the rear, or pulling a plow or other farming equipment, the weight was evenly distributed between the two axles. The four equally large wheels ensured maximum traction with low soil pressure and a high ground clearance of about
500 millimeters. Moreover, the all-wheel drive reduced slip, which particularly made itself felt on wet, loamy soil. Of course, the MBtrac also had a differential lock that could be engaged “on the go”.
In certain applications – for instance, corn harvesting or beet pulling – push operation in the reverse direction could prove advantageous. This made the tractor, which carried fixed, front-mounted harvesting equipment, more maneuverable. It operated like a self-propelled harvester and made optimal use of the turning circle of about 13 meters. For this purpose the entire unit consisting of driver’s seat, steering wheel, instruments, controls and pedals could be turned through 180 degrees inside the cab.
Both – push operation in reverse direction and operation under heavy load on muddy, wet terrain – only were possible owing to a newly developed, flexible, well thought-out synchromesh range-change transmission. The basic version consisted of a six-speed main group and an eight-speed working gear group; if desired it could be extended with a subsequent planetary gear group to include eight crawler gears. Vice versa, an optional overdrive raised the maximum possible speed from around 25 to 40 km/h. All gears could be used in reverse direction too simply by throwing a lever.
Power takeoffs, compressed air and hydraulics: optimal power transmission
Flexibility and convenient operation, in addition to pure pulling power, were prerequisites for efficient use of the tractor, which had to perform a vast range of tasks with a great many attachments. The hydraulic and compressed air systems of the MBtrac and the PTOs on both sides left nothing to be desired. A transfer case flanged directly on to the engine transmitted power to the PTOs, which even under load could be engaged individually or jointly by means of a pneumatically actuated clutch, independent of the transmission of power to the drivetrain.
A compressed air system featuring hydraulic transmission controlled the four expanding brakes. The compressed air system also operated the all-wheel drive, differential locks, parking brake, and as an optional extra, a combined single and dual-line brake system for trailers. The hydrostatic power-assisted steering with separate oil circuit made controlling the large front wheels child’s play, even in difficult terrain.
The developers took great care in designing the hydraulic control system. At a working pressure of 200 bar the pump capacity was 45 or, alternatively, 60 liters per minute. In addition to the connections for the rear power lift and an adapter, plug connections for two more adapters with separate return lines were available so that implements could be operated in all three mounting areas. With a 52 liter oil supply, the maximum permissible quantity that could be delivered was 45 liters, enough even for the largest hydraulic cylinders of implements.
As standard, at the rear the MBtrac 1100 and 1300 had a conventional power lift (maximum lifting force 6,500 daN) including the mechanical Servotrak wheel pressure booster. Depending on cylinder cross-section, the standardized three-point linkage could be loaded with 35,000 or 50,000 N. As an optional extra an electronically controlled power lift with tractional resistance control, positional control and mixed control was available. This was needed, for example, to operate mounted and semi-mounted plows or to do cultivating work or work with subsoilers. In addition, a laterally stable front power lift with lifting power of 12,000 or 25,000 N was available.
Customers recognize the benefits immediately
MBtrac 1100 and 1300 met with an extraordinarily favorable customer echo. Particularly where heavy, sodden soils had to be coped with, as in the north German marsh country or during the autumn beet harvest, the talents of the new vehicle were impressive. The enthused comment of Josef Schiele from Hamlar in the Donauries region, who bought an MBtrac 1300 in May 1977: “You should have seen how it was last year. ‘That can’t be true!’ you would have said. The beet-laden trailers often were up to their axles in mud. The MBtrac managed to pull them out. Such pulling power – and then the comfort – that’s what we need.”
Otto Reinke of Re-Ha-Gemüse, a vegetable truck farm in Ellenstedt, agreed with him: “Pulling heavy trailers over frequently wet, sodden fields really is not a pushover.” Jan van Gunst, the first Dutch farmer who decided to buy an MBtrac 1300 – which he did right at the 1976 RAI show in Amsterdam – was more precise: “Owing to its overall design, this tractor has practically no slip and therefore does not cause unnecessary and harmful soil compression. If I fit this excellent, powerful tractor with twin tires on all four wheels – and that’s what I plan to do – then I have the ideal machine for multiple-row sugar beet harvesting techniques.”
“In my opinion the MBtrac simply affords more possibilities,” said David Wright, in August 1977 the first British customer to put an MBtrac 1300 into service. Wright, who plants wheat, potatoes, peas, onions and narcissuses on 380 hectares of marshy soil knows what he’s talking about: “It’s an extremely powerful machine. We’re looking into the option of front-mounted equipment use, in addition to the heavy tilling implements. I get through with the big MBtrac even in the wet.”
Overseas, road construction or forestry: the MBtrac does a fine job everywhere
Whether beet lifting or corn drilling, the cultivation of cabbage, potatoes and wheat or the mowing and windrowing of rape: in agriculture the heavy-duty all-wheel-drive tractors immediately found a great many jobs which they accomplished better than conventional tractors. The MBtrac came along well overseas too. In 1980 an MBtrac 1300 went to Guatemala, where it made itself useful in cotton farming. In Australia, where even then the average farm was imposingly large – between 250 and 500 hectares, compared with a very modest 19 in Europe –the tractor immediately met with keen interest. On February 9, 1979, Barry Cooke, cattle breeder from Myrup in Western Australia, whose enterprise Prime Exporters exported 280,000 young unshorn sheep annually to the Middle East, acquired three MBtrac 1300 which he used to harvest fodder. The decisive factor, apart from the tractive performance, was the multiple equipment mounting options front and rear, which permitted substantial rationalization of operations.
The heavy-duty tractors also convinced road builders: after the MBtrac 1300 won the pulling power test at the Orange Field Days three times in a row, Australia’s most important road construction company, Coates Hire, ordered three units of this tractor model in 1980. They pulled 16-ton roller drums at 20 km/h through rocky terrain and, straightaway, took care of jobs which until then only track-laying tractors had been able to do. Nothing appeared impossible for it. For example, in 1979, during construction of the autobahn ring around Hanover, an MBtrac 1300 with cage wheels worked its way through swampy ground where any other vehicle would long since have given up.
At the 1978 Interforst show Daimler-Benz introduced the forestry tractors MBtrac 1100 F and 1300 F. Though similar in design to the successful lighter-weight MBtrac 800, their dimensions differed. They adopted a number of design modifications like the continuous underpan or the sprag from the MBtrac 800. Both tractors were available with 2 x 6 or 2 x 10-ton double drum winch.
In the very snowy winter of 1978/1979, resourceful farmers in Lower Saxony simply got their MBtrac 1300 out of the shed and without hesitating began clearing snow. But industry too appreciated the advantages of the MBtrac 1300. At the Krupp Rheinhausen steel mill, around the clock the tractor hauled 70-ton trailers holding semi-finished rolled products, so-called billets, from the rolling mill to the distributing crane. The Thyssen Edelstahl-Werke, makers of high-grade steel in Krefeld, who started out with the MBtrac 800, also used the MBtrac 1100 and 1300 in three-shift operation.
Problems with the production volume despite everything
The MBtrac 1300 was well received from the start. Daimler-Benz sold 3,000 all-wheel-drive tractors in the first two-and-a-half years since the series was launched in mid 1973; by April 1979 the number had risen to 10,000. The MBtrac 1300, in particular, furthered sales. It was simply superior to other tractors in its field in many ways. The reactions of satisfied farmers, but also the response from faraway countries with huge areas under cultivation appeared promising. Soon even the 125 hp of the MBtrac 1300 did not appear to be the last word. Gaggenau presented a new flagship with 150 hp in 1980: the MBtrac 1500. Four years later the MBtrac 1300 and 1500 even won the Gold Medal in the practical test of the Royal Agricultural Society. In 1983 250 MBtrac went to Britain alone, three times as many as the year before, while the market as a whole was declining – a tendency which would persist.
In the longer run, the same developments which had furthered the rise of the MBtrac, and which the MBtrac gave further encouragement to, viz., concentration in agriculture and increasing rationalization in conjunction with a sharp decline in the number of farms, ultimately set limits to the MBtrac. From 1980 to 1986 new tractor registrations in Germany fell 22 percent; in Europe, almost 30 percent. Simultaneously the number of all-wheel-drive tractors increased: a proof of the correctness of the MBtrac concept, which now, of course, was taken up by other manufacturers too.
MBtrac sails under a different flag today
For these reasons the unit production volume never went beyond 3,000 units annually, a level which the MBtrac already reached in the 1970s. And while Gaggenau was launching an entirely new series of eight MBtrac tractors in 1987, Daimler-Benz was in the process of going together with Klöckner-Humboldt-Deutz to form the Trac-Technik-Entwicklungsgesellschaft (tractor technology development company). In this company, KHD, holding 60 percent of the shares, had a bigger say, despite the fact that the MBtrac had a far more convincing concept than the Intrac. Finally, when Gaggenau launched a new Unimog series based on entirely new components in 1991, the fate of the MBtrac, now no longer compatible with the new Unimog, was sealed (particularly also seeing as the MBtrac successor generation had turned out ten to 15 percent more expensive and would have been very hard to establish in the market). After a production run of 20 years and worldwide sales of 41,365 units, production was discontinued in Gaggenau.
But the multi-talent was far from dead. A company in Trier took up the ball and through today builds a vehicle modeled after the MBtrac. The Unimog general distributors still make sales and service for it their concern.