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October 26, 2010

My Dad's story - Making of independent India's first tractor (Part 2)

Picking up the story from where I left a month ago.

(First Part :

In order to understand the challenges the Indian team faced in manufacturing the indigenous tractor my Dad felt it important for everyone to appreciate what is a tractor and understand how the "design to manufacturing" process works. ( transition to production in bpo parlance).. Part 2

Tractor came into existence in the late 19th century as a farming invention for pulling agricultural machinery for plowing, tilling, disking and planting seeds in the fields to grow crops. The design & construction of the tractor had to take into account the practical aspects of farming. To a discerning eye , tractor will appear as an odd member of the automobile kingdom. And in many ways it truly is.

Curiously unique thing about a tractor is unlike other automobiles it does not have a chassis. In an automobile everything is mounted on the chassis. This tractor design is keeping in mind the purpose of the tractor which is to ride on uneven, rough bumpy surfaces in the field which would create enormous stresses on the chassis. Instead in a tractor there are three main casting parts - engine, clutch and transmission systems and all the three are bolted together to create a quasi chassis. It is also amongst the select few automobiles with different sizes of front & rear wheels. With the rear wheel in size. All two-wheel drive tractors are rear powered as in the power from the engine is transmitted to the rear wheels also called the driving wheels while the front wheels act as assist wheels and are used for steering purpose(changing direction) only.

Reason for the driving rear wheel being so large is to generate higher torque and create better traction, as unlike other automobiles, farm tractors have to negotiate through muddy, loose soil, watering areas, uneven surfaces etc. Additionally the size of the rear-tyres determine the center of gravity of the tractor and therefore provide stability to the tractor in absence of a chassis. Similarly the front tyres are smaller as they help keep the tractor stable in terms of its center of gravity and also provide ease of steering for the driver. And it is from its existential purpose - generate Traction + using Motor that Tractor derives its name. A term credited to Charles W. Hart and Charles H. Parr who build the first prototypes of the modern "tractors" in 1903.

Though the design is geared to create higher torque it has to sacrifice speed in the equation. As motorist's stuck behind a tractor on single lane road would have realized.Another distinct feature of the tractor that is visible from the outside is the exhaust ,that appears like a smokestack.It is so designed to prevent the hot exhaust fumes from affecting the crops and the soil in the fields.

Manufacturing tractors involves various raw materials and some critical propriety components for electrical, instrumentation panel on the dashboard, fuel injection system, hydraulic system, air cleaner, coolant system, brakes system etc. Each manufactured component requires different manufacturing processes. On front it has front axle bracket & housing, the front wheels are fitted
using a king pin inserted in the housing. Rear wheels are the giant wheels connected through the real wheel axle the power from the engine is transmitted to these wheels. Most of the castings used in the tractor manufacturing are made of cast iron, some from malleable steel and a few from aluminium. The transmission system involves gears & shafts. For the various phases , the engine assembly consisting of piston, piston rings, liner, engine values was reserved for the last phase as it involved the most precision manufacturing.

In the Engineering industry for any new product development especially one involving so many parts, the design team works as the mid- wife facilitating birth of an idea. Drawings that the design team creates are the blue prints. The concept is put on paper -- all parts, sub-assemblies, final -assembly , finished product and details of each parts required for the assembly (nuts, bolts, screws etc) are designed. Based on the design specifications few prototypes are made and tested against the required parameters of strength, hardness etc. Later the parts are assembled in sub-assemblies and subjected to variety of tests in case of any problems observed either while assembling or testing further corrections are made. If the performance is as desired more intense tests are conducted to determine the factor of stress (maximum stress the part or the assembly can withstand). Based on the test results and corresponding data , necessary, required modifications are carried out and iteratively the design of the product is finalized.

Next step in the march from "design to manufacturing" is to convert the set of design drawings and prototype models into a manufacturing process. Process that determines how each component would be mass manufactured and later assembled into sub-assemblies - Engine, Trasmission etc and into the final assembly. That is the function of the Process Engineering group.

(Disclaimer: Both the images are of the respective owners - 1. Mahindra Gujarat Shaktiman tractor 2. Old Ferguson tractor design )

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