Tech Chat | Why do most tractors have smaller front wheels and larger back wheels?

2022-09-29

The large and small wheels of a tractor are very eye-catching. Why are the wheels of most tractors small in front and large in back?

Working Environment

The working environment of the tractor is complex, with various soils either loose or sticky and often bumpy. In addition, the tractor itself is very heavy, so the tires need to be wide, so as to increase the contact area between the tire and the ground, reduce the pressure, and prevent the tractor from sinking into the soil.

Generally, tires have deep patterns, which increase friction and minimize tractor work and slippage. And the tractor tires are large, so the distance between the tractor body and the ground will be higher, it will be more convenient to adapt to the bumpy soil, and there will be enough space for the ground crops.

Working Principle

The vast majority of tractors have small front wheels and large rear wheels. Generally speaking, the front wheel of the tractor is the guide wheel, and the rear wheel is the driving wheel. That is to say, the front wheels of the tractor are used to guide the direction, and the power is directly transmitted to the rear wheels, which drive the tractor to move.

Why are the front wheels so small?

Due to the harsh working environment, the resistance of the ground to the wheels is very large. Once the resistance increases, the efficiency of the tractor will inevitably decrease. Therefore, try to reduce the resistance as much as possible. If the front tire is small, the resistance will be relatively small. The front wheel is responsible for steering. If the front wheel is large and wide, the tractor adjusts the steering wheel regardless of the increase of the turning radius. If you want to overcome the resistance of the wheel by turning the wheel, you have to pay more power, and the time-consuming power drive is inefficient. The small front wheel makes it light and easy to control.

Why are the rear wheels wide and big?

In fact, both the rear and front wheels are subject to resistance from the soil, and because the rear-wheel drive type is responsible for the forward movement of the tractor, the width of the wheels creates more friction, preventing the tractor from slipping or falling into the soil.

Generally, when tractors work in the field, they always have to drag agricultural implements, such as seeders, plows, fertilizer spreaders, etc. These implements are usually fully loaded. When the agricultural implements are involved in the tractor, the tractor is about to burden a part of the weight.

In this case, the center of gravity of the tractor moves backward, and the load on the rear wheels is much greater than that of the front wheels, so the rear wheels do more work than the front wheels. If the two wheels are the same size, when the tractor is working, the rear load of the tractor will be too large, which will easily cause the front wheel of the tractor to lift up and fail to work normally. This is also why the tractor must be counterweighted before it goes to work. Therefore, the rear wheel of the tractor is generally wider and larger than the front wheel.

So how do we install an auto-steering system in this situation?

In this case, the angle sensor is usually mounted on the front wheel, since the front wheel is the steering wheel.

When the front wheel of the tractor is deflected due to terrain or other factors, the angle sensor can obtain the real-time change of the forward direction of the tractor according to the change of the front wheel, and transmit the data to the flat plate. The software obtains the angle value in real time, and controls the motor to adjust the steering wheel in time, so that the tractor runs in a straight line without manual control.