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29 2 Safety notes Further notes The following notes are designed to complete the Opera- Tractors are mainly designed for hitching implements that To obtain the greatest possible towing force, particularly If an extra implement is attached, the extra loads must 1. Front axle payload: 4WD tractors.
The front axle normally bears 40% of the tractor weight on the road without implements; it may thus be necessary to add an extra weight on the front end to ensure that the front axle has traction.
If an implement is mounted on the front end of the tractor, check the weight of the fully loaded implement by placing the front axle on a scale: the maximum axle load must be less than the capacity of the front axle.
Check the maximum payload capacity of the front axle (maximum weight allowed on it) in your Opera- tion and Maintenance Manual). 2. Rear axle payload.
The maximum permissible payload for the rear axle depends on whether or not the tractor is carrying a weight or towing a load.
When the tractor is only carrying a load, without tow- ing, the wheels must have sufficient capacity that is ensured if the tyres are of the exact size and have the specified number of plies.
In certain conditions, extra weight may be applied to the rear axle but it is not normally necessary unless the ground offers very little grip.
When fully loaded, the weight of the tractor must be less than the maximum permissible ballasted weight since the tractor cannot be loaded right up to the maximum static payload for each of the axles, front and rear, at the same time. 3. Ballast and wheel slip.
Wheel slip must be measured for the tractor to oper- ate efficiently during tillage.
On normal terrain in good operating conditions, wheel slip should be between 4 and 10%.
On loose soil, wheel slip can exceed 12%.
If wheel slip is found to be greater than this amount, proceed with care as operating conditions might quickly become unstable and cause early tyre wear.
In certain conditions, it might be better to add ballast in order to reduce wheel slip, but this increases the workload of the transmission and thus reduces the working life of the tractor.
Read the operation handbook or ask your Dealer who will be able to help you ascertain the maximum ballast weight you can use in normal working conditions.
Using dual wheels or wider tyres, the tractor will have greater grip but the workload on the transmission will also be greater in dry and difficult soil conditions.
Dual wheels or wider tyres can sometimes be mounted for use on slippery or sandy terrain but the axle weight on hard, dry surfaces must be limited as the greater grip provided by wider tyres can damage the transmission.
The only torque limiter in transmission is wheel slip. 4. Front axle lead when four-wheel drive is en- gaged.
In a 4WD tractor, the ground speed of the front wheels must be slightly greater than that of the rear wheels, in order to ensure traction.
The front wheel advance must be preferably between 1% and 4%, at an rate not over 5%.
Greater percentages may be used only on very soft ground.
The tyres supplied with your tractor have been checked for the correct advance of the front wheels, but when you change them, make sure you use tyres of the same make and size in order to maintain the same speed ratio between front and rear wheels.
If tyres of different makes are used, their size and internal pressure may modify this ground speed ratio, or advance. This could increase the load on the front axle and lead to unacceptable operating conditions, excessive tyre wear and, in extreme conditions, dam- age to the front axle or to the transmission.
Changes in the weight of the tractor, in the pressure or size of the tyres can cause the tyres themselves to bounce. This is not only annoying for the driver in the cab, but it can also cause a loss of grip and excessive wear in the transmission unit. |