Pros and cons of front suspension
Pros and cons of front suspension
Tractors fitted with front axle suspension systems offer
many advantages but not, it seems, for some types of
loader work. Mike Williams reports
THE last five years have brought a big increase in the number of tractors available with some form of suspension on the front axle.
The main advantages are claimed to be a smoother ride for the driver, more controllable steering for improved safety on rough surfaces and, according to some reports, more efficient front wheel traction from four-wheel-drive models.
Front suspension first appeared on big tractors in the 120hp plus sector but the idea has become so popular that several manufacturers are now including it in the options list for tractors from about 80hp upwards – the power range most often used for front loader work.
For the vast majority of loader operations front axle suspension has no significant effect but it can reduce the accuracy of jobs which demand precise positioning such as loading or stacking boxes or pallets.
Inaccuracy can occur due the front of the tractor moving vertically as the suspension adjusts to the weight carried on the loader.
When the driver moves the loader control lever to the lift position the front of the tractor starts to move down as the weight brings a response from the suspension. At the other end of the lifting sequence, when the load is placed on a trailer bed or a stack of boxes, the suspension pushes the tractor and the loader up as the weight on the suspension reduces.
Most front axle suspension systems allow total vertical movement in the 80-100mm range, but the actual movement due to the weight changes during loader work is less than this because most systems are self-correcting and return automatically to the mid position.
Tractor manufacturers are aware that the suspension effect could be sufficient to interfere with precise load positioning and if this happens the advice from the tractor makers is to switch the system off.
"It depends on the type of job you are doing," says James Barlow, product specialist for Case IH tractors. "If youre using the loader for muck handling, for example, the suspension system does not affect the work and the driver gets the benefit of a more comfortable ride.
"But for a job like pallet handling the suspension movement can be a disadvantage and we would recommend switching it off. Case tractors use an electronic control and when it is switched off the suspension is locked and that stops the vertical movement when the weight changes."
The suspension also reacts when heavy equipment is mounted on the front linkage, but there are unlikely to be situations when this is a disadvantage, Mr Barlow explains. *
For most loader jobs where precise positioning is not needed, the front linkage effect is not noticed.
Equipment mounted on the front linkage provides a constant load and does not often affect its performance.