Better Farming - November 2016

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54 FarmNews First > Better Farming November 2016
MACHINERYAT WORK
the front axle and the corresponding 60 to 70 per cent on
the back axle. The 30/70 split is increasingly becoming the
norm, especially for a tractor that has to use its own
weight to pull.
One such example would be a cultivator that does not
transfer any weight onto the tractor pulling it. While
pulling the cultivator, the tractor is overloaded on the
front as opposed to the back, and will likely go in power
hop mode. And power hop puts the tractor into an uncon-
trollable state of bouncing. In severe cases, the tractor
even breaks free from ground contact. If you have never
experienced power hop, talk to someone who has - it is
an unnerving experience. You lose all control and end up
going nowhere. You waste a whole lot of time and money,
spinning your tires and wasting fuel.
On a MFWD tractor, the front axle runs faster than the
back axle. The different axle speeds are needed to account
for the different tire sizes so that the back tires will not
push over the front tires. So the front will always need to
be able to “slip” to get rid of the extra ground speed it
runs.
Overloading the front of the tractor causes the front to
pull too much and it will try to drag the back along. At a
certain point, the front tires are inevitably going to break
free from ground contact and possibly cause power hop or
a mechanical failure somewhere in the drive line.
For average duty pulling, you need approximately 120 lbs.
of weight per unit of horsepower. A 200 hp tractor, for
example, would need approximately 24,000 lbs. total
weight with approximately 7,200 lbs. on the front and
16,800 lbs. on the back.
A lot of tractors are built in such a way that the front is
likely heavier than the recommended weight, while the
rear is a lot lighter than recommended. So, putting a set of
front weights on the tractor makes it look impressive, but
does not improve performance. In fact, the addition of
this weight on the front might hinder your performance
with some unfavourable side effects - like power hop.
On several occasions, I have suggested that farmers
remove their front weights or hang them on the back.
Those who took this advice were pleasantly surprised.
Unless you need those weights on the front for lifting a
heavy three-point implement, don’t hang them on the
tractor until you have the rear of the tractor properly
weighed down with a set of wheel weights or a ballast
weight hanging on the quick hitch. The latter type of
weight gives you the flexibility to remove it quickly if
necessary.
If you are using an implement that will transfer weight
to your tractor, you will need to account for that weight in
your calculations. And, as noted in the October edition of
Better Farming, remember to adjust your tire pressure so it
will carry the weight properly but still allow enough flex
in your radial tires for proper weight distribution and
traction.
When in doubt, ask your tire supplier to provide small
portable weigh scales so you have accurate weight and
pressure recommendations directly from the experts. BF
Jaap Kroondijk is a farm boy mechanic who lives near
Woodstock.
Following our discussion about ballasting, one of
my customers made his own weight bracket to
hang onto his quick hitch.