Over two thirds of the south pulpwood is delivered to
its final destination by truck. Almost every load of
wood or logs is trucked at some point during the
transition from stump to mill. Trucking is often the
most expensive part of a timber harvesting operation and can
run as high as 50% of the total logging cost.
Southern loggers hauling timber are faced with high equipment
costs, low profit margins and strict government regulations.
Whether or not a logger can stay in business often
depends on the efficiency of the trucking phase of his
operation. Since the Surface Transportation Assistance Act was passed
in 1974 truck weight loss have become increasingly restrictive in
most Southern states. Log trucks are often targeted by
mobile highway crews using portable scales on the less traveled
secondary roads. Trucks are checked for individual axle in
tandem weights as well as gross weight. Overweight finds
air usually expensive, often costing a larger several weeks
profit. Maximizing the legal payload on every trip to
the mill is one of the most effective ways to
reduce trucking costs. But this is easier said than
done for a lager loading his trucks at a remote
woods landing accurately. Estimating the weight of a load
of logs or pulpwood is difficult under the best circumstances
, even for the most experienced longer trees different greatly
in size, shape, density and center of gravity
. The weight of an individual law could varias Muchas
several£100 depending on its species and size, where
it was cut and even the time of year log
trucks. Axle weights depend upon the exact placement log
on the trader. Even variables such as mud at
the landing or the amount of fuel in the tanks
can affect the truck's weight distribution. The longer is
caught in a serious dilemma. Needs to load each
truck to its maximum payload but not go over the
legal limit as he need faces. Stiff, overweight
, fine. A recent study of three paper mills
by researchers from Virginia text Department of Forestry showed that
in their attempt to avoid overweight finds, many lagers
were regularly under loading their trucks at a cost of
several$1000 per year in lost revenue. A potential
solution to this problem has evolved in recent years due
to advances in technology. Elektronik weighing devices are now
available that can provide an accurate estimate of a truck's
weight. Three major systems are onboard truck scales,
loader mounted scales and portable weighing pads. On board
scales have been around for several years but are a
relatively new concept for Southern loggers. The on board
scale system consists of three components. Load cells,
an indicator and a cable to connect to load Cell
consists of strain gauges mounted within a high strength steel
bar. In this onboard system, load cells are
installed at the primary load during points on the tractor
and trailer, usually at the tractors, fifth wheel
mounting brackets and at the trailers equalizer hangers on each
side of the rear tandem As the trailer is loaded
. Electric current passing through the strain gauges is altered
due to the very slight bending of the load cells
. Although you can't see this bending with your naked
eye, it is precisely measured by the amount of
resistance met by the electric currents. Thea Trick impulses
then fed through the cable to a digital indicator in
the camp where it is converted to await reading.
Most on board systems can display net or gross axle
or tandem, and the total vehicle weight in their
study, the Virginia Tech researchers found that a set
of onboard scales reduced the longer load weight variability by
more than one time and consistently produced weight readings within
1% of the mill certified scales on board scales offered
the advantage of a fast, accurate readout for individual
axle or tandem waits a zwelling gross vehicle weight This'll
is especially important in states like Virginia, where weight
allowances are vigorously enforced. Thes units require very little
maintenance load. Cell should be kept free of caked
mud or ice on the trailer. Plug connection for
the indicated cable must remain dry to ensure accurate weight
readings, Log truck should be parked a level and
straight as possible during loading, and the trailer brakes
should be released once in operation. The weights recorded
by the onboard scales should be compared periodically with the
weights recorded at the mills scales. If the comparisons
begin to show a consistent difference of more than a
few£100 theon board scales should be recalibrated by adjusting
the weight readings on the indicator to agree with the
mills certified platform scales. A set of onboard scales
currently costs about$4500 installed so outfitting a large fleet
of trucks can be expensive. Recalibrating the units when
the tractor is pulling several different trailers can also be
a problem. Even so, relatively few Southern loggers
who have purchased onboard scales for their trucks have been
pleased with the results. And many claim to have
recovered their investment in a very short time. And
you're not going down there with, well, four
or 5000 pounds less. Well, you know, you
guess at it and you can't You can't never come
up, right. And you've got to try to
stay under and you try to stay on it.
You're gonna be four or 5000 pounds under. Yeah,
you got There are four or 5000 pounds every trip.
It soon mount up quite a bit. Yeah,
but having a system on, are you making more
money? I'd hate to run without a Moselle loader
. Mounted scales offer an alternative to onboard scales,
but our newer and less tested under Southern logging conditions
. One loader mounted system measures the way to the
logs through the increase in hydraulic pressure as the logs
airlift. The system was originally designed for front end
loaders, but has recently been adapted for use on
knuckle boom loaders, with some success. In Loder
mounted scales, a pressure transducer is connected to the
loaders stick boom hydraulic cylinder by a small hydraulic line
boom is operated to lift the logs. Transducer senses
the pressure increase and converts it to an electron ICS
impulse. This impulse is then transmitted by cable to
a computerized indicator in the loader cab, where it
is converted to a digital weight reading. Most indicators
have the ability to accumulate the individual grapple load weights
into a running total as the trailer is loaded.
In order to attain the necessary accuracy with a loader
mountain system logs must be weighed with the boom in
the same relative position each time. Some systems have
a switch that is automatically activated and records the weight
as the moon passes through the prescribed position. Other
systems called to the loader operator to manually trigger the
weight recording when the boom is in the proper weighing
position. Manufacturers of this system have reported accuracy to
within 2% of the total load weight. Other studies
have not shown this high degree of reliability. Floater
mounted systems provide an estimate of the Net vehicle payload
only so they might not meet the needs of a
lager operating in a state where individual axle and tandem
weights are strictly enforced. Since the cost of this
system is currently around$6 it offers a low cost
alternative for a lager operating several trucks in a situation
where gross vehicle weight is his prime concern. Ah
, third system that offers a potential solution for loggers
is portable weighing pads. Portable pads have been used
in agricultural applications for many years but are new to
the logging industry. Modern portable weighing pads used electronic
load cells similar to those in onboard scales, but
they way only one axle or tandem at a time
. The load cells are usually connected to a digital
indicator that could be placed at a convenient location for
the truck driver to read from the cab. Since
portable pads provide a reading of individual axle or tandem
, wait only gross vehicle weight must be computed manual
. In addition, since weighing is done after loading
is completed, required load adjustments may cause production delays
. Typical pads weigh about£1000 and can be transported
from one logging site to the next, however,
care must be taken to construct a suitable bed for
the pad to rest on at each weighing location.
About 12 inches of crushed stone on a firm and
level site provides a good base for the pad and
ensures accurate weight readings. Portable weighing pads currently start
at about$4000. They appear to be best suited
for logging operations on large tracts here. The pads
, along with the loader to make weight adjustments,
could be set up on a main hall road where
they would only have to be moved infrequently. In
addition to these three high tech weighing methods, there
are a few other methods of estimating truck weight that
are worth mentioning. Using a plumb bob and string
with graduated markings, it is possible to get a
rough weight estimate of a log Trucks payload. Carefully
measure the deflection distance between the trailers, leaf springs
and frame. One logger claims to be able to
consistently estimate the weight of his loads within£2000.
Using this method for the logger who is good at
math. There are several formulas and computer programs available
that will predict the weight of individual trees or logs
. Given the species length, diameter and some taper
information. Most of these formulas require only a small
handheld calculator and could provide a fairly accurate estimate of
net payload. Unfortunately, obtaining the measurements it takes
to use these formulas probably takes more time than the
average lager can afford. As a logger. Think
of the advantages you could gain by hauling the maximum
legal payload on every truck and not having to worry
about overweight fines or traveling out of your way to
avoid weighing Cruise depending on your individual situation. One
of these in woods weighing systems described here may provide
a tool that could make your logging operation more efficient
and more profitable. Thank you.