Mechanical Technology — August 2013
5
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On the cover
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The Dodge ISN roller
bearing tightens concentri-
cally onto the shaft and grips
through the width of the bearing for
better support and longer life.
The Dodge Torque Arm is a shaft-mounted
speed reducer. A patented twin tapered
bushing system for locking the reducer
onto a shaft also allows for easy removal
after long periods of use.
reputable brand that uses only the best
materials and forgings to achieve the
expected life of 40 years and more for
its slewing rings,” says Trevelyan.
“In the aftermarket, we can supply
completely new rings, but we can also
undertake refurbishments,” adds Tyler.
“These rings often have gears, which
also wear. If the bearing condition is
still sound, we can have the old ring
refurbished.”
Unitised bearing solutions
Bearings International is a distributor of
two of the world’s top unitised bearing
brands: namely Link-Belt and Baldor
Dodge. “Unitised bearings are designed
as replacements for open bearings for
environments where you never want
the rolling elements to be exposed to
the environment. These bearings are
pre-mounted into the housing under
clean conditions. They leave the fac-
tory sealed, greased and with all the
clearances accurately preset,” explains
Trevelyan.
“When you mount a traditional bear-
ing using an adaptor sleeve. The bearing
is pushed onto a taper, expanding the
inner ring, which reduces the clear-
ances inside the bearing.” Tyler tells
MechTech
. This residual clearance in
the bearing must be set correctly using
a feeler gauge. If the fit is too loose,
the shaft may move within the sleeve,
and if too tight, then the bearing may
run abnormally hot, due to the insuf-
ficient clearances,” he says. “Getting it
right is an art and increasingly, we are
losing the on-site tools and skills to do
this properly.”
Unitised bearings solve the problem.
Trevelyan explains: “Link-Belt has just
introduced its Shurlok adapter mount
for its heavy duty unitised-bearing
range.
“The unit comes completely as-
sembled with a built-in tapered sleeve
and collar. To mount the bearing, you
slide the unit over the shaft with the
collar loose. Then you tighten the collar
nut to drive the sleeve into the bearing
and lock the sleeve onto the shaft. The
Shurlok system incorporates strain
gauges, which change colour as the col-
lar tightens. All the fitter has to do is to
tighten the collar until the strain gauge
colour changes to blue. Then he knows
the clearances are perfectly set. And, if
he over tightens, the gauge shows red
which tells him to slacken off a little.”
Dodge ISN unitised bearings have a
similar taper locking arrangement, but
without the strain gauge. “These are
mounted by tightening to a zero point
and, from there, each bearing comes
with its own specific mounting instruc-
tions; to tighten by an additional
3/4 of a turn from the zero
point, for example. It’s that
simple, and more importantly,
its quick,” Trevelyan advises.
“Another improved product made
by Dodge is a sleeve mounted ball
bearing version of their unit called the
Grip Tight. “Standard ball bearing units
usually mount with grub screws locking
directly onto the shaft, but if you have
a slightly out of spec shaft, you bear-
ing won’t sit concentrically, which can
cause vibration and early failure. With
the Dodge Grip Tight sleeve mount, the
bearing tightens concentrically onto
the shaft and grips through the width
of the bearing for better support and
longer life.”
The seals on the Grip Tight range
are also far better than standard bear-
ing seals, and offer the advantages of
a grease-purge design – excess grease
is forced out, purging contamination
and obviating over greasing. “Both the
ISN and Grip Tight mount utilise the
easy on, easy off feature, which makes
dismounting as simple as loosening the
collar, which withdraws the sleeve from
the bearing for trouble-free removal,”
adds Trevelyan.
Going back to the Link-Belt range,
Trevelyan says that this design, while
designed to flush contaminants, also
offers a wide range of sealing options.
“Link-Belt seals are accessible from
the outside of the bearing so they can
be changed quickly without taking the
bearing apart,” he says.
Dodge shaft-mounted torque
arms
The Dodge Torque Arm is a shaft-
mounted speed reducer that incor-
porates many of the installation and
maintenance advantages of its Dodge
ISN unitised bearing range: a patented
twin tapered bushing system for locking
onto a shaft; a patented sealing system;
and a steel motor mount system. “As
well as the standard torque arm reducer,
Dodge also manufactures a motorised
torque arm, which is a unitised torque
arm eliminating the belt drive and al-
lowing a direct B5 flange IEC motor
mount,” Trevelyan explains.
A key feature of the product is the
way that the reducer is mounted to the
shaft. “One of the biggest problems with
reducers like these is removing them
from a shaft after long periods of use.
Dodge’s twin-tapered locking system
guarantees that the box can be removed
from the shaft without damaging either.
“The modular design approach also al-
lows a number of different gear ratios
to be accommodated in the same case
and with the same shaft size – and the
ratio range goes from 5:1 all the way
up to 40:1,” says Trevelyan.
“Bearings International’s specialist
bearing range is complimented by a
complete range of specialised leading
brand transmission products to cater
for the harsh environments encountered
in the Southern Africa market,” Tyler
concludes.
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