CBC’s range of Martin Flex and Fenner Flex
tyre couplings provide all the desirable features one requires when looking for
a flexible shaft connection. Both Martin Flex and Fenner Flex tyre couplings
come with the convenience of Taper Bush mounting for fixing to the shaft. The
tyre coupling is a “torsionally elastic” coupling that gives designers,
engineers, and maintenance personnel the versatility needed to meet many
applications found within the industry today.
The variety of different flange arrangements,
in either F (Face) or H (Hub) flange, allows the Taper Lock Bush to enter the
hub from inside the coupling (F Flange). This allows the tyre coupling hub to
be mounted against the bearing on a shaft, which will reduce overhung loads. Or
the Taper Lock Bush is able to enter the hub from outside the coupling (H Flange),
which, in some applications, may assist with ease of installation. Please see
pictorial configurations below.
A feature offered by the Martin-Flex and
Fenner Flex tyre couplings, which are not commonly available from other
manufacturers, is the addition of a spacer unit accommodating for standard
distances between shaft ends (DBSE). This often facilitates ease of maintenance
for pump applications of 100, 140, & 180 mm DBSE. For further details,
please refer to Figure 1 below.
A further design option offered by both the
Martin-Flex and Fenner Flex tyre couplings, again not provided by other
manufacturers, is the addition of a fly wheel unit, which is designed to
accommodate standard SAE flywheel designs and many other original equipment
designs for combustion engines. These flywheel couplings use chloroprene
flexible elements and employ standard F and H type driving flanges, as pictured
below in Figure 2.
The tyre coupling offers excellent shock
absorbing properties, reducing vibration by up to 30%. It can also accommodate
simultaneous misalignment in all planes, without imposing any undue loads on
adjacent bearings. The natural rubber element can be used in ambient temperatures
between -50 degrees Celsius and +50 degrees Celsius. Also available from CBC,
and now the industry standard, is a Chloroprene Rubber element with an
allowable temperature range from -15 degrees Celsius to +75 degrees Celsius.
This element meets the requirements of the Australian Fire Resistant Anti
Static (FRAS) standards, set for rubber products that are designed to be used
in flame proof environments. In addition to this safety factor, this material
also has excellent resistance to contaminated environments including oil and
Installation of a Tyre Coupling
Installation of a tyre coupling, including Martin Flex and Fenner Flex tyre couplings is as follows.
- The Taper Bush should be cleaned to remove
any grease, oil or contaminants. The shaft and the bore of the tyre coupling
hub, into which the taper bush is to be installed, also needs to be cleaned of
oil, grease, dirt, or metal filings.
- It is a good idea to check both the bushing and the tyre coupling are free of nicks and burrs, and are not showing signs of cracking or damage. Place the taper bush in the tyre coupling hub, ensuring half holes are matched to make complete holes, taking note to match holes, and not threads. Each complete hole must be threaded on one side only.
- To facilitate ease of fitment, all threads should be oiled, as well as the point of the set screws or threads. Under the head of the cap screw should also be well oiled. Place the screws, but do not tighten, into the holes of the tyre coupling hub with threads on the hub side. Shown as in Figure 3 below.
4. The taper bushing should be free in the tyre
coupling hub. The assembly can then be located onto the shaft, into the desired
position. Insert the required key into the keyway. Note that there must be an
air gap between the top of the key and the taper bushing keyway.
5. Check that there is no grease, oil, or lubricant
between the outside surface of the taper bushing and the inside tapered surface
of the tyre coupling hub, to which the bushing is being installed. This outside
surface must be completely free from any lubrication.
6. Ensure the tyre coupling is located in the
desired position. The required gap between the hubs is to be measured and set
at the specified distance by measuring the assembled length across the hubs.
Refer to dimension M in Figure 4 below.
7. The screws now need to be alternately
tightened to ensure taper bushing is pulled up evenly and squarely into the
8. Correct seating of male and female tapers
requires some attention to ensure they are seated squarely. This includes
slight impact against the large end of the taper bushing. A torque wrench is
then required to tighten the screws to a specific torque as per the table in Figure 5 below. Tightening of these screws must, again, be done alternately to
ensure correct seating of the taper bush squarely into the hub. The torque
setting information relative to each size taper bush is provided with the
installation sheet in the packaging with new bushes. It is important that the
slight impact applied to ensure correct seating is undertaken with a softer
material against the face of the taper bush to prevent damage.
9.The Specified set screw torque should be checked again after the hammering and
tightening process has been carried out a number of times, and the torque is
maintained without further adjustment.
10. Before installing the tyre element, ensure the coupling
is within the alignment specifications: Up to 4 degree Angular, up to 3mm
Parallel, and up to 8 mm Axial.
11. Different methods of shaft alignment include the
| Method||Accuracy |
| By eye ||This is a very rough and inaccurate method of
It does not allow for issues such as thermal expansion.
| 6 inch rule ||This is better than ‘by eye’. This method has a
low degree of accuracy, |
and should only be used in an emergency and on small
(<7.5 kW) drives.
| Taper gauge || A low degree of accuracy, this method assumes
that the faces of the |
coupling are parallel to the shaft and to each other.
|Rim and face, Single dial,|
|Often requires custom brackets and equipment and
requires very experienced |
This method also assumes the couplings are
and square. When correctly applied, this method can be very
accurate, but time
Bar sag is a factor of rim and face alignment
methodology, which is an
influencing factor that is, unfortunately, not often
| Laser ||This method is fast and offers the most accurate
Some laser alignment devices have become so user friendly that
knowledge and training is required to operate them to achieve accurate
12. Once the tyre coupling hubs have been aligned
and the correct spacing has been achieved, the element is taken and the tyre is
opened. It is then fitted over the tyre coupling flanges, ensuring that the
tyre beads are seated properly on the flanges and clamping rings. To ensure
proper seating, it may be necessary to strike the outside diameter of the tyre
with a small mallet and, when correctly seated, there should be a gap, or
split, between the ends of the tyre.
13. Tighten the clamping ring screws evenly, half a
turn at a time, working around each flange until the required screw torque is
14. NOTE: It is important to return to the taper
lock bushing and check the torque settings of the screws, and re-tightening if
necessary following a period of running under normal operation.
15. It is a good idea to consider filling the unused
holes of the Taper Lock bush with silicon or grease to prevent dirt or
corrosion filling the hole. This will facilitate ease of future removal.
16. At this time it may be prudent to check the
clamping ring screws, working around each flange, until the required screw
torque is achieved.
To view a video demonstration of how to fit a
tyre coupling, Click Below.
or Fenner Flex tyre coupling is a versatile option for connecting shafts,
offering excellent vibration absorption, misalignment capability, and cost
effectiveness. Alternative makers of tyre couplings available from CBC include
Rathi, Tyreflex, Optiflex, Rexnord Omega Coupling, and Viva Coupling. CBC Power
Transmission technical personnel require the following basic criteria to
undertake a selection.
- Input power
- Speed (RPH)
- Shaft sizes
- Distance between shaft ends
- Duty cycle (stop/starts etc)
- Operating environment
these criteria ensures the demands of the application may be met with the most
suitable, cost effective and maintenance-friendly option.
There are many
alternative tyre coupling designs available from the CBC range, including HRC
Couplings, Grid couplings, gear couplings, disc couplings, and flywheel
couplings. Each offers a varying range of advantages and disadvantages.
Selecting the correct tyre coupling for the application is critical for
achieving a maximum design life.