3. INTRODUCTION
As we know, the main function of wheel is to support the load of
the vehicle and passengers and to resist the side force, created by
turning.
Resistance is also necessary so that will absorb hard knocks and
accidental damage.
With the development of the all metal wheel, which could be mass
produced and the pneumatic tyre, the designers were able to take
care of the need for lightness, combined with strength, stiffness
and low cost of manufacture.
In India, the first tyre factory was set up in 1936 at Calcutta. At
present there are large numbers of concerns engaged in the
manufacture of a variety of tyres in orders to meet the
requirements.
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4. WHEELS
A wheel is a circular component that is intended to rotate on an
axle bearing . The wheel is one of the main components of
the wheel and axle which is one of the six simple machines.
Wheels, in conjunction with axles, allow heavy objects to be
moved easily facilitating movement or transportation while
supporting a load, or performing labor in machines.
The power developed by the engine has been transfered through
the clutch, gearbox, propeller shaft and the differential to the rear
axle.
Wheels are connected to the rear axle. As the rear axle turns,
wheels also turns and the vehicle moves on the road.
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5. ESSENTIAL REQUIREMENTS OF
WHEELS
They must be of maxmimum strength to take weight, road
shocks, driving torque and all sorts of loads which not only
change in magnitude and direction but are most unpredictable
and demanding.
They must be of minimum weight weight so as to keep the
unsprung weight at the lowest.
Perfectely balanced both, statically and dynamically.
It should not be too expensive.
It should be easy to change, easy to clean and be of good
aesthetic quality.
It must be strong enough to resist local deformation as and when
the wheel hits against a road kerb or any other obstacle.
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6. WHEEL ASSEMBLY
The wheels assembly generally thought to consist of hub, disc,
rim, tyre and tube.
The wheels not only support the weight of the vehicle, but also
protect it from road shocks.
Whereas the rear wheel moves the vehicle , and the front wheel is
used to steer it.
All the four wheels must resist the braking streeses and withstand
side thrust.
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7. TYPES OF WHEEL
1. Disc wheel
2. Wire wheel
3. Split wheel
4. Heavy vehicle wheel
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8. DISC WHEEL
This type of wheel consists of a steel rim and a pressed steel disc.
The rim is rolled a section, sometimes riveted but usually welded
to the flange of the disc.
The disc performs the functions of spokes. The disc is frequently
dished to bring the point of ground contact under the large wheel
bearing.
The wheel assembly is bolted to the brake drum. This disc is often
perforated with the slots near the rim, which acts as a fan to blow
air on the brakes.
A hole in the rim serves to accommodate tube valve.
This type of wheel is simple, cheaper and robust in construction.
Most commonly used in heavy motor vehicle like cars, buses,
trucks and tractors.
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10. WIRE WHEEL
It consists of a separate hub connected to the rim with a number of
wires.
The headed inner ends of the spokes fit in the hub holes and the
threaded outer ends fit in the rim holes, where the mushroom-headed
nuts are screwed through the rim holes to tighten the spokes.
All the spokes must be of correct length and at correct tension to
hold the rim, centrally around the hub.
The spokes do not straight out as radii from the hub, but alternate
spokes are screwed to slope forwards and backwards towards the rim.
The forward sloping spokes absorb braking torque and the rearward
sloping spokes convey driving torque.
The holes in the hub are arranged in the inner and outer rows so that
one set of spokes slopes towards to the rim from the outer row of the
hub and the other set slopes outward to the rim from inner row of hub.
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11. These sideways inclinations of the spokes hold the wheel upright
against cornering loads and side thrusts.
A rubber chafing band is fitted in the well of the rim to keep tube
touching the spokes nuts.
The tension of the spokes may be tested, when the wheel is free of
load, by tappering them, which should produce an equal ring from
each spoke.
It allows free circulation of air around the brake drum.
They are lighter in weight than other types of wheels and used in
light motor vehicles such as racing cars, scooters and motor cycles.
Figure : Wire wheel 11
12. SPLIT WHEEL
The split wheel is made in the from of two dishes which fit back to
back and are clamped by a separate outer ring of studs and nuts.
The flanges of the disc thus give a seating for tyre and clamp on
the beads.
A thick section rubber ring is fitted in the gap b/w two beads. The
main advantage of split wheel is that it may be easily taken out of
the wheel by unscrewing the nuts and separating the two disc.
Figure : Split Wheel 12
13. HEAVY VEHICLE WHEEL
The wheel are made in same way as the disc wheels but much
thicker plate is used.
To lighten the wheel and also to increase air flow to the brake
drum, large holes are made around the disc.
The wheel nut recesses are usually machined instead of being
embossed.
In the case of twin rear wheel, the inner wheel may have a longer
valve stem to reach through the outer wheel for ease of inflation and
pressure check.
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14. RIMS
The rim is the "outer edge of a wheel, holding the tire” It
makes up the outer circular design of the wheel on which the
inside edge of the tire is mounted on vehicles such
as automobiles.
For example, on a bicycle wheel the rim is a large hoop
attached to the outer ends of the spokes of the wheel that holds
the tire and tube.
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15. TYPES OF RIMS
There are mainly two types of rims:
1. Flat base rim
2. Drop centre rim
Besides these two there are other types of rims which as follows:
Split side ring
Flange side ring
Split lock ring
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16. FLAT BASE RIM
The centre portion of this rim is flat.
One side of rim is removable so that the tyre can be installed
or removed without stretching the bead. This is known as
continuous base type rim.
In the demountable split ring type of flat base rim, the rim can
be collapsed to a smaller diameter for mounting or
dismounting the tyre.
It is used almost on all trucks and other heavy duty vehicles.
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17. DROP CENTRE RIM
The center section of the rim being lower than the two outer
edges, this allows the bead of the tire to be pushed into the low
area on one side while the other side is pulled over and off
the flange.
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