The document discusses traveller lag in spinning, which is the difference between the speed of the spindle and the traveller. This lag is caused by the traveller not having its own drive and being dragged behind the spindle. High contact pressure between the ring and traveller can generate heat due to friction. Different types of yarn require different travellers in terms of form, mass, material, and size to match the yarn and spindle speed. The material and mass of the traveller must balance heat generation and distribution, wear resistance, and maintaining proper yarn tension.

2. The traveller imparts twist to
the yarn, and enables winding
of the yarn on to the cop.

3. TRAVELLER LAG
• The length wound on to the cop per unit time
corresponds to the difference between speed of
spindle and traveller. And this should be equal to
that of front roller delivery speed.
• The speed difference due to lagging of the traveller
relative to the spindle, since the traveller does not
have a drive of its own but is dragged along behind
the spindle is known as ‘Traveller Lag’.

4. • High contact pressure (up to 35 N/mm2) is
generated between the ring and traveller during
winding, mainly due to centrifugal force.
• The pressure induces strong frictional forces which
in turn lead to generation of significant amount of
heat.
• This is the kernel of the ring/traveller problem.
The low mass of the traveller does not permit
dissipation of heat in the short time available. As a
result the traveller speed is limited.

5. • Travellers are required to wind up yarns of very
different types: coarse/fine ; smooth/hairy ;
compact ; voluminous ; strong/weak ; natural
fibre /synthetic fibre.
• These widely varying yarn types cannot all be
spun using just one traveller – variety of travellers
are needed. Difference are found in: form, mass ,
raw material , finishing treatment of the material
, wire profile , size of the yarn clearance opening
for the thread. Spinners must make wise decision
according to conditions.

7. FORM OF TRAVELLER
• The traveller must be shaped to correspond
exactly with the rings in the contact zone, so
that a single contact surface, with the
greatest possible surface area, is created
between these two elements. The bow of the
traveller should be as flat as possible, in
order to keep the centre of gravity low and
thereby improve smoothness of running.
These are used in short staple spinning mills.

9. Wire profile also influences both the behaviour of the
traveller and certain yarn characteristics, namely;
• Contact surface of the ring
• Smooth running
• Thermal transfer
• Yarn clearance opening
• Roughening effect
• Hairiness

10. • The material of the traveller should:
• Generate as little heat as possible
• Quickly distribute the generated heat from the area
where it develops (the contact surface) over the
whole volume of the traveller
• Transfer this heat rapidly to the ring and the air
• Be elastic, so that the traveller will not break as it is
pushed on to the ring
• Exhibit high wear resistance; but
• Be somewhat less hard than the ring, because the
traveller must wear away in use in preference to the
ring.

11. • In view of these requirements, travellers used in the
short staple spinning mill are almost exclusively made
of steel. However, pure steel does not optimally fulfill
the first three requirements. Accordingly, traveller
manufacturers have made efforts over several
decades to improve running properties by surface
treatment. Suitable processes for this purpose are:
• Electroplating, in which the traveller receives a
coating of one or most metallic layers, e.g. nickel and
silver; or
• Chemical treatment of the surface to reduce friction
and pitting.

12. TRAVELLER MASS
• Traveller mass determines the magnitude of frictional
forces between the traveller and the ring, and these in
turn determine the winding and balloon tension.
• If traveller mass is too small, the balloon will be too big
and the cop too soft; material take-up in the cop will be
low. An unduly high traveller mass leads to high yarn
tension and many end breaks. Accordingly, the mass of
the traveller must be matched exactly to both the yarn
(fineness, strength) and the spindle speed.
• If a choice is available between two traveller weights,
then the heavier is normally selected, since it will give
greater cop weight, smoother running of the traveller and
better transfer of heat out of the traveller and better
transfer of heat out of the traveller.