This document discusses various take-up mechanisms used in looms to maintain consistent pick spacing in woven fabrics as the cloth builds up on the cloth roller. It describes the components and functioning of intermittent and continuous take-up motions, including direct and indirect systems. Factors that can cause periodic faults in pick spacing are examined, such as faulty gears. Methods to calculate the wavelength and width of faults for different faulty components are provided. Positive and negative take-up systems are compared, and methods for maintaining constant warp tension are discussed, including weight and lever arrangements and tension controlled by springs.

2. TAKE UP
+ ve take up - ve take up

3. -VE TAKE UP

4. RACK WHEEL AND CATCH

5. WORM AND WORM WHEEL

6. +VE TAKE UP
Intermittent (Direct & Indirect)
• Actuates itself only after beat up of new pick insertion
by sley.
• Ratchet and pawl arrangement
• Narrow and lighter looms
Continuous (Indirect)
• Operates continuously to draw the woven fabric.
• Worm and worm wheel arrangement.
• Wider and heavy looms

7. TAKE UP
Direct take up
• The cloth is wound directly onto a driven roller.
• Rate of rotation of the driven roller has to be reduced
progressively as the cloth builds up so as to maintain linear
rate of take up.
• (Dia, speed of rotation reduces)
Indirect take up
• Cloth is drawn forward by frictional contact with the take up
roller, which is drawn forward through gearing at required
uniform rate, the cloth being wound up on to a separate roller.
• Slippage may produce several pick spacing variation, to avoid
it take up roller is always covered with coff. of friction.

8. Guide
Roller
Cloth
Roller
Take/
Emery
Roller
Indirect
(Spun Yarn)
Anti Crease Bar
Guide
Roller
Direct
(Continuous
Filament
Yarn)

9. • 5 wheel Take Up: motion gets transmitted to
take-up roller directly through 5 gear train
• 7 wheel Take up: motion gets transmitted to take-
up roller directly through 7 gear train
Intermittent +ve Take up
+ve Take up
 Here motion gets transmitted to take up roller directly
through gear train.

10. 7 wheel take up
Beam Wheel
Compound Pinion
Compound
wheel
Change/ swing Pinion
Change wheel
Ratchet Pinion
Ratchet wheel

11. Beam Wheel
Compound Pinion
Compound
wheel
Change/ swing Pinion
Change wheel
Ratchet Pinion/
Standard Wheel
Ratchet wheel
For each pick, the ratchet wheel (A) is turned
by one teeth.
The amount of fabric taken up for each pick
which corresponds to the pick spacing can be
calculated as follows.
Pick spacing = 1/24× 36/CW×24/89 ×16/90
×15.05 = 1.015/CW inch.
Picks/inch or PPI = CW/1.015
Or, PPI = CW*0.98
or, CW= 1.015 PPI
Generally, PPI in the cloth is slightly < no. of
teeth in CW
If cloth contracts 1.5% lengthwise, when it is
taken out of the loom. PPI= No. of teeth in CW
PPI = CW*0.98 +1.5% contraction
PPI =0.99 CW or, PPI = approx. 1 CW (only
if standard wheel = 36 T)
•NOTE
There is shrinkage in length when the
cloth is taken out from the loom because
the cloth will relieved of its tension under
which it was held on the loom.
Both standard wheel and change wheel can
be changed to get required PPI.

12. PERIODIC FAULTS
•Any faulty gear wheel or eccentricity in a gear in the train can lead to a periodic
variation in pick spacing which produces a fabric defect known as weft bar.
•If the wave length ( λ ) of this periodicity is ranging between 1/8 (0.125) to 10 inch,
the effect is readily seen in the fabric.
•Therefore, take-up systems are designed in such a way that the occurrences of such
periodicities can be avoided.
•Theoretical Dividend: it is a no. calculated directly from gearing arrangement of the
take up motion. If PPI is calculated by using this no., it will not be correct because all
fabric contracts lengthwise.
•Practical Dividend (Constant): 1.5% contraction is when added to theoretical
dividend

13. •If one tooth on wheel G is faulty, then it will
create a jerk in the take-up system whenever
this faulty tooth meshes with wheel F. This
will happen just once in one complete
revolution of wheel G.
If one tooth of G is faulty, it produces a
periodicity of λ= 15.05 inch.
Therefore the fault will reappear after every
15.05 inch in the fabric.
The width of the fault will be = 1/90 × 15.05
inch = 0.167 inch.
•if one tooth on wheel F is faulty, then it will
create a jerk in the take-up system whenever
this faulty tooth meshes with wheel G
1 faulty tooth of F produces λ=16/90*15.05
=2.5 inch
Width of fault will be same with that of fault
produced by a faulty tooth of wheel G
= 0.167”
Beam Wheel
Compound Pinion
Compound
wheel
Change/ swing Pinion
Change wheel
Ratchet Pinion/
Standard Wheel
Ratchet wheel
Case I: One tooth of one wheel is faulty
Faulty
Wheel
Wavelength of
fault
Faulty Wheel Width of the fault
A OR B
CW OR D
E
F 2.5” F 0.167”
G 15.05” G 0.167”

14. Beam Wheel
Compound Pinion
Compound
wheel
Change/ swing Pinion
Change wheel
Ratchet Pinion/
Standard Wheel
Ratchet wheel
Since, E & F are on same shaft,
•1 faulty tooth of E produce λ=16/90*15.05
=2.5 inch
The width of the fault due to one faulty tooth
on wheel E will be =1/89×16/90×15.05 inch =
0.028 inch.
• 1 faulty tooth of D or change wheel produces
λ= 24/89 × 15/90× 15.05 = 0.676”
•1 faulty tooth of B or A produces λ= 36/CW×
24/89× 15/90×15.05= 24.34/CW”
Width of fault will be same with that of fault
produced by a faulty tooth of wheel CW & B
= (24/CW) × 0.028= 0.672/CW”
Width of fault will be same with that of fault
produced by a faulty tooth of wheel A
=(36/24.) × (0.672/CW)= 1.008/CW”
Faulty
Wheel
Wavelength of
fault
Faulty Wheel Width of the fault
A OR B 24.34/CW” A 1.008/CW”
CW OR
D
0.68” CW & B 0.672/CW”
E 2.5” E & D 0.028”
F 2.5” F 0.167”
G 15.05” G 0.167”

15. Beam Wheel
Compound Pinion
Compound
wheel
Change/ swing Pinion
Change wheel
Ratchet Pinion/
Standard Wheel
Ratchet wheel
Case II: All teeth of one wheel are faulty
• G or F = λ= 15.05/90 =0.167 inch
•E or D = λ= 15.05/90*16/89= 0.028 inch
•CW or B = λ= 15.05/90*16/89*24/CW
= 0.676/CW inch
•A = λ= 15.05/90*16/89*24/CW*36/24
= 1.015/CW inch
Case III: Any one wheel is eccentric
• G or take up roller= λ= 15.05 inch
•E or F = λ= 16/90*15.05= 2.5 inch
•CW or D = λ= 24/89*16/90*15.05
= 0.676inch
•A or B = λ= 36/CW* 24/89*16/90*15.05
= 24.34/CW inch
CONCLUSION
Majority cases either one of the
defective wheels is liable to produce
dangerous periodicities for 7-wheel
take-up.

16. 5 wheel take up
Ratchet wheel A, having 50 teeth, is
turned by one tooth for every pick.
The amount of cloth taken up for each
pick which corresponds to the pick
spacing can be calculated as follows.
Pick spacing = 1/50×CW/120 ×15/75
×15
= CW/2000 inch.
picks/inch or PPI = 2000/CW.
If cloth contracts 1.5% lengthwise, when
it is taken out of the loom (There is
shrinkage in length when the cloth is
taken out from the loom because the
cloth will relieved of its tension under
which it was held on the loom.)
Emery roller/
Beam Wheel
Stud Pinion
Stud Wheel
Ratchet wheel
Change wheel
PPI= 2000/CW+ 1.5% Contraction
PPI= 2030/CW
PPI=K1/CW (K1= Practical Dividend)

17. Continuous Take up Motion (Shirley Take-up)
•Wheel A is driven continuously by chain and sprocket at one quarter of the loom speed i.e.
picks per minute.
•It drives change wheel (CW) through the career wheel B.
•A single worm ( D) on the same shaft of CW drives a worm wheel E on the take-up roller
shaft.
The amount of cloth taken up for each pick corresponds to the pick spacing can be calculated
as: Pick spacing= ¼ * 60/CW * 1/150 *10 = 1/CW”
Pick spacing= 1/PPI PPI=CW
Thus the number of teeth on the change wheel is equal to the pick per inch

18. •E or D = λ= 1/150*10=0.067 inch
•A or B or CW= λ= 1/CW*1/150*10= 0.067/CW”
Case I: All teeth of one wheel are faulty
Case II: Any one wheel is eccentric
•E or take up roller = λ=10 inch
D or CW = λ= 1/150*10= 0.067 inch
•A = λ= 60/CW*1/150*10= 4/CW”
CONCLUSION
From the above calculation it is clear that there are no periodicities of λ between 1/8 to
10 inch, so the risk of dangerous periodicities is eliminated in Shirley take-up motion.

19. Anti crack motion or Crack Preventers
Reference: Thiagarajar

20. Let Off Motion
• -ve Let off
• +ve Let off

21. -ve Let Off Motion

22. •One side of the chain is connected to the loom rail at L and other end is wound
on the ruffle to about 1.5-2 coils and is connected to a hook E
•The hook is connected to a long lever F by means of pin J with notches in the
lever F
•A weight hangs on the lever

23. Working
•Let off is worked by the pulling action of take up motion, assisted by the action of reed
beating the weft to the fell of the cloth, increasing the warp tension.
•Let off occurs when  in warp tension is sufficient to overcome the static friction
resisting the rotation of beam. Beam stats moving and tension drops. It continues till warp
tension is not sufficient enough to overcome dynamic friction. (Short term tension
variation)
•To rectify the tension variation,
 by  amount of weight on the weight lever F
By adjusting the position of weight J on the lever (Done manually, tension may not be
regulated evenly)
By changing the position of pin J on the lever
By  or  the no of turns around the ruffle
• Medium term tension variation (co efficient of friction between ruffles and chain/ropes)
•Long term tension variation (beam weaves down from start to finish)

24. R = radius of warp on the beam
r = beam ruffle radius
Tt = tension in the chain on tight side (attached with
the weight lever)
Ts = tension in the chain on slack side (attached
with machine frame)
W= weight
x = the distance between fulcrum point and chain
on tight side
y = the distance between fulcrum point and weight
(variable)
T = tension in the warp sheet (variable)
F = frictional force at the beam ruffle

25. Taking moments about the beam centre we have:
T R = F r
The frictional force F =Tt - Ts
where μ= coefficient of friction between chain and
beam ruffle
and θ = angle of wrap in radian made by the chain on
beam ruffle.
Now, taking moments about the fulcrum H of the lever,
we have:

26. Equation 5 shows that the condition needed to achieve a constant warp tension
is to maintain the ratio constant. Thus as beam radius R reduces, the
distance y must be reduced by moving the weight towards the fulcrum H in
regular interval to balance the warp tension. For example, if the beam radius
decreases by 25%, the distance y must be reduced by 25% to maintain a constant
warp tension.

27. Controlled -ve Automatic Let Off Motion
Shirley Let Off
Controlled: Rate of let off is governed by position of floating back rest.
-ve: beam is turned by the tension in the warp sheet acting against a frictional
resistance.
Automatic: it maintain constant warp tension from start to finish of the beam.

28. + Let Off Motion (To prevent long term tension variation)
OBJECTIVE: In which the beam is turned at a rate which tends to maintain a constant
length of warp sheet between the fell of cloth and the beam. So, applying warp tension
being separate from beam driving mechanism.
1. A means of applying tension to the warp sheet and for keeping the constant tension
as the beam weaves down.
2. A means of detecting small changes in the length of the warp sheet between the fell
and the beam
3. A method of utilizing these changes to vary the rate at which the beam is turned.
CONDITIONS :
1. Constant tension
2. Constant warp sheet length delivered.

29. A tension
controlling
mechanism
Beam driving
mechanism
1. Weight and
lever method
2. Tensioning
by spring

30. + Let Off Motion
Explain the following mechanism in detail with appropriate figures
•Roper let off
•Bartlett let off
•Ruti B let off
•Toyoda let off
•Hunt let off
•Saurer let off’
•Cimmco let off
Assignment 1

31. Tension controlling mechanism
A means of sensing the change in the warp sheet length is by use of back rest/whip
roller/back rail which is set to pressed upward against the warp sheet
– to detect change in length
– tension applied
F= Force exerted by back rest on warp sheet
F= {W*(a/b)*(c/d)} + f
f= constant force due to weight of lever
A= short term lever or swing lever through
which back roller is suspended
With this system, warp tension will be constant
if it is solely dependent upon force F.
But, there are these possibilities of sources of
variation:
A
Weight and lever method

32. EFFECT OF WARP BEAM DIAMETER
As the beam goes down, the angle of warp sheet from the beam changes and this
change is responsible for gradual change in warp tension.

33. If resultant of warp tension T before
and after is the back rest is R¹. Since,
system is in equilibrium, R¹ is
balanced by equal and opposite force
R². The magnitude of R² is
determined by force F and another
force G (Stress in short arm from
which back rest is suspended)
Case 1 (back roller is freely rotating)
T= F/{2 cosɑ. Cos (ɑ-θ)} (ROBIONSON APPENDIX)
T= Tension on warp sheet
F= force exerted by back roller on warp sheet
ɑ= half of angle b/w top and bottom sheet
θ= inclination of swing lever w.r.t to vertical
(b) As dia  angle between top and bottom sheet 
F remains unchanged in direction and magnitude because weight W remains constant. But due
to change in angle of wrap R¹ R² (b) differ from R¹ R² (a).
T (b) < T (a)
ɑ
ɑ
θ

34. Effect of angle θ
There is large
fall in tension.
Warp tension will by
20% from start to finish
This  in warp tension will
not occur if the angle of
wrap is kept constant
By using supplementary
roller
Warp tension remains
unchanged from start to
finish. BEST arrangement
for a freely rotating back
roller
Remedy

36. Case 2 (for fixed back rest)
Usually back rest is floating freely on bearing at the end of two swing lever arms –
No frictional effect
If bearing are crude or any obstruction in rotation- medium term tension variation.

37. Tensioning by spring
•Dead weights are replaced by springs.
•With weight and lever method, the downward motion of back
roller (in order to keep constant rate of let off) has no
appreciable effect on warp tension because F remains constant
(for the upward moment of weight lever)
•In case of spring loaded motion, Downward movement of back
roller- compresses the spring – F 
 Diameter causes  in warp tension by spring compression.
So a beam feeler is employed to avoid variation.
•Beam feeler is in contact with yarn, feeler movement is
transmitted to spring in such a way to prevent an  in stretch or
compression as beam weaves down
•Abrupt changes in the back rest position has no effect on the
warp tension when using weighted motion, but wd spring
loaded motion spring length changes at these points and warp
tension also changes.
A) Spring is in compression
B) Spring is in tension

38. Beam driving mechanism
•The movement of back roller as it senses change
in length between the fell and the beam has to
be converted into change in rotation of beam
•Beam is driven by ratchet wheel driven by pawl.
•The shield encircles part of a ratchet wheel
•Turning movement of ratchet wheel depends
upon position of shield

39. •Shield moved anti clockwise  ratchet wheel
is turned less because shield prevents the pawl
from engaging the teeth of ratchet wheel.
•Shield moved clockwise  ratchet wheel
moves fast
•If warp length 
Wt lever A  anti clockwise
Short lever B  turn shield clock wise 
ratchet wheel moves fast  speed up let off
•If warp length 
Wt lever A  clockwise
Short lever B  turn shield anti clock wise 
ratchet wheel moves slow  slow down the let
off motion

40. Bartlett Let Off motion (cotton & rayon cloth)

41. •Tension is applied to warp threads through
floating back rest by means of spring S, one
at each side of loom.
•Short Arm lever that carries the back roller
are subsequently horizontal, so that there is
no need to compensate for variation in warp
tension due to change in angle of wrap of
warp sheet.
•On the other side of loom (not shown) a
similar spring is compressed between collar E
and a fixed stop on the loom
•On the other side spring will be compressed
more as the beam weaves down.
•It is now to reduce the compression of the
spring on the other side of the loom by an
equal amount so that the sum of two forces
exerted by two springs will be constant.
Collar

42. •As the beam weaves down  lever A turns
anticlockwise moves rod C upwards through
aeries of link  turns elbow lever D to move
anti clock wise  lower end of slotted over a
rod that caries a spring which is compresses
between collar E and slotted lever D.
•The effect is to length the spring as the beam
weaves down by the same amount as the
uncompensated spring on the other side is
shortened.

43. •Beam  driven by ratchet wheel R on
short vertical shaft which also carries a
worm J
•J  drives a worm wheel spur gear on
same shaft  drives the large beam wheel
Ratchet wheel  pawl  operated by rod
•Rod F moves to right each time as the sley
comes forward by projection H, which
receives a reciprocating motion of constant
amplitude from the sley sword
•As the back roller moves down the warp
beam weaves down,  collar will move to
right G rod will move rod F to the left 
this bring Y closer to H and rod F receives
more movement tuning the ratchet wheel
more.