8:4:1
Shaft Speed Ratio for 5/3 Twill Weave
For a 5/3 twill weave, the typical ratio between the rotational speeds of the crank shaft (X), bottom shaft (Y), and tappet shaft (Z) is represented as X:Y:Z.
Understanding Loom Shaft Speed Relationships
In many loom mechanisms, especially those utilizing tappet shedding for weaves like the 5/3 twill, specific gear ratios are maintained between the main driving shafts.
- The crank shaft provides the primary rotation for the loom's operation.
- The bottom shaft is often geared to rotate at half the speed of the crank shaft. Thus, $X:Y = 2:1$.
- The tappet shaft, responsible for controlling the shedding motion, commonly rotates at a much slower speed, often geared down significantly from the bottom shaft. A typical ratio is $Y:Z = 4:1$.
Combining these relationships:
If $X:Y = 2:1$ and $Y:Z = 4:1$, we can find the overall ratio $X:Y:Z$. Let $Z=1k$. Then $Y=4k$. Since $X=2Y$, $X=2(4k)=8k$.
Therefore, the ratio $X:Y:Z$ is $8k:4k:1k$, which simplifies to $8:4:1$.
This specific ratio is required for the complex shedding sequence needed for patterns like the 5/3 twill weave using tappet shedding.
Important Questions from FABR Loom Mechanisms Shedding
- Group I lists the components of the weaving machine and Group II lists their functions. Match the component with its function.
Group I Group II P Conjugate/matched cams 1 Driving the cloth roller with slip
driveQ Worm and worm wheel 2 Continuous positive take up
motionR Friction clutch device 3 Motion of sley in rapier loom S Lease rod 4 Separation of the warp sheet
forming the shed Amongst the following, the correct condition(s) that will reduce bumping during weaving is/are
- Group I lists weaving machine related parameters and Group II contains the shortcomings of these parameters. Match the machine related parameter with its shortcoming.
Group I Group II P. Variable heald staggering 1. Not favourable for heavy fabric Q. High eccentricity ratio 2. Reduction in shed height R. Fixed heald staggering 3. Reduction of sley dwell S. Late shedding 4. Higher vibration in weaving machine Group I gives a list of loom motions and Group II contains loom systems. Match the motion from Group I with the corresponding system from Group II.
Group I Group II P. Shedding 1. Matched cam Q. Picking 2. Seven wheel R. Beat-up 3. Rapier S. Take-up 4.Jacquard Determine the correctness or otherwise of the following Assertion [a] and Reason [r]
Assertion: In shuttle loom, late shedding is preferred for filament weaving.
Reason: In late shedding, the timing of shed dwell matches with the timing of shuttle travel through the shed, and therefore, it minimises the rubbing of warp yarns.
