Question

All the mechanisms in shuttleless looms are set with respect to

• A. Cam shaft
• B. Index wheel
• C. Fly wheel
• D. Break wheel

Hint:

• Loom mechanisms (shedding, picking, beat-up, etc.) must be precisely synchronized.
• This synchronization is achieved by timing all motions relative to the angular position of the main drive shaft} (crank shaft) of the loom.
• An index wheel} (a disc marked in degrees) or an electronic encoder is mounted on this main shaft to indicate its angular position.
• Settings for all mechanisms are specified in terms of degrees of the main shaft rotation (e.g., "shedding closes at X degrees").

Answer 1

The Correct Option is B

In a loom, various mechanisms (shedding, picking, beat-up, let-off, take-up, stop motions) must operate in a precisely synchronized sequence. This timing is typically controlled relative to the rotation of a main shaft or a primary timing element. The question asks what these mechanisms are set "with respect to" in shuttleless looms.

• (a) Cam shaft: Cam shafts are used to drive specific motions, particularly for shedding (tappet or dobby shedding) and sometimes for picking in older looms. While cams provide timing for individual motions, they themselves are driven and timed relative to a master timing system.
• (b) Index wheel (or Main shaft, Crank shaft, Timing disc/encoder): Modern looms, including shuttleless looms, have a main drive shaft (often called the crank shaft, as it drives the sley for beat-up) from which the timing of all other motions is derived. The position of this main shaft is typically indicated in degrees of rotation (0 to 360 degrees for one loom cycle/pick). An "index wheel" or a timing disc/encoder attached to this main shaft provides precise angular position information. All machine settings and timings for different mechanisms (shedding change, weft insertion start/end, beat-up, etc.) are specified in terms of degrees of this main shaft rotation.
• (c) Fly wheel: A flywheel is used to store rotational energy and smooth out speed fluctuations in machines with cyclic loads, like looms. It's part of the drive system but not the primary reference for setting the timing of various mechanisms.
• (d) Break wheel (Brake wheel): A brake wheel is a drum or disc to which a brake is applied to stop the machine. It's part of the braking system, not the timing reference.

In shuttleless looms (and modern looms in general), the settings for all coordinated movements are precisely timed relative to the angular position of the main shaft (crank shaft). An index wheel (graduated disc) or an electronic encoder on this shaft provides the reference for these settings (e.g., "shedding crosses at 300 degrees," "weft insertion begins at 70 degrees"). Therefore, "Index wheel" is the most appropriate answer representing the reference for setting loom mechanisms. \[ \boxed{\text{Index wheel}} \]