Crusher selection by Taggart’s rule: choose a jaw crusher rather than a gyratory when (tonnes per hour) divided by gape^2 (cm^2) is less than what value?

Introduction / Context:
Taggart’s empirical rule provides a quick screen for selecting between jaw and gyratory crushers based on capacity requirement and required gape. It is useful during preliminary plant design.

Given Data / Assumptions:

• Metric form using tonnes per hour and gape in cm.
• Decision threshold separates jaw preference from gyratory preference.

Concept / Approach:
Taggart’s rule states that a jaw crusher is preferred when (T/hr) / (gape in cm)^2 is less than approximately 0.0184. Larger values indicate a need for the higher-capacity continuous-duty gyratory design.

Step-by-Step Solution:
Compute index I = throughput / gape^2 (consistent units).Compare I with the empirical threshold ≈ 0.0184.If I < 0.0184 → choose jaw; otherwise → choose gyratory.

Verification / Alternative check:
Textbook tables reproduce this threshold in various unit systems; in inch–short ton form a different numerical constant appears but the guideline is the same.

Why Other Options Are Wrong:
0.00184: too small; would unduly bias toward gyratories.0.184 or 1.84: too large; inconsistent with the commonly cited metric value.

Common Pitfalls:
Mixing units (cm vs mm or inches); misreading the square on gape; applying the rule outside preliminary screening.

Final Answer:
0.0184