Tag: science & technology

Acme threads are a specific type of trapezoidal thread with a 29-degree angle, commonly used for power transmission. Square threads have parallel sides rather than a trapezoidal profile, and 'Butters' is likely a misspelling of Buttress threads, which are triangular/asymmetric, not trapezoidal.

The M-system and E-system are both metrology standards used for measuring surface finish (roughness). M-system (Mottling system) and E-system (Envelope system) provide different ways to characterize surface texture - M-system uses mean line parameters while E-system uses envelope parameters. Gears (A) use specialized gear measuring systems. Screw threads (B) have thread measurement systems. Flatness (C) is a geometric tolerance measured differently.

Hydrostatic lubrication uses an external pump to pressurize and force lubricant between surfaces, creating a full fluid film even before motion starts. This means there's essentially no metal-to-metal contact at startup, giving the lowest starting friction among all lubrication types. Hydrodynamic (B) relies on relative motion to build pressure, so starting friction is higher. Mixed (C) and boundary (D) lubrication both involve some surface contact at start.

In rigid flanged couplings, bolts primarily experience shear force due to torque transmission between shafts and bending moment from any misalignment or external loads. The bolts don't directly carry torsional loads - that's what the shafts transmit.

Surface tension minimizes surface area, causing small water droplets to form spherical shapes. For falling rain drops, air resistance distorts this ideal shape, but surface tension is the fundamental reason for sphericity.

Hydrostatic lubrication maintains a complete fluid film even at zero speed by externally pressurizing the lubricant, giving very low starting friction. Hydrodynamic lubrication relies on relative motion to generate pressure film, so starting friction is higher.

Bernoulli's equation requires steady, incompressible, inviscid flow along a streamline. Turbulent flow is unsteady by definition and involves significant energy dissipation due to eddies, violating Bernoulli's assumptions. Rotational flows can also violate the irrotational requirement.

The Acme thread has a trapezoidal profile with sides inclined at 29°, designed for power transmission and easy manufacturing. Square threads have rectangular profiles, while buttress threads are asymmetric for unidirectional loads.