FORMULA SHELF 3 of 370

The arithmetic behind the work: what to measure, what to type in, and what the answer comes out as. Every formula says what the symbols mean and gives a worked example, so you can check it against a job you have already done.

Quick calculators. A calculator appears where the formula is a single, clean equation with clear symbols. It is a convenience, not an authority: double-check every result yourself, especially doses, loads, torque and safety-critical settings.

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Workshop 2 formulas

Efficiency of a machine

efficiency % = (useful output / input) x 100

SYMBOLS · a gearbox is 95-98%, a chain drive 96-98%, a screw jack 20-40%, an electric motor 85-95%

UNITS · %

HOW TO USE

Friction and heat are the losses. A lower efficiency means more fuel, more electricity and more heat to shift away.

EXAMPLE

A 1 kW motor driving a 400 W pump is 40% efficient, which means something is rubbing.

efficiency losses friction machine

Gear ratio and overall ratio

ratio = teeth on the driven gear / teeth on the driving gear ; overall ratio = the product of each ratio

SYMBOLS · a ratio above 1 turns the output slower and stronger

UNITS · ratio

HOW TO USE

Whether you are rebuilding a gearbox, a mixer or a seedling thinner. Work it out on paper before you order the gears.

EXAMPLE

A 16 tooth pinion driving a 48 tooth gear is a 3:1 reduction.

gear ratio gearbox pinion reduction

Physics 1 formulas

Gear ratio MOST USED

ratio = teeth on driven gear / teeth on driving gear ; speed out = speed in / ratio ; torque out = torque in x ratio

SYMBOLS · ratio = driven teeth / driving teeth; speed out = speed in / ratio; torque out = torque in x ratio

UNITS · dimensionless

HOW TO USE

For a gearbox, a quad final drive, a mower gearbox or a winch. A 3:1 reduction triples the torque and drops the speed to a third. The power stays the same, less the losses.

EXAMPLE

A 12-tooth pinion driving a 36-tooth gear is 3:1.

gear ratio box torque speed

SOURCES & PROVENANCE 1 listed

This page is an AI-organised index. The label means the grouping and cross-links were compiled with AI; the information itself comes from the public-domain books, reports and manuals listed below. Open any source to read the local copy or follow the link to the original publication.

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Formulas collected and indexed with AI. The calculators are convenience tools; double-check every result before using it.