Architect Registration Exams: Study and Notes: Traction

Friday, June 19, 2009

Has a worm and gear interposed between the driving motor and the hoisting sheave.

Thus,

the Driving motor can be smaller, cheaper, high speed unit rather than the large, low speed unit that a gearless installation would require.

Motor = depends on type and drive system, either DC or AC

Car speeds = upt to 450 fpm

Rise = Maximum of about 300 ft.

Can attain almost same high quality , accurate, smooth ride as gearless

Components:

DC or AC motor

Shaft directly connected to a brake wheel and driving sheave

Hoist ropes placed around the sheave.

Absence of gears = motor must run at relatively same low speed as the driving sheave.

Economy = not practical to build motors to operate at very low speeds.

Gearless is for medium and high speed elevators, 500 fpm and above (fpm = feet per minute)

Motor HP = ranges 20 to 400 hp.

Passenger service = is the typical usage, capacities of 2000 to 4000 lb, up to 10,000 lb has been built.

Below 500 fpm required = geared machines are used, see next post

Maximum car speeds = 2000 fpm currently

Pros = gearless is quieter, more efficient, less maintenance, longer life

Rise = optimum for greater than 250 ft rise and where smooth high speed operation is desired

Intermediate range of rise and speeds (150-250 ft and 400-500 fpm) = geared and gearless become an option

International elevator companies, may need metric conversions

1kg = 2.2 lb

1 m/s = 198.6 fpm

Architect Registration Exams: Study and Notes