Fracture of Drive shaftgreenspun.com : LUSENET : Elevator Problem Discussion : One Thread
How unusual is it for a drive shaft to fracture? When it fractures, will the elevator car suddenly move up ("pulled by the counter weight)? Are there brake to prevent an elevator car from suddenly moving up?
-- Howard Medoff (firstname.lastname@example.org), October 08, 2004
this happend recently in the city i live in in the uk, the car will 'free fall ' up depending on where the fracture occurs, ie : before or after the brake, most new lift instalations have a bi- directional safety gear to address such problems and to answer your first question it is not verry common at all
-- (email@example.com), October 08, 2004.
I haven't heard of many. A shaft broke on a construction elevator during Scotia Plaza construction in Toronto about 15 years ago. One or more construction workers were killed when it hit the overhead. I think the inquest found misalignment and much vibration.
There's a Devices Branch Information Bulletin out about some Armor basement geared that cracked where the diameter had a step in it.
On another one all the spider bolts sheared but they said someone used oversize bolts and filed them down to fit.
Auxiliary braking device is required on new or modernized elevators in Canada since 1994 (perhaps 1990, but I think M94). For geared machines usually a hoist rope gripper, sometimes a sheave jammer, to stop up overspeed and uncontrolled movement with open doors, even if the hoist sheave becomes detached from the rest of the machine.
-- Barry Finch (firstname.lastname@example.org), October 10, 2004.
One went about 10 years ago on a building in Bradford UK The lift was 300 Ft/min or 1.5 m/s 16 persons and was going into slowdown when travelling up to stop 2 floors from the top. the output shaft had been turned down from 4" to 3&7/8ths and there was no radius on the machining. This gave a definite point for the fracture to start. The outboard/pedestal bearing was slightly out of line causing flexing on every journey. When the snap happened the gearbox casting and the pedestal held the drive sheave vertical and the lift ran straight into the shaft top smashing off guide shoes, bringing in the safety gear and demolishing the counterwieght buffer
-- geoff judge (email@example.com), October 11, 2004.
I seem to recall hearing that Chifley Plaza in Sydney Australia had some Otis gearless machines snap some drive shafts. Apparently it was a manufacturing fault from the Argentinian factory. Xrays showed up some others begining to crack as well
-- JJ (firstname.lastname@example.org), October 11, 2004.