OT..Question for Elevator Mike!!

darrenj

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Feb 2005
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Hey Mike..Question for you concerning Elevators....

I was recently stuck in an Elevator..( and the person i was with wasn't even good looking..they were a male employee...!!!)what i think happened was this..I was going up..to the 19th floor and the on the way there was jerk and it felt like the elevator was falling..Now i dont it actually fell but i think it stopped suddenly causing the upward momentum to continue..this caused the cable to go slack then the car "fell" the inch or two to tighten the cable..(On the right track so far?) After this Jerk happened the car stopped and wouldn't move..(Insert popular elevator manufacture here!!) came in and reset then the car moved to the closest floor and was cool again..aside from the change of underwear!! (I hate heights and were suspended between 18th and 19th floor..thats about 260' to the bumpers down in the parking garage!!)

I called the building maintenance staff and they said.."dont go any where!"...Followed by lots of laughter..they then asked if there were any other passengers in the car..io told them who was with me and after more bouts of laughter i was told to "Hang on!!"..More laughter..(The building Manager i have worked with for many years so he can get away with this stuff with me..)..The elevator mechanic was in the building at the time doing maintenance in the other tower so i was only in there for about 15 Min's or so..

First question..what would of caused the sudden stop..
2nd question..why after it stopped would it not start again..
3rd question..a couple of times in the past this elevator would be going up then slow down and stop then start to desend..then slow down stop and start to assend..why?
4th..Why does the car pull up slightly when going down..(By this i mean if i get on the 10th floor i can feel the car travel upward momentarily then go down..Is this to release the breaks or just make it easier on the passengers guts??

Lots of questions i know but am just curious..Starting to get a hate on for these things...

D
:)
 
Last edited:
darrenj said:
I was going up..to the 19th floor

I am not sure why, I never realized that Canada had big buildings. I have only been inland as far as London, Ontario, and I don't remember anything that tall there.

But then, out here in the cornfields west of Chicago, we have two 10 story high rise buildings, and the next two towns over have three. Other then that, 3 or 4 stories for a hospital is big.

regards.....kc

BTW, Mike should personally take a "Road Trip" and check it out!
 
IMHO If one of them coders I end up with re-working there codes have been doing anything with this elevator logic control...
 
First question..what would of caused the sudden stop..

Could be any number of things but my 1st quess is that the car door clutch bumped a landing door lock pickup device, disgingaging the door interlock contact. This would in effect cause the elevator to come to a screatching halt.

2nd question..why after it stopped would it not start again..

Either the lock keeper (with the shorting bar), didnt fall back into the lock, or the car stopped while it was still in the clutch.

3rd question..a couple of times in the past this elevator would be going up then slow down and stop then start to desend..then slow down stop and start to assend..why?

The car was likely lost and was trying to find a reference location to correct position. When this happens watch the PI in the elevator car.


4th..Why does the car pull up slightly when going down..(By this i mean if i get on the 10th floor i can feel the car travel upward momentarily then go down..Is this to release the breaks or just make it easier on the passengers guts??

This is called roll back due to overcounterweighting. The elevator counterweights weigh 40% more then an empty car. (In the center of the travel with 40% of the capacity on the car it should be balanced.) However the hoist cables have mass also. so when the car is at the top of the hoistway all the hoist cables are on the other side of the driver adding to the counterweight. Normally in a high rise building there will be a compensating rope or chain on tied to the bottom of the car to balance the load of the hoistropes regardless of position.

So what's happening here is this car may not have compensating ropes, and/or the timing between the brake pick and driveing of the hoist motor is too long, releasing the car with no power and therefore it rolls back. In a perfect world the motor will be started at Zero RPM, then the brake picks, a contact on the brake then tells the motion controller to start the run. Then you would get NO roll back.

Actually there's no good reason for rollback. It's a matter of good maintenance & adjustment. Problem is there's a lot of elevator guys who simply dont always understand how to correct it given the huge varity of motion controls out there, and it dosnt really cause a safety problem.

A few years ago we took over a 5 unit job that all the cars shuttered and had considerable roll back. The shuttering was caused by a friction drive feedback DC tach. One of our machinist devised a new tach mount and that ended the shuttering. The brake was a timing function, so we added a switch to the brake and resetup the drive to provide field current, then pick the brake, then move the car, which then provided for zero roll back. Major difference in ride comfort, but really had nothing to do with safety.
 
Why is it, in a three story building, there is a 90% chance the elevator is NOT on your floor?
 
Fred Raud said:
... how come when i keep pressing the button over and over the elevator doesnt get there sooner????

As a stunt one time I coded the car buttons on an elevator to cancel all calls but that floor when you tapped in the CW code for that floor. So when you would do this the elevator would drop all the previous calls and make a streight run. I only did it to confound a know-it-all Sparky, and it was removed before the final inspection. So somewhere out there, theirs an electrical journeyman pounding on elevator buttons, totally convinced that the elevator will infact come faster.....;) Sometimes you just gotta have a little fun..
 
Wino said:
Why is it, in a three story building, there is a 90% chance the elevator is NOT on your floor?

Maybe 9 out of 10 people dont want to be where you are...This might be resolved through regular bathing, winning the lottery, or taking the Dale Carnagie course, or maybe even by taking Beano.
 
Thanks Mike...Damn elevator in that building still gives me the willies...Stoped on me twice today..desended slowly till it hit 15th floor then took off up to 19...Scares the living **** out of me every time!!

I hate heights!!

D
 
Darren,

It sounds like it's losing count; might be a all relay system with a binary counter, or all relay stepper. Actually sounds like and old WestingHose. If there's 19 floors then there's 57 telephone type relays involved in the counting circuit alone. One questionable contact and it falls apart and has to start over from a known position. So it homes to a selector switch that corrects the counter.

A few years ago we took on a problem job that was 33 floors. It took an average of three trys to make it to the penthouse. I tried to get the owner to pop for a PLC based stepper but he wouldnt budge so we opted out. Within a year they upgraded with another company, after a legal battle with their tennents and lots of vacancys.
 
It was built in 83 and it certainly dosnt sound like the old relay relays one from the mech room door..I have seen a few of those and still wonder how in the hell they run for so long!..I also saw on the old relay system a Turntable (For want of a better word)It basically was a cog that turned a gear down a scale model The gear would trip a limit switch at certain points so the system knew where the car was..Next time i am in the building i will take a short video of it..Its kinda cool if you poeple have never seen it before..Lots af noise..relays clicking DC motors running..

As for the building i am in at the moment you can tell its a DC drive running the motor becouse of the destinctive "Drive" sound that all motors make when run from an inverter..

D
 
Darren,

The "turntable" you discribe is an Otis "pie plate" selecctor. Each pie plate is actually a shorting bar for each floor zone. The contacts ride on the carrage. They were actually pretty reliable for the time. They are driven from a steel tape that attaches to the elevator car.

In 1983, most manufactures were still installing all relay jobs & DC MG field control. Unless it was upgraded later, I would bet $5.00 that it's all relays. When the elevator comes under load you can hear the generator bogg down. High pitch to low pitch to high pitch.. Dampening motors, resistance grids, rotary exciters..the works. Looks like Frankenstiens Lab..

Warning: These machine rooms are VERY DANGEROUS. There's lots of exposed high voltage D.C. and unguarded moving machinery. Snag you pants on a hoist cable and your entire body will be reshaped to fit through a 6" x 8" hole instentanously. Stand too close to a flyball governer and you'll end up with a compound fracture of the tibia. Touch ANYTHING on the controller and you'll dissapear in a poof of smoke. In short, I dont need a video...I've already seen it, thanks anyway.
 
We have a "passenger" elevator in our mill building.
7 floors. Doors on both sides. Is not running more than it runs.
It was installed in 72-73 and is still maintained by the same company.
Last night I was waiting for the elevator for a few minutes when the new service guy shows up and tells me the elevator is down.
He asks how many floors we have, He had never set foot in our plant before and it was his first week working for the elevator company.
I felt so sorry for the guy in his pressed pants and spanking new (clean) coat in our dirty, dusty plant, I gave him a hand. Walked up to the 3rd where the car was just below the floor. After he figured how to 'pick' the door open, we found someone had jammed a 10' piece of 6"X 1/2" flatbar steel into the car diagonally and it was actually bent like a loaded spring. We think the yahoos that muscled the steel in, couldn't get it out and started jumping on it and caused a safety lockout.
The cool thing was we accessed the doors on the next floor and I provided a ladder by which he let himself down onto the car. There are manual controls on top of the car and he brought the top of the car to the opening and we rode the top of the elevator car up and down inspecting the shaft door limits.
I've been in this plant 22 years tommorrow and it was one of the most interesting experiences I have had. We found the problem and the next morning the staff guy in charge of the elevator maintenance told me that the elevator service guy had called to say that he really appreciated that electrician that showed him around the plant. I'm sure he'll be back.
Anyway back to work,

Brian.
 

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