Home Forums General Discussion Technical Questions OTIS 6850 BJ SELECTOR CRASH

Brings back a lot of memories long hours setting those up and the pride and the satisfaction you get when all your stops are good and floor levels are right on, it is almost really worth it until the tape breaks and you get to do it all over...oh how I miss those days..

Add to the above-

The floor bars themselves are presummed to have not moved?

They initially get set up from scratch, by centering them on the synchronous panel while at floor level, as best as I can remember.

If you have an advancer panel, then you will have "SLS" cams, that unwind once the advancer has dogged out onto a pawl, and the car is leveling into the floor. (GK wing hits contact, strengthening the motor field, for more torque for the stop) This unwinding of the SLS cams drops out the speed switches. (They don't control the pick of the speed switches, that is done by a timer board) ARCO Towers in Los Angeles had 8 speed switches. A long ass S-curve, for fast cars, and no close-loop feedback. Ah, the sh*t we used to do before processors!

Note that each SLS cam # does not necessarily correspond to the same speed switch #, you gotta check the print. Saw a job at UCB, aka US Bank, downtown Los Angeles, 62 story job, (aka the Towering Inferno in 1987), where the adjustor kept tapping the same SLS cam around, expecting the corresponding numbered speed switch to drop out. The definition of insanity is doing the same thing over and over again, expecting a different result. As his dumb helper, I looked at the print, and showed him his error. That was a bad day for me, and the last time I was his helper again. Big pussy was so conceited....

At the master floor, check that each SLS cam drops out the speed switches (weakening the gen field) in regular, evenly spaced increments. You undo the tape sheave hub while at master floor level, crank the center pole of the selector away from floor level, (depending on how fast the job is, it might need several floors of cranking for 2, 3, or even 4 floors of slowdown) then put a meter accross SLS 1, then rotate the center pole towards floor level, and note the degrees on the vernier when the meter indicates the first SLS cam has changed states. Repeat for the other SLS cams, and for the pie plate contacts. Then do the same for the other direction, coming into the master floor. You should end up with a list in the up direction, and one for the down direction, indicating at what degree of rotation away from floor level each switch actuated at. (i.e., 280, 210, 180, 150, 110, 83, 50, etc, something like that)

So in short, you are checking the degrees of selector rotation on the vernier, from where the switch(es) change states, to where you are level with the master floor. The point is to ensure that all selector slowdowns and pie plate switches are evenly spaced, (no wild anomalies, no dead spots, etc), providing a smoothly constructed S-curve profile to the generator field. If your slowdown is too gradually tapered, it may bomb through the floor. If it is too abrupt, it makes an uncomfortable ride, and heats things up. Same sh*t you do with a hydro valve, or parameters in software for a modern processor-based, program-driven traction with VVVF drive.

The speed switches drop out, and the opening of their n/o contacts inserts more resistance in series with the main generator field. weakening the field and slowing the car. Never adjust a resistor to compensate for a cam out of adjustment. You can create hot-spots, and in effect require too much heat dissapation accross too small an area of a resistor, making it melt. (If not now, then later!) I think it's better the use as much of the tube as possible, so it can dissapate it's rated watts, and adjust the cams as neccessary. But it also depends on your desired floor-to-floor times.

Man, I can't beleive we are still talking about this old stuff!

As years go by, "cowboy" techs desperate for a quick fix have changed things, bent pie plates, moved things around without proper justification, and the S-curve is likely f'd up.

Also, you might have a "music box" on the car top, it's roller actuated by long ass cams in the hoistway, one at each terminal. These are the "auxilary means of slowdown, in case the normal means fail". These contacts are in parallel with the selector contacts. Back in the old days, the adjustor would have the helper run the car into the terminals, while he turned the adjusting screws for each contact. If the contact had a slight spark, that meant the music box was breaking the circuit before the selector, and he'd back off the adjustment until the spark "just" dissapeared. This meant that it was the selector contacts were doing the primary slowdown functions, and the music box was a close secondary means of slowdown, "just" behind the normal means. You could also rough-set them by measuring given distances from top or bottom floor level, and adjusting them to actuate at those pre-set elevations.

Also, with only the genny leveling field active, you want to compare the "base speed" in both the up and down, with a balanced load, (passing the master floor", to check the compounding. Add or remove turns to equalize the base speed up + dwn. (This is assuming the car + cwt have been balanced first)

Also, make sure your LU and LD pie plate contacts are close enough to the plate, so that the dead zone is no more than 1/4" each way, for 1/2" total. Put them too close together, the car can oscillate at the floor level. (Thought I was gonna say "jack off" at floor level, didn't you!)

If you have two door zone contacts, moving them towards the center of the plate will advance pre-opening, and moving them away from the center of the plate will retard pre-opening. In the USA, the car sill must be level with the landing sill, by the time the doors are 3/4 the way open.

All the above is only off the top of my head. It could be a little inaccurate. I haven't worked on that stuff for over 20 years.

That is why I mark them with my sharpy!

Always got to love those quick fixes,eh?

You know who many times I've had to readjust them just because someone didn't take the time to simply meg the motor.
It's amazing leveling problems can be fixed by just blowing out the carbon dust.

There was this one time when I got called to a job because of this and they sent over an"expert".
I let fiddle with it all day,he couldn't get anywhere.
He left and would be there again the next day.
Well,I grabbed my little portable air compressor,got there a little early and blew out the motor.
He shows up and everything is fine.
I just told him I didn't know what happen.

A plastic bag or sheeting ,duct tape and a vacuum to suck up the dust inside the contained blowout area works great.