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#24864 - 09/27/18 02:43 PM Otis 72 machine bearing  
Joined: Oct 2015
Posts: 3
Rando Offline
stranger
Rando  Offline
stranger

Joined: Oct 2015
Posts: 3
Hello fellow elevator people! Greetings from Kansas! I have an Otis 72 machine that we recently put new ropes on. It is a two to one set up with a sheave on top of the car and a sheave on top of the counter weight. The machine is double wrapped with a secondary sheave in the overhead. About a week after roping it I heard a strange noise. After investigating I found out the armature had shifted about 3/16th of an inch towards the brush ring end. Needless to say the brake shoe is now rubbing on the inside of the machine sheave and has carved quite a deep groove. This scared me for a number of reasons. After consulting the Unitech book we Odered a new bearing for the brush ring end of the machine. I have many questions because I nor has anyone else from my shop replaced one of these bearings. Is the bearing pressed into the upright? Or does gravity and the set screw hold it in place. There is no race with the bearing so I assume it uses the oil as a sort of race. We have the bearing and are ready to do the job. If anyone has any pointers or advice I would sure appreciate it.
Thanks for the help
Rando

#24865 - 09/27/18 05:09 PM Re: Otis 72 machine bearing [Re: Rando]  
Joined: Jan 2014
Posts: 736
Rolly Offline
old hand
Rolly  Offline
old hand

Joined: Jan 2014
Posts: 736
I believe that machine bearings are sleeved Babbit bearings, Uses a COPPER chain to circulate the oil. Has to be copper to be anti-magnetic. There are 2 types of copper chains, One looks like a bicycle chain which kinks up and causes the bearing to freeze up due to lack of lubrication. The correct chain is called Universal Chain and is made of copper loops and will not kink and bind to insure oil circulation. Use Otis #2 Bearing oil for lubrication. If your not an Elevator Company I highly suggest you have them replace it or you will be doing it several times due to lack of knowledge. A lot more to it then any Building Maint Man will ever know, Make sure whoever you contract to do the job has Babbit Bearing knowledge.

#24867 - 09/28/18 03:31 AM Re: Otis 72 machine bearing [Re: Rando]  
Joined: Apr 2013
Posts: 17
slider Offline
stranger
slider  Offline
stranger

Joined: Apr 2013
Posts: 17
The secondary sheave is not in perfect alignment with the drive sheave by design. Rather it is set 1/2 a groove off. When the ropes are installed the offset must be kept in mind and the ropes must be installed accordingly. For instance, if standing in front of the machine looking down to the secondary sheave, the secondary sheave will be either 1/2 a groove over to the left or to the right. If the sheave is set to the right, then the first rope will be Installed in the first groove on th left side of drive sheave, will go down to the secondary sheave moving over 1/2 of a groove to the right, go around the secondary sheave, then back up to the drive sheave moving over 1/2 a groove to the right and into the 2nd groove, down to the 2nd groove on the secondary sheave again moving over 1/2 a groove to the right. Other ropes will follow suit: IF the secondary sheave is set to the right but the ropes are installed starting with the first groove on the right side of he drive sheave, the armature will be pulled over toward the brush rigging. The bearings in that machine are babbit with no means to hold the armature in any specific place. There is some significant end play. Since this problem started soon after the ropes were replaced, I would suspect the ropes were installed backwards.


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