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684 Ellis Street
The Chew Bldg.
Cartwright Hotel
1904 Franklin St.
291 Geary St.
Mills Building

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The Chew Bldg.

The Chew Building, San Francisco, CA
Contractor:  Otis Elevator Co., Inc.   
Major alteration of 1920 Otis overhead winding drum corner-post.  Lowered the machine room a landing. New Hollister Whitney #54 machine, GEM controls, sling, platform & cab and fixtures. 

RCB Elevator Consulting, LLC and its associate structural engineering firm performed all of the elevator and building engineering required to make the conversion.  This included performing all field surveys.

Project Description

This was a very interesting project in that the existing top landing served the attic and the entrance was only about 4 feet high.  It had been locked out for some time.  The access to the old machine room was via a vertical ladder from a room at the attic at roof level.  The hoistway overhead was accessible from this room via a screen enclosure.  The motor-generator, installed during a previous control alteration, was in this room as well.

It was decided to essentially abandon the original machine room with the existing equipment disconnected but largely left intact.  The original access was closed off and new access added from the outside for fire access purposes.

By eliminating the low height top landing, we were able to relocate the machine room to the attic/roof level with sufficient overhead clearance.  That attic overhead room thus became the new machine room. 

There was about a 4° slope in the existing floor, accounting for a 10" difference in elevation from one end of the room to the other.  We also found that the existing building beam framing the hoistway at the lower end was insufficient to carry the load for the new system at that end of the machine beams.  Fortunately, there was a second, parallel beam only a few feet away. 

Both problems of the slope in the floor and the beam strength were solved by a adding bridging beams that spanned the two existing building beams.  That end of the new machine beams connected to the bridging beams at their midpoint via a steel block, which spread the load evenly among the two building beams.  A new, level floor of metal deck plate was installed supported by the new machine beams at the center and additional ship channels at the outside.

There were numerous other engineering issues were resolved relating to the corner-post elevator arrangement and the very small hoistway size.  We worked with the elevator contractor and the many equipment manufacturers to work all of these problems out during the design phase.  This greatly reduced the field labor, administrative costs and elevator downtime resulting in a more profitable project of higher finished quality and a satisfied owner.

Before Alteration  

This view of the original machine room shows the original overhead winding drum machine and an old relay controller from a previous upgrade.  This machine room was accessible via a vertical ladder from the roof level. 

Here visible are the ladder and the screened-in hoistway overhead.

Looking down the top of the hoistway, the abandoned short top landing and corner-post car top are seen.

The car top showing the antiquated equipment and tight conditions.

After Alteration  

This is the same room as seen in the picture above showing the ladder and screening.  The new Hollister Whitney #54 isolated machine and new metal deck flooring are shown.

The new Otis Gem control system.

Drawings & Engineering

Click on the drawing above to open the full drawing set in PDF format.  To see drawings in landscape view, click on your Adobe Reader's Rotate Counterclockwise image button.  Note drawings cannot be printed or altered.  All drawings and artwork are the property of RCB Elevator Consulting, LLC and may not be used, copied, or in anyway used without the owner's consent.

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