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

Please feel free to call to discuss a project or to find out more about RCB Elevator Consulting, LLC


rich AT blaska DOT com


Also see our sister company:

for unique elevator products, including:

Retracta Ladder®
Powered Retracta Ladder®
Adjusta Ladder™
Seismic Fishplate
Low-Profile Fishplate™
Rope Align Block™
Deflector Sheave Isolator™

We also have a reciprocal marketing relationship with:

See CodeDataPlate.com for code compliant elevator data plates, tags & signs.  Also see their written Maintenance Control Program.

1904 Franklin St.

1904 Franklin St, San Francisco, CA
Contractor:  Western State Elevator Co., Inc.
Major alteration of 1923 Spencer duplex, 350 FPM, 10 story, overhead traction.  New Northern Elevator Co., Ltd. machines, controls, door equip, slings & platforms, safeties, governors, cabs & fixtures.  The elevators had been previously altered in 1959 by Pacific Elevator Company.

RCB Elevator Consulting, LLC performed the elevator engineering required to make the conversion.  This included performing all field surveys.

Project Description

This project required some very non-traditional thinking to accomplish one of the original goals to make the car doors open to the full clear width of the hoistway entrances, which the original doors didn't by about 2 inches.  When we designed the new slings & platforms, the C-channel stile just behind the front return panel conflicted with the refuge space for the car doors - same as the original stile.  Therefore, we designed a "Z" shaped bent plate stile that closely followed the line of the platform with the web parallel to the line of the doors (see drawings below).  This allowed the car doors to pass the stile and open to the full entrance width.

Another unique design solution was required due to the original elevator corner-post configuration whereby there are no divider beams and only 2-1/2" of running clearance between the two platforms (rather spooky to survey the job riding one car top with the other car running at 350 fpm - kind of like being near a large scissors in action...).  The problem was that no one made a type B safety that when installed would clear each other by the required minimum code running clearances.  In fact, most safeties would not clear at all.  We and the equipment manufacturer for this job, Northern Elevator Ltd., came up with the solution of using their standard #B1 safety but manufactured without the typical reinforcing fins that jut out from the sides nearest the rail.  We calculated that those gussets weren't necessary for the lower loads imposed by this systems 1,750 lbs. capacity & 4,925 lbs. gross load, as that safety was originally engineered for loads to 11,000 lbs gross load.

A more common engineering feat for us is to reinforce the existing elevator guiderails.  A condition often overlooked in major elevator alterations, guiderail stacks - especially the counterweight guiderails and brackets - were not originally designed for seismic loading.  Some codes are very prescriptive, requires spreader brackets where building brackets span greater than 10 feet.  However, very often those original building brackets are woefully inadequate structurally.  You will often see 1/2" x 2" bar stock with a simple, un-reinforced bent leg and one 5/8" lag bolt connecting it to the structure.  Structural calculations easily show these brackets failing in a modest earthquake.  On many of these, you can see for yourself how weak these guiderail systems are by grabbing hold of an 8# rail from the car top and shaking the entire rail stack like a 3" sapling.  We have shown that these existing rail stacks can be reinforced to comply with today's most stringent seismic standards for loading and deflection by adding specifically designed and engineered reinforcing brackets.


The very attractive entrances were retained and upgraded.  One obvious advantage to the corner-post, no divider beam arrangement is the closeness of the two entrances. 

Picture shows the tightness of the hoistway.

This shows the original wood platform and drum safeties that were replaced.  It's easy to see how the safety clearance aspect was an issue.

Again, the tightness of the safety conditions and with the entrance door equipment.

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.


  Home | Elevator Engineering | Elevator Modernization | Structural Engineering | Elevator Articles | Client Access | About Us