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