Larz Allen - Metal, Wood,  and Stone Designs

Technical Files

Reflective helical stairs in mahogany

This project required a number of creative solutions to complete. I called on several large companies to provide me with stringer material re-sawn to a length, width and thickness which would bend to the diameter desired. No luck. I consulted an old friend who had run into a similar problem with some curved windows. He constructed a vertical power feed from scratch. The spring loaded variable speed ten inch tall side winder, sliced the twenty foot long twelve inch wide boards within one-sixteenth of an inch, top to bottom, end to end! This was a fabulous start but the end was months away. The stringer laminating went as planned. One and a half atmospheres of vacuum pressure provided the clamp, accurate math provided the lay-out. Next was the hand-railings. This stair required three railings on each side of each stair. One sits on top of the stringer, one lays under the hand-cap which its self is five and a half inches wide. It was some time after the contract signing that I was told the hand-cap was to come to a peak in the middle. The outer slope was convex and the inner concave. I hoped the solution to this problem would appear in time. Meanwhile 2600 linear feet of strip laminations needed to be purchased or machined in-house. I chose the latter. Having worked with curved hand-rail glue-ups before and realizing the over sized hand cap would require 14 pieces twisted and glued into a helical curve, I invented method. Some ten years back I was working with patterns that nestle into each other like Yin & Yang. I found the most efficient shape to be the Sine Curve. I molded the wood to this shape on each side of the laminations. This meant it was only necessary to clamp the material in one direction and the glued surfaces have a natural tendency to nestle. The project was back on schedule. Fitting the treads was made manageable because the stringer laminations had no spring-back. The hand-cap was peaked by elevating a planer and ramping the material accordingly. Each peak angle of the four hand-caps required its own curved ramp. The results pleased everyone involved. The installation went smoothly. I look forward to my helical challenge.


Helical Mono-Stringer

This project was not a commission; I regard it as a fabrication thesis. It was sometime after I started I realized this. As a builder I normally seek custom work that is technically challenging, stairs, railings and the parts that make railings often become my task. Because I work in metal and wood clients call for spiral stairs. Because the Internet offers a variety of spiral stair choices it is hard to be competitive. I decided to take the pole out of the spiral. This requires the construction of a hollow helical box beam whose dimensions will be decided by others! (Namely the client.)This required constructing formula with two variables, the distance between floors and the diameter. That seems simple enough except all of the parts are constructed in two dimensions then stretched into three dimensions then welded. This contortion is known as necking and each material and material thickness will behave differently. This needs to be figured into the equations. I found that creating a tension condition like a ribbon around a can kept my elevations on the mark. Plumb fins welded to the first wrap separate the parallel sides. Material was selected that would comfortably accomplish the bend then be laid flat to prove the material to be with in elastic limit. This material was then layered together and plug welded through a pattern of precut holes. Welds had to be applied in an order which best distributed heat. The top and bottom plates must twist into position then be skip welded to a continuous bead. If the plates are twisted beyond their elastic limit the heat from welding will result in ugly flat spots. I have yet to install one in a home. As in every step of this process there is properly some more learning ahead. I have installed straight mono-stringers in the past. The extra light is unmatched by conventional stairs. These stairs do not conform to building codes thus are limited to private dwellings.


The Barn Project

The barn is a recording studio. The assignment was to create access to the copula lounge. The client visited my home and saw a giant lawn sculpture that was actually a climbing and swinging apparatus. I wanted the children to see how geometry creates strength. When thin material is constructed into a matrix it becomes very strong. The idea was for them to interact with architecture realizing as opposed to memorizing why things are strong. The result was very light and strong. This became the design direction for tasks at the barn. This studio gets its name because it is a reassembled century old barn. For this reason I was told not to cut any of the existing roof rafters. This was a problem; an access ladder would have to be prohibitively steep and uncomfortable. Because the access hole would take up a large portion of the copula floor, I suggested a new solution, an elevator. I had seen a storage area lift in the past that fueled the design. Even though the word safety was viewed as an oxymoron now the client cracked a smile and said let it be so! Given enough motorcycle chain, sprockets, shafts and space I drive almost anything any speed. He said boastfully as he tripped over his bootlace and banged his head. I had recently discovered [constructing an electronic gate] a heavy-duty door operator has a reversing contact switch suitable for my multi-floor auto stop and re-start demands. The correct ratio gear head eliminates back driving and a fusible link allowed me to calibrate the load. Too much load pops the fuse at start. The adjustable cantilevered platform is going to require a photo. Wooden rollers are pushing and pulling on shafts in front of and in back of the parallel guide pipes. The back shaft is adjustable; this tilts the platform to a comfortable angle. When the platform comes to rest at the copula floor height the access hole is filled. This is the safest possible condition, well besides staying off the contraption altogether. I did the floor and furniture as well. Because the manifesto clearly states, "harvest the light" nothing is made of solid material. Patterns of daylight reach the recording floor. This was the goal.



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