Iterative Progression

In furniture or product design often what you hope will be a good design ends up with obvious room for improvement. This is why initial builds are considered to be prototypes. It takes seeing and testing the first prototype to realize where flaws exist or where there is room for improvement in aesthetics or strength or performance or functionality or simplicity of build.

Shown here is a sequence of Balans style chairs I designed and made. Inspired initially by the original rocking Balans chair my pursuit was to find a design that was simple to build, adjustable, and stable.  In my PhDesk article photos you can see most of an earlier 3 caster perch version done as a class project by my students. The design was static with no adjustability or flexibility. Link:  PhDesk Article

Imbuia Wood Collapsible 

My Imbuia and leather prototype above improves on that earlier student design with knee pads that could rotate to meet your shins at a whatever was the most comfortable angle.   Initially the frame post beneath the seat was intended to be moved to different positions along the lower rails. This prototype revealed that changing the angle of the seat would also tilt the caster stems off vertical and reduce the ease of rolling the chair around. The frame could collapse by lifting the center post off the pin it rests on. Collapsed it would  fit in a smaller box for shipping or storage.

3 wheels Adjustable Height

Highest Perch Position

The 3 wheeled version above could be adjusted in height/angle.  This design isolates the caster base from the adjustability of the seat and knee rest. An aluminum push button  releases the aluminum post when pushed in and locks the post position when released. Knee pads pivot to meet shins at the most comfortable angle.

4 Wheels Adjustable

In use.

While there is an economic benefit to using 3 casters rather that four, a 3 point footprint comes with a flaw discovered in use. They could tip and roll out from under the occupant when leaning to the back right or left.  This four wheeled version eliminated the tipping flaw of all the 3 wheeled versions.  This version stretched the frame back so the back caster beam was behind foot clearance. It had the same push button height adjustment and pivoting knee rest as the 3 wheeled version above.  

The sharp bend in the center frame of the 3 and 4 caster versions above required making them from 80 very thin veneer layers of wood. A  later version used far fewer and thicker wood layers by changing the center frame to a smooth arc from under the seat down to the rear caster beam. Below is a simplistic rendering of the arced frame. It also had a seat that could be slid forward or back and locked in position with a cam lever.  The arc made room under the frame for occupant heels to meet or cross. This final version was gifted to the International Woodworking Fair management office in Fall 1988.  I'm still looking for any photos I might have of it.

Arced Frame Render

The final version was the simplest build, the safest to sit on, and had adjustable height, seat position adjustment, and pivoting knee rests.  It was a design that only came about after making and using the previous designs. They were all built in a university fab lab and benefited from being tried out by several students and other professors. Feedback gained from each version led to advancements in later versions.  This sequence shows iterative progression in action.

An even later iteration I designed is my rocking Balans.  You can read about it HERE.   

Comments and questions are encouraged!

4D