Monday, December 1, 2014

Model & Sketches: Work Stool

Today's post deals with another offshoot that arose as a result of the workshop. I wanted to create a portable perch stool to accompany the workshop. I needed it to be able to be stable and comfortable but also compact so it could be stowed along with or inside the workshop. I had the idea to use a bicycle seat for a stool head after trying out a number of perch stools, both at the IMM cologne a few years ago and after a talk in NCAD in dublin by Simon Dennehy from Irish design firm Perch. I had the pleasure of using a few more recently when I interned in Oslo for Peter Opsvik and used a version of one of his own designs the Capisco chair while working in the office.

As regards comfort I can't be certain this arrangement of a bicycle seat would work out however I considered the availability of a huge variation in bicycle seats a particular bonus in this regard. I also done some rudimentary testing using three seats. One large sprung leather seat and a semi rigid seat from family member's and my own bike and a rigid Selle Italia seat (pictured above) I bought for this project. As long as I kept the same swapping out function possible on this stool I figured I could try a range of seats like the slimmer more rigid types by the likes of Selle or SDG to a big sprung leather seat such as those made by brooks. More on the testing later.

When I began sketching up possible designs for this seat the initial designs were based on the types of materials I thought might be easiest to work with and easy to shape, namely square wooden beams. After exploring a few different options for the construction of the chair I began to realise the design I was working on was too "chunky" to fulfil the compact part of the brief and I began working on methods for creating a folding chair.

From the image above and below you can see on the right hand side of both attempts to thin out the legs by tapering them towards the floor and cambering the outside surface.

These relatively simple modifications were to take a big leap when I decided to also include some sort of footrest by carving out two small ledges on either side of the leg.

It was at this point and you can see it in the image above right and below left initial sketches of an idea to incorporate a form of anthropomorphism into the design in the form of deer legs. In a separate sketchbook I spent a little while sketching deer and their legs particularly the front leg when straight. Without the large muscle at the top the front leg creates a very elegant curve and the ankle towards the foot of the leg flares to form a sort of ledge.

This design feature became a little more refined as the process went along including such ideas like biasing the angle of the ankle forwards to provide a more comfortable footrest from an upright sitting position. There are also detail sketches of options to create the folding mechanism joint at the top of the leg.

In the sketch above you can see some details of work done on the construction details of the stool. This is namely the order of cutting that might create the now fairly complex shape of the leg joint. Again below left there is another exercise to work out the cutting order which might most efficiently create the central section of the stool.

At the bottom of this page there is also consideration of how to secure the legs when folded together. With the square legs the thought was to tether them together in some way, while these later approaches and others I considered were an attempt to minimise the feature that might eventually secure the legs when folded.

Following this sketching I decided to build a rough model of the chair so I could perhaps explore a little more how this design might look and might function. Using some scrap pieces of balsa left over from a previous project I began to build the model. I was working to a rough scale of 1:10 for this model.

As you can see in the image above I did create the rough shape of the legs though I didn't contour the back of the legs. The central seat post was rounded from a thinner piece of slightly harder scrap balsa and the hole for the post was cut using progressively larger gimlets to ensure the piece didn't crack.

The contours of the seat were carved using small files. Though the seat itself is not a perfect reproduction of the seat I'm proposing to use on the prototype the dimensions are to scale and the position of the attach point is correct. One thing I noticed from this model is that where the users legs drape down over the chair leg is at the widest point. At the very least this means that portion should be softened if not made less wide to accommodate the user. Whether or not this will actually prove a problem will require a full scale mock up but I may thin this section on the mock up to avoid any collisions in that area.

One attribute of the model which is a limitation of the materials I used is the joining mechanism of the seat and post. In reality this mechanism allows for the seat to change angle. There are two prevailing types of these posts too a straight post and one which curves back just before it connects ot the seat. The advantage of this is that it could allow me to set the seat at a deeper position to change the centre of gravity of the user over the tripod base.

In general the things that can be taken from this exercise are the potential for the width of the legs where they join the centre to affect the comfort of the user, further the idea of using a recessed rather than straight seat post to modify the centre of gravity of the user should the chair prove unstable in some way. I'm not entirely sure about the angle of the footrests either thought I think that is something that can be further teased out with a full scale mock-up or prototype.

John O'Shea

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