October 11, 2010
I needed a desk that looked solid and part of the builtins surrounding it, but that could be moved fairly easily without lifting it. To move around easily, I wanted it to have wheels, but I didn’t want them to be visible at all. I also didn’t want the desk to move once it was in position (no accidental rolling). If I installed braking casters under the desk, the whole desk would have to be elevated and the wheels would be partially visible. Furthermore, I’d have to get to the break levers on each of the wheels, which would be awkward.
I went in a different direction, inspired by an old episode of The New Yankee Workshop. In the episode, Norm creates a work table that sits solidly on legs at the same height as the table saw. Simple retractable wheels are made with door hinges and casters. I liked this so much for the workshop that I made one.
My desk would use a similar technique, only more compact and, because of that, slighly more mechanically complicated. The wheels are completely hidden when retracted.
The best way to describe this is through a series of pictures. First, to provide the overall picture, the desk currently looks like this (the drawers do not yet have fronts – I’m in the process of making raised panel fronts for them)
Hidden inside the bottom of both columns of the desk (below the bottom drawer) are the components of the retractable wheel system.
The first component are the wheels/casters. The casters are mounted on strips of plywood, with a total of two casters per strip and two strips per column. The strips are attached to the inside of the columns with hinges. Here’s one of the strips, all attached:
And here’s a view of both strips attached, looking down from the top of one of the desk’s columns.
At this point, the plywood mounted wheels flip up and down freely on the hinges.
Mounted above the wheels is a piece of plywood that forms the bottom of the storage area (the part where the drawers will be mounted) of the desk. The underside of this bottom piece has mounted a couple of strips of plywood, reinforced (and weighed down) with some angle iron. These strips are also mounted on hinges.
When in the down position, these stilts support the wheels, keeping them from retracting. When up, they allow the wheels to flip up and out of the way.
In the New Yankee Workshop table, the stilts were very long. When the table was lifted, the stilts swung down with only the power of gravity and locked the wheels down. This did not work so reliably for the desk, since the stilts are only a few inches wide. To assist the process, I installed some cord that could be pulled to lift the stilts up and pull them down. To make things work smoothly, I used some small pulleys in places where the cord changed directions.
This picture shows the first cord, which, when the middle pulley is pulled, forces the stilts into the downward position (where they will hold the wheels up).
Two separate cord setups are needed for each desk column. Pulling one of the cords pulls the stilts down, pulling the other pulls the stilts up. Here’s a video that shows this work in isolation:
Here’s a picture of the full array of pulleys and controls, installed into one of the desk’s columns.
And a short video of it in action, on its side:
Once all assembled into the desk, it’s operated in the following manner. From a rested (wheels hidden) position, you lift the desk a little bit (while sitting on a chair at the desk) with your knee and simultaenously pull the cord that moves the stilts into the down position (perpendicular to the bottom). At this point the wheels will take the load of the desk so you can wheel it around.
From the wheels down position, to get it to the rested (wheels hidden) position, once again lift the desk slightly with your knee and pull the cord that draws the stilts up (into a more parallel position with the bottom). Stop lifting with your knee and it should be resting completely on the floor with the wheels totally retracted and hidden.
This short video demonstrates the process:
For a more detailed description of the build, see this flickr set.