An electric rocking chair is believed to be quite a rare piece of furniture. Atleast The Stiff Adjusters haven't heard any rumours about similar devices. This rocking chair was built with a very fast method, it took only about two weeks to complete it. This was greatly motivated by the fact that the chair was to be given as a present in Eki's birthday party (30 years!).
The specifications were mainly done via email because of hurry and also because Adjusters were geographically located quite far away from each other. Sometimes words were not enough to describe various ideas, so here are some early sketches in digital format (sent as email attachments), which tried to illustrate the functions of the chair.
The actual rocking chair was found from a local flea market, it had some minor defects, but those were easy to fix. The motor for the rocking mechanism is a wind screen wiper motor disassembled from one scrapped Skoda 120 LS -82 type landscape transportation device. The motor was still perfectly functional even though the vehicle had been lying under one Finnish birch for some years. The stiff construction and the force of this motor created accepting growling in adjusters' minds, especially when compared to nowadays nanomalic motors.
The limit switches in the rockers of the chair and other switches were bought from one electronics dealer, who is selling cheap but low quality components. Other material needed were mains transformer, relay, rectifier, some wire and of course some cable ties and naturally hot glue. The weight, which actually rocks the chair and the hinge for it were welded from some left-over pieces of iron.
The final assembly was started two days before the party. The motor and hinge were screwed to the bottom of the chair, positioning was done on-line. We wanted to test the rocking also without the synchronizing system, but in this case the motor speed needs to be adjusted by supply voltage and still some phase shift usually occurs. However, a rocking chair that rocks by itself is a pretty funny-looking device [video clip (257 kB)]!
On the last evening before the party we assembled the rest of the parts, trying to optimize the switch positions in rockers to maximize the rocking amplitude. In the beginning the switches were attached with clamps, until the optimal placement was found and the switches were screwed to the rockers. We also found out that the rocking amplitude was greatly affected by the weight of the person sitting in the chair; our trimming worked best for persons around 75 kg.
The chair was donated to Eki spring -99, after which it has confused and astonished people visiting Eki's residence.
Story by Upi
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