The creative brief
Summer is a cumin in Berlin and my wife is busy planting the balcony so that we can enjoy our evening cocktails in a fragrant, colourful environment. Young plants grown in Dutch greenhouses do give you a really quick start but much patience is still required. As an impatient man, I thought about what I could conjure up that gives instant satisfaction for friends of the floral.
The technical brief
The mechanism was to be as simple as possible. A handle rotates a cam which friction drives a wheel perpendicular to it, so that the wheel and its shaft are both lifted up and down and rotated a little. Petals are attached to the other end of the shaft and as the shaft is lifted, the petals should open up to reveal an egg-shaped centre.
Petals & hinge
To get the shape of a petal I used a piece of plastercine pushed against a wooden egg. From this I made two templates in card, to mark up my lime wood for cutting on a bowsaw.
Plastercine petal and two card templates
First cut for petals
Second cut and carving for petals
Instead of trying to hinge each petal separately, I bent a piece of brass rod into a ring and cut two holders to grab the ring in a sandwich.
A hinge for 6 petals
And when this is all assembled it looks like this
6 petals hinged on a centre piece
The base mechanism
The base has four chunky dowel legs. Two of the legs have holes to take the 8mm dowel axle with its cam and its disc-shaped crank
Parts for the base mechanism
The assembled base mechanism
There is a short video showing the effect of turning the crank.
Youtube link “https://www.youtube.com/watch?v=gQMXmhIrygE”
The flower and its “cage”
Adding a wooden egg into the centre of the petals completes the flower
The open flower
To push the petals up when the flower is closed, a wooden ring is required at just the right height. A certain amount of experimentation shows the correct height and some trimming of the outside of the petals gets them all to move synchronously.
A ring/cage at just the right height
The flower jammed when open and didn’t want to close again. A lead washer fixed that.
Lead washer to increase downward force
It was caused by the vertical activating rod tilting due to the off-centre upward pressure from the cam. It’s a delicate balance between the diameter of the dowel and the diameter of the hole in which it moves. I used a 10 mm dowel in an 11 mm hole and that was too loose. Maybe a 10.5 mm hole would have been better, maybe I should have used a much slimmer dowel to reduce the surface area subject to friction? I will just have to try it and see in future.
What did the critics say?
My severest 4 year old critic asked “are those rabbit’s ears?
It only has 6 arms so it can’t be an octopus
Something from outer space?
This finished piece has a very short narrative. Each turn of the crank opens & then closes the flower. That is not much of a story. Nevertheless my official tester played with it happily for quite a while. I think it is more something to entertain kids and is of less interest for adults. I had fun making it and learned a bit, so I am content.
Video link “https://www.youtube.com/watch?v=uwzTALIhS_c”
Download the images