The Birds
The original Guinness clock featured the Alice in Wonderland Mad Hatter character in the top of the tower “fishing” in the tub and catching what initially looked like a whopper of a fish. But as he reeled it in, a smaller fish emerged from the large fish’s mouth, then an even smaller one emerged from this fish’s mouth. Lastly, as it almost reached his rod, a tiny fish emerged out of the fish’s mouth.
I have no particular interest in fishing as a hobby, but I do like birdwatching. As explained in the previous section, my clock will have three birds of prey rising and circling out of the tub while a model of myself filming them leans out of the top of the minaret. I had originally thought it would be good to have the birds flapping their wings too, but the mechanism for this was becoming too complicated. The mechanism for the soaring birds was complicated enough and took me quite some time to design. I felt that the birds could be soaring on thermals and so do not need to flap their wings!

The image below shows my original design sketch of the proposed mechanism. In the bottom of the tub is a square block with a support wheel on each side on which a circular wooden turntable sits. It is held in place by an electrical slip ring bearing allowing electrical connections to the raising/lowering motor fixed to the top of the turntable.

Attached to the centre of the turntable is a tall Perspex hollow rod. This forms the guide and support for three rings. Each ring has a bird attached at 120 degrees apart from each of the others; only one ring is shown in the diagram. The top of the tube is connected to a geared motor attached to an arm fixed 

The original fish

to the top of the minaret tower just below the “house” module. This motor, when energised, rotates the Perspex tube, birds and turntable, at the required speed.
In order to raise and lower the birds, a geared motor is fixed to the top of the turntable. This motor has a capstan (old cotton reel) attached to its shaft. Connected to this capstan is a length of strong fishing line which passes through a hole near the bottom of the Perspex tube, under a small pulley and up through the inside of the tube to the top.

Initial bird mechanism design

Slip-ring mechanism

Here it passes over another small pulley and emerges through a hole in the side of the tube. It then drops down the outside of the tube to where it is connected to the uppermost bird ring. A bath chain then connects this to the other two rings with suitable slack between that they are separated vertically by some distance. When the top bird ring has reached the top, all slack in the chain will have by then been taken out and the lower end of the chain activates a microswitch which cuts off the motor.
Also Sprach Zarathustra - Richard Strauss
00:00 / 00:00

Turntable support and slip-ring

By reversing the supply to the motor, it then rotates in the opposite direction lowering all three bird rings until the bottom one hits a stop. The remaining two continue until the second hits the top of the bottom one and stops while the top ring continues until it reaches the top of the second ring - are you with me? At the same time, it actuates another microswitch which cuts off the supply to the motor and the whole thing stops. The controller will then shut off the supply to the motor that rotates the birds.
In order to make sure the rings rotate with the tube and turntable, a square hollow Perspex rod is attached to the side of the circular tube. In the diagram this is just shown as a metal rod but was changed later. There is a cut-out in the ring to fit around this rod. The diagram indicates that the rings are made of Perspex and slide up and down the Perspex tube. However, I anticipated that they might jam due to the up and down forces being applied on one side.
A quick experiment proved this to be the case. I splashed out and bought three linear bearings. These ran freely up and down but were quite heavy and tall but did the job. I chose a version with a cut-out in the side to allow the square Perspex rod to cause the rings to rotate with the tube and turntable. Below are some annotated images showing the components of the mechanism.

Close-up of turntable mechanism

Key:

  1. Raising/lowering capstan

  2. Raising/lowering motor and gearbox

  3. Lower pulley

  4. Raising/lowering fishing line

  5. Raising limit microswitch

  6. Raising microswitch link line and spring

  7. Three screw stops to support rings when lowered

  8. Lowering limit microswitch

  9. Three supports for rain cover (inverted flowerpot dish)

  10. Support column for limit switch actuating lever

  11. Lowering limit switch actuating lever

  12. 30mm diameter Perspex tube guide

  13. Tube fixing clamp (electrolytic capacitor clamp)

Turntable mechanism

One image below shows the turntable installed in the bottom of the tub. You can see the capacitor clip that will hold the bottom of the Perspex tube. The other image shows the rain cover in place. This should minimise the effect of rain and the inevitable liquids emerging from the bubble machine above from getting everything too wet. The cover is an inverted flowerpot drip tray with cut-outs to accommodate the Perspex tube and square guide rod (both shown) along with the actuating cords and rods for the limit switches. Not shown is a plastic guide that collects the ball chain as the birds descend. This stops the chain piling up under where the bottom linear bearing would come to rest. If that happened, the top bearing would not descend far enough to activate the cut-off limit switch and the motor would over run.

Turntable installed in base of tub

Rain cover in place

The top of the tube is rotated by a geared motor in a housing at the end of an arm attached just below the minaret house, as shown in the picture below. The three linear bearings can be seen in another image lower down, which show the birds attached to the bearings by means of stiff wire arms wrapped around grooves in the bearings and soldered tight. The birds are all carved out of solid blocks of Basswood, being somewhat denser than Balsawood but still easy to carve.
I chose three birds of prey: A red kite, as we often see these on our trips down the M40, a Buzzard, which is very common around where we live, and a Barn Owl as they are magnificent birds and I once did a water colour painting of a couple of them. You can see the various stages of production in the images below. I downloaded some images from the internet for each bird: side elevation, top view, bottom view and front view, and adjusted them to the correct size of 14cm wingspan. This would allow the bird to just fit between the tube and the top rim of the tub as it emerged. Having printed these out, I roughly copied them onto the three blocks of wood and cut them out with a band saw. They were further shaped using a power file, knife and glasspaper. 

Rotation motor and support arm

Basswood block

Barn owl cut to shape

Top view of painted birds

Underside of birds

The carved birds were then painted with white paint and finally decorated with acrylic paints. A small hole was drilled into each belly to fix the bird onto the wire arms of the linear bearings.
 
As a final flourish, I compiled an audio recording of the birds’ sounds which plays as they rise out of the tub.
Bird calls -
00:00 / 00:00
The finished mechanism can be seen below.

Close-up of birds in "flight"

Finished birds mechanism

© 2018 by Peter Wagner. Proudly created with Wix.com.