On top of the minaret on the original Guinness clock, there featured a spirally-striped chimney out of which the head of an Ostrich emerged, complete with its characteristic dilation (“beer glassitis”) of the neck. As the Ostrich rose and rotated left and right, the chimney also rotated. The picture below shows this and the original mechanism.
Ostrich and chimney
I decided to keep the rotating chimney but replace the Ostrich with a model representing myself and my wife Penny on our wedding day standing outside St. James Church in Bushey. It was a wet day, so we are holding an umbrella.
I found a wedding cake topping of a suitable couple (made from resin). It cost £4 including postage from China! It doesn’t look much like us, but never mind! I took a photo of the church, laminated it (the photo, not the church) and attached it to the wooden disc on top of which was fastened the couple.
The requirement to have the chimney rotate and the wedding couple rise out of the top actually became quite a design challenge. The reader may well come up with a better solution, but in the end, I decided upon the mechanism shown in the diagram below.
Cross-section of chimney and wedding couple mechanism.
The chimney was made from a plastic drainage pipe, a little larger than standard, being around 90mm diameter. It needed to be cut into two pieces, the bottom piece contains the drive mechanism and is fixed through the roof of the minaret and attached to a baseboard inside, just above the manikin of the videographer. The upper rotating part needed to be attached to the bottom part by means of a ball race mechanism. A ball race whose outer diameter was the same as the internal diameter of the tube, was bought. The outer ring of this ball race was glued to a wooden ring underneath it, which, in turn, was screwed to the top of the bottom tube. The inner ring had a brass tube inserted inside and glued to it, protruding both above and below. Another wooden ring was attached to the top of the brass tube, allowing a suitable clearance gap so it didn’t rub on the outer ball race ring. This wooden ring was screwed to the bottom of the upper tube. All this allowed the top tube to rotate relative to the bottom tube and with a large central hole for the rising mechanism to pass through – more on this later.
The brass tube extends through the lower wooden ring and was attached to a large nylon gear with a central hole. A small drive gear was located in a bearing attached to the underside of the bottom ring. All this can be seen in the picture below, albeit upside-down. A long block of wood was screwed to the inside of the bottom tube allowing a motor and gearbox to be fixed. This was connected to the drive gear via a universal coupling and drive shaft.
Ball race assembly shown upside-down.
The gap between the two sections of pipe was covered by cutting a small section of pipe, splitting it from top to bottom and opening it slightly so it would slip over the bottom of the top pipe, thus creating a spacer. Another larger section was cut, similarly split, and glued over the spacer so it protruded below the bottom of the pipe. The gap created where the section was split was filled by a small piece of pipe glued in place. The lower static part of the pipe was painted the same blue as the minaret roof. The upper rotating section was painted black and white spiral stripes as in the original. As the chimney top rotates, the stripes appear to rise up the chimney. The hard part was aligning the whole bearing mechanism so the chimney didn’t wobble as it rotated!
Now on to the rising mechanism. Initially, I bought a linear actuator which would have been perfect for the job, but it took far too much current, and the voltage drop across the current sensing resistor in the controller was too much. It took far too long to move the required distance. The speed, even at full voltage was much slower than the specified no load speed. So I made my own using a linear slide with a nylon rack screwed to it. The bearings of the slide were screwed to the mounting block inside the bottom tube, and a geared motor with a gear was fixed onto the block so the gear meshed with the rack. A screw was attached to the rack so as to actuate two limit switches at the extremes of its travel. These limit switches (with parallel diodes to allow reverse direction through the open switch) cut the power to the motor at the end of travel.
Linear slide and rotation motor assembly.
The picture above shows the linear slide, rack, driving motor and limit switches attached to the mounting block. It also shows the chimney rotation motor and coupling also attached to the block. The block was finally inserted into the bottom tube of the chimney and screwed in place. It was a very tight fit! A hole needed to be cut in the wooden base on which the bottom of the chimney was attached, to allow the slide to descend through it. The wooden disc holding the wedding couple was attached to the top of the linear slide by a metal extension arm, as shown in the diagram above.
I found a 3D CAD design of an umbrella on the internet and asked a young friend of mine if he could 3D print a scaled-up version of it. He very kindly obliged, and once painted, it was attached above the heads of the wedding couple so as to just miss hitting the top of the chimney when the bride and groom were in their down position. This served to keep the rain out of the mechanism. Thanks, Johnny Jones for your help!
The sequence of operation is as follows. The minaret doors must be opened first as the top part of the minaret contains a bubble machine – see the next section. The chimney starts to rotate and the wedding couple rise out of the top of the chimney. All the time the chimney is rotating, bubbles are blown from the top of the minaret through the open doors - the bubbles taking the place of confetti! A short piece of organ music is playing as the couple appear. The music was a piece I wrote that was played at our wedding. The bubbles and chimney continue to rotate until it is time to close down, when the couple descend and the chimney stops rotating and the bubble machine stops. Only then can the minaret doors be closed.
Finished chimney showing umbrella.