engineer

tim   .

                                                      


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.   hunkin

                                                         


cartoonist

 

TOBAR CLOCK

video 


Tobar toys ( www.hawkin.com ) are a local company who are flourishing and in the process of moving to a much bigger building on Ellough industrial estate Beccles, Suffolk, England.  Worried that the new building looked too anonymous, Toby Templer (the owner) asked me to design something to put outside. Backwards wall clocks had been one of his best selling lines for many years so we jointly decided it would be a good idea to make a big one - it is 6m or 20 ft diameter. It needed something to give it a sense of scale so there is a life-size 'worker' on top. It also needed some obvious movement so the hands oscillate. 



The main shaft, based on off-cuts from our local stainless steel tube stockholder.


The hands and mechanism ready for a first trial. The minute hand wobble was too violent, but it showed up the parts that  needed to be more rigid.


The clock drive box at the centre of the dial. The hands are turned by a 1 RPM synchronous motor, via a worm gearbox. the windscreen wiper motor at the top wobbles the whole central unit at about 6RPM.  


Inside the control board which will be inside the building. The clock at the top is a radio clock to reset the big clock if there's a power cut or to readjust for daylight saving. Posh clocks use GPS to do this but as radio clock now only cost 10, it was an attractive low tech, low cost option. 


I've been teaching myself CAD (Solidworks) and started designing the dial and bezel with it, but then I realised I'm so much more confident with REAL 3D stuff that a physical model might be better. This is my ten to one scale welding wire model. I was so much happier out in my workshop physically designing it by welding than I could have been on the computer. CAD can never give you a good lifestyle, however useful it obviously is. Having made all the important decisions, it didn't take long to transfer the model to CAD. Also, an accurate physical model is a much more intuitive aid for discussing the project with Graham,  my highly skilled electrician, with the client, and with Gisleham Industries, the company who will fabricate it.  Mid way through the fabrication Mark, the welder said how much he liked working from the model "drawings so often get confusing"  

A month later, the frame has just arrived back from being galvanised! We were all worried about how much the hot dip process would distort the frame. Mark is a bit grumpy as the two halves matched so perfectly before it went, but the two sides are less than 6mm out - nothing that a bit of 'fitting' won't sort. 

Another 6 weeks, its now April the 23rd and we are on site. All the aluminium panels have been fitted and removed to be powder coated. The frame had to be split in two again to be transported to the site. I realise the galvanising had distorted it by much more than I'd thought - nearly 50mm in places. I've since discovered that box section distorts much worse because it has to be lowered into the galvanising tank very slowly to allow the air out of the inside of the section. So for quite a long time part of the frame is hot and the rest is cold - and this is what causes the distortion. 

Anyway the clock is finally all going together.  It all feels very unnatural. I'm used to a smaller scale when is easy to redesign things while they are being made. On this large scale I had to design everything at the start and then cope with the technical problems as they crop up. Its just not possible to change anything much.   Also I instinctively prefer finishes that improve with age, so why have I ended up trying to make all this paint and vinyl lettering look so perfect? And who but an idiot would attempt to build anything with such a large number of panels that all need to be perfectly butt jointed together. (With a butt joint any slight variations in the width of the gap between the sheets or variations between the level of one sheet and the next are highly visible.) I've also run out of cash as the fabrication took twice as many man hours as I'd guessed.  

Despite all this its very exciting. All the butt joins have rivetted together remarkably well, a tribute to Mark, who welded the framework and cut and drilled the panels before painting. Everything is so different from looking at it on the screen in my CAD program, where I can multiply the scale of anything at the touch of a button. Here its enormity presents new challenges at every turn. The 25x25x3mm box section which I think of as 'rigid', becomes quite bendy on this scale. The 2mm thick aluminium plate I also think of as rigid, dents if we tread anywhere on the dial. Doing any task to the frame takes much longer than I'm used to, simply because there's so much of it. If the weather hadn't been perfect we would never have got it all together in 4 days in time for the crane I'd booked the week before. 

 
The crane arrived on Friday April 27th. As I feared, the driver couldn't move it from into position from the place we had been working on it so we had to roll it onto place along a narrow roadway. This photo shows a bad moment when it grounded on the kerb.


Finally in place ready to lift! It looks so much bigger now its vertical.
The team that built it from left: Mark, Graham, Tim and Andy


And the inside looks exactly like my model. Now I see it supported by the crane, the framework looks right, not over engineered as I had been thinking.


The finished effect. There's a fast road, just to the left of this photo, and drivers keep hooting their horns, I guess to try and attract the attention of the 'worker' on top. I'm amazed how large the clock looks. Despite all my drawings I assumed that the vast scale of the building would always dwarf it, but I was wrong. 

 

Postscript 2015

After a few years Tobar went bust. The clock was removed in April 2015 and now sits on the entrance to Diss business park, about 20 miles away.

 

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