John Smeaton's 300th Birthday (8th June 2024)

We have a change from the normal focus this week, instead of anything related to Formula 1 or far-flung places, we are celebrating the 300th birthday of John Smeaton, credited as the first Civil Engineer. (I haven't met him, but we'll party for him nonetheless.)

Smeaton had what would be now considered a very varied engineering career, from steam engines to lighthouses. But as a bridge engineer myself, it was only fitting that we held a tribute to the best of his bridges.

Coldstream Bridge spans the River Tweed stretching between England and Scotland. I read it was built with 9 spans, but the most I can see in recent photos is 6, of which 5 are more elaborate than the other. Perhaps I could have spent a little more research to find more details, but we were limited by the size of the largest cake board I could buy (24"), replicating just the big 5.

Smeaton's Coldstream Bridge

Replica in stone

Heidi took charge with the cake making element, and I have to say, it's outstanding. If it wasn't for the challenge set to us, I'd have quite happily just eaten the four trays of Madeira sponge.

Tally made volumes of rice crispy/marshmallow/chocolate mixture suitable to form the arch shapes. A complex mix went along the lines of stealing marshmallows between cooking, and squeezing wayward pieces of chocolate into the mouth. When we found our calculations to have underestimated the volume of rice crispy cake we'd need, we resorted to topping up with Cocopops - Tally conceded that she could spare 30g from her breakfast cereal of choice.

For forming the arches, we took an approach somewhat different from Smeaton. Rice crispy mush was pressed into a lunch box with a Pringles tube half-submerged. When set, we removed the formwork and sliced the structure unto discrete widths of arch. Breakwaters, piers and road deck are formed of sponge, smeared in buttercream (again Heidi's excellence) and clad in fondant icing.

It seemed only fitting to appoint a Coldstream Guard and the Easter Bunny on patrol. 

A major fault in the centre span and a separation in pier 1 threatened the structural stability, so we paused for a photo and cut in. Left with a volume of cake 4 times bigger than anything we usually make, we've donated and delivered individual spans to friends; only 2 spans remain to find a home. 

Not the best bridge I've built in my career, nor the very best cake, or even artwork we've created, but some fun all the same. Happy birthday John Smeaton (born 8th June 1724).

A reluctance to photos during cake mixing

Mallow mess making

Enginuity at work

The structural properties of buttercream adhesion should be included in the next edition of the Manual of Contract Documents for Highway Works

Before the bombardment of sugar coatings

Interestingly, they both chose to work wearing headphones

Within 2 hours, there's not much left.

Much like the real thing, our bridge has a plaque commemorating the great construction. Read it carefully.


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