The Disassembly of Harvey: A Vertical Oscillating Steam Engine.
By Harriet Knightley
By Harriet Knightley
Meet Harvey. The Oscillating Vertical Steam Engine built in 1870, by Harvey & Co. Made with cast and wrought iron, brass, and steel, with a bottle green painted finish on the bearings.
He is a stunning testament to British engineering and iron production, so much so that he has been in demand for a number of years to go back on to display after being taken off gallery from the Science Museum in London.
During my work placement at the Science Museum's large object store in Wroughton, where Harvey was being stored, my challenge was to get this beautiful engine back up to display standard ready for his loan to The London Museum of Water and Museum in Kew Bridge for early September. The trouble was the engine had suffered from flash corrosion across all exposed surfaces of the wrought and cast iron components. That included those hard to reach areas and in just six weeks. The only way to do this was to plan dismantling Harvey; however, how do you safely remove a one-ton flywheel from a historic engine? There's a question….
The extent of the flash corrosion on the exposed iron surfaces would need a considerable length of time from a conservator to remove the corrosion due to the sheer size of the engine and the intricacy of some of the components. Flash corrosion is a rapidly occurring corrosion where the exposed iron 'flashes' that infamous orange surface. The 'flash' refers to the speed at which the corrosion occurs-this sometimes can be seen over a few hours!
It is caused by water that is allowed to dry on the surface of the metal; unfortunately in Harvey's case, this was rainwater. The oxygen present in the water interacts with the surface metal, rapidly forming ferrous oxide, that infamous orange corrosion. This process is fast but forms a passive or stable layer that acts as a protective coating from further corrosion and so the engine was stable in its storage, but lost its suave looks.
To plan I had to ask myself, "What are the hazards and what do I need to avoid?" The most obvious was the weight of the object. It is nearly 2 tonnes of metal! It is also a kinetic, or moving object, so movement is key to the understanding of the objects function and what I need to protect. Some key facts of this object also give some deeper clues that really affected my plan. Due to the age of the engine we suspected that asbestos was used as an insulator for the cylinder and possibly the outlets, as the carcinogenic material we know today was widely used in the industry during this period. So there's now a no-go area to maintain the seal, which meant I had to keep those components assembled!
The simplicity of the design helped me understand how to support the engine as I worked. I asked myself these questions: Allowing for the weight, what would happen if I removed that bolt? How should the engine move; why is it when this valve part moves that the cylinder shifts in that direction? How are these attached and can I remove them? And what on Earth does that do? Said the very innocent brand-new conservator… but that's ok. Observation is key to understanding the puzzle. No panicking necessary! Just make a plan.
Eureka! I had a plan. To access all the parts, the valve, limited parts of the gasket, and the flywheel had to be disassembled, leaving the cylinder and piston rod in place. I could disassemble most by hand, all but that flywheel, due to my lack of Wonder Woman strength. It was time for some advanced tools: roll in the gantry crane.
1 Gantry crane
1 Pair of steel toecap boots
3 Willing conservators
1 Large space
Placing the engine beneath the centre of the anchored gantry creates an equal weight distribution to allow the flywheel to be raised and removed evenly. I had to attach the straps to make sure the flywheel would balance correctly, I chose to put them around the top of the wheel.
This had to be even to allow the flywheel to be lowered in a controlled manner with the secured crane onto a skate for ease of movement around the crankshaft. Gently does it! The crankshaft was soon conserved and gleaming!
I started to appreciate the elegance of the design that ultimately taught me how to disassemble and reassemble the engine with confidence. This engine was built to perform this with its cleverly considered design.
It's like a domino effect… Observing the movement of the engine allowed me to link how the valve moved and what I could remove safely, without disturbing the asbestos that was safely sealed in the cylinder.
We became quite close, Harvey and I. I learned the intimate nature of conservation and learned that all objects, no matter their size, should be approached with the same consideration and delicacy… Just some may need some steel toecaps and a crane to handle.