Introduction
This is a copy of the introduction in the original book.
Introduction
The full size ‘George Henry’ was built by the De Winton Company and used at the Penrhyn Slate Quarries in 1877. All the dimensions and full history can be found on the Talyllyn website as well as a photograph. I have tried to make my version as close as possible to the original but for a modern working engine there has to be a compromise; the biggest visible differences being in the lubricator and the vacuum brake system. The original had three lubricators, one on top of each cylinder and one on the regulator. These were of the type which allowed tallow to melt and enter the system. Today, this is not really feasible. A mechanical lubricator could be used if a method of driving it could be found. I elected to go for the hydrostatic type. The full size GH only had a hand operated brake. The two steam pipes from the regulator worked two injectors. As it’s not easy to obtain another supply of steam, I fitted twin axle pumps which are more than adequate.
Although much of the construction is quite simple, it is not recommended that this is a project for a beginner. The construction of the cylinders and the slide bars means quite complex patterns have to be made for casting. These can be difficult to mount for machining in the mill. The rest of the engine is not difficult to construct, although fitting some of the parts can be, in particular, the piping up in the final stages.
The prototype had problems with the valve chest and this was due to an error in the pattern. Rather than make a new pattern and having the castings made again, the casting was adapted so that the valve chest could be constructed separately. This was made of steel, and proved to be an excellent way of making the valve chest. There were none of the problems of drilling holes from the ends of the cylinders to the valve chest for steamways as is usual. The resulting steamways were large and clear of obstructions.
One drawing is not given and this is the one for the chute. The reason for this is that there might well be variations in the shape and size of the firehole (a rectangular hole would make firing easier but harder to construct) which will affect the angle of the chute.
I found that I needed to get to the underside of the engine to complete the pipe work. Rather than try and construct some sort of frame to allow the engine to be rotated, I simply stood it on its end. There being no buffers to worry about as they are simple blocks. These and a block of wood kept it upright and surprisingly stable, although I did use the precaution of using a rope lashing.
The page of pre-digital photos for the full sized George Henry will help with construction as no drawings are given for the dummy steam pipe. One photo shows how this appeared. These photos will also help anyone who wishes to keep to an accurate model. There are also two pages of photos taken during the construction which explain better than words. This includes a photo of the chute as there is no drawing. Note the bridge across the top which stops any flames going up between the jacket and the boiler.
I hope you enjoy building it. My time taken was just over 1000 hours, but then I had to make a lot of it up as I went along. Expense should be a consideration too. The boiler being the most expensive part, although I kept the price down by doing much of the work myself and getting a friendly boiler maker to supply the kit, roll the barrel and then finish it off.
Colin MacEke 2009.
In the UK model engineers mostly use copper to make their boilers. Only the larger 7.25" consider using steel. The advantages of copper are long life free of corrosion with only a de-scale occasionally, excellent conductivity, easily worked and silver soldered. Rules are quite strict. A steam and pressure gauge test annually and an hydraulic test to 1.5 times working pressure to be held for 30 minutes every four years. I made my boiler to work at 100psi but 80 would be quite sufficient. The front buffer blocks I had cast in aluminium but if you need traction to pull heavier loads then make them of cast iron.
If you are thinking of saving money by making a steel boiler, drastic changes to the boiler design would be needed. Having built two engines with steel boilers my advice is don't. You have to add tannin to the water to avoid rusting. Steel boiler tubes (special grade steel) have a short life in my experience and are very expensive to replace. You can't make these boilers yourself as a certificated welder is required or you won't get insured. Hydraulic test every two years and an expensive thickness test of the shell may be needed every few years depending upon your insurer.