Biscuit Tin Steam Engine. Part 1.

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Tony Bird

Senior Member
Feb 20, 2011
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Cardiff, South Wales, UK

The following is a building log of a model steam stationary engine recently completed.

Over the years, a lot of the projects that I have worked have come about in unusual ways, and often by chance. I am a member of the Cardiff Model Engineering Society, who twice a year holds a ‘Bring and Buy Auction’. At these auctions it is possible buy almost anything from precision tools, construction materials down to what might at best be described as possibly useful junk, the only auction rule being that if it isn’t sold it is taken away.

Lot 4398 (lot numbers continue from the last auction) that was purchased in October 2022 was definitely in the latter category; of possibly useful junk. A project which was being worked on at the time was coming to an end and needed some 6 BA screws to finish it. Lot 4398 was a large Huntley and Palmer biscuit tin which among a lot of dirt and rusty metal things and a Heinz food jar that was labelled 6 BA, so the biscuit tin and its contents were purchased for two pounds.

When the heavy biscuit tin was taken home, and its contents examined, it was found that among the dirt and rusty bits of swarf it contained some potentially good items. Which were a set of raw bronze cylinder castings for an inside cylinder 3.1/2” gauge locomotive, some flywheels and flanged wheel casting along with a lot of screws, nuts and bolts as well as the basis of this narrative; a collection of parts of a twin cylinder double acting oscillating steam engine.

These parts consisted of an axle with disc cranks with what looked like a bronze eccentric and two aluminium flat belt pulleys, a complete and an incomplete cylinder, a reversing valve and a ‘T’ pipe connector. (P.01).

001 BTE Engine parts..JPG

There was also a mystery part which was only kept because it was painted the same colour as the other parts. (P.02).

002 BTE Mystery bits..JPG

It was decided to clean up the engine parts before a decision was made on whether to continue and try to make a working model.

The axle with its attachments was the first to have some attention. Its construction was interesting as the disc cranks had stub axels and two set screws were used to hold them into the centre section with its two flat belt pulleys and eccentric. (P.03).

003 BTE Axle apart..JPG

Another point of interest was that though both of the disc cranks had been drilled for the same size crank pin one of the crank pins was smaller in diameter and been sleeved to fit the hole. The larger crank pin fitted the only piston rod’s big end. The parts of the axle assembly were cleaned and painted where necessary and two new crank pins of the larger size fitted. When the axle parts were assembled it was found that the crank pins were set at about 80 degrees to one another not 90. To remedy this, the crank pins were repositioned using new threaded holes for the set screws. (P.04)

004 BTE Axle finished.JPG

The cylinders were next. There were enough parts to make one complete cylinder assembly, which consisted of a cylinder with two cylinder covers one having a packing gland, a trunnion rod and a piston fitted with a rod and big end. The other cylinder was missing a cylinder cover and a complete piston assembly. The construction of the cylinder was a bit different; having the steam ports and trunnion fixed separately to it, they being hard soldered in place. The bronze used judging by its colour had a high copper content. The parts were cleaned using citric acid and polished with a brass scratch brush. (P. 05).

005 BTE Cylinder assembly cleaned.JPG

The above parts were defiantly part of the same model; the reversing valve might be, as it was painted the same colour. (P.06).

006 BTE Reversing valve..JPG

In its original form the reversing valve probably wouldn’t be used in the rebuild, so it was taken apart and cleaned. (P.07).

007 BST Reversing valve cleaned..JPG

The last part of what might also have been part of the model; the ‘T’ type pipe connector was cleaned in citric acid and polished using a brass scratch brush. (P.08).

008 DSC06029.JPG

All the parts that were found that might be part of the engine with the exception of the mystery part had had minor repairs and had been cleaned. (P.09).

009 BTE Componants cleaned.JPG

It was decision time! Over the years quite a lot of part made models have been completed and there was often a lot more work involved than was first envisaged, it often requiring quite a lot of reengineering to get a reliable working model. As I was at the end of a project and with the knowledge that there would be a lot more work needed than I thought, a start was made.

To be continued….

Take Care. Tony.

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