Biscuit Tin Steam Engine. Part 2.

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Tony Bird

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Hi,

Having decided to go ahead with the project, some drawings and sums were needed. The model had been made using Imperial dimensions. The cylinder had a bore of ¾” and the cranks had a throw of 5/8” giving a stroke of 1.1/4”. Quite a large engine, so should be quite powerful!

A drawing was made that showed the relative position of the cylinder to the axle there being a distance of 80mm (3.1/8”) between the axle and trunnion centres. (P.10).

010 BTE Axle & cylinder position.jpg


A drawing made of the cylinder and this was the first indication that the model had probably never been completed and run. At TDC and BDC the piston had less than 1mm to the cylinder cover, more akin to an IC engine than a steam engine! (P.011).

011 BTE Cylinder drawings.jpg


It was decided to go ahead with the project and tackle the clearance problem later. One of the advantages of a project like this when there are no plans to follow is that you can make it up as you go along, so the model sort of evolves rather than being designed and it also means you can use whatever materials are to hand, which speeds the construction and reduces costs. A start was made by cutting a 8” (200mm) long base plate for the engine from some 4” wide (100mm) ¼” (big 6mm) thick mild steel plate. (P.012).

012 BTE Cutting base plate..JPG


The bearing stands for the axle were made from some recycled 2” (50mm) black iron angle ¼” (big 6mm) thick. (P.013).

013 BTE Bearing brackets.JPG


The two bearing stands were machined together in a lathe and later shaped using a milling machine, (P.014).

014 BTE Bracket shaped..JPG


The bearing stands were painted with undercoat and bronze bearings and brass oil pots were fitted. (P.015).

015 BTE Axle bearing bracket finished..JPG


The finished bearing stand and assembled axle were bolted to the base plate. (P.016).

016 BTE Axle mounted on base.JPG


A start was made on the cylinders a wooden lap being used to finish their bore. (P.017).

017 BTE Lapping cylinder.JPG


It was found that the steam ports on one of the cylinders were off-set. (P.018).

018 BTE Off-set ports.JPG


Which wouldn’t have been a problem had they pointed to the centre of the bore. Having resorted to sums it was found that the error was 1.8mm (big 1/16”). (P.019).

019 BTE Off-set ports.jpg


This was going to require certain about of cogitation; which doesn’t hurt too much if you are sat down with glass in hand. To be continued……
 

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