1931 New Meccano models instructions
This is a model of a Doxford Marine Oil (Diesel) engine based on instructions that were published in the 1931 edition of Meccano Book of New Models as "Doxford Type Internal Combustion Engine." These engines were first  developed by engineering company William Doxford and Sons Ltd. of Sunderland in 1914 the last engine of this type was built in 1980. They were used to mainly to power cargo ships and liners the engines were powerful, low revving and could be huge some were the height of a three story house. The Doxford engines had opposed pistons that is to say two in each cylinder so a two cylinder engine would be the equivalent of a conventional four cylinder type. The model is far from a scale model but does demonstrate well the principle features of the Doxford engine, showing how the opposing pistons are linked to the single crankshaft. There is also a third cylinder called a scavenger this pushes air through each cylinder after each cycle of the engine to clean the cylinder of any burn debris. This was very much needed as the fuel used was dirty heavy oil basically crude. The model instructions made no mention of operating it with either a motor or by hand operation, my version is hand operated with face plate and handle on the end of the crankshaft. One of the complications was building the crankshaft using 16 p/n 62 cranks, the alignment was difficult.  The long rods connecting the upper opposing piston tended to jam causing the cranks to slip out of true but patience prevailed. I solved this by giving a tiny bit of slack, I undid the grub screws on the couplings holding the horizontal rod connecting the two vertical rods and this did the trick. (no doubt the rods I used were not perfectly straight). I have used 1970's yellow and zinc finish parts. At the time the plans were published parts were dark red and green, my original thought was to used those colours.You can see the engine working clicking on the YouTube link below.
Underside showing crankshaft
Page first published March 05 2024 Revised April 17 2024
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