Meccano 1788 Paddle Steamer Engine скачать в хорошем качестве

Meccano 1788 Paddle Steamer Engine

If I had known how much of a “faff” this build would be before I started I wouldn’t have started (if that makes any sense). William Symington built this engine to be fitted to a double hull paddle boat designed by Patrick Miller. It apparently worked when trialed on Dalswinton loch on October 14, 1788, although only at 5 mph and even then with some manual cranking assistance needed. This steam engine design (patented) used a continuous chain and pawl gears to convert oscillating piston movements to rotative motion and it doesn’t work well. Another issue with the prototype is its inefficient use of steam. It has two cylinders, but these are single rather than double acting – evidenced by the valves at the base of the cylinders which allow steam in to power the cylinder on the up stroke and then exhaust the steam into the condenser below on the down stroke. This means that only 25% of the potential power is being realised. It appears to have been little more than a proof of concept exercise, which proved its fundamental failings. Little surprise then that after a few attempts to improve it Symington dropped the concept. His next (successful) steam paddle boat, the Charlotte Dundas, used a direct acting crank system to drive a paddle wheel. A model of this oscillating engine appeared the 1934 Meccano New Models manual (pictured). It is nicely detailed but quite small and the instructions give no clue as to how to power the model. Some brave soul overcame this and quite some time ago I saw a video demonstrating the model working, although very poorly – not the builder’s fault incidentally, just a fundamentally poor design. It quickly became obvious to me that the oscillating chain system could only spin the paddle wheels in short jerks with a gap in power transmission while the cylinders “reset” for the next stroke. The boat must have progressed in a series of pulses. Very interestingly, the designer of the 1934 model went some way to addressing the problems. Instead of both paddles being driven simultaneously (but infrequently) as in the prototype, one gear/pawl is over-mounted and the other under-mounted so that the paddles receive power strokes alternately. A chain drive (not present on the prototype) links both paddles, so that the power stroke on one paddle is transmitted to the other paddle on its “idle” stroke. A clever idea, but I decided to build my model twice the scale of the 1934 model and attempt to replicate the original drive as closely as possible just to see how it worked. I used Meccano chain combined with spring cord around the pawl pulleys to replicate the looped drive system and it “worked” in as much as the paddles turned in gentle jerks, probably much like the prototype. It’s a very interesting window on a blind alley engineering development and it makes for a bonkers modelling opportunity. The pictures include a full scale replica of the Dalswinton boat and the engine. It’s surprisingly small with the twin hull boat being only 25 feet long with a 7 foot beam. For those interested in engineering pilgrimages, the replica boat can be found by the loch in the grounds of Dalswinton House in Dumfries and the engine in the Science Museum in London.