My research for the Anzani Fan Type engine model exposed a lot of prospects for other engine models that have not been built by anyone yet. Among these was the opposed two cylinder water cooled, 25HP Darracq engine of 1909. While not as popular as the Anzani, this small engine was used by several of the pioneers of flight. Alberto Santos-Dumont used it in one of his Demoiselle aircraft (See l'Aerophile, page 435, 1 October, 1909) Examples of the 25HP Darracq are on display in museums in Paris, Budapest, Toronto, and Oslo. Several people have posted images of these in blogs and there are many articles about Alexandre Darracq and his enterprises on the net.
I found patents for this engine at the US (961938, June 21, 1910) and French (407283, September 23, 1909) patent offices. The engine was described in "Some Recent Light Aeroplane Engines" in The Horseless Age, July 13, 1910 and a detailed illustrated technical description of it can be found in The Aero magazine of March 8, 1910.
I made a set of drawings for this model by tracing the Patent drawings. I will post these in PDF format in the Plans section of this forum.
After finishing some, but not all the ultimate tasks on the Anzani I longed to return to making chips. The drawing for the Darracq crankcase was finished and I found a couple of pieces of aluminum for the case halves in my stock box.
I glued a drawing of the case to each halve and roughed out the exterior shape and drilled holes for the through bolts and cylinder center holes and then roughed out the inner recesses of the crankcase and timimg gear cavities. These cavities will be finished with a dremel tool. They do not require any great precision, just enough to give clearence for the crankshaft and timing gears. I left a .020" raised ring on one case and a corresponding relief on the other so that the halves will register correctly together and with a fixture that will hold them during machining.
I made a couple of gauges attached to dummy shafts to measure the interior clearences for the crank and rod and the beveled timing gear.
I milled across on the centerline of the crankshaft with a round nose endmill as a guide for boring the hole for the crankshaft. This hole is the same size at the front and center bearing journals and smaller at thr rear journal. My plan was to drill and ream for the front and rear journal and then to bore the center journal with a piloted boring tool that fit the front and rear journals and would make a precise hole in the center established by the pilot section. This didn't work out very well as the strain from the boring caused the tool to break at the small pilot section.
This problem was overcome by a new tool drilled to accept the smaller diameter fittable rear journal pilot and with a fairly agressive cutter to cut the center journal bore. After this operation was finished and the bushings made, a dummy crankshaft fit quite well with minimum clearance and revolved with no drag when the cases were clamped together.
I found patents for this engine at the US (961938, June 21, 1910) and French (407283, September 23, 1909) patent offices. The engine was described in "Some Recent Light Aeroplane Engines" in The Horseless Age, July 13, 1910 and a detailed illustrated technical description of it can be found in The Aero magazine of March 8, 1910.
I made a set of drawings for this model by tracing the Patent drawings. I will post these in PDF format in the Plans section of this forum.
After finishing some, but not all the ultimate tasks on the Anzani I longed to return to making chips. The drawing for the Darracq crankcase was finished and I found a couple of pieces of aluminum for the case halves in my stock box.
I glued a drawing of the case to each halve and roughed out the exterior shape and drilled holes for the through bolts and cylinder center holes and then roughed out the inner recesses of the crankcase and timimg gear cavities. These cavities will be finished with a dremel tool. They do not require any great precision, just enough to give clearence for the crankshaft and timing gears. I left a .020" raised ring on one case and a corresponding relief on the other so that the halves will register correctly together and with a fixture that will hold them during machining.
I made a couple of gauges attached to dummy shafts to measure the interior clearences for the crank and rod and the beveled timing gear.
I milled across on the centerline of the crankshaft with a round nose endmill as a guide for boring the hole for the crankshaft. This hole is the same size at the front and center bearing journals and smaller at thr rear journal. My plan was to drill and ream for the front and rear journal and then to bore the center journal with a piloted boring tool that fit the front and rear journals and would make a precise hole in the center established by the pilot section. This didn't work out very well as the strain from the boring caused the tool to break at the small pilot section.
This problem was overcome by a new tool drilled to accept the smaller diameter fittable rear journal pilot and with a fairly agressive cutter to cut the center journal bore. After this operation was finished and the bushings made, a dummy crankshaft fit quite well with minimum clearance and revolved with no drag when the cases were clamped together.
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