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MG MGA When winter prevents you getting your A out. BBS discussion at MG-Cars.net
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MG MGA - When winter prevents you getting your A out.
| For you guys on the other end of the globe here is little project you can knock up on your lathes when you have finished with the carby sub stacks! http://www.wimp.com/tiniestengine/ Mike |
| Mike Ellsmore |
| Mike, What puzzles me is that the camshaft timing gears seem to have the same diameter as the crankshaft gear. (see image). How is this so? Mick  |
| M F Anderson |
| Can't get video, so can't see. But, either that's not the end of the crank, ie it's a reduction drive, or he has a bad moment coming when he tries to start it! FRM |
| FR Millmore |
| Two stroke engine, perhaps. |
| Barney Gaylord |
| Barney is correct - the model is only an air driven motor(albeit a 12 cylinder one) ie the driving force is compressed air on a 2 stroke cycle. Mike |
| Mike Ellsmore |
| Mike, I do not follow. Two stroke engines do not have camshafts. They do not need them. This engine has inlet and exhaust valves side by side in the cylinder head in the normal four stroke layout. Could you describe the sequence of events as you see it? Mick |
| M F Anderson |
| Note that it can never run as a normal engine as it has zero capacity for spark plugs. Where are the piston rings? The grooves were in the pistons. It is however a beautiful machining job. |
| darnoc31 |
| thinking of it as a 2-cycle ICE really confuses things. Think of it as a 12 cyl compressor in reverse. A compressor does: Suck intake-exhaust-suck intake-exhaust and GETS power from the crank. This engine does: pressure intake-exhaust-pressure intake-exhaust and PRODUCES power at the crank. Instead of reed valves or a rotary valve, it has a camshaft driven valves. I actually had an antique 2-cycle outboard engine with real valves (Valves used o-rings for sealing, had valve stems, driven by a cam lobe on the crank) The type of valve used does not define a 2-cycle vs 4 cycle engine. |
| Chuck Schaefer |
| I think it's a two-stroke diesel marine engine. (model) |
| John DeWolf |
| Let's face it guys if its not made of cast iron with the usual 4 pistons and other normal twiddly bits - we're lost..! Nice bit of modelling though... Pete |
| P N Tipping |
| Certainly beyond my stub stack machining capabilities! Now, if it was a kit of parts I would buy it. Steve |
| Steve Gyles |
| The camshaft gears being the same size as the crankshaft gear doesn't matter. Two things matter: Gear ratio and material. As long as the gear ratio times the camshafts with the movement of the pistons everything is fine. The only thing that would be of interest on a full scale motor is if the materials all could withstand the stresses and strains on the gears. In fact, the cool thing is that this is exactly what all major auto manufacturers look for today; parts commonality. My 2007 S2000 innder door handles are the same door handles as the 1992 Civic Si door handles it replaced. Honda has gotten away with ordering how many door handles for over 15 years. What I would like to find is a video that I saw over 10 years ago that had a matchbox sized Ferrari that had a REAL gasoline powered V-12 engine in it. It has the builder reaching his finger in the footwell and revving the engine in the car...! The end of the video had the car being placed in a matchbox! |
| J DeRienzo |
| You comment "The camshaft gears being the same size as the crankshaft gear doesn't matter" is rather strange. If it is a four stroke the camshaft gear must be twice the size of the crankshaft gear to get the 2:1 ratio. The gear teeth on both shafts must be matching in size and shape in order to mesh. This means that the camshaft gear must be twice the size if it has twice the number of teeth. I think the comments on two stroke engines and air compressors hold the key to it all. Mick |
| M F Anderson |
| Is the stuff you guys smoke in Ohio legal? |
| Mike Ellsmore |
| Lots more here for folk who can get video: http://www.craftsmanshipmuseum.com/enginerun.htm I've seen a lot of these in person, some running. I watched some of them progress from ideas to running over the years. Ron Colonna's 270 Offy might be my favourite. FRM |
| FR Millmore |
| Mike, the miniature Ferrari with working V12 engine does exist and is a miracle of engineering. It's not what they smoke in Ohio, it's the size of the matches they use to light up that must be impressive! http://www.youtube.com/watch?v=vxYRa0pqxlw |
| N McGurk |
| They must smoke the same stuff in Cumbria as I don't see "the car being placed in matchbox" at the end of the video. All the same it is very impressive engineering and model making. Mike |
| Mike Ellsmore |
| Psychologists will say that our memories are never spot on...even when we are absolutely certain. I remember a model MUCH much smaller...that worked, but like I just said... Unfortunately, I haven't lived in Ohio long enough to know what they smoke. I'll be leaving the state before I get much more chance to investigate either! I would agree with the two stroke part. That would explain the gearing but then goes into the question why put a valve train on something that could be lighter and have less moving parts and mass... Must be winter... |
| J DeRienzo |
| I suppose a ported two stroke would not work as an air motor. |
| Barney Gaylord |
This thread was discussed between 13/12/2011 and 14/12/2011
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