Layden B Posted November 11, 2006 Share Posted November 11, 2006 BOSCH ZR3 2SPK magneto, that is frame model ZR, 3 cylinder, fires 2 sparkplugs at the same time hence the 6 sparkplug leads. It is missing the cover on the shaftend and points cover. My question is what is the probable application for such a beast? The bevel gear on the input shaft speaks "aircraft" to me. Link to comment Share on other sites More sharing options...
Aanderson44 Posted November 11, 2006 Share Posted November 11, 2006 6 leads, two firing simultaneously? That means a 3-cylinder engine--surely an aircraft engine, but what one? 3-banger aircraft engines were pretty danged unusual.Art Anderson Link to comment Share on other sites More sharing options...
mlander Posted November 12, 2006 Share Posted November 12, 2006 My old book written by Herschel Smith States this;Three cylinder radial enginesBristol-Lucifer 1925Walter-Polaris 1928 Jacobs L-3 1929Aeromarine 1931 This book is not complete enough to list magnetos. M.L. Anderson Link to comment Share on other sites More sharing options...
Ivan Saxton Posted November 13, 2006 Share Posted November 13, 2006 Dykes list Lenape as maker of sveral models of 3 cyl aero engine. No dates are given.You can date the magneto, though, as Bosch consecutively numbered all magnetos manufactured, irrespective of size and type. 1900 1-60991901 to 96391902 144171903 241341904 425711905 757531906 1232101907 1853291908 2512681909 4345661910 6463451911 9335081912 13353311913 15679651914 17580301915 1798093I am sorry my list goes no later than this, but it might be helpful to people in other cases. I have a brand new Simms 4 aircraft magneto, very well made, but it has no advance/retard control. This 3 cyl 2spark has. Why would they run aero engines without being able to adjust the spark advance?Ivan Saxton Link to comment Share on other sites More sharing options...
Guest carlnut50 Posted November 13, 2006 Share Posted November 13, 2006 This could be from a 6 cyl engine if it ran at crankshaft speed instead of off the camshaft.You get 3 power impulses per rev on a 6 cyl engine and the other 3 sparks would be on the exhaust stroke. Some modern cars do this with 3 ignition coils on a 6 cyl engine firing 2 sparks at once. They call the exh spark a waste spark. Link to comment Share on other sites More sharing options...
Layden B Posted November 13, 2006 Author Share Posted November 13, 2006 Serial on this at over 3 million probably makes it 1920s. Have some literature on Anzani 3 cylinder but they do not show Bosch mags, neither does the Lawrence L-2 or Wright "Gale". Link to comment Share on other sites More sharing options...
Ivan Saxton Posted November 14, 2006 Share Posted November 14, 2006 I am not sure about the waste spark application. we need to think about the arithmetic from simple basics. The rotation of a magneto armature breaks the magnetic flux across the poles twice per rev; each one a spark(in coordination with point opening, of course. So a magneto on a 4 cyl is run at crankshaft speed and takes two revs to give four sparks. The distributer gearing inside the mag has a 2:1 reduction. Magneto for a six has to spin 3 revs for 6 sparks, so the armmature has to run at 1.5 times crankshaft speed. That three would have to be geared for 1 1/2 revs per two turns of the crank, ie it should be geared at 3/4 crankshaft speed. If it was set to run a 6 cyl engine on a waste spark system, it would have to be twice as fast as that, ie 1 1/2 times crankshaft speed. So it should be possible to run it on a six: There is one reason it could be an advantage, but other compelling reasons that you would be better not to stretch the friendship.The advantage would be that because the magneto is spinning faster it should have a more enthusiastic spark at low rpm for starting. This may be fine for a low speed engine, but at high speeds there may be things you would worry about. I had to make a new HT slip ring for the pick-up, and whereas the slip ring for a normal magneto has a bronze ring, my 2 spark ZR4 for the 1918 Mercer had two opposite segments inserted in the bakelite assembly. I cannot remember how I did it, but I do know it was a fiddle to make and insert them so they were loked in and would not make a lazy short circuit. You see, each segment connects to a different end of the secondary winding.Other problem is that each spark has to jump two gaps simultaneously, and the higher the compression pressure, the harder it is to ionize the spark gap and fire the charge. And aircraft engines may cruise at a fairly wide throttle opening. (Of course you could cheat a little by running 50/50 water/ethanol "water injection" to give more polar component to the mixture to help the spark. It doesn't really appeal, and I doubt whether it would have been one that Herr Bosch would advocate. I have never had trouble fireing the Mercer, even on the armstrong starter with the 2-spark, so the possibility of hotter spark nfor starting is probably an illusiory advantage.Ivan Saxton Link to comment Share on other sites More sharing options...
Guest merton.hale Posted May 20, 2011 Share Posted May 20, 2011 Hello All, This is my first post here. I came across the picture of the magneto. I looks very similar to one I am working with. I would need more pictures to be sure.Where did you get it? If it is the right thing I probably would want to buy it.3 cylinder? No. 6 cylinder engine with TWO magnetos, two spark plugs per cylinder. It may be from a BENZ 4 engine. I'm helping to restore one. It was used to power a WWI aircraft call an LVG CVI. She is a beautiful old beast. Weighs 450 kgs.If I knew how to attach a picture (if you want) I could send/attach a picture.Not many of these engines still exist - maybe about 12 worldwide. If you have more pictures please send and I'll look more carefully. We have full manual that explains how system electrics work. Link to comment Share on other sites More sharing options...
nzcarnerd Posted May 20, 2011 Share Posted May 20, 2011 Ivan, that list of Bosch serial numbers up to the mid teens seems to be readily available, but I have never been able to find any info from later years. We have a single cylinder Bosch mag on a lawn mower which we believe to be mid 1920s. It would be good to be able to date the mag which would then give a clue to the date of the mower. Link to comment Share on other sites More sharing options...
Rust Rustler Posted May 21, 2011 Share Posted May 21, 2011 Bosch magnetos are wonderfully easy to date up to 1915 regardless of which factory or country they were manufactured because the parent factory in Germany Licensed all production consecutively for example, the factory in the United States were Licensed to produce ten thousand magnetos in a given year and were allocated the serial numbers accordingly. Unfortunately the parent factory lost it's Patents and Licensing rights during the argument of 1914 - 18Noel Link to comment Share on other sites More sharing options...
Guest Cengine Posted July 17, 2014 Share Posted July 17, 2014 Do you still have this 3 cylinder magneto ? I'd be interested in buying it. Link to comment Share on other sites More sharing options...
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