Old Git Posted May 16, 2014 Share Posted May 16, 2014 (edited) Does anyone know what the gear ratio was on the Cromwell? Also, any indication of number of teeth on the gear wheel and the pinion? I think, IIRC, there was about 50 teeth on the gear wheel? Edited May 17, 2014 by Old Git spollings Quote Link to comment Share on other sites More sharing options...
Old Git Posted May 18, 2014 Author Share Posted May 18, 2014 Found it in some scans from the manual... 3.71:1 (40mph) on the Type D's and moved to 4.5:1 (32mph) on the Type E and F. Quote Link to comment Share on other sites More sharing options...
lssah2025 Posted May 18, 2014 Share Posted May 18, 2014 I have early vehicles are 3.7 to 1 final drive 39.5mph at 2550rpm Later vehicles 4.5 to 1 final drive 32.5mph at 2550rpm But I think this could be adjusted by removing the electrical governors that are incorporated in each magneto, they are set to prevent maximum engine speed from being exceeded, they let unburned fuel go into the exhaust system so the engine won't go above the set speed limit. I have heard that some crews removed the governors so they could go faster... Quote Link to comment Share on other sites More sharing options...
GeePig Posted May 19, 2014 Share Posted May 19, 2014 But I think this could be adjusted by removing the electrical governors that are incorporated in each magneto, they are set to prevent maximum engine speed from being exceeded, they let unburned fuel go into the exhaust system so the engine won't go above the set speed limit. I have heard that some crews removed the governors so they could go faster... 'they let unburned fuel go into the exhaust system' - unburned fuel from where? Do you know how that was supposed to work? trevor Quote Link to comment Share on other sites More sharing options...
lssah2025 Posted May 19, 2014 Share Posted May 19, 2014 (edited) 'they let unburned fuel go into the exhaust system' - unburned fuel from where? Do you know how that was supposed to work? trevor The governors operate by short circuiting the high tension current to the sparking plugs. This results in unburnt mixture passing to the exhaust pipes and exploding there, It is, therefore, bad practice to "drive on the governors." Each magneto is fitted with an automatic advance and retard mechanism and governor which limits the engine speed to 2550 rpm. Edited May 19, 2014 by lssah2025 Quote Link to comment Share on other sites More sharing options...
Old Git Posted May 19, 2014 Author Share Posted May 19, 2014 I have early vehicles are 3.7 to 1 final drive 39.5mph at 2550rpm Later vehicles 4.5 to 1 final drive 32.5mph at 2550rpm Yeah that's what I have too! By my reckoning there ought to be 52 teeth on the spur gear and 14 on the Pinion, but I'd still like to see a nice clear pic of those two gear wheels! It's interesting that there's not a picture anyway on the Inet of a disassembled final drive for a Centaur or Cromwell! Quote Link to comment Share on other sites More sharing options...
GeePig Posted May 20, 2014 Share Posted May 20, 2014 The governors operate by short circuiting the high tension current to the sparking plugs. This results in unburnt mixture passing to the exhaust pipes and exploding there, It is, therefore, bad practice to "drive on the governors." Each magneto is fitted with an automatic advance and retard mechanism and governor which limits the engine speed to 2550 rpm. Ah, I see, I thought that there was some system bypassing the engine trevor Quote Link to comment Share on other sites More sharing options...
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