PREPRINT: Printed to stimulate written or oral discussion. Subject to revision. All pa- pers presented at Meetings of the Society of Automotive Engineers are the exclusive property of the Society, from which permis- sion to publish this paper, in full or in part, after its presentation and with credit to the author and the So- ciety may be obtained upon request. The Society is not responsible for statements or opinions advanced in papers or discussions at its Meetings. Highlights of German Tank Transmission Design and Development By Lt.-Col. EV~ McEWEN, RoE.M.E. Assistant Director Fighting Vehicle Design Department British Ministry of Supply For presentation at the SAE GERMAN ENGINEERING EVALUATION MEETING Horace Ho Rack..1.anl Educational Memorial Detroit f Michigan March 4 1946 , of AUTOMOTIVE ENGINEERS, Inc., 29 West 39th Street, New York 18, N. Y. societyDownloaded from SAE International by Imperial College London, Sunday, August 04, 2019 Downloaded from SAE International by Imperial College London, Sunday, August 04, 2019-1- INTRODUCTION Themost striking thing about the German tank transmissions, starting before the1939/45 warandcontinuing right uptothecollapse ofGermany, isthepractical monopoly held bytheFriedrichschafen combine ofZ.F. (Zahnradfabrik Friedrichschafen) andMaybach. Itistruethat anumber oftransmissions were, infact, manufactured elsewhere, notably byZahnraderfabrik Augsburg (VormalsJoseph Renk) butallthedesigns which actually went into production were originated intheFriedrichschafen offices. Even attheendofthewar,allthemajor projects, except one, were sponsored byMaybach orZ.F. although oneofthese wasinconjunc tion with J.M.Voith, whoalso hadtheremaining major project. This inbreeding ofdesign, apart from causing heartburning among rival manufacturers andinventors, ledtoacertain lack ofprogress. TheMaybach gear boxes found inPzkpfw III &VI(Tiger) differ mainly inthesubstitution ofall- hydraulic forvacuum-hydraulic control, andthefirst really newdevelopment by Maybach wastheMechydro unit which wasonthestocks atthetime ofthecollapse. Z.F. designs showed more changes: allembodied the "Aphon" gear mounting, but there wasavariety ofsynchronizing andselection means, from plain dogclutches inPzkpfw I&IIthrough multi-plate synchronizers inPzkpfw III &IVtocone synchromesh inPzkpfw V(Panther) andtheelectro-magnetically controlled boxbeingdeveloped atthe end. Independent firms apparently received only just sufficient backing fromtheHeereswaffenampt (Wapruf 6)toserve asananswer toaccusations offostering a monopoly, andhydraulic transmissions, except intheexpendable remote controlled demolition vehicle B.IV,were nottaken very seriously until thecapture, late inthe War, ofAllied vehicles fitted with them. Allthrough, thedesigns show complexity, lavish expenditure ofman-hours,first rate workmanship andextremely ingenious detail design, butanapparent inability tousesimple means toanend. THE WAR-TIME TRANSMISSIONS: Pzkpfw I&II. ThePz.Ihadafive-speed forward and onereverse straight-forward crash gearbox ofZ.F.design andPz.IIwassimilarly equipped with anAphon Z.F. gearbox having sixforward andonereverse speed. The Aphon principle, which was well known before thewar, wasoriginally produced forquietness although itwas subsequently claimed tohave ahigher load carrying capacity than theorthodox shaft gearbox. Itscharacteristic feature isthat each gear wheel ismounted direct inthegearcase with apair ofbearings, theshafts passing through thebore of thegears being used purely forthetransmission oftorque andrelieved ofallbend ingstresses. Theconstruction is,however, expensive inrequiring agreat deal of boring inthemachine shop andalarge number ofball androller races. Pzkpfw III-Maybach Variorex. Thedesire foreasier gearchanging appears tohave been behind theintro duction inPz.IIIoftheMaybach Variorex gearbox. This device contains theusual Maybach principle ofsynchronization bymeans ofover-running inclined face