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L76 Peugeot 1912

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#1 DiegoCalut

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Posted 16 November 2017 - 13:45

Hello. I´m obsessed with this little matter of what was inside the camboxes of the L76 Peugeot and would like to follow the printed trail since the very beginning, analyzing the information from an engineer´s point of view.


I´ve unsucessfully tried to find the original Faroux article for August 31, 1912 from La Vie Automobile from which W.F. Bradley derived his own for the Automobile, September 26, 1912 issue. I´d like to check on the accuracy of the latter and could anyone here suggest a link to the former French article? 


Thank you. 


Diego Calut


#2 Vitesse2

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Posted 16 November 2017 - 14:09




#3 DiegoCalut

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Posted 16 November 2017 - 17:27

Well, this is Très Grande Vitesse2 !!!! Thank you very much.  :wave:

#4 robert dick

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Posted 17 November 2017 - 16:49

The 7,6-litre Peugeot described in the magazine "The Motor"/London/1912 -
on 2 July 1912

on 17 September 1912

and on 3 December 1912

Photos -
rear axle

Ernest Henry and Paolo Zuccarelli

#5 DiegoCalut

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Posted 21 November 2017 - 16:59

Wow Robert Dick, this is a surfeit of unsuspected information! It will take me some time to digest it. I had prepared the following as an ice breaker but I see I´ll have to reassess some of my assumptions regarding Charles Faroux and William Bradley´s roles in publicizing the description of the L76. However I´ll post it as it is and request commentaries and criticism:


I think I should introduce myself via a short resume, so that you may know where I come from. My name is Diego Calut and I was born in Argentina sixty-five years ago in a French speaking family of automobile enthusiasts. In his youth Grandpa raced an Amilcar, a Georges Irat and a 16 valve Bug in North Africa. I myself raced karts and offshore powerboats, graduated with a degree in Industrial Engineering and lectured on Internal Combustion Engines at my alma mater for a few years. Right now I´m finishing the construction of a rear-engined two-seater sports car of my own design.


Although aware of the epochal 1912 L76 Peugeot for more than forty years I didn´t start to pay close attention to its valve gear until I happened upon a series of articles by Griffith Borgeson in Automobile Quarterly. GB spins a very compelling story and it got me obsessed with the contents of the L76´ camboxes. I´ve been lurking in the The Nostalgia Forum for quite some time and I´m amazed at the amount and quality of the information exchanged. I hope this subject will interest some members and that they might be willing to contribute information and criticism.


GB used to write about such and such piece of information “polluting the historical record” and mindful of this I decided to start at the beginning and analyze the design from an engineering point of view, going through the available information in chronological order. The first description in print of the L76 Peugeot that I´m aware of is the La Vie Automobile article of August 31, 1912 by Charles Faroux, for which Vitesse2 kindly supplied a link. From it we learn that Peugeot agreed to supply information and pictures for the article and made Georges Boillot available to do the honors. CF forewarns the reader that he will withhold certain data and design specifics. He doesn´t tell us whether he actually had a look at the contents of the cambox or these were described to him by Boillot, truthfully or not. Maybe CF contributed his penmanship in order to convincingly cloud the description of the valve gear, repaying Peugeot´s courtesy.  In fact, I think that CF, Boillot or both of them went a bit further and outright tried to deceive the reader as to the nature of the valve gear. It then behooves us to question his every word.


Following is the transcription of the relevant parts of the original article as regards the valve gear:


“Les culasses sont hémisphériques et les soupapes sont placées a 45º. Afin de donner une large section de passage aux gaz et de permettre au moteur de respirer librement, chaque cylindre possède quatre soupapes, deux d´admission et deux d´échappement. Leur diamètre est de 60 millimètres et leur levée de 11. Leur mode de commande est particulièrement original. Nous ne rencontrons pas ici les culbuteurs habituels qui eussent peut-être donné quelques mécomptes aux grandes vitesses de rotation que devait atteindre ce moteur. Chaque rangée de soupapes est surmontée d´un carter semblable à celui représenté par la fig. 3 et renfermant un arbre à cammes. Ces deux arbres à cammes sont commandés par une paire de pignons enfermés dan le carter que l´on voit ouvert, au sommet du bloc des cylindres sur les fig. 1 et 2 et entrainés au moyen d´un renvoi d´angle par un arbre vertical placé à l´avant du moteur. Chaque arbre porte huit cammes, agissant chacune à l´intérieur d´un excentrique portant le poussoir et d´une seule pièce avec lui. Le poussoir ne portant pas de galet, celui-ci est porté par l´extrémité de la came. On conçoit que la forme de l´excentrique a dû faire l´objet de longues études, car c´est d´elle que dépend en partie le réglage de la distribution. Ces poussoirs, réglables par un écrou, sont d´ailleurs rappelés par un ressort visible au-dessus de chacun d´eux quand la camme cesse de les enfoncer. Ils sont placés dans le prolongement des queues de soupapes et les attaquent directement.”  


This is my translation of the preceding text and would like for the French speaking members to go over it and point any inaccuracy they may find.


“The heads are hemispherical and the valves are placed at 45º. In order to obtain a large area for the passage of gases and to allow the engine to breathe freely, each cylinder has four valves, two intake and two exhaust. Their diameter is 2.362” and their lift .433”. Their mode of actuation is particularly original. Here we don´t find the usual rocker arms which could maybe have caused some mishaps at the high revolutions that this engine had to reach. Each row of valves is surmounted by a housing similar to the one represented in fig. 3 enclosing a camshaft. These two camshafts are driven by a couple of spur gears enclosed in the housing that can be seen open, on top of the cylinder block on fig. 1 and 2 and driven by a set of bevel gears via a vertical shaft located at the front of the engine. Each shaft has eight cams, each working inside an eccentric comprising the pusher integral with it. The pusher not including a roller, the latter is located at the extremity of the cam. The shape of the eccentric must have been studied extensively, as the valves´ timing is partly dependent on it. These pushers, adjustable by a nut, are recalled by a spring visible above each of them when the cam ceases to depress it. They are located in line with the valves´ stems and actuate them directly.”


We can see that the illustrations in the article are retouched copies of the originals on the Gallica website, links to which were kindly posted by Robert Dick. We can readily see that when CF refers to “a housing similar to the one represented in fig. 3 …” he is hoodwinking us. There´s nothing similar, it is the very same one. 

#6 robert dick

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Posted 22 November 2017 - 12:28

Description of the 7,6-litre Peugeot in the French magazine "Omnia", 6 July 1912:

#7 DiegoCalut

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Posted 22 November 2017 - 18:16

Allright then. I have to assume that Griffith Borgeson had not found the articles forwarded by Robert Dick and that Peugeot had not been as stingy, information wise, as I had been led to believe. Neither Charles Faroux nor William Bradley seem to have had any kind of exclusive or advance information.


The article from The Motor /London for 3 December 1912 shows very clearly the design of the “excentrique” (which I´ll call a follower) yet introducing a certain amount of deceit, I think. This is puzzling as it could not possibly fool the rival firms´engineers, only the average magazine reader. I am referring to the roller-tipped cam which makes no sense at all. It doesn´t reduce the friction between cam and follower as the cam´s maximum acceleration and deceleration occur away of the tip. The introduction of the roller generates a discontinuity from the shape of the cam to the circular shape of the roller which, in turn, generates a shock between the roller and the follower. Further, the roller doesn´t stay continuously in contact with the follower and has a tendency to skid that wear flats. I don´t know what kind of cam curves they were using at the time but I´m pretty sure that the nose of a cam meant to be used against a flat-faced follower, as per the drawing, would have had a rather smaller radius, rendering the design physically unworkable. If the follower had been curved-faced then it might have worked geometrically but with the same defects previously mentioned. The third possibility would be for the follower to incorporate a roller but this would require an extremely wide and asymmetric follower which wouldn´t fit inside the pictured cambox.


There doesn´t seem to be any logic to the “excentrique” name for the follower. Its definition is exactly the same as for eccentric, that is “a disc or wheel mounted eccentrically on a revolving shaft in order to transform rotation into backward-and-forward motion, e.g. a cam in an internal combustion engine.” However, in the drawing we can clearly see that the camshaft axis doesn´t intersect the follower guides´ axis, these axes being “désaxés” or offset. Maybe this was originally construed as being “excentrique” and the adjective turned into a noun? In any case there is a technical reason for this, to keep the follower at 90º from the camshaft. This would mandate the latter to turn clockwise in the drawing. Such feature would help explain the very slight asymmetry that I perceive in the frontal picture of the engine, the recall spring being a little bit to the left of the camshaft housings. Of course, had the originator of the “excentrique” noun been perfectly candid he could have described this part as an “étrier” or stirrup. For some reason in 1913 Peugeot changed the design to the L-shaped flat-faced follower, I assume that to achieve better control over the follower alignment. Maybe they also switched from a curved-faced follower to the flat one but I think it is more probable that the stirrup was flat-faced in the first place. In my opinion the cams had no rollers and the followers were flat-faced.


Finally, I wonder why this scheme was chosen when a flat-footed mushroom type follower would have been simpler, cheaper and lighter? 

Edited by DiegoCalut, 22 November 2017 - 18:17.

#8 robert dick

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Posted 23 November 2017 - 11:44

In principle, the "excentrique" or semi-circular tappets used in 1912 were direct forerunners of Ernest Henry's L-shaped tappets used in 1913 - the L-form implying a simplification of the semi-circle guides below and above the camshaft. Henry's cup-type tappets used in his 1919 or 1920 Ballots followed in a third step, a definite solution in the simplification. A leading idea behind all three solutions was the absorption of the lateral forces.

= = = =

The 1912 3-litre Peugeot (or more exactly "Lion-Peugeot") had only two valves per cylinder (4 valves in 1913), but obviously the same type of tappets as the 7,6-litre brother.

The only description of the 1912 3-litre I could find mentioning a two-valve head - La Revue de l'Automobile, 25 June 1912 (published before the race):
Description of the 7,6-litre in the same magazine, mentioning patented valve tappets:

Btw - a wonderful map of the Dieppe course:

#9 DiegoCalut

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Posted 23 November 2017 - 14:02

In truth the inverted-cup tappets used in the Ballots were not invented by Henry but by one Albert Morin and patented in 1916, I believe.