14 replies to this topic

[psalt]

I am researching the history of finger followers used by Honda, Mercedes, Delage, etc.. Some text credit FIAT with the 1921 GP engine, but it looks like Planche's 1914 Frontenac iron engine had them. The photo's and drawings of the 1920 Indy Frontenac also show them. It is a bit confusing with all the corrections and recorrections concernings the 1912-13 Peugeot's, but I think it is clear now that they never had them. Anyone know of an earlier twin cam with finger followers ?

Paul

[Allan Lupton]

By finger follower I assume you mean what many of us would refer to as a rocker.
The 1912 Peugeot did not have rockers, using a direct-acting stirrup tappet.
There were not many o.h.c. twin-cams before the Peugeot so if you are interested in that layout alone I can't help, but I can point out that rocking lever cam followers were used in many other layouts in early engines such as this Crossley gas engine

Edited by Allan Lupton, 11 April 2010 - 17:54.

[psalt]

By finger follower I assume you mean what many of us would refer to as a rocker.
The 1912 Peugeot did not have rockers, using a direct-acting stirrup tappet.
There were not many o.h.c. twin-cams before the Peugeot so if you are interested in that layout alone I can't help, but I can point out that rocking lever cam followers were used in many other layouts in early engines such as this Crossley gas engine


No, a finger follower is not a rocker, it is a lever pivoted from the side, with the free end between the cam lobe and the valve stem.

You can usually tell the old engines that have them from the outside, because the pivot was mounted on a little plate for adjustment. The 1912 Peugeot was erroneously credited with the Delage stirrup, but this error was corrected by Borgeson before he died, after he had repeated it several times in print . Photos of the engine and the actual 1913 engine show that it used "L" shaped tappets. Some sources say the Sunbeam and Humber, Peugeot copies, also had finger followers, but this appears to be repeating the same error by copy.

[VAR1016]

By finger follower I assume you mean what many of us would refer to as a rocker.
The 1912 Peugeot did not have rockers, using a direct-acting stirrup tappet.
There were not many o.h.c. twin-cams before the Peugeot so if you are interested in that layout alone I can't help, but I can point out that rocking lever cam followers were used in many other layouts in early engines such as this Crossley gas engine

Well I have always considered a rocker as a device pivoted somewhere around its centre or somewhere around 66/34% for a ratio of 1.5/1. A finger follower I understand to be pivoted at one end, the other acting onto the valve stem, with the cam acting from above the follower. I cannot quite make out the valve system in your picture of that splendid engine!

Paul

Edited by VAR1016, 11 April 2010 - 18:48.

[David Birchall]

Didn't Bugatti use something like this in his early engines?

[psalt]

Didn't Bugatti use something like this in his early engines?

The really early Bugatti 4 cyl used very odd, curved, rectangular section, tappets, four to a block. The later post 1921 8 cylinder engines used finger followers. The Bugatti U16 aero engine look like it had finger followers with rollers, but it was not in the US until 1918 at the NJ Dusenberg plant. I am looking for a pre 1915 inspiration for the Frontenac iron engine.

[Allan Lupton]

To my way of thinking the only fundamental difference between a rocker with the fulcrum between the input and output and one with both input and output on the same side of the fulcrum is that one reverses the direction and the other does not. You can build either sort to have any ratio that you may need (within reason).
They were both rockers when and where I learned my mechanical engineering so perhaps time and location have changed things but I can't see why they should.

Show me a photo of the 1912 Peugeot engine that shows it has not got the stirrup - I can't recall seeing that.

The top of the rocking lever of the Crossley engine can be seen next to its valve and the roller follower can be seen at the base of the rocker, next to the camshaft. The inlet valve seems to be automatic, so only one cam, lever and mechanically operated valve.

[psalt]

Show me a photo of the 1912 Peugeot engine that shows it has not got the stirrup - I can't recall seeing that.

You probably don't recall it because there are no internal photos of the 1912 Peugeot engine, only external photos, and no surviving engines, only 1913 engines. A 1913 engine has been dismantled, photographed and drawn and it has "L" shaped tappets. The 1912 engine has the same offset casting on the cam covers. Borgeson erroneously continued the silly idea that the 1912 engine had desmodromic valves with stirups, Peugeot drop them for the "L" shaped tappet and Delage copied them for the 1914 Type "S". He corrected this error in "The Signature of the Artist" in AQ. Most of the Peugeot and Delage drawings in books are incorrect and if you look at photos of the actual Delage parts, the Peugeot casting could not have accomodated the "upper stirup guide". There is a good description in "The Modern Gasoline Automobile-1916 edition". Curiously, this book avoids all the errors in later books and accurately show the operation of the Delage valve gear with the central yoke guide.

I just got a PM that suggests that the Indy Bugatti's of 1914-1915 had a three valve, finger follower head, and one was dismantled by the White Motor Company in 1915. The early Frontenac iron engine finger followers look very modern and close to the current design.

[bradbury west]

I am not an engineer so will ask in all innocence; what was the mechanism on the Curtiss OX aero engines, since I recall they have long rockers, especially the engine in the car built by Soichiro Honda pre 1920 IIRC. ?
Roger Lund

[psalt]

[quote name='bradbury west' date='Apr 11 2010, 21:54' post='4284322']
I am not an engineer so will ask in all innocence; what was the mechanism on the Curtiss OX aero engines,


Do you mean this:


Looks like rockers, not finger followers, to me.

Pushrods and pull rods, with later roller rockers conversions to reduce wear.

[bradbury west]

Thank you
RL

[David Manson]

de Dion Bouton in 1901, the 'finger' serving to lift the exhaust valve and release compression.

[Allan Lupton]

You probably don't recall it because there are no internal photos of the 1912 Peugeot engine, only external photos, and no surviving engines, only 1913 engines. A 1913 engine has been dismantled, photographed and drawn and it has "L" shaped tappets. The 1912 engine has the same offset casting on the cam covers. Borgeson erroneously continued the silly idea that the 1912 engine had desmodromic valves with stirups, Peugeot drop them for the "L" shaped tappet and Delage copied them for the 1914 Type "S". He corrected this error in "The Signature of the Artist" in AQ. Most of the Peugeot and Delage drawings in books are incorrect and if you look at photos of the actual Delage parts, the Peugeot casting could not have accomodated the "upper stirup guide". There is a good description in "The Modern Gasoline Automobile-1916 edition". Curiously, this book avoids all the errors in later books and accurately show the operation of the Delage valve gear with the central yoke guide.

What is an "L" shaped tappet please? If it's like the 1914 TT Sunbeam, then it is much the same as a stirrup without the part-circular top and as it also has a guide protruding upwards through the cambox, it's not easy to tell from the outside which is within. Oh and the stirrup is not desmodromic as its connection to the valve is "push" only.
Are you also saying that the detailed cutaway drawing by L.C. Cresswell that appears in Pomeroy's "The Grand Prix Car" is fictitious? If not, then what was its basis?
I no longer have easy access to period material, so can't check what was written/illustrated in 1912/13.

Anyway the point I made in my first post was that Peugeot did not use rocker followers, and you seem to agree.

[psalt]

What is an "L" shaped tappet please? If it's like the 1914 TT Sunbeam, then it is much the same as a stirrup without the part-circular top and as it also has a guide protruding upwards through the cambox, it's not easy to tell from the outside which is within. Oh and the stirrup is not desmodromic as its connection to the valve is "push" only.
Are you also saying that the detailed cutaway drawing by L.C. Cresswell that appears in Pomeroy's "The Grand Prix Car" is fictitious? If not, then what was its basis?


Picture a mushroom tappet with a vertical guide coming up from the edge of the cap.

Yes, the Cresswell drawing, and the drawings in the Autocar and the Automobile are bogus. No Peugeot or clones had stirrups that surrounded the lobe, that is a hacked Delage desmo feature. The two Cresswell drawings (pages 268 and 128) in the same book contradict each other and are obviously incorrect if you have ever seen the actual engine. This is a very messy issue, Borgeson made a big deal about "correcting" the record in his book, but he didn't get it quite right and had to add about 20 pages of text in three different articles to correct himself.

[DiegoCalut]

The really early Bugatti 4 cyl used very odd, curved, rectangular section, tappets, four to a block. The later post 1921 8 cylinder engines used finger followers. The Bugatti U16 aero engine look like it had finger followers with rollers, but it was not in the US until 1918 at the NJ Dusenberg plant. I am looking for a pre 1915 inspiration for the Frontenac iron engine.

Paul, the 1912-13 type 18 5-litre Bugatti had finger followers, just like the aero engine and all other 3-valve Bugatti engines. There's a picture in Conway's Bugatti book.