Engineering details of GP cars of the twenties and thirties show interesting variations.
Lets start with the use of bucket/pot tappets or finger followers. What are the merits of each? More specifically the Maserati 26 series used pots but later I believe the 4CL used fingers. Can the knowledgeable provide more details on the early Maserati cars please?
1920s/30s race car engineering
Started by
Richard Cass
, Nov 19 2004 21:21
5 replies to this topic
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#2
robert dick
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Posted 20 November 2004 - 11:04
Both systems, bucket/pot tappets and finger followers, were the preferred solutions to neutralise the side thrust from the cam in high performance engines. Both systems had their respective advantages and disadvantages.
Concerning the 1927 1.5-litre Delage which used finger followers Laurence Pomeroy wrote : "Triple valve springs were used and rather small followers were interposed between the cam and the valve stem, these being one of the least satisfactory parts of the engine and liable to rapid wear." But a high performance engine had to be regularly serviced and the worn followers could be quickly/easily replaced.
In case of bucket tappets, the accessibility for adjusting clearance was more complex.
Concerning Maserati, the replacement of the bucket/pot tappets by finger followers was not solely founded on technical reasons but also on the career of the engineers behind it.
After WWI, the bucket/pot (or inverted cup) tappets were used in the 1919 4.9-litre and the 1920 3-litre Ballot straight-eights, designed by Ernest Henry. These Ballots had a lot of influence on the American straight-eight Millers which used this type of tappet in the 3-, 2- and 1.5-litre engines.
A batch of 2-litre Millers appeared in September 1923 in the Gran Premio d'Italia/Monza with Murphy, de Alzaga and Zborowski.
During the following year, 1924, ex-Fiat engineer Giuseppe Coda and Alfieri Maserati designed a straight-eight for Diatto which had a lot in common with the Miller, including the bucket/pot tappets. There is no proof that a Miller was dismantled and inspected by Coda and Maserati, but the similarity between the engines is so obvious that it was probably the case.
The Diatto appeared in the 1925 Grand Premio d'Italia and in 1926 became the first Maserati, the tipo 26.
Coda was one of the best engineers and his Diatto was just in need of some development work. So there was no reason for the Maserati brothers to replace the bucket/pot solution when further versions of the tipo 26 appeared until the thirties.
The finger followers were the preferred solution of the Bertarione/Becchia/Jano/etc... gang, and became popular especially with the Fiat 804/404, the outstanding car in 1922. When Officine Maserati changed hands by the end of the thirties, the Maserati brothers lost their exclusive influence. Engineers with Fiat background played along. So the finger follower tradition from Fiat found its way into the Maserati engine.
Concerning the 1927 1.5-litre Delage which used finger followers Laurence Pomeroy wrote : "Triple valve springs were used and rather small followers were interposed between the cam and the valve stem, these being one of the least satisfactory parts of the engine and liable to rapid wear." But a high performance engine had to be regularly serviced and the worn followers could be quickly/easily replaced.
In case of bucket tappets, the accessibility for adjusting clearance was more complex.
Concerning Maserati, the replacement of the bucket/pot tappets by finger followers was not solely founded on technical reasons but also on the career of the engineers behind it.
After WWI, the bucket/pot (or inverted cup) tappets were used in the 1919 4.9-litre and the 1920 3-litre Ballot straight-eights, designed by Ernest Henry. These Ballots had a lot of influence on the American straight-eight Millers which used this type of tappet in the 3-, 2- and 1.5-litre engines.
A batch of 2-litre Millers appeared in September 1923 in the Gran Premio d'Italia/Monza with Murphy, de Alzaga and Zborowski.
During the following year, 1924, ex-Fiat engineer Giuseppe Coda and Alfieri Maserati designed a straight-eight for Diatto which had a lot in common with the Miller, including the bucket/pot tappets. There is no proof that a Miller was dismantled and inspected by Coda and Maserati, but the similarity between the engines is so obvious that it was probably the case.
The Diatto appeared in the 1925 Grand Premio d'Italia and in 1926 became the first Maserati, the tipo 26.
Coda was one of the best engineers and his Diatto was just in need of some development work. So there was no reason for the Maserati brothers to replace the bucket/pot solution when further versions of the tipo 26 appeared until the thirties.
The finger followers were the preferred solution of the Bertarione/Becchia/Jano/etc... gang, and became popular especially with the Fiat 804/404, the outstanding car in 1922. When Officine Maserati changed hands by the end of the thirties, the Maserati brothers lost their exclusive influence. Engineers with Fiat background played along. So the finger follower tradition from Fiat found its way into the Maserati engine.
#3
dbw
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Posted 21 November 2004 - 08:14
bugatti sucessfully used finger followers to actuate three valves with a single overhead cam!...the bug twincam used a faithful clone of millers buckets..
how 'bout bugatti's infamous "bananna" tappets that allowed four vertical valves per cylinder to be operated by a single overhead cam ....
how 'bout bugatti's infamous "bananna" tappets that allowed four vertical valves per cylinder to be operated by a single overhead cam ....
#4
robert dick
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#5
Richard Cass
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Posted 23 November 2004 - 21:25
Thanks dbw and Robert.
As a newcomer to the forum I wonder whether this thread is too wide – any advice welcome. I had not visited the Bugatti Trust site for a long time. Well worth the visit. Bugatti was very ingenious. I was looking in one of my favourite books Automobile Design Great Designers And Their Work and found cut away diagrams of Jano’s Alfa engines. His P2 used finger tappets but he moved to a variation of Birgkt’s mushroom type for the 6 cylinder 1500 and 1750 and the 8C series. Whilst on the subject of Alfa Romeos I wonder why the later 1934 Tipo B (P3) changed to reversed quarter elliptic springs similar to Bugatti's cars.
As a newcomer to the forum I wonder whether this thread is too wide – any advice welcome. I had not visited the Bugatti Trust site for a long time. Well worth the visit. Bugatti was very ingenious. I was looking in one of my favourite books Automobile Design Great Designers And Their Work and found cut away diagrams of Jano’s Alfa engines. His P2 used finger tappets but he moved to a variation of Birgkt’s mushroom type for the 6 cylinder 1500 and 1750 and the 8C series. Whilst on the subject of Alfa Romeos I wonder why the later 1934 Tipo B (P3) changed to reversed quarter elliptic springs similar to Bugatti's cars.
#6
robert dick
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Posted 24 November 2004 - 14:30
The Alfa P2 was a pure factory racing car, in the sense of the Fiats and the Delages. These engines were never used in touring or sports cars. The 6C and 8C Alfas were produced in larger numbers and were used by "normal" customers. So it is understandable that Jano switched over to the mushroom solution.
Originally the quarter elliptics of the P3 were probably intended to suit the Dubonnet front suspension which appeared at the same time.
Originally the quarter elliptics of the P3 were probably intended to suit the Dubonnet front suspension which appeared at the same time.
