Nothing new...

Browse pages
Current page

1

Current page

2

Current page

3

Current page

4

Current page

5

Current page

6

Current page

7

Current page

8

Current page

9

Current page

10

Current page

11

Current page

12

Current page

13

Current page

14

Current page

15

Current page

16

Current page

17

Current page

18

Current page

19

Current page

20

Current page

21

Current page

22

Current page

23

Current page

24

Current page

25

Current page

26

Current page

27

Current page

28

Current page

29

Current page

30

Current page

31

Current page

32

Current page

33

Current page

34

Current page

35

Current page

36

Current page

37

Current page

38

Current page

39

Current page

40

Current page

41

Current page

42

Current page

43

Current page

44

Current page

45

Current page

46

Current page

47

Current page

48

Current page

49

Current page

50

Current page

51

Current page

52

Current page

53

Current page

54

Current page

55

Current page

56

Current page

57

Current page

58

Current page

59

Current page

60

Current page

61

Current page

62

Current page

63

Current page

64

Current page

65

Current page

66

Current page

67

Current page

68

Current page

69

Current page

70

Current page

71

Current page

72

Current page

73

Current page

74

Current page

75

Current page

76

Current page

77

Current page

78

Current page

79

Current page

80

Current page

81

Current page

82

Current page

83

Current page

84

Current page

85

Current page

86

Current page

87

Current page

88

Current page

89

Current page

90

Current page

91

Current page

92

Current page

93

Current page

94

Current page

95

Current page

96

Current page

97

Current page

98

Current page

99

Current page

100

Current page

101

Current page

102

Current page

103

Current page

104

Current page

105

Current page

106

Current page

107

Current page

108

Current page

109

Current page

110

Current page

111

Current page

112

Current page

113

Current page

114

Current page

115

Current page

116

Erudite historians have no doubt looked at the interesting question of when the first ic engine, with’ mechanically operated overhead valves appeared and when such valves were first operated by an overhead camshaft. Leaving aside Ernest Henry’s pioneering of twin overhead camshaft (multi-valve) racing engines for Peugeot from 1912, reference to Gerald Rose points to Fiat having used oh valves, in hemispherical combustion chambers, operated by push-rods and rockers, as early as 1905, which Rose explained “gives more perfect utilisation of the forces of the explosion than any other arrangement”. Pipe had a similar layout in 1904, as had the

Prince Henry Benz of 1908, but with pent-roof heads. It is rather surprising to find that according to Rose many manufacturers were still using automatic inlet valves for racing as late as 1903 and that De Dietrich and Hotchkiss were still using them for this purpose in 1904. Mercedes had, of course, seen the light as early as

1901, with push-rod-operated inlet valves but retaining side exhaust valves, as Renault are thought to have done for their 1902 Paris-Vienna victory.

If Fiat pioneered both valves overhead, in hemispherical heads, soon to be widely copied, although Peugeot’s four valve heads necessitated pent-roof combustion chambers, who first used the hemi-head and oh camshaft? Hugh Conway has shown me an American patent taken out by the two engineers named Welsh of Pontiac, Michigan, in November 1907, for just such an arrangement, albeit possibly intended for gas-engine usage. They had oh valves at 90 deg included angle, operated from a central oh camshaft via rockers, with rollers bearing on the cams. The patent drawing shows a four-cylinder engine with the oh camshaft driven by a vertical shaft and bevel gears from the front of the crankshaft, this drive forming part of the patent specification. All of which suggests a car rather than a stationary engine.

The inventors claimed that the 45 deg inclined valves gave the minimum combustion chamber wall area to swept volume and that the oh valves as located gave a free exhaust and only a slightly heated inlet charge The reduction in valve bounce consequent upon using an oh camshaft in lieu of push-rods was not referred to, but in 1907 engine speed would have been low in normal usage, so that this advantage would have been less apparent. Was this the first ohc engine? I feel sure someone will tell me it wasn’t, and even allowing for time that probably passed between building an engine to the Welshs’ specification (if this was done) and patenting it, Pomeroy was told that Mercedes raced an ohc six-cylinder car with vertical valves in 1907, while by 1908 the fast Clement-Bayard racing cars had inclined valve ohc engines. – W.B.