A minor matter

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

Current page

117

Current page

118

Current page

119

Current page

120

Current page

121

Current page

122

Current page

123

Current page

124

This heading does not refer to the still-popular Morris Minor, nor will it interest those vintage-car folk who might think it is about the Calthotpe Minor. It has been sparked off by an epoch-making discourse which appeared last year in Autocar, in which Edward Eves told how the young Louis Renault and his three-year-old Renault Fils et Cie pioneered the side-valve engine and several other innovations as well. Eves showed that such an engine was used for the 1902 / 03 Model-K Renault and a minor mystery arose only because it was not clear whether such an engine had featured in the Renault light-car that won for Marcel Renault the important Paris-Vienna race of 1902 against opposition from far larger cars, or whether that racing voiturette had retained automatic or atmospherically-opened inlet valves. The matter was, in my view, very convincingly cleared-up by Kent Karslake in our issue of last February, so this outpouring is not about the Paris-Vienna Renault but about the valve arrangements on veteran cars in general. In passing, though, I would say that while this minor mystery was in the public eye, Motor Sport asked Renault’s PRO for a photograph of the engine of the P-V racing-car in their Paris Museum. The reply was that the only one available was of the complete car. Apparently no-one was prepared to take a camera and obtain a picture for us. However, no sleep was lost, as the engine of the car in the Museum is rumoured to be non-original, anyway. . . .

The first four-stroke petrol engines had to have inlet and exhaust valves and it was logical to put the latter beside the cylinder, as a side valve, as it had to be mechanically lifted from its seat on the exhaust stroke, and operate it from a cam in the engine’s base-chamber, but to use an inlet valve in the head, sucked open by the descending piston and closed against the pressure of a light valve spring. This was beautifully simple, especially with a single-cylinder engine. The disadvantage of letting nature open the inlet valve was that it did not respond until the pistol had descended some considerable distance downwards, on its inlet-stroke, because before this there was insufficient “vacuum” to overcome the action of the valve spring. Nor could the inlet valve be kept open after b.d.c., for as the piston rose on its compression-stroke there was no suction to pull the valve down. For this reason, and to get as large an inlet valve area as possible to combat its timing deficiencies, automatic inlets were located in the head, above the piston. Had they been placed at the side of the cylinder, they would have had to be sucked open against not only valve-spring pressure, but their own weight, and I doubt if it would have worked, but if anyone knows of such an engine I stand corrected. . . .

When greater efficiency was called for and valve timing and overlap began to be understood, inlet valves were also mechanically operated. and it seemed logical to put it or them at the opposite side of the cylinder(s) to the exhaust valves — the T-head arrangement — with a separate cam or camshaft to prod them, Mercedes probably being the first to do this, in 1901. At the expense of a wide cylinder block this enabled cross-flow of induction and exhaust to be achieved, and it enabled large valves to be used. The T-head engine survived up to WWI, a notable example being the sporting Alfonso Hispano Suiza.

When Mr. Eves, in the aforesaid article, wrote that “Louis Renault had the distinction of putting into production the World’s first side-valve engine”, what he really meant was the first side-by-side valve, L-head, engine. It was logical to line up all the valves, inlet and exhaust, of a four-cylinder engine along one side of the crankcase and actuate them from a common camshaft, an idea, Eves says, brought to Renault Fils et Cie by M. Viet, De Dion Bouton’s designer, whose ingenious layout apparently found no favour with his then-masters. Overhead valves, whether opened by push-rods and rockers on an overhead camshaft, or camshafts, were in the future. So, for the moment at all events, I can spare you such minor matters as the different reasons why later engines sometimes had four overhead valves per cylinder, which should be larger, the inlet or the exhaust valve (remembering that, for instance, Mercedes used one inlet and two exhaust valves per cylinder for their 37/90 hp. engine, whereas Ettore Bugatti opted for two inlets and a single exhaust valve per cylinder on most of his cars), or which production car had four side-valves per “pot”. — W.B.