"
Q. What is it for?
A. It helps to overcome the "inertia" and momentum of the
reciprocating parts of the engine, and enables the engine to
pass the center without a jar.
Q. How would you increase the cushion in an engine?
A. By increasing the lead.
Q. What is lead?
A. It is the amount of opening the port shows on steam end
of cylinder when the engine is on dead center.
Q. Is there any rule for giving an engine the proper lead?
A. No.
Q. Why not?
A. Owing to their variation in construction, speed, etc.
Q. What would you consider the proper amount of lead,
generally.
A. From I/32 to I/I6.
Q. What is "lap?"
A. It is the distance the valve overlaps the steam ports when
in mid position.
Q. What is lap for?
A. In order that the steam may be worked expansively.
Q. When does expansion occur in a cylinder?
A. During the time between which the port closes and the
point at which the exhaust opens.
Q. What would be the effect on an engine if the exhaust
opened too soon?
A. It would greatly lessen the power of the engine.
Pages:
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143