|
|
Milling Machine & Lathe
While everyone knows that general machinery
is used for the everyday machining that needs to be done
while re-building an engine, many overlook an area which
I feel is of great importance, lightening. The value of
this was brought home to me many years ago during a
development project with David Vizard.
 On doing the
calculations we were shocked to discover that each
piston / rod assembly at 7000 RPM was exerting a load on
the crank of 19+ tons by re-designing these components
we came up with an engine that could rev up 9000 RPM
without reaching the 19 tons loading of the standard
components, so we had a race engine that revved higher
and produced more power than the standard engine, but
actually put less stress loading on the crankshaft. One
word of
caution! Please remember that just hacking
chunks of metal off components, while definitely
lightening them, can seriously weaken them! Great care
has to be taken when calculating exactly where to remove
metal without weakening the component. In some cases it
is actually better to scrap the original component
altogether and get a completely new, better and lighter
one made from scratch. A very good example of this is
pistons.
One last point about which there is always much
confusion, lightening a flywheel will not add one single
horsepower to an engine, however it will make it seem to
have done,
 BUT AT A COST ! Most manufacturers,
particularly these days of getting maximum M.P.G., like
to fit very heavy flywheels. Two reasons for this,
firstly they make any engine, and in particular the
smaller engines feel very, very smooth. A heavy flywheel
irons out all the “thumps” and roughness in an engine.
Secondly, a flywheel is a kinetic energy store, on the
way up to any certain RPM it will absorb energy from the
engine, once the RPM is reached and stabilised, all the
energy from the engine passes through to the driving
wheels. However back off the throttle and the engine
ceases to produce power immediately; at this point the
energy stored in the heavy spinning
 flywheel will
continue to drive the car forward, while only gradually
losing energy, and using no fuel to do it! This is great
for manufacturers M.P.G. figures.
So you need to
consider what you want from your vehicle, especially if it is your everyday road car. Lightening the flywheel
will allow the vehicle to
speed up faster and respond to
the engines power sooner, it will also mean that you can
leave braking later (great in a competition car) as the
engine now acts as a break to slow the car down faster
when you take your foot off. The down side is fuel consumption almost always drops a little and, depending
on the degree of lightening, the engine will become less
smooth and certainly harsher, not a problem in a
competition vehicle, but worth thinking about if you do
long journeys or are taking the family on
holiday.
See Also
|
