RA> The leaf springs above each journal are linked at the ends
RA> to the next one over, so that all work together equalizing
RA> the weight from one axle to the next, and the next...
RA> The suspension on a steamer is much more complicated than
RA> the drive rod system! Note also that the rotating mass of
RA> all the drive rods, and half (exactly) of the main rods,
RA> can be counter-ballanced in the wheels.
GP> This remaining "half" becomes a major problem, it could be as
GP> much as 1 tonne moving up and down at 4 times per second on
GP> one axle, which is a force to be reckoned with! If the driven
GP> axle is equalized with its neighbours, the "hammer blow force"
GP> is spread over all the equalized springs, not just the single
GP> driven axle spring. So a result of equalization is that the
GP> loco is less able to cope with with the unbalanced forces
GP> than a non-equalized loco.
Actually, no. The main rod's mass may be resolved into two: One
mounted at the crankpin, moving in a circle; and the other at
the crosshead joint, moving _horizontaly_. The crankpin mass may
be counterballanced in the wheels, as any other rotating mass.
It's the horizontal component that can't be ballanced, which
provides torque around a vertical axis. Since the horizontal
component is at right angles to the equalization, there is no
interference. The mass of the other side rods can be completely
counterballanced, as their centers of mass describe a circle
(not an elipse as the main rods' do). Notice that the counter-
weights on the main drivers are larger than those of the others?
That's why.
RA> [fully] sprung and equalized. The equalizing system adjusts
RA> the spring tensions so that all axles receive their share of
RA> the burden. Note that lead and trailing truck axles are
RA> typicaly included, but at a lesser rated burden.
GP> (If all axles are equalized, the loco will flop forward or
GP> backwards to the limit of axle travel. Its been built! ;-)
You are quite right. You have caught me in an oversimplification.
Depending on the design of a particular locomotive, axles are
grouped into sections which are not equalized with each other.
Consider the common 8- or 10-wheeled locomotive: a 4-4-0 or a
4-6-0. The lead truck will be equalized within itself, and the
drive axles among themselves. The locomotive would then be
supported at three points: the pivot of the lead truck, and the
centers of support of the left and right sides. The torque
resulting from (forward) tractive effort will shift some of the
locomotive's weight from the lead truck, onto the drivers.
The drivers may share this added burden equally.
I think I may elaborate on this in another message; look for
"Steam Loco Design", or some such topic, to "All".
Reggie Arford
___
 X SLMR 2.1a X Gesundheit diem - sneeze the day!
--- Maximus 3.01
---------------