I'm going to write this bit about the crankshaft
for the newbie . . maybe that's me . . :-)
First, do you have one? . . open the engine compartment
with the engine running . . see those wheels and stuff
going round and round ? . . . keep things you're fond of
away from them . . :-)
The generator (or alternator) is that round doo-dah on the
upper end of what we refer to as the "fan-belt" . . .
at the bottom of the fan-belt loop is what we call the
"crank-pulley" . . . it is hanging off the end of crankshaft.
Ok . . looking at that lower pulley, which by the way is
where the timing marks are for tuning, you can locate the
one end of the crankshaft . .
At the opposite end of the engine . . up front, is the
flywheel/clutch setup . . the flywheel is pinned and bolted
to the far end of the crankshaft . . . if you have an
automatic tranny, that's where the torque converter is
instead of a flywheel . .
Between the crank-pulley you're looking at and the flywheel
end you're visualizing, the crankshaft runs thru the engine
directly in line with the piston jugs "up and down" and
"side to side" . . . two planes of alignment . .
When they talk about "align-boring" or "line-boring", this
is the relation-ship that's being referred to . .
Specifically, there are 4 journal bearings that hold the
crankshaft in place, thus aligning the crank itself with
the pistons . . .
Do I need one? . . . yeah . . this is where all the monkey
motion of the entire engine comes together and the engine's
power is pumped into the flywheel, et al . . .
What is a crank? A crank is defined as a device that
translates a reciprocating motion into a rotary motion.
The reverse is also true . . :-)
From the Starter's point of view, it converts the rotary
motion of the starter to a reciprocating motion at the
pistons to get the first fires lit . .
Once the engine is running, the pistons are making the power
and that is translated and communicated down thru the cranks
to the main shaft where it is transmitted to the flywheel.
There is a crank for each piston so there are four of them
on the crankshaft . . .
This crank thing . . remember your bicycle sprocket? that's
a crank also . . think of each leg as a piston. . .
Now lose the sprocket and send the drive power out thru
the shaft instead . .
In addition to the connections at the flywheel and
crank-pulley, there are 2 gears on the main crankshaft that
drive the cam-shaft gear and the distributor drive gear.
These are inside so can't be seen . .
While these two internal gears on the crankshaft do draw some
power, their main purpose in both cases is to turn some other
device that makes the valves open on time and the dizzy spark
to get there at just the right time in the combustion
chambers of the pistons. . .
That cam-shaft gear I spoke of, right in the end of it's
center is the drive-shaft for the oil pump too . .
another mouth to feed . . :-)
I should mention "Stroke". . another term you'll hear. . .
That is the length of that lever-arm on the crank times 2
for a complete revolution . . the piston is moved the full
length of the "stroke". ie. the 1600 engine has a 69 mm
stroke in stock form . . .
To "stroke" an engine means to put a longer than stock
stroked crank in . . ie. I mention a 74mm crank, you can get
them on up to what?, 82 mm or so for the type1 engine . .
There are a few stroker cranks for the type4's but the price
is pretty rare too . .
When you "stroke" an engine, you are increasing the
displacement of the engine . . [stroke X bore = disp]
I cover the generals of the "Counterweighted crank" in the
post on "cranks, flywheels , weights" etc., .
I'm going to add one more weight on this post . . 1-1/2 lbs.
That's the weight of a stock pressed-steel crank-pulley
of a type 1 engine . . I don't care for my scale tho . .
it is the 100 lb floor scale . . it's not too accurate at
the 1-1/2 lb range . .
If you want to get even more involved with crankshafts, I
mentioned a couple references in the "weights" post . .
If you want the best possible advice on how to set up and
"bed" your crank into your case go get into Hoover's "Sermons"
I will continue to tout "rebuild your air-cooled VW" by
Tom Wilson for a better understanding and any rebuild work.
well . . I think that's it . . :-)
"pushin' back the darkness" . .
west