Reply to: EXPLODING PARTS
Dale Cook writes:
... the water pump "exploded"
in a gush of fluid when they went to restart the car!....
***** This reminds me of the story of the exploding Norton alternator rotors.
See, I have this Norton Commando. It's not a car, no, but it's very very
British, believe me! The "character" of the bike derives in large proportion
from its "Vertical Twin" engine. This is a high-compression, long-stroke
affair with two pistons that rush up and down *TOGETHER* at breakneck speeds.
They turn a flexible bolted-up crankshaft with only two main bearings, one at
each end, and a flywheel in the middle. Since both the pistons are pushing and
pulling at the middle of the crankshaft, the whole thing flexes up and down,
especially when that ten-to-one compression hammer-of-Thor bashes down on one
of the pistons.
The alternator rotor bolts right up the end of that crankshaft. It is
made of a group of magnets embedded in melted carburetor stuff, and formed into
a nice round assembly. This whirls around inside a stator which is suspended
in midair on three spindly little aluminum legs. When you install your stator,
you have to measure the clearance to the rotor; if it's wrong, you bang on the
spindly little legs until it's right. I often wonder whether the little legs
will sproing back again while I'm out riding. Maybe it's better not to think
of such things. At any rate, there is about six thou of clearance between that
rotor spinning at full crank speed, and the stator. Oh, yes, the whole mess
was made by, *guess who*, LUCAS.
Now it happens, that there is a failure mode for these rotors, where the
embedded magnets start to disengage themselves from the alloy body of the
rotor. There is a force called "centrifugal force" which urges them to do so.
My physics teachers always told us that there is no such thing as "centrifugal
force", but it seems pretty real to me. Anyway, in the life of many
Commandos, there comes a day, when the magnets just let go, and the rotor
"explodes". What makes this so interesting, is the close location of the
stator. There are several possible outcomes:
* The little stator legs hold valiantly, and the rotor breaks off the end
of the crankshaft. ( $$$ )
* The stator legs AND the crankshaft hold their ground, and the engine
stops cold. This is probably the cheapest variant, but you have to walk home.
* Here's the outcome I like: The little legs holding the stator loose
out, and the stator spins at crank speed, SUCKING THE WIRE HARNESS into its
casing.
Well, I'm sorry to bore everybody with this long non-car diatribe, but its
the only good exploding-part story I know. Anybody got any more?
- Jerry
p.s. No, my rotor hasn't exploded. Yet. I'm looking forward to it, though.
:-)
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