From: tomb@drutx.ATT.COM (BarberTB)
Newsgroups: rec.motorcycles
Subject: Spagthorpe Pug, the original minimalist motorcycle
Keywords: Spagthorpe, Chuck, torque
Date: 14 Aug 92 15:40:10 GMT
Distribution: rec
Organization: AT&T, Denver, CO


Pug - The original Spagthorpe

With all the recent talk about the various Spagthorpe models, I
am surprised that no one has mentioned the original Spagthorpe,
the Pug.  It is a relatively little-known motorcycle, so perhaps
it should not be surprising that no one else has heard of it. 
It is, to be sure, one of the most fascinating episodes in the
history of motorcycling, both because of the remarkable design
of the machine itself, and of the incredible sequence of events
that took place that one fateful Sunday afternoon.



To truly understand the Pug, it is first necessary to understand
the men that built her.  One must understand that in those days,
minimalism wasn't simply the right thing to do -- it wasn't even
a word.  Nonetheless, it was a philosophy that the designers
understood all too well, particularly the chief designer, Hairy
Rasterhead.  Minimalism was, for Hairy, an obsession.  So much
so, in fact, that he could see no point in having different
names for his two main assistants, and so hired two very capable
engineers, both named Chuck.  Although on some occasions, such
as when going into town on Saturday nights, he was heard to
introduce himself and his assistants thus: "Hi, I'm Hairy.  This
is my helper, Chuck, and this is my other helper, Chuck.", he
generally just referred to the pair collectively as "Chuck". 
But I digress.



Although there are no known remaining photographs of the Pug, if
indeed any were ever any taken, much about its design has since
been pieced together from several first hand descriptions that
were written at the time.  The engine was apparently taken from
one of the early airplane engines, both having been built
sometime in the 1890's (the exact year is not known).  The most
unique aspect of these engines was that, rather than the
cylinders being fixed to the frame, and the crank free to
rotate, the crank was attached to the frame, with the cylinders
free to rotate about the crank.  The beauty of this system, as
it was applied to the Pug, is the way in which it facilitated
the most singularly simple drive mechanism that has ever been
conceived, before or since.  The crank was attached to the frame
at the location where today the rear axle is found, at the end
of the rear fork, except there was no swing arm as such, it
being a rigid mount.  (The frame itself was, however,
handcrafted of seasoned hickory, which offered some measure of
absorption of bumps.)



The two halves of the fork were set fairly wide apart, as was
necessary since the cylinders rotated in the space between them,
just as the rear wheel does in a modern motorcycle.  The crank
had a single "throw", to which two pistons were connected via a
pair of very unique and ingenious connecting rods.  It has been
reported that the rods were, curiously, manufactured from
military-spec eating utensils, with one forked and straddling
the other, permitting the two pistons to orbit in the same
plane, centered in the space between the rear forks.  This
arrangement has variously been referred to as the "one forked
and straddling the other, permitting the pistons to orbit in the
same plane" arrangement, or the "missionary" arrangement, or,
more simply, the "humping-couple" arrangement.  But I digress.



The two cylinders were opposed (180 degree offset) to one
another, and connected to each other via a rigid cast-iron
block, which rotated on two bearings on the crank, located at 
either side of the crank throw, and each just inside the fork.
As the pressure in the combustion chamber increased, the pressure
against the head caused the cylinders to rotate as they pushed
away from the pistons, which rotated along with the cylinders,
but pulled away from the heads in doing so since the center of
their circle of rotation, the crank throw, was offset from the
center of rotation of the cylinders, the crank itself.  On one
side of the cylinders a single magneto winding was attached, the
pulse being generated by a permanent magnet attached to the
crank.  On the other side of the cylinders a small cam shaft was
connected to the crank via some gearing arrangement that caused
the cam to turn at precisely half the rate of the cylinders.  It
is not known exactly how this was done, but it is believed that
this was the only toothed gear arrangement to be found anywhere
on the machine.  A pair of exposed rods for each cylinder were
driven by this cam; these rods actuated the valves via a set of
rocker arms, also exposed.  It is not known how the fuel tanks
were connected.  There may have been a single tank attached to
the cylinders, but since this problem was also solved in the
airplane application, it can be assumed that it was solved here
in a similar fashion.



The wheel consisted of a forged iron ring bolted to the ends of
the cylinders, with two additional supports running from the
ring to the block, each centered between the two cylinders where
they connected to the inner surface of the ring.  A solid layer
of hard rubber was then riveted to the metal ring.  Here, then,
was the beauty and the elegance of the Pug design: neither chain
drive nor shaft drive, but *direct* drive.  Simplicity defined,
pure and, well, simple.  There was no shaft effect, and no chain
to rattle around, stretch, and generally make a nuisance of
itself.  Neither before nor since has there been another design
so elegant and so, well, simple.



The diameter of the wheel was about half a meter; the
circumference about 1.6 meter.  At about 400 rpm, the machine
reached its top speed of about 640 meters/minute, or 24 mph. 
Due to the large moment of inertia of the rotating part of the
engine, it idled at 200 rpm.  To start the bike, one simply ran
along side until the speed reached about 12 mph, at which it
point it would start and you simply jumped on.  It was, to be
sure, the very of essence of simplicity.



Sadly, though, this was a machine well ahead of its time, and
did suffer from several minor technical difficulties.  First of
all, there was the difficulty climbing hills.  The engine itself
was actually capable of more power than could be used (on level
ground).  The work required increased more rapidly with velocity
and rpm than did the power generated, so that above 400 rpm, the
incremental power required was greater than the incremental
power generated.  It was consequently unable to climb hills with
slope greater than about 5 degrees, requiring the rider to
frequently dismount, run along with the bike for so long as it
would continue under its own power, and eventually push the bike
when it died as the slope became too steep.  More serious than
this drawback, though, was the torque reaction problem.  The
moment of inertia of the bike, about the crank, was very small,
due to the fact that most of the mass of the bike was contained
in the rear wheel.  Even the feeble amount of torque generated
was enough to cause the front end of the bike to come off the
ground during modest acceleration.  It was generally necessary
to build the speed up very slowly, taking it from 12 mph to 24
mph over a period of several minutes.  Even without the weight
transfer of acceleration, the reaction to the engine torque
alone was sufficient to cause the weight on the front wheel to
be too small to generate sufficient steering force and stability.



The person who discovered the solution to this problem was,
remarkably enough, the test rider, Scratchin' Itches-Fetching
Ping Pong Balls (who was referred to by Hairy as simply
"Scratch").  Scratch took one look at the situation and
proclaimed, "If you turn that there wheel around the other way,
the torque reaction will reverse, transferring the weight to the
front wheel.  Turn that there wheel around the other way."  The
only problem with this was, of course, that the machine would
now run backwards, with the steered wheel following the power
wheel.  This required the rider to turn around and face the
other direction, and steer the bike by reaching around his back.
This was a lot like steering a small boat with an outboard
motor; you had to move the steering arm in the direction
opposite to the direction that you wanted it to go, thus the
term "counter-steering" was born, although it is still generally
misunderstood even to this day.



The steering problem was partly solved by extending the
handlebars further, so that they came up along either side of
the rider.  This limited the extent of the steering rotation,
though, but Scratch, being the resourceful dude that he was,
soon learned to increase the extent of the steering rotation by
leaning off to one side of the bike, a technique that he
referred to as "hanging off", and that is still practiced to
this very day by many of his modern disciples.  The
reversed-direction solution worked fairly well, with only a
minimal amount of traction loss at the power wheel, which was
referred to as "torque steer".  The only remaining significant
problem was that the trail of the steering wheel was now in the
wrong direction.  This was solved by merely using a
near-vertical rake angle and a large amount of negative-positive
(positive-negative?) offset in the front (make that rear)
triple clamps.



And thus was the Spagthorpe Pug born.  A truly remarkable
motorcycle, to be sure.  Test runs went pretty well for the
first few weeks, consisting primarily of low-speed runs back
and forth to determine the handling characteristics.  Scratch,
however, grew increasingly impatient to attempt to set a new
land speed record.  Hairy and Chuck did some calculations and
were convinced that the engine would actually generate greater
power if only there were some way to get the rpm up higher. 



Exactly what happened next is not clear.  The few surviving
accounts of what happened that fateful Sunday afternoon disagree
to various degrees, but it seems that what happened went
something as follows.  Once again, it was Scratch who had the
breakthrough idea.  He realized that if the bike was ridden down
hill, the force of gravity would add to the acceleration
generated by the bike, causing it to go faster, which would
increase the rpm, and permit the engine to come into its power
band.  So they pushed it to the top of a dirt road that wound up
the side of a mountain.  And then they started to push it down,
and Scratch jumped on, and Hairy and Chuck stood and watched in
amazement at what happened next.  The bike took off like nothing
they had ever seen before, accelerating even harder with every
incremental increase in speed.  Faster and faster, reaching 30,
40, 50 mph and beyond, still accelerating.  60, 70, 80 even 90
mph, now shaking violently.  The acceleration began slowing,
though, and gradually it hit 95 mph, and then slowly 100, 101,
and 102 mph.  Chuck realized that Scratch was rapidly
approaching Dead Man's Curve, and they yelled at the top of
their lungs, while Hairy simply stood and watched in amazement,
completely dumbfounded.  Scratch reached 103 mph, and then,
barely, 104.



Exactly why Scratch didn't make the curve isn't clear.  Some
speculate that the excessive inertia in the wheel made it
impossible for the lean angle to be increased sufficiently fast.
Regardless, Scratch did miss the curve, and at the same instant
he went flying over the edge of the cliff, the Pug hit, yes, 105
mph, *ludicrous speed*.  Nobody had ever reached ludicrous speed
before, much less stopped from ludicrous speed.  The wheel and
crankshaft broke away from the bike frame, which went with
Scratch over the cliff.



The wheel and crank landed, amazingly enough, back in the road
further down the side of the mountain.  Without the inertia and
weight of the frame and rider to resist rotation of the crank,
something totally unexpected happened.  The rotation of the
wheel slowed down, and the crank began rotating furiously. 
Hairy, Chuck, and Chuck had run as fast as they could down the
road, and when they caught up with the wheel, they found it
wedged between two large rocks, stationary, with the crankshaft
rotating furiously inside.  Hairy took one look at it and
proclaimed, "Eureka!  I have discovered the answer!  The
cylinders can be attached to the frame, allowing the crank to
rotate, and the rotational motion of the crank then transmitted
to the wheel by ... something!"



As for Scratch, the last words that he was heard to utter as he
went flying over the cliff were largely incomprehensible; the
only word that Hairy and Chuck could recognize was "champion",
but they never figured out exactly what it meant.  He was never
seen again, and no body was ever found.  Curiously, his jacket
was found, even more curiously, with not a single scratch on it.
Many speculated that since no one had ever stopped from
ludicrous speed before, that it might be physically impossible
to stop.  In retrospect, this logic seems questionable, since in
fact no one had ever even reached ludicrous speed before.



Hairy spent the last years of his life trying to perfect his new
invention, "shaft drive", as he called it.  He was largely
confounded by the same basic problems of the direct drive
system.  His oldest son Chian, however, after watching his
father lift his prototype frames countless times with a rope and
pulley, hit upon the idea of a flexible drive mechanism, where
the rope would be made from metal plates linked together with 
pivoting pins running across to the opposite plate.  Although
the proper spelling somehow got lost over the years, there can
be no doubt as to the origin of our modern "chain" drive.



As every story must have a moral, so must this one, although you
would never have guessed it.  Since there is no way that you
could possibly have deduced it, I am obligated to spell it out:
in the end, what really matters is not *what* you ride; it's the
ride itself.



Cheers,

Tom