This Scooter

MECHANICS
and
HANDICRAFT
If you can fix a bike, you can build a
put-put that's almost as convenient as
a second car and costs far less to run.

By Howard G. McEntee
OU simply get on this homemade scooter
Y
and go. There's no clutch, no gearshift.
Open the throttle and you're off. Tackling a
grade? It shifts down automatically. When
the going is easy, it shifts up again.
Hard to build? No. Though it looks like

These are the main parts, but you'll need such

extras as bolts and nuts, 1/2" and 3/8" pipe, lock

washers, sheet metal for fenders, wheel dust

seals, and brake and idler springs.

something off a sweet-running assembly line,

it isn't a tough job. If you can take a bike
apart and get it together again, you can
handle this, too.
Scooters are taking thousands to work,
school, play, and the corner drugstore for
just pennies a day. And no wonder. These
little puddle jumpers are a cinch to handle.
They park on a grease spot, and can be
licensed at bargain rates. This one's a bargain in other ways, too.
What's it got? A lot, in view of today's
high prices. Here's what your $75 buys:
An easy-starting, lightweight two-cycle engine, an automatic clutch with variable drive
ratio, an efficient brake, pneumatic tires,
chain drive, lights, and a spring-mounted
foam-rubber seat.
The engine is the most expensive item,
but fortunately there are reliable two-cycle
engines available for $25 or less.* If you
have a suitable engine or can rebuild a used
one (see PS, June '51 p. 187), this figure
can drop to the vanishing point.
What'll it do? You won't beat even a
Model A from the light in this little job.
But the take-off is smooth, and you'll get
where you're going at something like 20
miles an hour. Although it would bust before making Pikes Peak, it will take you up
easy grades and can be walked up stiff ones

under its own power. The brake is effective,

starting is a cinch, and roadability is good.
The machine is light enough to carry if
necessary, and one man can put it into an
auto luggage compartment.
Welding does it. The cost includes $6
for welding the frame, and it's money well
spent. Although you could bolt or rivet the
frame together, you'd have to overlap members or provide gussets at all joints. But
welding service is available everywhere,
and a welded frame is much easier to make,
neater looking, and stronger.
You'll find most welders cooperative, especially if you cut and fit frame members
correctly and clamp them in proper alignment. Electric welding is preferable. It's
less likely to warp the stock.
Cutting the frame. Two 45" lengths of
angle iron must be cut, bent, and welded at
two points. For the 30 upward bend, cut
through one flange of each piece 12 1/2"
from an end. Watch yourself, for these
members are not identical; you need a right
and a left. Bend the uncut flange, spreading open the cut. Then have 1/8" reinforcing
plates welded across the breaks.
The second bends are in the other
flanges, and require narrow notches. These
are closed up by bending, and need no
reinforcing, just careful welding. The front
of the frame is filed to fit around the head.
Try to make the two parts a reasonably close

POPULAR SCIENCE

Measuring 12 1/2i" from ends of main

frame members, cut through one flange,
and bend the other up about 30. Be sure
to make one right, one left. Cut 1/8"-thick
braces to be welded across the breaks.
Weld across them inside the angle also.
First bend (at right) has been welded
in both members and a 3/8"-wide V notch
cut 2" above it. Second bend closes these
notches, ready for welding. Clamps hold
a crosspiece in place. Head (in hand)
will be welded to rounded frame ends.

match, but don't fret about it, for welding will close up small gaps.
Assembling the frame. The fork turns
in ball bearings like those in the wheels, but
made for a 3/8" axle. The 1" pipe for the
head can be bored out in a lathe to fit the
bearings, or filed by hand, since the outer
race does not turn. Cut the angle brace.
Then wire it and the head in place for
welding, or drill the frame members for a
clamping bolt and have the holes welded

up later. Make sure the head is vertical

to the frame, as viewed from the front, or
your wheel will be askew.
Note that, except for the axle slots, no
holes are made in the vertical flanges of the
long frame members. All other holes go in
the top flanges, which don't carry much of
the load.
The scooter shown was assembled mostly
with square-shoulder carriage bolts, for
which you must file the hole square. This

Diagonal frame brace is welded between the head

and first crosspiece. This and center one are angle

stock, the rear one flat iron. Round off corners that
touch fillets inside frame sides, for a close fit. Bore
ends of head for bearings, and drill fork crosspieces
for kingbolt, before welding.

Makings of a wheel hub. Ball bearings are in

place in the shells. Center spacer must clamp
between inner races without binding the bearings. A lathe is ideal for facing spacers squarely
to length. Felt seals prolong bearing life. Bolts
and nuts clamp hub together.

Industrial type sprocket used here was bored

out to clear the axle spacer. Sprocket is set off
by four spacers 1 9/16" long, cut from 3/8" pipe.
Spacer ends against sprocket are square, but
inner ends are filed to contour of hub shells.
The holes in the shells must be opened out to
clear 1/4"-20 bolts.

Front engine mounts rest directly over the

center frame crosspiece. The rear ones sit on
the bearing hangers, and therefore are 1/8"
shorter. All mounts are cut from 1/2" pipe. Iron
straps across them provide an inboard support
for the engine base, in which the mounting
holes are 3 1/4" apart.

takes only a few seconds and saves time

in assembly, because it isn't necessary to
fumble underneath with wrenches to hold
a bolt while cinching up the nut.
Lock washers under all nuts are, of
course, a must if you want the scooter to
be roadworthy. Don't under any circumstances omit them.
Wheels. These are 10" by 2.75" tubeless
pneumatics, inflatable through a valve.
Valveless (semi-pneumatic or zero pressure)
tires give a harder ride. Be sure to get the
heavy-duty grade, since light-service tires
of both types aren't recommended for much
more than wheelbarrow speeds. ,
At least the rear wheel must be the lugbase type, having molded protuberances on
the tire that fit indentations in the hub.
Make certain you have this kind, or you may
find the hub going around while tire, scooter,
and rider stay put.
To prevent the bearings from turning directly on the axle, the inner races must be
clamped against a center spacer. This and
outside spacers can be cut from ordinary
1/2" pipe drilled out a bit. Each center
spacer must be carefully fitted. If too long, it
won't allow the hub to be assembled; if too
short, it will bind the bearings. Each wheel
must turn freely when clamped with axle
nuts with the center spacer in. Start with
this spacer a trifle long, and shorten it a
little at a time.
The front axle is simply a 1/2" hex bolt
5 1/2" long. If you can't get one 8" long
for the rear axle, use a square-head
machine bolt or a 1/2" shaft threaded at
both ends.
Chain drive. The roller chain shown is
No. 41, 1/2" pitch and 1/4" wide. This is
stronger than necessary. Similar chain 1/8"
wide is stocked by bicycle stores and will
serve as well.
The sprockets should give a ratio of
about 2 1/2 to 1. The large (32-tooth)
sprocket is fastened to the rear hub with
1/4"-20 bolts on spacers cut from 3/8"
pipe. Mount the wheel and spin it to help
you true up the sprocket.
Countershaft. Bearings are the selfaligning type, which make assembly easier
than rigid bearings. The 1/2" countershaft
must be at 90 to the frame, with the rear
axle parallel to it, for quiet chain operation.
The small sprocket (13-tooth) must be
pinned to the shaft. Setscrews will not hold.
Drill a hole through hub and shaft, ream
with a No. 3 taper reamer, and drive in a
taper pin.

A crossbar of 1/2" shafting is filed flat where it

crosses the frame, and bolted on. Brake lever
is welded of 1/2" pipe and 1" strap as at
left. It pivots on the crossbar. So does the
idler bracket on the drive side and the kick
stand on the other. Pointed end of brake lever
strikes frame crosspiece as a stop. Brake
band is looped over, riveted, and notched to
form clevis as at right. Clevis pin is
unthreaded portion of a bolt. Lower end of
brake band is bolted to frame crosspiece.
Engine will rest directly on straps, not on nuts
shown.

A shaft collar goes between this sprocket

and the nearer bearing. The brake drum
takes the side thrust at the other bearing.
Leave just a little end play.
Brake. Use a 3 1/2" steel or cast-iron flat
pulley for the drum if possiblea die-cast
one will wear rapidly. The scooter shown
has an iron V pulley with the sharp ridge
turned off the flanges. Pin the drum fast, or
use two setscrews tightened against flat
spots on the shaft.
The brake band is a flexible strip of 1/16"
by 3/4" steel. Bend the band around the drum
before riveting on some 1/8"-thick woven
brake lining. Bolt the lower end of the band
to the frame crosspiece and form the other
into a clevis as shown.
Extra holes in the brake lever allow for
adjustment, and a spring normally holds the
band off the drum. Braking action tends to
wrap the band around the drum, which
makes the brake very responsive.
Engine. For the engine shown, cut four
mounts from 1/2" pipe and two straps of
1/8" by 1" stock. These give an inboard
support for the engine base, which is
narrower than the frame.
The engine comes with a governor, which
should be removed. An auto choke cable
72" long is connected to the throttle. Attach a spring to hold the throttle closed
unless the button on the handlebars is
pushed.
The muffler on this engine interferes with

the drive pulley. Take it off, separate the

two aluminum castings, and, using the
mounting holes and port in one as a template, mark new ones on the other. Drill
and file them out. Plug unneeded holes with
bolts and gasket cement, leaving the original
cylinder port as the exhaust.
Before mounting the engine, put lock
washers under the three screws that hold
the crankcase to its base. Tighten the
screws hard. You don't want them to loosen
under vibration, for they are difficult to
reach with the engine in place.
Belt drive. It's the centrifugally controlled pulley, acting as both clutch and
variable-ratio drive, that makes the 1-hp.
engine perform as well as it does. Some
pulleys of this type will serve as a clutch,
but offer little or no ratio change. The one
I used, a V-Plex clutch model 18T9*, shifts
from a drive-belt diameter of 3/4." at rest to
one of 2 1/4" at high speed.
The keyway on the engine crankshaft
may not be long enough to let the pulley
slide close in. To remedy this, grind out
one of the two keys cast into the bore of
the pulley.
An idler keeps the belt taut. Adjust the
pull of the idler spring so that it holds the
belt taut over the entire shift range, yet
leaves the belt loose when the engine is
idling.

[Continued on next page]

Ends of frame head receive ball bearings like

those in the wheels, but with 3/8" hole. Here
the lower bearing is on the king bolt over lower
fork crosspiece. Spacer held in the hand goes
between the bearings inside the head. Short
spacer raises nut above top crosspiece for access. Be sure to use lock washer.

Motor pulley changes flange spacing as engine

revs up, changing ratio and also acting as a
clutch. Idler takes up belt slack. It consists
of two ball bearings bolted to straps that pivot
on the crossbar. Muffler has been reversed to
clear drive pulley. Its cylinder-mounting boss
is now the exhaust opening.

The best over-all drive ratio will depend

on the kind of roads you travel. In flat
country, with 13- and 32-tooth sprockets, a
4" pulley on the countershaft may suffice.
In hilly territory, a 5" pulley may be necessary, or you may want a smaller drive
sprocket.
Fork assembly. Like the wheel bearings, those in the head should be clamped
against a center spacer. Remember to insert

felt washers and dust caps to keep grease

in and dirt out. If you can't buy them, you
can improvise them from felt rings and
1/2" washers, with a smaller washer inside
the felt ring, as shown in the photos.
The trimmings. In fitting the seat support, make certain it clears the carburetor,
gas tank, and muffler by at least 1/4" all
around. Cut the floor boards from 3/8" or 3/8"
plywood, and attach them with 1/4" carriage
bolts.
Some states require a tail light, head
lamp, and horn before the scooter can be
licensed. Battery lights sold for bicycles will
serve, but if you want to use a magnetotype (battery-less) lighting outfit that is
powered from a wheel, better check its
legality in your state.
Trial run. Follow instructions on the
engine name plate for mixing oil with gasoline. Always close the fuel petcock and if
possible run the carburetor dry (which takes
several minutes) when leaving the scooter
overnight. Otherwise the carburetor jets
are likely to clog with oil, making starting
difficult.
Be sure to carry your starting rope at all
times. A scooter with a centrifugal clutch
can't be started by pushing, although in an

Seat frames are fastened with 1/4" bolts. Make

certain the brace in rear frame clears the carburetor amply. Kick stand goes on this end of
crossbar. Valve springs, turned over a pair of
nuts on each rear frame bolt, rest in shallow
holes in plywood seat. The seat must hinge to
give access to gas tank.

|34 POPULAR SCIENCE

emergency you can probably start the engine with a handkerchief, knotted at one
end and twisted into a short starting rope.
If the scooter tries to get away from you at
low engine speeds, lower the idling speed.
Also,check the belt idler tension. Fit a stop
to the idler bracket if necessary. On the other
hand, failure to "take hold" may be due to
too large a belt or insufficient idler tension.

Remember that most belts will stretch after

short use, so it's well to start with a slightly
tight one.
Up- and down-shifting will be governed
in part by the tension of the idler spring,
so you may want to experiment with this.
Get your license, practice on some lonely
road until you get the feel of the thing, and
you're set for happy scootering.
END

A quick yank starts the engine. Run carburetor dry when you slop, or jets may clog with oil.