VEHICLES
MATERIALS
Honda Rebel 250 rolling chassis We found a bike
with a blown engine (Figure A) for less than $500
on Craigslist, craigslist.org.
12V, 50Ah sealed lead-acid golf cart batteries ( 4)
Perm PMG- 132 electric motor
36V–72V PWM (pulse-width modulation) controller
0KΩ–5KΩ twist-grip electric throttle (potentiometer)
48V AC charger
48V–12V DC-DC down converter, or additional small
12V battery for lights, signal, and horn
½" steel angle beam, 80" long
Thick, long zip ties
¼" plate steel
#4 welding cable and lugs
Front/drive sprocket and rear/driven sprocket
The optimal number of teeth for each of these
will depend on the specs of your motor, the size
of your rear wheel, and your target top speed.
Consult a gear ratio calculator, such as makezine.
com/go/gearratio. You may need to order custom
sprockets.
El Chopper ET Builder’s Guide by John Bidwell
available from 21 Wheels, 21wheels.com
Honda Rebel 250 original factory service manual
Without this, the project would have been lost.
TOOLS
Welder
4" angle grinder with cutting and grinding wheels
Drill press
Metal band saw
Sawzall or other reciprocating saw
Wrenches and other standard auto shop tools
Heavy duty wire cutters/crimping tool
Rags and solvent for cleaning
Friends who can help
The El Chopper ET plans estimated the cost for the
whole project at $1,200.
The first version of my GomiCycle used a set of
4 big 80Ah lead-acid batteries, 2 of which were
free; I already had them lying around from an old
robot project. But they had suffered through the
heat and corrosive dust of Burning Man and were
in sad shape. We welded heavy, ultrasturdy trays
for the batteries using 2" angle steel (Figure B), and
held them down with strap steel and a padlock. Two
batteries fit in the engine compartment and 2 more
straddled the back, mounted like saddlebags.
But the batteries were a mismatched set, and
their performance proved disappointing. For the
next version, we bought new, smaller 50Ah batteries
and made trays to hold them that weighed 80%
154 Make: Volume 14
A
Fig. A: A used Honda Rebel 250 with a blown engine,
from Craigslist.
less. The smaller battery set was less powerful, but
the changes saved so much weight that the GomiCycle got roughly the same top speed and range as
before, 40mph and 15– 20 miles.
Mod the Frame
The first step in the GomiCycle conversion was to
strip the frame (Figure C). This was surprisingly fun
and fast to do with basic hand tools. Make sure you
save all the nuts, bolts, and other bits and pieces for
reassembly later. Clean the frame using rags and
solvent. Then use the Sawzall and angle grinder to
cut off the motor’s mounting points and tabs.
The original plans called for chopping and lengthening the frame to fit 4 batteries in the engine
compartment. Instead, we opted to retain the Rebel’s
original geometry. The relatively compact 50Ah batteries all fit in the compartment, arranged in 2 pairs.
We made trays for them out of ½" steel angle and
held them down with enormous zip ties.
We modified the frame’s swing arm, the forklike part that’s mounted on shocks and holds the
rear wheel. Following the original plans, we cut a
rectangular hole in the arm for the electric motor
to fit into, just in front of the rear wheel (Figure D).
Then we shaped and welded a custom bracket out
of steel plate to mount the motor (Figure E), making
sure its sprocket would align with the rear wheel
sprocket, which is critical for keeping the chain in
line and at the correct tension during travel over
rough roads.
Assemble the Power Train
The next step is to replace the motorcycle’s entire
original drivetrain — the engine, clutch, transmission,
carburetor, and exhaust system — with 4 batteries,
