Subject: Re: Sparky, the Electric Chair PICTURES
Date: 1996-11-05 13:28
(More tales of "Sparky, the Electric Chair", an electric quadricycle built
by the 7th-8th grade students at Barton Open School in Minneapolis MN.
The new school year began with about half of the students from last year
(now 8th graders) and a new crop of budding EV (Electric Vehicle)
enthusiasts (and boy, is "enthusiastic" the right word!).
The steering definitely needed work; this was established after losing
battles with a few immovable objects. The students decided to completely
rebuild it. They set goals, brainstormed a list of about 7 ideas, then
evaluated their ideas against the goals. Winner was a steering wheel with
rack-and-pinion setup (they are strongly attracted to anything that makes
it more car-like).
But finding the rack was a problem. They fell back to a cogged belt and
pulleys, then bicycle chain. The end result has the old crank sprockets
mounted in place of the handlebars, a third sprocket bolted to an old car
steering wheel, and a chain around the 3. Two flat aluminum bars are bolted
to the upper and lower frame tubes near the front fork bearings. A short
piece of threaded rod connects them in the center, and is the axle for the
steering wheel. An idler pulley to take up the slack is also bolted to
The result is magnificent! Steering is smooth and tight, with no shimmy or
alignment drift. Only problem was, the lower half of the steering
wheel got in the way of their legs -- so they cut it off (the wheel, not
Another group has started an electric bike, with the goal of making it
lighter and faster (since they can pedal as well as motor). No sooner did
they get the motor mounted than the Sparky team managed to shear off a
motor on a door frame. They promptly cannibalized the E-bike for parts,
leading to some interesting debates.
Next effort was to improve accelleration and hill climbing. The 2 motors
had 3" dia. wheels (actually cogged belt pulleys) that rub on the back
tires. A student's grandfather turned them down to 2.5". This markedly
improved accelleration and hill climbing, with maybe a 1 mph loss in top
On October 18th teacher John Klein, 3 students, and I presented Sparky at
the Minnesota Science Teacher's Association annual meeting. Teachers were
very impressed with the student's excitement, the fact that they had
actually built it all themselves, and the extremely low cost of the
project. Our goal was to challenge some of the other area schools to give
it a try (and see if they can beat us!).
Back at school, one of our batteries (which were free warranty returns to
begin with) was getting pretty weak. The deep-cycle marine battery still
has half of its original capacity; the other was a standard car battery,
which is shot. The students called battery dealers around the area, and
Trojan Battery Co. was kind enough to donate 3 new size 22 deep cycle
batteries. Two of them keep us under the 60 lbs weight limit for
Electrathon, and three... well, let's just say I know where the skid marks
are coming from in the hall that the custodians are complaining about :-)
The students in the class would like to extend an invitation to any school
in the area to follow in our footsteps. We'd be happy to come out to your
school to demonstrate "Sparky", show you how we did it, and how your
students can do the same.
C'mon -- we challenge you to do *better*!