Sent:     Friday, June 12, 1998
Subject:  [B*E*S*T]  E-Car Race 1998 Part 1 -- The Cars

For the past few years, a group of dedicated teachers and volunteer engineers
have been helping Minneapolis MN area 4th-6th graders get "up close and
personal" experience in the real world of science and engineering. But they
just think they're having fun building and racing their own cars!

We call ourselves BEST (Bridging Engineers, Scientists, and Teachers). The
grass-root program is frugally fueled by a $2000 grant from the Honeywell
Foundation, and a $500 grant from Cyberoptics Corp. This provided about $100
per team to buy parts, and race day expenses. Everything else is powered by
volunteers, donations, recycled materials, and the energy of the kids
themselves.

We had eight classes in seven schools participating this year. Each class has
a volunteer engineer "mentor", who visits the classroom about once a week to
advise and teach. But not help build; the cars are to be entirely student
designed and built -- no "daddy cars"!

The idea is not to build competitive cars, but to teach the students about
working with tools, the benefits of teamwork, and give them practical,
immediate applications for math and science. Kids learn far, far better when
they have a *reason* to learn!

Here's how it worked:

Last fall, we held an organizational meeting at my home. The teachers and
volunteers came over, and we ran them through the program exactly as the
students will. I lectured on design issues. They designed cars on paper. Built
models with Erector set parts, Legos, etc. Tested the models by rolling them
down a ramp to decide on the best design (which one rolled the farthest and
straightest). We didn't have time to motorize the models, but went straight to
scaling it up into a full sized working car.

Each person was told to bring some useful piece of "junk"; scrap lumber,
old bicycles, lawn furniture, etc. Ones that didn't were sent out to forage.
:-) Their car was a plywood box, lawn chair seat, two pieces of angle iron
along the bottom with a bicycle wheel bolted onto each at one end, and a
bicycle front fork and handlebars attached to the front by pinching it between
scraps of 2x4's. A surplus DC motor was attached to one end of a long board,
whose other end attached by a pivot bolt at the front of the car. A friction
wheel on the motor shaft drove one back wheel. A 12v battery, some house wire
and an on/off light switch completed the electrics. In just 10 hours, a dozen
rank amateurs turned into 10-year-olds and produced a working car from
scratch!

In the classrooms:

Our graduate teachers and mentors then went into the classrooms to repeat the
process. Last fall, the students designed their cars, built models, and
motorized the best of them with two AA batteries and toy motors.

The great thing about this process is that it lit the spark of creativity.
At first, the students thought in terms of purchased kits or toys; model car
wheels, Lego bodies, etc. Adapting these to another purpose is difficult.
There was a lot of frustration ("I can't do it, this is too hard"...). But
they soon graduated to "How about... What if... Let's just..." as they
discovered that "found" materials were more versatile and worked better.
The better designs used Coke cans or Pringle Potato chip covers as wheels,
cardboard boxes and popsicle stick bodies, rubber band drive belts, etc.

In spring, they started on the real vehicles. Each team was provided with
a surplus PM motor (rated 12v 15amp; $10 each from Amble's Surplus in
Minneapolis), a 30amp circuit breaker, a SPDT and DPDT knife switch (donated
by Bill Alexander of Humbolt State University), and a used 12v wheelchair
battery (donated by Bruce Rosenburg at Battery City in Minneapolis). The
battery was a Deka Dominator (Sonnenshien) sealed gelcell, 45 amp-hrs new, but
tested to deliver 30-40 amp-hrs.

The vehicles had to use the supplied battery and circuit breaker as the sole
source of power, but otherwise anything goes. This way, it didn't matter what
(or how many) motors or controllers they used; everyone had a fixed amount of
power and energy to work with.

The students built the cars in the classroom in most cases. They scrounged
most of the materials, and did the work either after lessons, or after school,
during recess, etc. The teachers and mentors provided most of the tools, and
some parts that the students couldn't locate.

Teachers reported that the effect of the car on the class was amazing. Morale
skyrocketed. Assignments got done on time. Subjects that could be connected to
the car got their rapt attention. Students with learning disabilities found
new areas where they could excel.

And now for the cars:

Dowling Elementary School

I mentored teacher Joe Rossow's 5th grade and 6th grade classes at James
Dowling Elementary School in Minneapolis, so I know the most about the process
there.

The 5th graders were extremely energetic and ambitious. They couldn't decide
on the best design, and so decided to build *three* vehicles; a 3-wheeler
(tricycle), a 4-wheeler (car), and a 5-wheeler! The latter was very
interesting. They noticed that an ordinary ball rolled farther and straighter
than any of their model cars, and decided that a unicycle was the best
design. But none of them could ride a unicycle. So they'd build a unicycle
with 4 training wheels; front, left, right, and rear!

The 3-wheel team progressed quickly. They built a triangular frame out of
2x4's and skinned it with 1/4" hardboard. The rear 2x4 served as the rear
axle. Big lag screws thru 20" bicycle wheels with the bearings removed. Front
fork from a 16" bicycle. The 16" bicycle's rear wheel was mounted in front,
with a chain drive to the motor.

Now, I have to tell you how I work. I will answer the students' questions, but
won't tell them what will work in advance. They need to use the scientific
method. Ask questions, gather data, make a hypothesis, and test it themselves.
They learn by doing, not by lecturing or copying. So they discovered that:

 - it's important to measure; holes have to be in the right places and
   straight, so the wheels all point in the same direction.
 - bicycle wheels work terrible without the bearings.
 - a 1:1 chain drive from a motor that runs at 2000 rpm makes the wheel
   spin really fast, but it can't move under its own power.
 - a rakish "chopper" angled front fork looks cool, but steers poorly.

They rebuilt it. This time, a piece of conduit for a rear axle, threaded rod
all the way through, with bike wheels and bearings at each end. They put a
crank sprocket in front (held to the front wheel's sprocket by bolts in its
teeth thru the crank sprocket). Result; still too slow (chain ratio about
3:1). And the 5/16" threaded rod back axle was too weak, and bent.

Rebuilt again. They put the 16" bike's front tire in front, and drove it with
a 3/4" dia. friction drive from a motor mounted on a piece of plywood on the
front fork. The evaporation rate of ball bearings was very high; they
disappeared while the back wheels were off. So, they used a piece of threaded
rod, and two 12" dia. pneumatic garden tractor front wheels which had built-in
ball bearings. Now it works, but is very slow.

Rebuilt some more. This time, they used two motors, one for each back wheel,
3/4" dia. friction drive on each. This allowed the original caliper brake to
be used on the front wheel. The controller was a DPDT knife switch wired to
put the motors either in series or parallel. Works pretty good, still slow,
but efficient; only draws 4 amps in series, 9 amps in parallel. Tried 3"
diameter pulleys on the motors. No faster, and current shot up to 20 amps in
series and tripped the 30 amp breaker on fast. Race day was upon them, so
they decided to go for endurance rather than speed. With perhaps a little
wishful thinking, they named it "Speedy".

The 4-wheelers built a similar frame, but it had a flat aluminum bar as the
front axle with a shopping cart wheel bolted to each end. Rear wheels were
from a 20" bike, bolted by one end to metal plates screwed to the wood frame.
The right side used a bike rear wheel; it was fairly strong with its heavier
axle and coaster brake arm for support. But the left side used a front wheel,
and was rather weak. Given the ministrations of vice grips and lost parts,
they ran out of 20" bike rear wheels assemblies. So the right wheel was
supported by 2 metal plates (one on each side of the 2x4 frame), with a
piece of 3/8" threaded rod thru them for the axle. The bearings were in
place, but as they were running against the threaded rod and ordinary nuts,
it worked mostly as a sleeve bearing.

Copying the 3-wheelers, they also used a chain drive, first with a 4:1 ratio
(wheel sprocket on the motor and crank sprocket on the wheel). Still too fast,
no torque. They changed to a 60-tooth minibike sprocket on the wheel, and an
11-tooth motor sprocket. These sprockets required a wider chain than bicycles,
so they laboriously recycled a rusty piece of farm equipment chain, flexing
and oiling each link until it worked.

This worked well once moving, but it didn't have much starting torque.
The motor they had chosen happened to have a shaft on each end. So they
coupled a second motor to the first with a piece of gas line hose and hose
clamps.

Now there was plenty of starting torque. So much that the hose would wind up
like a pretzel, and pull itself off. They filled it with sand. That kept it
straight but it still wound up. So they added a piece of garden hose over the
first hose. That did it; now they had a reasonable drive system.

They arranged knife switches so they could run one or both motors, and could
run the motors in forward or reverse. Reverse activated the coaster brake;
that was their brakes!

The shopping kart wheels were found to be turkeys; too small, too much rolling
resistance. They decided to copy the front end of the 3-wheelers. Three times
they mounted it; each time it wouldn't steer because they had the fork so
close to horizontal.

All this time, the 5-wheelers were plodding along. They were methodical and
thorough, but progress was slow. They built a great 5-sided frame out of
plywood skinned 2x2's with carefully mitered joints, etc. But they couldn't
hang onto enough wheels of the same size. Other groups would scavenge parts.
They'd hide the wheels, then forget what they did with them. Or take them
home, and forget to bring them back. But they kept finding more and piled up
an impressive collection of bicycle wheels; at one point I counted 20!

Then they hit the wall. Mounting 5 wheels rigidly to a frame made a vehicle
that was very stable and rolled easily, but was (understandably) unsteerable.
I was secretly rooting for them to succeed, but my own rules kept me from
helping. (OK engineers; how would YOU steer a 5-wheeled unicycle :-)

So in the last week, the 5-wheeler and 4-wheeler teams decided to join forces.
They tore the 4-wheeler apart for pieces, and sawed off the front of the
5-wheeler, turning it into a 4-sided frame. They built an indescribable
structure to mount a bicycle fork and wheel on the front for steering. The
two 20" bike wheels with two motors and chain drive to one rear wheel was
retained.

They tested it the day before the race, and it was quick! With a light driver,
you can't run fast enough to keep up. The whole school was plastered to the
windows, or ran outside as they raced around the parking lot. They named it
"254", the first 3 digits of a Pizza place that advertises fast delivery (and
gave the team a free pizza one day after school).

Meanwhile, the 6th graders had seen last year's winning car, Morris Park's
"Road Runner" (a.k.a. the "Coffin" :-) and fixated on it as their design.
They built a ladder frame out of 2x2's and skinned it with plywood.

But sadly, this class was a group of individuals and not a team. They fought
and argued, and sabotaged each other's work in subtle and not-so-subtle ways.
So 6 weeks before the race, teacher Joe Rossow and I agreed to let them fail,
and their car was dropped.

A few of these students were still enthusiastic; so much so that they
voluntarily came in during breaks and after school to help the 5th graders
with their cars. To appreciate a 6th grader voluntarily working with 5th
graders, try to imagine Yasir Arafat going to Netenyahu's son's bar mitzvah.

Armatage School

The Armatage team was run by teacher Mike Farnsworth and mentor Bob Aske. Bob
is a great engineer, and had taken the teacher's car home and carefully
documented how it was built as an example for his students. The students
apparently decided that since the teachers did it that way, it must be the
right answer. (This illustrates why I don't give the students any hints as
to what I think is the "right" way to do it).

The body was a 20" x 48" x 6" plywood box, with 2" angle aluminum along the
lower left and right sides. The angle aluminum extended past the back of the
box so a 26" bicycle wheel could be bolted to each. The motor was mounted to
one end of a 1x6 piece of pine, whose other end pivoted on a bolt in the body.
Half of a Lovejoy jaw coupling (about 2" dia.) was mounted to the motor shaft
as a friction drive on one back wheel. The front end was the fork and
handlebars from a 20" bike. The controller was an on/off switch. Bicycle
caliper brakes were provided on each back wheel. The seat was a child safety
seat with padding removed (giving it a real Nascar look)!

Jefferson Community School

Teacher Doug Fielder was aided by mentor Eric Viken. Their frame was a
rectangle made of 2x4's with 4 carriage bolts in each corner. A couple 2x2
crossbeams in the center added strength and also supported a plywood bench
seat. It was another 3-wheeler similar to the Armatage car, using two 26"
bike wheels in the back, and a 24" bike wheel and fork in the front.

The chain drive system was interesting. Two 1/2" bolts served as axles to
support two rear wheel deurrailers, each with 5 sprockets. The deurrailer's
bearings and free-wheel clutches allowed them to rotate freely. One chain ran
from motor to deurrailer #1, a second from deurrailer #1 to #2, and a third
chain from #2 to the wheel. They couldn't shift while driving, but had a lot
of flexability to pick drive ratios by putting the chain on different pairs of
sprockets.

They had mounted a rear wheel on the front, and could pull on its chain to
activate brakes on the front wheel. There was also a friction brake on one
back wheel.

Sonnensyn Elementary

Teacher Eileen Johansen and mentor Rick Cash were seasoned pros from last
year's race. Last year, their students did not quite finish the car by race
day. They wound up testing it at the track, and suffering breakdowns that did
not allow them to finish. So Rick and Eileen put a lot of emphasis on getting
it done early this year!

Kids are incredibly adept and unscrupulous manipulators. The tools they are
most familiar with using are adults! So under the time pressure, they conned
one of the dads into building a frame for them. They designed it, and he did
the cutting and welding.

It was welded square steel tubing about 2 foot wide by 8 feet long. The two
rear tires were held by front bicycle forks, with their stems inserted and
welded horizontally into the ends of the square steel tubing. A front bicycle
fork was welded onto the front for steering. A machined steel coupler on the
motor held a small sprocket, which drove a jackshaft with small and large
sprockets. A second chain from the jackshaft drove a back wheel.

It was a beautiful piece of work. It was also very heavy, and not very
maneuverable due to the length.

Scenic Heights

Teacher Jan Sellman was assisted by engineer Clarence Ogburn (and Bob Aske
and I a little in the frantic last week). Their car was a carefully built
wooden box frame, with two 24" bike wheels in back, and the front half of a
24" bike in the front. The bike frame was cleverly bolted to the box with
just 4 pieces of angle iron.

They also decided to use a chain drive, but found bicycle sprockets didn't
allow a large enough ratio. So they added a jackshaft. A 1-5/8" v-belt pulley
on the motor drove a 10" pulley on a jackshaft made out of a front bicycle hub
with all the spokes removed. A 3:1 chain drive then drove a back wheel.

Morris Park Elementary

Teacher Susan Seyer was helped by engineer K.C. Jones (not a misprint :-).
Their car looked a lot like a go-kart, but with a wooden frame. It was a
4-wheeler, with 6.00 x 6" farm implement tires. The front and rear axles were
steel rods. The front axle was held by a 2x4 with a pivot bolt in the middle.
Steel wire from each end of the front axle went to a bicycle handlebar, which
was tilted to steer.

A single reduction 4:1 ratio bicycle chain drove a back wheel. Their
controller was easily the most sophisticated. There were 3 pedals (door
hinges), that operated 3 pushbutton switches. About 20 power resistors from
Radio Shack were wired to these pushbuttons so they could run the motor at
several different speeds depending on which and how many pedals they pushed.

The workmanship on their car was excellent. The kids did most of it
themselves, but were closely supervised. Morris Park had gotten a late start,
because the engineer that had originally volunteered moved to Texas without
telling anyone. There was precious little time to build the car, so the
students needed a bit more direction in order to get it done in time.

Last but not Least

Two cars from last year were also in attendance. Sonnesyn's 5th graders (now
6th graders) are now at several different schools, as 5th is the highest grade
at Sonnesyn. But one of the students picked up their car a week before the
race, and managed to get it partially working.

The "Stinger" as it was named, has a bolted angle iron frame and plywood skin.
A classroom chair is the seat. A coaster wagon's front end provides steering,
with bicycle handlebars bolted to the wagon handle for more leverage. The 26"
back wheels are from a garden cart. Each has a 20" bicycle rim (with the tire,
hub, and spokes removed) attached to the 26" wheel's spokes as a big pulley. A
v-belt runs around this pulley and a 1-5/8" pulley on the motor to power it.
She only had time to get one motor working, but it moved under its own power!

Several of Morris Park's 5th graders (4th graders last year) worked
frantically to get their "Road Runner" running again. And they kept working on
it on race day, right through the first two events! They finally got it going
in time for the Endurance race. They weren't able to qualify, but were allowed
to take a few exhibition laps, and put in many more laps running around the
parking lot.

And then...

Friday, May 15: The last day before the race. As teams work feverishly on
last minute details, the storm sirens sound. Tornadoes rip through the area.
Trees are down, rain pours out of the sky, golf ball size hail pelts cars,
and 1/3 million people lose their electricity.

Can they finish in time? How will they charge their batteries before the race?
Will the race even take place?  Read Part 2 for Race Day!


Lee Hart