Make: Volume 52

I contacted Bob and he explained that

angled “legs” are the key to directional

movement. Folk toys often used broom

bristles or thin wooden strips, he explained.

Aha! Progress.

The next problem was devising a new

source of vibrations. Initially, I banged

drumsticks on a large plastic pan, which

did move my critters forward. Still, I sought

a more consistent vibration. I considered

speakers playing set tones, or motors with

off-center weights attached to their shafts.

After making little progress, I again reached

out to Bob. He sent me a video in which the

teeth of a gear turned by hand engaged the

edge of the track. How simple! Here’s my

classroom version of Bob’s invention.

MY RUMBLEBOT RACEWAY

The vibrating track is a 6"×30" piece of

poster board, about

1

/

16" thick (Figure

B

).

This track rests in table saw blade

grooves cut into 2 wooden sides made

from ¾" plywood, 32" long and 6" tall.

The grooves begin about 1½" up from the

bottom and are about

3

/

8" deep. (None of

these exact dimensions are crucial.)

A wooden strip, cantilevered over the

track, creates 2 lanes for the racers.

A single gear about 2½" in diameter,

mounted on an axle, grates against one

end of the track to drive my Rumblebots. A

freestanding base allows adjustment of the

gear’s position on the track (Figure

C

).

THE RUMBLEBOTS

For the bots themselves, I settled on two

basic designs. In the first, I cut a block

of styrofoam to fit in a given lane. On its

bottom, I cut angled grooves with a razor

saw, perpendicular to its length. Into these

grooves I placed paper, cardboard, pine

needles, pins — most anything imaginable

— to serve as legs (Figure

D

).

In the second design, I took index cards

and angled the front and back in similar

directions. I then cut wedge-shaped legs on

the front and back (Figure

E

).

RUMBLEBOT RACERS —

A FAMILY SCIENCE PROJECT

I offered Rumblebot Racers as a Family

Science project to my 6th graders. This

means it was not required, nor were any

rewards (candy, extra credit) given. Rather,

the joy of learning was the motivator for

students. I encouraged them to work with

friends or family members. I made them

a video to explain the project, at makezine.

com/go/rumblebots-explainer.

Nineteen students built rumblebots.

Two of our custodians even participated.

(Their first design featured porcupine quill

legs!) Many of my students, taking my

suggestion of researching “bristlebots,”

used toothbrushes. To my dismay, I finished

second to one of my students! Here is Alex

with her winning rumblebot (Figure

F

).

HOW DO STUDENTS BENEFIT?

Here’s what Alex had to say about the

project: “I watched the video and made a

list of materials I needed. I followed your

suggestion on the video and researched

Bristlebots. I saw they were made from

toothbrushes and motors. I tried using

some old, used toothbrushes, and also

hairbrushes. Toothbrushes worked best.

The toothbrush tipped over easily, so I

attached a cardboard top to keep it upright.

To test my rumblebots, I placed a piece of

cardboard over two pencils and tapped on

the cardboard. Once I knew they worked,

my mom bought some new toothbrushes.

I tried connecting two and three together,

but one by itself worked best for me. I liked

beating Mr. Stith!”

Another student, Felicia, built a bot that

did not move forward, only bounced up and

down (Figure

G

). Her design problem?

Vertical legs. Did this mean Felicia’s effort

was a waste of time? “I still had fun thinking

up my own design, and I’m glad I did the

project. I saw that when we put the Q-tips

into the block at an angle, it did move

forward!” (Learning achievement unlocked!)

The world our students inhabit grows

more and more virtual every year. Much of

what they experience is through a screen. I

love seeing students manipulate materials

according to their own designs (as opposed

to fitting one Lego into another). You can

see all the student rumblebot designs and

watch actual races at makezine.com/go/

rumblebot-races.

Next, I’ll challenge my students to create

Rumblebot Sumos (push opponents out of

a central zone) and a Rumblebot U-Turn

(execute a half-circle turn, and exit the

surface on the same edge as they started).

Who knows what projects my students may

soon be designing for others?

Hep Svadja

A: Bob Knetzger, [B, C, E]: Hep Svadja, [D, F, G]: Doug Stith

B

D

C

E

F

G

makezine.com 85

makezine.com/52

See race videos, more photos, and

share your rumblebots at makezine.

com/go/rumblebots-raceway.

Rumblebots

Raceway

A

M52_084-5_Rumblebot_F1.indd 85 6/14/16 2:18 PM