My 12 year old is enrolled in science olympiad competition. He has to
make a robot that will pick up a tennis ball and move it somewhere
It is limited to 30cm in any dimension, so RC tanks would be too big.
I thought that we could buy a 8 channel RC mobile platform and use a
couple of channels to add a lifting and grabbing component.
My question is where can I purchase such a platform, there has some be
some place that sells them, but nothing comes up.
I would really like to find something that runs a lot slower than a
typical RC car.
Size is the problem. If not for the size, I could easily buy an RC
tank, rip off the turret and add a claw. The problem is that all RC
tanks are too big. I believe that they are all made in China at one
factory and are all essentially the same tank, with different shells
that are put on for various retailers.
Maybe you could use a pair of odd frequencied 4-way controllers. One
for movement of the vehicle and the other for the pickup arm/grabber.
Wait, I just googledit. "radio control modules 8-channel" has lots of
Just gear it down, Ig. Zimple.
Why not build your own platform, Iggy? Buy tracks and remove some
links to scale it down for your size requirements. Use steppers to
run them slower or gear them down. Use your CNC mill to make aluminum
parts from (da ta ta daaaaah!) Billet Aluminum! Have your son program
it with your instruction. This is a perfect opportunity to get him
involved in your business.
P.S: Be sure to show pics of what you guys come up with.
I've been building exactly that, Ig.
Little robots for the older grandkids.
I have three wheeled units them in various stages of assembly,
and one on tracks.
I don't have any pics up yet, but I can direct you to parts sources.
If your email address is valid, I'd be happy to send info.
Drawings, schematics, code, etc.
I used a small aluminum plate for the base, geared dual motor unit for
motion, a 1" dia "trackball" type nose roller, and a Propeller P8x32
processor (Quickstart board) for the brain.
MY code is all written in Spin, but the drivers (objects) from the
Parallax Object Exchange are a combination of Spin and Assembly.
Most of my parts came from Pololu (I can't pronounce it either)
and they have quite a range of robot kits.
Remote control via universal TV remote control unit. Cheap and easy.
IR remote sensor/decoder:
The interface circuit board is 5" diameter circle, but could be shaped
any way you wanted.
My "Q-Bug" robots claim to fame is that they are not supposed to fall
off of the table. The "floor sensors" detect if it is safe to move.
Dual Motor Drive unit: (a bear to assemble!)
Dual motor controller board:
No servos are used so far, but I may add a Ping sensor (ultrasonic
range finder) and use a very small servo to move it back and forth
for scanning the area. But at the moment that looks more like a
complication than a feature. The floor sensors are working fine, and
that's all I wanted to do.
I'll post some pics.
See what you think.
"Ignoramus26083" wrote in
message news:I7ydnVNBPLPuqhXPnZ2dnUVZ email@example.com...
Could you strip the components from an RC tank and assemble your own
chassis from thin plywood, aluminum extrusions and press-in bushings,
with a raised idler to shorten the footprint of the track?
You'd have a stronger mounting base for the claw and the freedom to
redistribute the mass to counterbalance it.
Yep. That's the Tamiya track chassis.
It's the same one I used for my project.
Downside - it only has a single motor gearbox, so as built it can not turn.
You have to replace that with a double motor gearbox to be able to tuen it.
I have a boe-bot, it uses R/C servos that have been modified for continuous
rotation for the wheel drive motors. Do you think the Tamiya tracked
chassis would be easily adaptable to R/C servos? If not, it might be
interesting to take the electronics out of a servo and connect to the double
motor gearbox. The first servo's I worked on had wires going to the motor
and pot, I reversed them myself, seems the newer stuff has the board
soldered right on the motor.
Not the track chassis.
I doubt those wheels could be adapted to servos all that easily.
It _could_ be done, of course, but ...
The wheels are special two-piece things with a gap in the center for the
web on the back of the track.
They ride on a solid axle - about 3/32" I think.
All but the drive wheels are free-wheelers.
There is quite a bit of tension on the the wheels because of the
tracks. The tracks themselves are made up from short pieces.
Right out of the box they were so tight that it looked like they were
going to come apart at the connections.
I moved the front axle back about 3/16" to take some of that out.
RC servos would be attractive because of the simplicity of hooking up
the electronics. All the "software" is in the transmitter and receiver.
Plain motors, on the other hand, need transistors for control.
That means something to run the transistors... software for on/off.
PWM to control speed.
I think I've got him running though.
Check the web page I scraped together last night about this.
Those robots all look interesting. For future robots,
also consider using 18650 type batteries instead of AA's.
Two 18650 Li ion batteries take up slightly more room
(about 34 cc for 2 ea 18 mm x 65 mm batteries) than four
NiMH AA's (about 31 cc for 4 ea 14 mm x 50 mm batteries)
but weigh less (ca 68 g vs 88 g) and and pack 50% more power
(2 x 3.7 V x 2.5 Ah = 18.5 Wh, vs 4 x 1.2 V x 2.5 Ah = 12 Wh)
and in simplest form cost half as much per set. (I think some
versions have low voltage shutdown protection and cost more.)
The necessary charging and discharging protection circuits aren't that
easy to design or test unless you have experience with battery power
circuits. Lithiums are great if you can buy the controller, otherwise
sealed lead-acids may be the easiest for non-EEs.
NiCad and NiMH are harder to charge properly, but easy to find an
inexpensive charger for.
Inexpensive 1-cell and 2-cell Li ion chargers are as easy to use for
18650 cells as NiMH chargers are for AA cells. See eg
(or click the "18650 battery charger" link at
If the cells are made up into a battery pack, then yes, more
issues might arise. For simple robot apps, using 2 cells in
series is fairly straightforward.