you then need to get a separate
12V power supply which can be
both expensive and bulky.
The iNDi 16x4 Pro Charge has
both 110V AC and 12V DC inlets
so that you can use it both
indoors with the linecord provided
or outdoors with the separate
12V leads.
I purchased three of these
chargers in the summer of 2006 for
use at a summer “Combat Robotics”
camp I was teaching.
They will automatically detect
cell type and will charge from 1-15
cells (1.2 to 18V packs) at an
adjustable 0. 5-5.5A rate. They will
also discharge a pack at up to 4A.
One of the three chargers
ordered stopped working shortly
after receipt but was promptly
replaced by the manufacturer. All
three also gave off a strong smell of
hot oil the first time they were used.
The fan is also rather noisy.
They have proven simple to use
and reliable. They are very quick to
set up, come with all the required
leads, and the high charge rate has
proven very useful to quickly
recharge the NiMH GP2000 18V
packs used in the robots. SV
RioBotz COMBOT
TUT RIAL SUMMARIZED:
Design Fundamentals – P2
● Original Text by Professor Marco Antonio Meggiolaro, Summarized by Kevin M. Berry
Professor Marco Antonio
Meggiolaro of the Pontifical
Catholic University of Rio De Janeiro,
Brazil, recently translated his
popular book The RioBotz Combot
Tutorial, into English. Last month,
SERVO summarized the first part
of a key chapter “Design
Fundamentals.” This month, we
continue the series with the second
part of this chapter. Marco’s book
is available free for download
at
www.riobotz.com.br/en/
tutorial.html. All information
here is provided courtesy of
Professor Meggiolaro and RioBotz.
Beginning the Design
Once you’ve decided on the
general configuration of your bot
(disk spinner, drum, flipper, etc.),
it’s time to start allocating the
component’s weight. A good rule of
thumb is the 30-30- 25-15 rule
shown in Table 1. This was created
by Grant Imahara for his book
Kickin’ Bot: An Illustrated Guide to
Building Combat Robots. Riobotz
refines this rule a bit, as shown in
the two righthand columns.
The second rule of thumb is
KISS: Keep It Simple, Stupid. Sketch
it up in CAD, PowerPoint, or by
hand on graph paper. Play around
with lots of design options, getting
the whole team involved. Remember
to place fragile items like speed
controllers deep inside the machine.
Keep everything compact; space
costs weight. Also keep in mind the
need to repair items in a hurry
during an event, so some space
around connections is helpful.
Calculations
TABLE 1
GRANT’S
GENERAL RULE
30%
SYSTEM
• Drive System (Motors,
Transmission, Wheels)
• Weapon System (Weapon, 30%
Motor, Transmission)
• Structure and Armor 25%
• Batteries and Electronics 15%
All material used with permission of
RioBotz, Marco Antonio Meggiolaro.
FOUR WHEEL TWO WHEEL
DRUM BOTS DRUM BOTS
20% 15%
35%
35%
30%
15%
40%
10%
Professor Meggiolaro recommends performing some level of
stress analysis during the design
phase. While this is a valid point,
many builders just aren’t able to go
to that extreme. In Chapter 6 of his
book, he goes into extensive detail
( 65 pages!) on calculating various
factors about your bot. Another
tip is to use tables gained from
builder’s experience such as the
one shown in Part 1 of this
30 SERVO 07.2009
