26 SERVO 12.2013
Stall Torque: 0.35 in-lbs for 11:1; 1.6 in-lbs for 50:1
Stall Current: 1.3A
Shaft: 3 mm diameter, 1.5 inches long
Weight: 0.99-1.02 oz
Cost: $22.94
Comments: The Finger Tech Robotics Silver Spark
gearmotor is a very well made and durable drive motor
option for the 1 lb class. It has been used in weapon
focused 3 lb robots with a decent amount of success.
With a wide range of ratios available ( 11.1, 22. 2, 33. 3,
50, 83. 3, 100, 200, 300, and 600:1), it is easy to find an
option that fits your needs. These motors are also
capable of handling much higher voltages than their
competitors, and have been run as high as 22.2V
(though >10V does decrease motor lifespan) in a combat
application.
The long shaft gives you plenty of options for both
wheels and supplemental shaft support, though the
latter isn't often needed in the 1 lb class. These
gearmotors have relatively large pitch gears and because
of that they're far less prone to stripping under load.
This can often make the difference in a match and is one
of the reasons they're very commonly found in
1 lb bots.
Kitbots 1,000 RPM Gearmotor
Dimensions:
.98-.03 inches
diameter, 2. 14
inches long
Nominal Voltage:
12V
RPM: 930
Shaft: 4 mm
diameter
Weight: 3 oz
Cost: $12-$24
Comments: There's
very little in the way
of dedicated gearmotors for the 3 lb class right now, and
the Kitbots 1,000 RPM gearmotor is at the top of the
pile. This somewhat generic looking gearmotor is
effectively the off-the-shelf drive option for the 3 lb class.
There are other gearmotors out there, but they're often
either difficult to attain, out of production, or
unrealistically expensive.
Kitbots offers a "battle hardening" service that
improves the durability of these gearmotors for $12, and
it's worth either having them do it or following the
instructions they have posted and doing it yourself.
This motor is prone to voltage spikes, so it is
recommended that with some compatible ESC options
you pair it with a 0.01 µF capacitor to protect
the motor controller.
Gimson
Robotics
GR02
Dimensions: 1.6
inches square ( 40 mm),
3. 8 inches long
Nominal Voltage: 18V
RPM: 810 for 24:1;
542 for 36:1
Stall Torque:
106.8 in-lbs for 24:1; 160.2 in-lbs for 36:1
Stall Current: 61.6A
Shaft: 12 mm with flat
Weight: 1 lb
Cost: £ 29. 80
Comments: The GR02 is a gearmotor from the UK and
is meant to function as a replacement for modified drill
gearboxes in the popular 30 lb class. With the size and
weight of this gearmotor, it is also suitable for the 12 lb
class. The shaft on the GR02 can be troublesome for
some builders, however, they offer a wheel hub solution
that pairs with the 12 mm shaft which minimizes this
issue. They're also shipping the gearboxes with an
external bearing kit which can be used to help handle
the shock loads that often come with an
overhung wheel drive setup.
BotBitz GM36 19:1 Gearmotor
Dimensions: 1.42
inches diameter
( 36 mm), 3. 7 inches
long
Nominal Voltage:
12V
RPM: 900
Stall Torque:
29. 7 in-lbs
Stall Current: 52A
Shaft: 8 mm with flat
Weight: 0.93 lbs
Cost: $40 AUD
Comments: The GM36 is the Australian solution to the
same problem the GR02 addresses in the UK. Cordless
drill gearboxes are nice and off-brand models can be
quite cheap, but year to year the design, motors, and
ratios can all change, making it difficult to get a reliable
known motor. These gearmotors are also meant for the
30 lb weight class, though are certainly compact and
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