weight increase due to the gearbox
which explains the relatively low
power-to-weight ratio. But, even
disregarding that, the performance
of this motor is still not too high.
The reason many builders use it is
due to its convenience, it is easily
mounted to the robot, and it is one
of the few high power DC motors
that comes with a built-in gearbox.
Care should be taken with the NPC
T64 gears (shown in Figure 6, with
red grease). They might break under
severe impacts if used to power
weapons. As recommended by the
manufacturer, only use them as drive
motors.
An excellent motor for driving
middleweights is the Magmotor S28-
150 (a.k.a., Ampflow A28-150). It is
used in our robots Titan and Touro.
A good weapon motor for a
middleweight would be the
Magmotor S28-400 (a.k.a.,
Ampflow A28-400) with
higher torque and power,
which we use to power
Touro’s drum. Using a
single S28-150 to power
the weapon of a
middleweight is not a good
idea. There’s a good chance
that it will overheat.
Because of that, to spin
the bar of our
middleweight Titan, we use
two Magmotor S28-150s
mechanically connected in
parallel by acting on the
same gear of the weapon
shaft.
The D-Pack motor is a
good candidate to replace
the Magmotors, besides
being much cheaper.
However, its electrical
resistance is so low that it
almost shorts the batteries
and electronics. Because of
that, its current must be
limited if used with speed
controllers. Otherwise,
there’s a good chance of
damaging the electronics,
especially since this motor is
usually overvolted to 24V
instead of powered by its nominal
12V. If used with solenoids to
power weapons, make sure that
they can take the high currents
involved. This motor is difficult to
find even in the US.
TABLE 1
Name
Voltage (V)
Poutput_max (W)
Weight (lb)
Power/Weight
Istall/Ino_load
Kt (N×m/A)
Kv (RPM/V)
Rmotor (W)
Ino_load (A)
Bosch GPA
24
1,175
8. 4
140
23
0.061
167
0.13
8.0
Bosch GPB
12
282
3. 3
85
25
0.042
229
0.121
3. 9
D-Pack
12 (nominal)
3,561
7. 7
462
63
0.020
485
0.00969
19. 6
De Walt 18V
24
946
1.0
946
128
0.0085
1,100
0.072
2. 6
Name
Voltage (V)
Poutput_max (W)
Weight (lb)
Power/Weight
Istall/Ino_load
Kt (N×m/A)
Kv (RPM/V)
Rmotor (W)
Ino_load (A)
Etek
48
11,185
20. 7
540
526
0.13
72
0.016
5. 7
Magmotor S28-150 Magmotor S28-400 NPC T64 (w/gearbox)
24 24 24
2,183 3,367 834
3. 8 6. 9 13.0
574 488 64
110 127 27
0.03757 0.0464 0.86
254 206 10
0.064 0.042 0.16
3. 4 4. 5 5. 5
SERVO 01.2011 33
