Project Description
 Requirements
 Basics – Drive Train Design
 Drive Train Types
 Testing
 Science/Engineering
 Conclusions

Built and tested seven drive train designs
 Simulated FTC match environments
 Tested each design with added weight
to mimic various robot weights
 Compiled and analyzed data to find
ideal configurations for each test

Meets strategy goals for the game
 Is built from available resources
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Time
Cost
Tools for fabrication
Part 1 of game manual
Rarely needs maintenance
 Is repairable within 4 minutes
 Uses minimal amount of space
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Decide strategy after kickoff
› Speed
› Power
› Mobility
Decide how many motors will be allotted
for drive train
 Decide robot weight
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Traction
Mobility
Speed
Offensive/Defensive ability
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Build for durability and test
› Find weak points
› Practice driving
› Have spare parts and assemblies
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Develop a project plan
› Allot time for development and building
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Learn technology
› Know motor capabilities and limitations
› Know electrical capabilities and limitations.
•Nimble:
2 wheel drive + 2 omni caster wheels
•Basic: 4 wheel drive, not connected
•Unity: 4 wheel drive, connected
•Robust: 10 wheel drive
•Whirlwind: 6 wheel drive
• AndyMark Wedgetop and Performance
Treads
•Track: 4 motors, connected
•Direction: 4 motors, not connected
Motor
Motor
Driven wheels
Omni caster
wheels
This drive train uses two direct drive 4” wheels with two 3” omni caster
wheels. This robot has a base weight of 7 lbs due to its 10”x18” 80/20
frame.
Motor
Motor
Driven
Wheels
Motor
Motor
This drive train uses four direct drive 4” wheels that are not connected to
each other. This robot has a base weight of 7 lbs due to its 10”x18” 80/20
frame.
Motor
Chain
Motor
Motor
Driven
Wheels
Chain
Motor
This drive train uses four direct drive 4” wheels that are connected to
each other using chain (not drawn in Creo). This robot has a base weight
of 9 lbs due to its 10”x18” 80/20 frame plus added chain and sprockets.
Motor
Gears
Motor
Motor
Gears
Motor
This drive train uses 10 chain driven 3” wheels that are geared together
with the 4 outer wheels raised. This robot was our competition robot from
the 2014-2015 season which weighed 55 lbs.
Motor
Motor
Motor
Motor
This drive train uses 6 chain driven 4” wheels with the outer wheels being
the AndyMark omni wheels and the inner wheels using either the
AndyMark Performance Tread or the AndyMark Wedgetop Tread (tested
separately). This robot had a base weight of 22.5 lbs.
Motor
Motor
Motor
Motor
This drive train uses 4 direct driven 3” wheels wrapped with Tetrix tread.
This robot had a base weight of 9 lbs due to the 10”x18” 80/20 frame.
This drive train uses 4 direct driven 3” omni wheels. Each wheel was
driven individually to allow for multidirectional travel. This robot had a
base weight of 7 lbs.
Straight Line Speed Test
 Pull Test
 Side Drag Test
 Spin Test
 Ramp Test
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Each test was preformed on standard field
tiles. The robot was weighed and tested at
10, 20, 30 and 40 pounds in addition to
the weight of the robot itself.
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The Straight Line Speed Test tested the
robot on how fast it would travel 16 feet.
The testing area had a starting area to
allow the robot to reach full speed prior to
the course.
Total robot amps were recorded for each
run.
Time to drive the 16 feet was recorded for
each run.
At least 4 tests were recorded for consistent
results.
The Pull Test tested how much weight the
robot could pull.
 Total robot amps were recorded for
each run.
 The amount weight lifted was recorded
for each test.
 The weight lifted was increased until the
wheels slipped or the motors stalled.
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The Side Drag Test tested how much weight
it took to pull the robot sideways.
 The amount of weight to pull the robot was
recorded for each test.
 Weight was added until the robot was
pulled sideways.
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The Spin Test tested how fast the robot
could spin 360 degrees.
 Total robot amps were recorded for each
run.
 Time taken to spin 360 degrees was
recorded for each run.
 At least 4 tests were recorded for consistent
results.
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The Ramp Test tested if the robot could climb a
ramp.
The ramp was a standard FTC ramp from the
Cascade Effect Game.
Pass/Fail was given if the robot could drive up
the ramp.
Estimated Robot
Speed vs. Results
Wheel Diameter * Pi * Motor speed = Inch/min
4" * 3.14 * 150 RPM= 1884 inches/min
1884 inches/min /60 sec = 31.4 inches/sec
3" * 3.14 * 150 RPM = 1413 inches/min
1413 inches/min /60 sec = 23.5 inches/sec
Tested Distance = 192 inches
Theoretical time to run course with 4" wheels
192 inches / 31.4 inches/sec = 6.1 seconds
Theoretical time to run course with 3" wheels
192 inches / 23.5 inches/sec = 8.1 seconds
Most robots at minimum weight tested at or
faster than predicted speed.
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Test Data
› Straight Line Speed Test (Seconds/Amps)
› Pull Test (Pounds/Amps)
› Side Drag Test (Pounds)
› Spin Test (Time/Amps)
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Overall Robot Performance
Test Distance 16 Feet
Track drive uses 3”
wheels, and, therefore,
gained at least 25% of
power advantage
compared to 4” wheels
+
--
+ Easy to design
+ Easy to build
+ Lightweight
+ Inexpensive
+ Long battery life
- Underpowered drive train
- Will not do well on ramps
- Easily pushed by other robots
- Not effective for defense
- Not able to support much weight
-- Maneuverability
+
=
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+ Easy to design
+ Easy to build
+ Lightweight
+ Inexpensive
+ Long battery life
+ Able to hold position
= Decent on ramps
= Decent maneuverability
- Not utilizing full potential out of all the motors
because they are not connected
- Not effective for defense
- Not able to support much
weight and move effectively
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=
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+ Relatively easy to design
+ Relatively easy to build
+ Light weight
+ Able to holding position
+ Preforms well on ramps
+ Utilizes full potential of motors
because they are connected
= Inexpensive
= Decent Maneuverability
= Battery life depends on weight
= Effective for defense
- Not able to support much
weight and move effectively
+
=
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+ Does well on ramps
+ Utilizes full potential out of all the motors
+ Very effective for defense
+ Supports robust robot well
= Decent Maneuverability
= Weight neutral
- Short battery life
- Difficult to design
- Difficult to build
- Expensive
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++ Maneuverability: spins on axis well
++ Supports robust robot well
+ Great at holding position
+ Does well on ramps
+ Utilizes full potential out of all the motors
+ Very effective for defense
+ Excellent battery life
+ Will support high gear ratio
= Weight neutral
- Difficult to design
- Difficult to build
- Very expensive
+
=
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+ Easy to design
+ Easy to build
+ Lightweight
+ Long battery life
+ Able to hold position
= Does decently on ramps with track treads
= Average Maneuverability
= Effective for defense
= Cost neutral
- Inconsistent turns make autonomous extremely
difficult
- Drive train needs to be geared up to reach
competitive speed
- Vulnerable, needs to be protected
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=
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+ Long battery life
+ Inexpensive
+ High Maneuverability
= Moderate weight
= Moderate to design
= Moderate to build
- Extremely difficult to program
- Not able to hold position
- Slow
- Not at all effective for defense
- Cannot go up ramp
The drivetrain can define a robot and is the most
important element of a design; the strength of the robot's
drivetrain can heavily influence its overall performance.
 The drivetrain must:
meet your strategy goals for the game
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› speed: The robot must be able to surpass the competition in any
direction at any time.
› traction: The robot must be able to effectively grip the various
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field elements without damaging the playing field or limiting
maneuverability.
maneuverability: The robot must be able to quickly navigate the
field, rotate on its axis, and escape out of harm’s way.
power: The robot must be able to conserve power usage to
ensure maximum overall performance during a match.
offense/defense: The robot must be able to meet strategic
objectives depending on team preference.
weight: The robot weight should maximize motor efficiency
without compromising defensive/offensive abilities.
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be built with available resources
› budget: The drive train construction costs should not exceed the
team-defined boundaries of the budget.
› tools required: The drive train should be designed to be built only
with tools that each team actually has. (No rocket boosters
unless you are sponsored by NASA)
› time: The drive train should be easily assembled/dissembled for
maintenance within a short time span.
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rarely needs maintenance
› durability: The drive train should be constructed to last so that
repairs are minimal. The drive train must be protected from harm.
› testing: Thoroughly test the drive train during construction to
ensure that it can handle match conditions.
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can be fixed within 4 minutes
› easily replace motors between matches
› easy to access critical components
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Uses minimal amount of space
› The drive train fits in designated space allotted by the system
envelope
Brainstorming and Design resources:

Decide strategy after kickoff. What will you focus on?
› Speed:
› Power
› Mobility
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Decide how many motors you will use on drivetrain
› 4 motors is ideal (2 weakens a design and 6 causes connection issues)
› chain/gear motors together to maximize power
› Wire motors on separate ports on motor controllers to maximize power
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Robot weight
› What weight will maximize
 traction
 mobility
 speed
 defense (limit other robots pushing while playing offense)
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Durability
› put the drivetrain under stress to test the durability
› identify weak points and correct them
› driver practice
› spare parts and assemblies
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Develop a project plan
› allot time for design, build, testing, software and driver practice

Technology
› motor capabilities and limitations
› AndyMark NeveRest 40 Motor (am-2964)
 Performance Specs:
 Gearbox Reduction: 40:1
 Voltage: 12 volt DC
 No Load Free Speed, at gearbox output shaft: 160 rpm
 No Load Free Speed, motor only: 6,600 rpm
 Gearbox Output Power: 14W
 Stall Torque: 350 oz-in
 Stall Current: 11.5 amps
 Force Needed to Break Gearbox: 1478 oz-in
 Minimum torque needed to back drive: 12.8 oz-in
 Output pulse per revolution of Output Shaft (ppr): 1120 (280 rises of Channel
A)
 Output pulse per revolution of encoder shaft (ppr): 28 (7 rises of Channel A)
 Performance Specs, mounted to AndyMark dyno:
 Max Speed (under load of dyno): 129 rpm
 No Load Current (under load of dyno): 0.4 amps
 Stall Current: 11.5 amps
 Stall Torque: 396 oz-in
 Max Output Power: 15 Watts
 Time to Failure at Stall: 2 minutes, 54 seconds
 Motor Case Temperature at Failure: 190 degrees F
› electrical capabilities and limitations
 Each motor controller should only power 1 drive train motor.
 Never connect more than motor to a motor controller port.
•Nimble:
2 wheel drive + 2 omni caster wheels
•Basic: 4 wheel drive, not connected
•Unity: 4 wheel drive, connected
•Robust: 10 wheel drive
•Whirlwind: 6 wheel drive
• AndyMark Wedgetop and Performance
Treads
•Track: 4 motors, connected
•Direction: 4 motors, not connected
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This robot has two motors that directly
drive two wheels. The drive wheels are 4
inch Tetrix wheels, and the non-powered
wheels are 3 inch omni caster wheels.
two AndyMark NeveRest 40 motors
 two 4in Tetrix wheels
 two 3in Tetrix omni wheels
 two 1010 aluminum extrusions 18" long
 five 1010 aluminum extrusions 10" long
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This drive train is easily constructed, but not
necessarily the best choice for any robot.
Due to a low weight, it draws less amps
than other drive trains, promoting good
battery life. Unfortunately, nothing else
stands out. Its straight line speed is only
average, it has low pushing power, it can
be easily pushed around by an opposing
robot, and it has trouble spinning under any
weight. Overall, this drive train is not
recommended for any game.
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This robot is powered by four motors that
directly drive the four 4" tetrix wheels. The
motors on each side are not chained
together in this design.
Four AndyMark NeveRest 40 motors
 Four 4" Tetrix wheels
 two 1010 aluminum extrusions 18" long
 five 1010 aluminum extrusions 10" long
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This drive train can maneuver around the
field under heavy weight, but it is only at
average or below average speeds. It is
easily constructed and does not draw a
large number of amps during movement. It
can push/pull an average weight, but it is
easily pushed around by other robots. It is
thus effective and passable, but not the
absolute best option for any task. It is
recommended to connect the wheels
together as in our 4 Wheel - Connected
drive train configuration.
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This robot is very similar to the previous robot
in that four motors are directly driving four 4"
tetrix wheels, but this time the motors are
chained together on each side.
four AndyMark NeveRest motors
 four 4in Tetrix wheels
 four Tetrix sprockets
 two sets of .25 Tetrix chain
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This drive train can maneuver around the
field under heavy weight, but only at
average or below average speeds. It is
easily constructed and does not draw a
large number of amps during
movement. It can push/pull an average
weight, but it is easily pushed around by
other robots. It is thus effective and
passable, but not the absolute best
option for any task.
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For this design, we used an already assembled robot
from the previous year instead of building a new
drive train for testing. This design has five wheels on
each side that are driven by chain with a total of four
motors. The middle three wheels are in contact with
the ground at all times and the outer two are raised
up off of the ground and are used for stabilization
and to help the robot go up a ramp with ease.
four AndyMark NeveRest 40 motors
 ten 3in Tetrix wheels
 four tooth gears
 six tooth gears
 four sets of .25 Tetrix chain
 twelve Tetrix sprockets
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NOTE: This was our competition robot from last year, so we were
unable to fully collect data for various weights.
Robot test weight - 55 lbs.
Straight line test (@55 lbs) - 6.4 Seconds
Stall Weight test (@55 lbs) - 25 lbs.
Slide test (@55 lbs)- 65 lbs.
Ramp test - Pass
Spin Test (@55 lbs) - 2.1 Seconds
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In summary, this robot is a very strong
defensive bot, and is not easily pushed
around the field. It is also very stable and
not easily tipped. However, it draws a
significant amount of current and so the
battery quickly drains during a match. It
is also expensive and rather complicated
to build.
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This drive train consists of four motors that are driving
a total of six wheels with three on each side by chain.
Four of the six wheels in this design are 4" Omni
wheels from AndyMark and the remaining two are
AndyMark high performance wheels. We tested the
wedgetop treads and the performance treads
separately, as demonstrated by the data below.
four AndyMark NeveRest 40 motors
 two AndyMark high performance wheels
 four AndyMark Omni wheels
 two sets of .25 Tetrix chain
 two 1010 aluminum extrusions 18" long
 five 1010 aluminum extrusions 10" long
 six 1010 aluminum extrusions 4" long
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It was incredibly good at spinning no
matter how much weight we added,
making it very maneuverable. This would
be a good offensive robot with decent
defensive capabilities, as it took a lot of
weight to move it. It is also optimal to
gear up this drive train for different
strategies, as its overall effective
performance would carry over to any
strategy.
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This robot is powered by four motors that
are connected together by tetrix
conveyor/tank tread.
four AndyMark NeveRest 40 motors
 four Tetrix tread sprockets
 two sets of Tetrix tank tread
 two 1010 aluminum extrusions 18" long
 five 1010 aluminum extrusions 10" long
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This drive train performed well in all but one of
the tests. Due to its 3" wheels, it's average
speed is lower than the other drive train which
all had 4" wheels (except for the holonomic). It
successfully pulled 45 lbs at max added
weight, giving it the top score in push/pull
power. It was not very efficient at power
usage, and it could not travel up the ramp at
any weight. Overall, this drive train is useful for
pushing power, but if used, it must be highly
protected and concealed within the robot
frame so that the tracks do not break upon
contact with an opposing robot.
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This robot is a 4 wheel holonomic drive
robot. Each wheel is powered
independently to allow for multidirectional travel.
four AndyMark motors
 four 3in Tetrix omni wheels
 1 18" square base plate - 1/8" aluminum
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This robot is highly agile at low weight,
but it struggles under high stress. It is
unable to go up a ramp or pull much
weight, so it is only good at scuttling
around. This drive train can be easily
pushed around, so it's not
recommended for defensive strategies.