 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 › Time › Cost › Tools for fabrication › Part 1 of game manual  Rarely needs maintenance  Is repairable within 4 minutes  Uses minimal amount of space

 Decide strategy after kickoff › Speed › Power › Mobility  Decide how many motors will be allotted for drive train  Decide robot weight › Traction › Mobility › Speed › Offensive/Defensive ability

 Build for durability and test › Find weak points › Practice driving › Have spare parts and assemblies  Develop a project plan › Allot time for development and building  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

Omni caster wheels Driven wheels Motor 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.

Driven Wheels 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.

Driven Wheels Motor Chain 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 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 season which weighed 55 lbs.

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 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.

OmniOmni OmniOmni OmniOmni OmniOmni Motor 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

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.

 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.

 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.

 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.

 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.

 Test Data › Straight Line Speed Test (Seconds/Amps) › Pull Test (Pounds/Amps) › Side Drag Test (Pounds) › Spin Test (Time/Amps)  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

+ Easy to design + Easy to build + Lightweight + Inexpensive + Long battery life + Able to hold position - 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 = Decent on ramps = Decent maneuverability + - =

+ 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 - Not able to support much weight and move effectively = Inexpensive = Decent Maneuverability = Battery life depends on weight = Effective for defense + - =

+ Does well on ramps + Utilizes full potential out of all the motors + Very effective for defense + Supports robust robot well - Short battery life - Difficult to design - Difficult to build - Expensive = Decent Maneuverability = Weight neutral + - =

+ 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 - Difficult to design - Difficult to build - Very expensive = Weight neutral + - = Maneuverability: spins on axis well ++ Supports robust robot well

+ Easy to design + Easy to build + Lightweight + Long battery life + Able to hold position - Inconsistent turns make autonomous extremely difficult - Drive train needs to be geared up to reach competitive speed - Vulnerable, needs to be protected = Does decently on ramps with track treads = Average Maneuverability = Effective for defense = Cost neutral + - =

+ Long battery life + Inexpensive + High Maneuverability - Extremely difficult to program - Not able to hold position - Slow - Not at all effective for defense - Cannot go up ramp = Moderate weight = Moderate to design = Moderate to build + - =

 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 › 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 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.

 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.  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.  can be fixed within 4 minutes › easily replace motors between matches › easy to access critical components  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  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  Robot weight › What weight will maximize  traction  mobility  speed  defense (limit other robots pushing while playing offense)  Durability › put the drivetrain under stress to test the durability › identify weak points and correct them › driver practice › spare parts and assemblies  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

 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

 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.

 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

 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.

 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

 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.

 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

Robot test weight - 55 lbs. Straight line test lbs) Seconds Stall Weight test lbs) - 25 lbs. Slide test lbs)- 65 lbs. Ramp test - Pass Spin Test lbs) Seconds NOTE: This was our competition robot from last year, so we were unable to fully collect data for various weights.

 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.

 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

 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.

 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

 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.

 This robot is a 4 wheel holonomic drive robot. Each wheel is powered independently to allow for multi- directional travel.

 four AndyMark motors  four 3in Tetrix omni wheels  1 18" square base plate - 1/8" aluminum

 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.