1

Drivetrains Presented by: John & Paul Hines

Purpose of this Presentation

• Drivetrain SelectionoTypes of drivetrainsoTypes of wheelsoDrivetrain mechanicsoBest drivetrain for your teamoMaintenance

Ideal Drivetrain

• Gets your robot where it needs to be, when it needs to be there

• Is robust and reliable• Can push/pull objects and other robots• Meets your strategy goals • Fits with the game• Can be built with your resources • Rarely needs maintenance• Can be fixed quickly

Basics

• Know your resources• Decide after kickoff:• Speed, power, shifting, mobility• Use the most powerful motors on

drivetrain• Don’t drive ½ of your robot… WEIGH IT

DOWN!• Break it early• Give software team TIME to work• Give drivers TIME to drive

Wheel Types:  Traction

Standard wheels with varying amounts of traction, stength and weight

AndyMark KOP

VEX Pro

AndyMark Plaction

AndyMark Pneumatic

Wheel Type:  Holomonic

Special Wheels that allow the robot to achieve Holomonic motion

Mecanum OmniCrab Module

Caster,Omni,Slide

DrivenWheel

+ Easy to design+ Easy to build+ Light weight+ Inexpensive+ Agile

- Not much power- Will not do well on ramps - Easily turned

Motor(s)Motor(s)

Drivetrain Types: 2 Wheel Drive

Chain or belt

DrivenWheels

+ Easy to design+ Easy to build+ Inexpensive+ Powerful+ Sturdy and stable

- Not agile- Turning is difficult

Motor(s)Motor(s)

DrivenWheels

Drivetrain Types: 4 Wheel Drive2 Gearboxes

DriveWheels

+ Easy to design+ Easy to build+ Powerful+ Sturdy and stable+ Many options:Mecanum, traction

- Heavy- Costly

Motor(s)Motor(s)

DriveWheels

Motor(s) Motor(s)

Drivetrain Types: 4 Wheel Drive4 Gearboxes

Gearbox Gearbox

+ Easy to design+ Easy to build+ Powerful+ Stable+ Agile*

 - Heavy ** - Expensive **

** - depending on wheel type

*2 ways to be agile

1. Lower contact point on center wheel

2. Omni wheels on front or back or both

This is very common in FRC

+ simple+ easy+ fast and powerful+ agile

Drivetrain Types: 6 Wheel Drive2 Gearboxes

Check out 1114’s Kitbot on Steroids• Simbotics.org

• Resources• Kitbot en

esteroides

Gearbox Gearbox

+ Powerful+ VERY Stable

- NOT AGILE - HEAVY - Inefficient - EXPENSIVE - Hard to maintain For turning, lower the contact point

on center of track wheel

Sole benefit: Ability to go over things

Will NOT push more than a well-controlled 6wd

Drivetrain Types: Tank Treads2 Gearboxes

Tank vs. Holomonic

Tank Drive2 Degrees of Freedom• Rotation• Forward-back Motion

Holomonic Drive3 Degrees of Freedom• Rotation• Forward-back Motion• Side-side Motion

4 wheel drive or 3 wheel drive+ Immediate Turning+ Simple Control – 4 wheel independent- No brake- Minimal pushing power- Jittery ride, unless w/ dualies- Incline difficulty

Drivetrain Type: Killough

+ Simple mechanisms+ Immediate turn+ Simple control – 4 wheel independent-  Minimal brake-  Minimal pushing power-  Should have a suspension-  Difficulty on inclines

Drivetrain Type: Mecanum

http://www.youtube.com/watch?v=xgTJcm9EVnE

Team 1346 Mechanum Drive

> Each wheel rotates to steer+ High-traction wheels+ No friction losses in wheel-floor interface+ Ability to push or hold position+ Simple wheels-  Complex system to control and program-  Mechanical and control issues-  Difficult to drive-  Wheel turning delay

Drivetrain Type:  Crab/Swerve

368’s Crab Drive in 2010

http://www.youtube.com/watch?v=q9uck-wRa_8

• Game dependent• Determined by wheel size and gear ratios• Controllable top speed: 15 ft/sec• Average 1-speed rate: 9 ft/sec• Good pushing speed: 4-5 ft/sec

Drivetrain Top Speeds

Center of Gravity (CG)

o Robot mass is represented at one pointo Mobility increases when Cg is low and

centeredo High parts = light weighto Low parts = heavy (within reason)

Which is more Stable?

Gearboxes/Transmissions

• Gear ratio determines top speed and motor load

• Single Speed and Shifting options

• CIMple Box shipped in 2011 KOP

• 1 or 2 CIMs per gearbox

• 2011 4 CIMs allowed

• Must be greased to reduce friction

Belts

+ Don’t Stretch

+ Can reach far- Need to buy in custom sizes

Chain Selection

#25  +  Lightweight  +  Easy to install  +  Smaller  -  Easy to derail  -  "Steches" over time

#35  +  Allows for slop  +  Minimal "stretching"  +  Heavy duty applications   -  More weight

Working with Chains

• Tensioningo Critical to keep robot from throwing chainso Must be accessible and easily adjustableo Does not need to be used on ALL chains but

should be on drive systems 

Look at other Designs!• Competitions• chiefdelphi.com• Team websites• YouTube• thebluealliance.com

Presented by:    Paul Hines    John Hines

Drive Types + Wheel Pictures www.AndyMark.com  (FRC Supplier)

Swerve Drive Revolution Custom Framewww.team221.com  (FRC Supplier)

Check out 1114’s Kitbot on Steroids• Simbotics.org

• Resources• Kitbot en esteroides