SUMMER INSTITUTE - ROBOTICS THE OHIO STATE UNIVERSITY Drivetrains.

SUMMER INSTITUTE - ROBOTICS

THE OHIO STATE UNIVERSITY

Drivetrains

GEARS!!!!

A gear is a wheel with teeth along its rim. It is used to transmit effort from one shaft

to another.

Gear Train!?!?!?

Combination of two or more meshed gears. Used to change:

the rate of rotation the direction of rotation the amount of torque.

Gear Ratio (Oh no! Not MATH!)

Gear ratio is also called “Mechanical Advantage”

Gear ratio Number of Driver Teeth

Number of Driven Teeth

Who lifts buckets these days? Let’s talk about CARS!!!

Your good ‘ol run of the mill transmission. sort of.

1st: 3.08:12nd: 1.93:13rd: 1.34:1 4th: 1.0:1

Types of Gears

• Spur gears

• Worm gear

• Rack and pinion

• Bevel gears

Worm Gears

Used to change speed and direction of rotation.

High gear ratios.Higher load capacity (TORQUE).

What is the gear ratio?

Rack and Pinion

Used to convert rotational motion into linear motion, or vice-versa.

Bevel Gears

Used for intersecting shafts. Most transmissions occur at right angles but

shaft angles can be any value.

Chains and Pulleys – sort of like gears…

Like gears, but pinions don’t meshTransfers motion longer distancesGear ratio equation works the sameSome pulleys don’t

have teeth, can slip

Caterpillar skid steerdrive system

The Task:

Develop a drive train to pull as much weight as possible up a ramp as quickly as possible.

You will have to make a tradeoff between TORQUE and SPEED (there’s that gear ratio again).

Here’s some math to help you out (what engineers do before they build things)…

P. 12

WWN

WII

P

FI

Sum of Forces parallel to plane = 0 P - WII - FI = 0

7

3

Check the length and height of the ramp

Static (Const. Velocity) Analysis

P. 13

P - WII - FI = 0 WII = W sin (slope angle) slope angle = atan(3/7) = ~23 degrees WII = 5 lbs (sin(23)) = 1.97 lb P = 1.97 lb + 0.5 lb = 2.47 lb Torque = P x Radius of Wheel = 2.47 x 0.875 = 2.16 lb-in = 34.6 oz - in

Torque

Speed

Stall

No Load Speed

Usable performance

Static (Const. Velocity) Analysis

OK! Any questions????