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”

Who lifts buckets these days? Let’s talk about CARS!!! Your good ‘ol run of the mill transmission. sort of. 1 st : 3.08:1 2 nd : 1.93:1 3 rd : 1.34:1 4 th : 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 mesh Transfers motion longer distances Gear ratio equation works the same Some pulleys don’t have teeth, can slip Caterpillar skid steer drive 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 W WNWN W II P FIFI Sum of Forces parallel to plane = 0 P - W II - F I = Check the length and height of the ramp Static (Const. Velocity) Analysis

P. 13 P - W II - F I = 0 W II = W sin (slope angle) slope angle = atan(3/7) = ~23 degrees W II = 5 lbs (sin(23)) = 1.97 lb P = 1.97 lb lb = 2.47 lb Torque = P x Radius of Wheel = 2.47 x = 2.16 lb-in = 34.6 oz - in Torque Speed Stall No Load Speed Usable performance Static (Const. Velocity) Analysis

OK! Any questions????