Mechanisms Presentation

Murphy's Law in Action

Dillon Voegeli

Jamier Boatman-Harrell

Jared WIttmayer

In this presentation:

➢ Rack and Pinion

➢ Bevel Gears

➢ Wedge Cam Follower

Rack and Pinion

Rack and Pinion

● Type of gear assembly

● Bar of gear teeth - “Rack”

● Rotating circular gear - “Pinion”

● Converts rotational motion

● into linear motion

Rack and Pinion

● Common Applications

– Automobile Steering

Rack and Pinion

● Common Applications

– Rack Railway

Bevel Gears

Bevel Gears

● Transmits rotational energy

through non-parallel shafts

● Characterized by a conical pitch

surface

● Crown gears are considered bevel

gears

Types of Bevel Gears

● Categorized by the geometry of the teeth and pitch surface

● Straight bevel gear

● Spiral Bevel Gear

● Hyploid Bevel Gear

● Zerol Bevel Gear

Applications of Bevel Gears

● Spiral bevel gears are commonly used in high-rpm applications, such

as motorcycle and helicopter transmissions

Applications of Bevel Gears

● Old pocket (mechanical) watches use a bevel gear to adjust the hands

of the watch.

Applications of Bevel Gears

● Grain mills would use bevel gear systems to turn grinding stones and

grind wheat into flour.

Wedge Cam Follower

Basis of Cam Follower Mechanism

•The cam is element of the system that drives the follower through a specified motion.

•The motion is maintained by the two elements by direct contact.

–In this mechanism the the follower has line contact with the cam creating higher pair mechanism

–Contact is kept by an external force. i.e. spring, gravity, or weight of follower.

Basic of Elements

•Cam: Imparts prescribed motion to another by direct contact.

–May be stationary, translate, or oscillate.

•Follower: The element in direct contact with the cam.

•Follower system: All elements moved by the cam.

–Maybe connected directly to follower or by linkage and gears.

–The system may also like the follower translate or oscillate.

•The drive: The prime mover that imparts motion to the cam or the the follower system of a stationary cam.

Cam Follower

Wedge Cam Follower

•Typically the followers for the wedge cam can be one of two.

–Knife/Wedge Follower

•Can follow complicated profiles, but wears fast due to frictional forces.

–Roller Follower

•Wear is minimized.

•Profile of the cam radius must not conflict or the roller may not follow the correct path.

•Wedge cam Follower’s cam component is a type of a Plate Cam.

–Plate cams

Motion Analysis of Wedge Cam

•Motion of the cam follower is dependent on the profile or shape of the cam.

•Therefore the profiles can create three types of motion:

–Uniform Velocity

–Uniform acceleration/retardation

–Simple Harmonic Motion

Wedge Cam Motion con’t

•The profile of the wedge cam is formed on one side of the cam.

•The cam reciprocating is caused pneumatic or hydraulic cylinder, rack and pinion, or some other linear output device.

•This profile gives the wedge cam translatory motion.

–The reciprocating motion drives the follower vertically.

–As the follower translate the force of the spring keeps in it along the profile as it may stay in motion.

•For applications of this systems in terms of linear movement or circular movement must be fluid.

–This includes instances where movement of the part is in two directions.

•There fore for this cam type constant velocity is needed.

Applications

•Merry-go-round, where the horses are attached to plate cams that make them raise and lower as the turntable spins around the motor.

•Mechanical paper punch

•Nut tapping machine