Mechanics Final Flashcards
How do chain drivers operate?
Tension
What are the advantages of chain drives?
- Versatility - Easily adjustable length
- Variety - Limitless Variations (Styles, spacing, and materials)
- Flexibility - Ability to bend back while maintaining positive engagement.
- Durability - Long operating life
- Can Operate in Harsh Environments - Withstand heat, water, oil, corrosion, etc
- Unlimited Shelf Life - Little to no deterioration
- Generally can be replaced without disturbing other components
- Large HP loads/speeds - Large load on large pitch, faster speed on small pitch
What are the disadvantages of chain drives?
- Loud as fuck
- Chains wear and elongate over time
- Lower speed on large pitch chains
- Sprockets tend to need replaced
In chain nomenclature, what does 0 denote? (For example, 50)
Normal weight
In chain nomenclature, what does 1 denote? (For example, 51)
Light weight
In chain nomenclature, what does 2 denote? (For example, 52)
Large roller
In chain nomenclature, what does 5 denote? (For example, 25)
No roller (Only typical of chains below 1/2 pitch)
In chain nomenclature, what does -# denote? (For example, 50-2)
Stranded chain/amount of strands (2 in this case)
In chain nomenclature, what does 20 – denote? (For example, 20 50)
Double pitch
In chain nomenclature, what does H denote? (For example, 50H)
Heavy (Link plate is same thickess as the next chain size up)
In chain nomenclature, what does C denote? (For example, C20 50)
Conveyor
In chain nomenclature, what does 3## denote? (For example, 300 50)
Stainless (Corrosion resistant, but not harder)
In chain nomenclature, what does 6## denote? (For example, 600 50)
Hardened and Corrosion Resistant
In chain nomenclature, how do you determine size? (For example, 50)
1st number out of 8 (excluding prefixes such as 300, 600, 20, and C). For this example, the chain is 5/8in
What is chain pitch?
The distance between flexing joints.
How are chains connected?
Either Connecting/Master Links or Offset/Half Links
What are Connecting/Master Links used for?
Even number of teeth on sprocket.
What are Offset/Half Links used for?
Odd number of teeth on sprocket.
How are the chain connectors held on?
Spring clip or cotter key/pin.
Which clip/pin is required for motion in both directions?
Cotter key/pin
Should you add lube to a self lubricated chain?
No.
How are heavy chains different?
The link plate is 1 size thicker. In other words, the link plate is the same thickness as the next chain size up.
Why would we use heavy chains?
When we need more shock load capabilities but have space limitations.
How are double pitch chains constructed?
Half the rollers, with double the link plate length.
Do double pitch chains transmit less load capacity than normal pitch?
No
How do we size double pitch chains?
Same as any other chain because the sprocket size is the same, despite the increased pitch.
Identify this chain: C20 62H
Conveyor
Double Pitch
3/4
Large Roller
Heavy
Identify this chain: 600 50H
Hardened/Corrosion Resistant
5/8
Heavy
Identify this chain: 304 40
Stainless
1/2
Standard Weight
Identify this chain: 60-3
3/4
Standard Weight
3 Strands
Identify this chain: 300 35-4
Stainless
3/8
Roller less
4 Stranded
What are the 3 basic classifications of belts?
Flat
V
Synchronous(Toothed)
Which component is driven by the belt?
Pulley
What is the driving “pulley” for flat belts?
Drum
What is the driving “pulley” for V belts?
Sheave
What is the driving “pulley” for Synchronous belts?
Sprocket
What are the advantages to belt drives?
•Inexpensive to install/maintain
•Reliable
•Simple design
•Easy to install
•No lubrication
•Wide variety of applications
•Adjusted for nearly any speed
•Pulleys are less expensive than chain sprockets
•Long pulley life
•Act as a clutch
What is the primary benefit to flat belts?
Have the flexibility to go around corners for special drive configurations.
How do flat belts drive?
Tension
How do V belts drive?
Friction
How do Synchronous belts drive?
Positive Tooth Engagement (and tension)
Which belt is ideal for low speed?
Flat
Which belt is ideal for medium speed?
V
Which belt is ideal for high speed?
Synchronous
How tight should a V belt be tensioned?
1/4in of deflection per foot of span (contact to contact)
Which side of a V belt is the tension side?
The side in which the sheave is pulling
Which side of a V belt is the slack side?
The side in which the sheave is “pushing”(paying off)
What are the two base construction categories for V belts?
Envelope and Raw Edge
What is the difference between Envelope and Raw Edge V belts?
Envelope V belts are enclosed in a rubber/fabric coating which protects from contamination and elements, Raw Edge belts are not.
Where would we use Envelope V belts?
Outdoors/Harsh conditions
When would we use Raw Edge V belts?
Interior/clean conditions
How can you tell the difference between Envelope and Raw Edge V belts?
Raw Edge V belts have visible cords
What is the bottom of a V belt and what does it do?
Cusion Rubber - Provides cord support.
What part of a V belt is above the Cushion Rubber and what does it do?
Tensile Cords - Carry the load.
Which part of a V belt is above the Tensile Cords and what does it do?
Insulation Rubber - Protect/Adhere to cord.
Which part of a V belt is above the Insulation Rubber and what does it do?
Backing Fabric - Resist Abrasion
How are classic V belts identified?
Letter Designation (A,B,C,D)
Identify this V belt.
C65
C - 7/8in(Classical V) 65- 65in inside length
What is the speed range for classical V belts?
Fractional to 500HP
What do double V belts look like?
Hexagonal
What does X denote on a V belt?
The belt is cogged.
What does a cogged belt refer to?
Belt with notches removed from the Cushion Rubber with the intent to increase flexibility.
What is the difference between Classical V and Wedge V belts?
Wedge V belts fit deeper into the sheave and provide better contact and strength.
How are Wedge V belts identified?
A number (denoting x/8in), the letter V (denoting Wedge V), and a number ending in 0 (denoting outside length with the first number(s)) The 0 at the end stands for outside.
Identify this belt.
7VX400
7 - 7/8in
V - Wedge Belt
X - Cogged
400 - 40in outside length.
How are Fractional Belts identified?
A number (x/8in denoting belt width), the letter L (denoting Fractional HP belt), and a number ending in 0 (Denoting length in inches for the outside of the belt, using the 1st number(s)) Last 0 stands for outside
What are Fractional Belts used for?
Drives with 1 or less HP.
What are banded belts?
V belts (either Classical or Wedge) banded together using insulation rubber and backing fabric for use in multi channel sheaves.
Why do we use banded belts?
Prevent uneven slipping from using multiple single belts. Eliminating rollover tendency.
How are banded belts identified?
Same as other V belts, but starting with a number and slash (x/) which denotes the amount of belts banded together.
What is the disadvantage of Synchronous belts?
No slippage due to positive
tooth engagement which leads to possible damage to clutch (if applicable) or other components.
What are the 2 types of bearing lubrication?
Grease and Oil
What is grease good for?
Lower Speed and Low Temperature
Easier to use/keep in bearing and housing
Why would we use oil
Higher Speed and High Temperature
What are the 2 types of oils for lubrication?
Petroleum and Synthetic
What oil is used for severe applications?
Synthetic.
What would we use for lubrication in low speed, high temperature situations?
Dry Lubricants
What do Linear Bearings provide?
Linear Motion (Up/Down, Side/Side, etc)
How are Linear Bearing typically comprised?
Fixed support component called a rail, way, or guide.
What is the purpose of bearing seals?
Keep contamination out, and lubricant in.
What are the two main types of bearing seals?
Contact and Non Contact
Which bearing seals type is best for high speed applications?
Non Contact (Such as Labrynth Ring)
Which bearing seals spins with the shaft?
Contact.
What are the benefits of mounted bearings?
Shaft support and reduction of friction.
What are the types of bearing mounts?
Pillow block (split and solid), flanged cartridges, cylindrical cartridges, and take up units.
Where are split housing pillow block units useful?
Where it is necessary to dismantle the equipment for bearing replacement on a regular basis.
How are flanged cartridge blocks mounted?
On vertical surfaces where the shaft passes through at a right angle.
What is the benefit of a piloted flanged cartridge type mount?
Increased mounting accuracy leading to less play.
What are take-up units used for?
Adjust the center distance between shafts or where belt tightening is required.
What do spherical and rod end bearings accommodate?
Wide range of misalignment.
What is the type of contact roller bearings have between races?
Line Contact
What are the four types of roller bearings?
Cylindrical, Needle, Spherical, and Tapered
What are some pros to cylindrical bearings ?
Highest radial load and speed capacity
What are some speed limiters on cylindrical bearings ?
Roller length-to-diameter ratio, grade of precision, roller guidance, type of cage, type of lubrication, shaft installation, housing accuracy, and heat dissipation
What is a “fixed bearing” ?
A bearing mounted in a fixed or secured pivot point at one end of the shaft
What is a “floating bearing” ?
The opposite end of the shaft from the mounted bearing. It allows axial forces to pass through. Allows thermal expansion.
T/F
Roller bearings are more sensitive to misalignment compared to ball bearings
True
What is the ratio for needle bearings?
6:1
Roller length is 6 times the diameter
What are the two types of needle bearings ?
Cage separated, and full complement style
What type of needle bearing accommodates higher speeds and precision rolling ?
Cage separated
What is another name for full complement needle bearings ?
Drawn cup needle bearings
What is the inner race of cage sepearated needle bearings ?
The shaft
What is the inner race of full complement style needle bearings?
The shaft
What is a common issue with full complement needle bearings ?
The rollers all falling out due to no separators
What is a reason needle bearings are selected compared to other roller bearings?
Heavy radial load in minimal space
Spherical roller bearings are good for what ?
Misalignment between 0.5 deg. to 2 deg.
High radial load and thrust load
What is the ratio for spherical roller bearings ?
4lbs. of radial load for every 1lb. of thrust load
What are the two components of tapered roller bearings?
Inner ring or CONE, an outer ring or CUP
