Belts Flashcards by shawn Burleigh

When reading stadia lines how do you figure out the distance?

Upper stadia - lower stadia / 100

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What are the thread classes and which fit class requires the most torque

1/2 - 12 UNC -3A LH

1/2 major diameter
12 threads per inch
UNC - thread class
3 tolerance class (class of fit)
- 1 loose 2 standard 3 close
A - thread type
A is external B is internal

3 close for requires the most torque

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When drilling brass how do you stop the drill bit from catching

File or hone rake angle to 0

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What are _______ for
Snub pulley’s
Take up pulleys
Bend pulleys
Idler pulleys
Troughing pulley

Increase arc contact
Increase belt tension
Change direction of belt travel
Support the belt on the unloaded side
Generate trough shape

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The ability for grease to resist deformation stiffness

Consistency

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Bearing codes

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When calculating safe working load the formula is? And if you have two different slings lengths which one do you use for the calculation and why?

Use the shortest sling because it will give you the smallest swl
H=vertical distance from load to shackle
L = length of sling

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Why is oil applied to the slack side of a chain?

When the chain is slack it will allow oil to get in between the plate

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What do you risk if the hourly volume is exceeded when using acetylene?

Acetone may begin to be expelled from the cylinder

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How is chain pitch designated

Al1022

First 2 numbers in 1/8th

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Where does the v belt ride in the sheave?

Sides of the belt

Gets its grip from the wedging action
Must not ride at the bottom of sheave

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When do you adjust variable speed belts?

Always adjust when machine is running

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What is a disadvantage of an open ended belt

Can only carry 1/3 of the load

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Why is preliminary clean up important for v belts?

Dirt and deposits degrade belts and create an imbalance which prematurely wears out equipment

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Why is it important to clean and inspect sheaves?

Check for cracks especially around the hub.

Build up of deposits can cause vibrations

Inside of groove is what grips belt must be free of contamination

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What two ways can you check sheave grooves?

Sheave groove gauge

New belt in sheave groove

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Cause of belt swell, soft and bottom seam starts to open up?

Excessive exposure to oil

Cut bottom or sidewall of belt?

Pried over with screw driver or damaged during install

Make sure tension is loose enough before forcing the belt on

Belt turnover?

Belt misaligned
Worn sheeves
Excessive vibration

Spin or burned belts

Insufficient tension

Contact with obstruction

Ply separation in a belt

Excessive tension

Substantial drives

Excessive belt stretch

Improper matching
Mixed old belts with new belts
Non-parallel shafts
Different manufacturers
Belt/pulley incomparable

Hardening and pre mature belt cracking

High ambient temperature

What defects are corrected by changing worn sheeves?

Uneven envelope wear
Ply separation
Belt turnover
Excessive stretch
Mismatched belts at installation
Cut through on top (joined belts)

What problems are resolved by proper tension?

Spine or burn Envelope wear Belt squeal Excessive stretch Excessive vibration

What symptoms call for replacing belts

Weathering or case cracks Envelope wear Excessive vibration Mismatched belts at installation

What is most important about a belt tensioning system?

Must be reliable in holding the belt to specific tension and holding the drive in alignment

When installing a new belt how much do you loosen the take up?

Enough so that you don’t have to pry the belts and they do not roll over upon assembly.

Fitting new belts involves?

Aligning the sheaves and tensioning the belt

Before installing new belts and/or sheaves you must:

- check for worn bearings by bumping, pushing, and pulling the shaft - check axial movement in the shaft by setting a dial indicator on the end. -check shaft for runout -if bearings and shaft runout are good. Rough align by placing straight edge over the two sheeves and shim accordingly

Maximum belt misalignment per foot is

1/16 “

Once sheaves are mounted on the taper what do you check for?

Axial runout (wobble) Place indicator reading of the face of the sheave

When using taper bushings what can cause runout on sheaves?

Improper tightening of the taper bolts

To tension individual belts what do you use?

Belt deflection gauge and deflection table. Tension belt until you get a deflection equal to the value on the deflection table.

How do you check tension on a banded v belts?

Us a special deflection gauge that spans the width of the belt

When should you not used idlers?

Reversing drives

What are some signs of to much tension on a new belt?

Bearings running hotter Higher amperage draws from motor

What are signs of not enough tension

Squealing sounds Smell of burning belts

What are signs of misalignment

Flapping belts on the tension side Excessive vibration could be sign of misalignment or run out

Repeat start up check after how many hours of running after new belts have been installed?

Every 8 hours for the first 24 hours

Chirps indicate

Dirt or dust in the sheave grooves or on the sides of the belt

If operating conditions for belts is above 60 degrees c what should you do?

Use heat treated belts