Supplied B1 Module 07A textbook: PDF pages 255–262.
Gears and tooth condition
Gears transmit rotary motion with a defined speed ratio and direction. Spur, helical, bevel and worm arrangements suit different axis and load conditions. Inspect teeth for pitting, scoring, cracks, abnormal contact and uneven wear. Check lubrication and retention as well as tooth appearance. A damaged tooth can contaminate other components and disturb load sharing. Contact patterns and wear measurements require the specified method. Similar tooth counts alone do not prove that gears have compatible pitch, pressure angle or helix geometry.
What must be considered beyond tooth count when matching gears? Tooth geometry and the required specification.
Backlash and alignment
Backlash is clearance between mating tooth flanks in the direction of motion. Some clearance accommodates lubrication and thermal effects, but excessive backlash can produce lost motion and impact. Too little can lead to binding and overheating. Measure at the prescribed positions while controlling movement of the mating member. Shaft alignment, bearing condition and housing distortion can change the result. Backlash is not the same as shaft end float. Adjust only by the approved method and verify the full range of operation.
What is gear backlash? Clearance between mating tooth flanks.
Belts and pulleys
Inspect belts for cracking, glazing, contamination, damaged teeth and separation. Inspect pulley grooves and alignment so the belt runs correctly. Set tension with the approved gauge and conditions; excessive tension loads bearings, while insufficient tension can slip or jump teeth. Do not pry a belt onto a pulley or apply dressing unless approved. Matched sets may need replacement together. A synchronous belt's positive drive does not remove the need for correct tension, tracking and tooth engagement.
What can excessive belt tension cause? Excess bearing loads and reduced life.
Chains and sprockets
Inspect chains for wear, stiff links, corrosion and correct joining-link installation. Inspect sprocket teeth for hooked profiles and abnormal wear. Chain elongation usually reflects wear at pins and bushes, not elastic stretching of intact side plates. Check tension, alignment and lubrication by the specified method. A new chain on a badly worn sprocket can wear rapidly. Guards and exclusion zones matter during functional checks because an exposed chain drive can trap clothing or fingers.
What commonly causes service chain elongation? Wear at pins and bushes.
Screw jacks and lever devices
A screw jack converts rotation into linear motion through a screw and nut, sometimes using recirculating balls. Inspect wear, lubrication, attachment security and the required backlash or free-play measurements. Check stops, travel and associated load paths. A worn jack may still move while having inadequate retention or unacceptable free play. Use specified loading conditions during measurement. Levers require sound pivots and bearings; excessive pivot clearance alters commanded movement and can make a correctly adjusted actuator appear inaccurate.
What does a screw jack convert? Rotary input into linear movement.
Push-pull rods and functional checks
Push-pull rods transmit both directions of linear force. Inspect tubes, rod ends, locking devices and thread engagement. Maintain required witness-hole coverage or engagement marks where provided. Adjustment changes geometry and travel, so verify clearances, stops and freedom of motion through the complete range. Use the specified independent inspection or error-capturing process for critical controls. Torqueing a locknut is not proof that the linkage has the correct length or that the rod end is within its angular limit.
Why check a linkage throughout its full travel? To detect interference, binding and incorrect geometry.
Apply the knowledge
Work through these examples before starting the quiz. Explain why the other choices would not meet the requirement.
A gear train binds after a backlash adjustment. Which condition should be considered?
Insufficient backlash or incorrect alignment — Too little tooth clearance can cause binding and heat.
A belt slips under load. What should be checked?
Specified tension, contamination and pulley condition — Slip may arise from tension, contamination or wear.
A chain is elongated and sprocket teeth are hooked. What is appropriate?
Assess the complete chain-and-sprocket set — Worn sprockets can accelerate wear of a replacement chain.
A rod end shows inadequate thread engagement. What is correct?
Rectify to the specified engagement and recheck geometry — A secure locknut does not compensate for insufficient engagement.