Unit 6: Harvesting and threshing machines - Practice Quiz

1 What is harvesting?

2 Which hand tool is commonly used for manually harvesting cereal crops?

3 Which machine cuts a crop and places it in a row on the field?

4 What is the main advantage of mechanical harvesting over manual harvesting?

5 A crop should generally be harvested when it has reached:

6 What is the primary function of a thresher?

7 Which component performs most of the threshing action in a conventional thresher?

8 What is the function of the concave in a thresher?

9 Which thresher component removes light chaff using airflow?

10 A spike-tooth thresher is named after the spikes fitted on its:

11 Why is a combine harvester called a "combine"?

12 Which part of a combine harvester cuts the standing crop?

13 What does the reel of a combine harvester do?

14 Where is cleaned grain temporarily stored in a combine harvester?

15 What is the main function of straw walkers in a conventional combine harvester?

16 A reaper covers hectares in hours. What is its effective field capacity?

17 A combine harvests at a rate of . How much area will it harvest in hours?

18 A machine has a theoretical field capacity of and an effective field capacity of . What is its field efficiency?

19 How much time is required to harvest at an effective field capacity of ?

20 A tractor develops a drawbar pull of while moving at . What is its drawbar power?

21 A wheat crop has mature grains, but its straw is still slightly green and moist. Which harvesting approach is most suitable when field drying is required before threshing?

22 During mechanical harvesting, many grains remain attached to uncut heads after the machine passes. Which adjustment should be checked first?

23 Which harvesting method removes mainly the grain-bearing portion while leaving most of the standing straw in the field?

24 A farmer delays cereal harvesting well beyond physiological maturity during dry weather. Which field loss is most likely to increase?

25 Why is a reciprocating cutter bar commonly fitted with crop dividers at both ends of a grain header?

26 In a tangential-flow thresher, how does the crop primarily move through the threshing unit?

27 A thresher produces excessive broken grain while leaving very little unthreshed grain. Which adjustment is most appropriate?

28 After threshing, a sample contains many light chaff particles mixed with otherwise clean grain. Which component setting should be examined first?

29 What is the primary function of the concave in a cylinder-type thresher?

30 A thresher leaves many grains attached to the ear heads in the discharged straw. Assuming the feed rate is normal, which adjustment is most suitable?

31 Which sequence correctly represents the major operations performed by a conventional combine harvester?

32 In a conventional combine, what is the main role of the straw walkers?

33 A combine is losing clean grain over the rear of the sieves, and the tailings return is low. Which condition is the most likely cause?

34 A combine reel is rotating much faster than the machine's forward speed in a standing cereal crop. What problem is most likely?

35 Why is the concave clearance of a combine often set wider at the rear than at the front?

36 A harvester has a cutting width of and operates at . What is its theoretical field capacity?

37 A combine has a theoretical field capacity of and a field efficiency of . How long will it take to harvest ?

38 A wide combine travels at and achieves an effective field capacity of . What is its field efficiency?

39 A harvesting machine develops a draft of while moving at . What drawbar power is required?

40 A combine harvests at an effective capacity of and consumes of fuel. How much fuel is required to harvest ?

41 A combine is harvesting a lodged cereal crop at with a reel-speed index of , where reel-speed index is the ratio of reel peripheral speed to forward speed. If forward speed is reduced to , what reel peripheral speed preserves the same index?

42 A reciprocating cutter bar has a knife stroke of and operates at complete cycles per minute. Neglecting velocity variation within each stroke, what is its mean knife speed?

43 Loss samples show of grain on the ground before harvesting, behind the header with the separator disengaged, and behind the operating combine. Which allocation is correct?

44 A farmer must harvest a dense, tangled forage crop containing occasional stones while minimizing soil contamination and avoiding severe plugging. Which machine-feature combination is most appropriate?

45 During direct combining, reducing grain moisture lowers incomplete threshing but sharply increases header shatter. Which change best addresses the dominant new loss without unnecessarily intensifying threshing?

46 A thresher cylinder of diameter must provide a peripheral speed of . What cylinder speed is required, to the nearest revolution per minute?

47 A spike-tooth thresher produces many cracked kernels while the straw still contains unthreshed heads. Cylinder speed and concave clearance are uniform and within the manual's normal range. Which condition most plausibly explains both symptoms occurring together?

48 Clean grain is being blown out with chaff, but the sample entering the grain outlet is otherwise clean. Which adjustment should be attempted first while keeping sieve settings unchanged?

49 A thresher handles of crop with a grain-to-straw mass ratio of . If of grain remains unthreshed, what is the threshing efficiency?

50 Compared with a tangential-flow cylinder of similar width, why can an axial-flow threshing unit often achieve effective threshing at a less aggressive instantaneous setting?

51 Which sequence correctly traces the dominant crop and grain flow through a conventional combine after the cutter bar severs the crop?

52 A combine's tailings return is overloaded, the grain tank sample contains unthreshed spikelets, and little clean grain is found behind the cleaning shoe. Which adjustment most directly addresses the underlying problem?

53 A conventional combine shows low cylinder loss but high grain concentration near the rear of the straw walkers. The loss rises sharply when crop throughput increases. Which action is most likely to reduce the loss?

54 Why is a hydrostatic ground drive especially useful when harvesting a field with rapidly varying crop density?

55 On a side slope, grain and chaff accumulate on the downhill side of a conventional cleaning shoe, causing grain loss despite adequate total sieve area. Which feature most directly corrects this mechanism?

56 A combine operates at with a field efficiency of . Approximately how many hours are required to harvest ?

57 A thresher shaft requires a torque of at . If transmission efficiency from tractor PTO to the shaft is , what minimum PTO power is required?

58 Owning a combine incurs annual fixed costs of and variable costs of . Custom harvesting costs . Ignoring timeliness effects, at what annual area are the two alternatives equal in cost?

59 A harvesting machine has a theoretical travel speed of , wheel slip of , and field efficiency of . How long will it take to cover ?

60 A crop yields . Sampling indicates preharvest loss of , an additional header loss of , and an additional separator-cleaning loss of . What percentage of potential yield is lost in total?