Harvesting Machinery Questions and Answers

Answer: B

The width of cut is about 1.07 m.

The thresher capacity is in kg of crop (grain plus straw), while the yield is given in kg of grain. With a grain to straw ratio of 60 : 40, each hectare carries 3000/0.6 = 5000 kg of crop:

\[ \begin{aligned} \text{area rate} &= \frac{2400\ \text{kg/h}}{5000\ \text{kg/ha}} = 0.48\ \text{ha/h} \\ &= 4800\ \text{m}^{2}/\text{h} \\ w &= \frac{4800}{4500\ \text{m/h}} = 1.07\ \text{m} \end{aligned} \]

Treating the 2400 kg/h as grain gives 0.8 ha/h and a width of 1.78 m, which is the trap in this question. The other widths do not correspond to the crop throughput at 4.5 km/h.

Answer: D

The threshing efficiency is about 96.63%.

Threshing efficiency is the threshed grain as a fraction of all grain fed to the machine. Threshed grain includes what reached the tank and the threshed grain lost over the walker and shoe; unthreshed grain is what came out still in the ear:

\[ \begin{aligned} \text{threshed} &= 135 + 0.65 + 2.4 = 138.05 \\ \text{total} &= 138.05 + 4.54 + 0.28 = 142.87 \\ \eta &= \frac{138.05}{142.87} = 96.63\% \end{aligned} \]

Leaving the walker and shoe losses out of the threshed grain lowers the figure toward 94.4%, the trap behind the lower options.

Answer: A

The grain yield is 2.36 t/ha and the cylinder loss 0.77%.

The test area is \(3.6 \times 20 = 72\ \text{m}^{2}\). The total grain on that area is the tank grain plus all the seed lost over the walker and the shoe:

\[ \begin{aligned} \text{total} &= 16.5 + 0.10 + 0.05 + 0.25 + 0.08 \\ &= 16.98\ \text{kg} \\ \text{yield} &= \frac{16.98 \times 10000}{72} = 2358\ \text{kg/ha} \end{aligned} \]

that is, 2.36 tonne per hectare. The cylinder loss is the grain the threshing cylinder failed to thresh, which is the unthreshed seed over walker and shoe:

\[ \frac{0.05 + 0.08}{16.98} \times 100 = 0.77\% \]

The free seed over the walker and the shoe counts as separation and cleaning loss, not cylinder loss. The total material over walker and shoe is mostly straw and chaff and is not grain at all. The other yield figures are far above what 16.98 kg on 72 m² gives.

Answer: B

The theoretical capacity is 5.25 t/h.

Each knife cut removes a slab of straw whose cross-section is the throat (width × clearance) and whose thickness is the length of cut. The number of cuts per minute is knives × speed:

\[ \begin{aligned} V &= 0.45 \times 0.15 \times 0.010 \times 4 \times 540 \\ &= 1.458\ \text{m}^{3}/\text{min} \\ m &= 1.458 \times 60 \times 60\ \text{kg/h} \\ &= 5248.8\ \text{kg/h} \approx 5.25\ \text{t/h} \end{aligned} \]

(the first 60 is the bulk density in kg/m³, the second converts minutes to hours). The moisture content is not needed because the bulk density is given for the straw as fed. 1.31 t/h is what you get with one knife instead of four, and the larger values do not follow from these dimensions.

Answer: A

The reel speed index varies from 1.25 to 1.5.

The reel of a combine or reaper pushes the crop towards the cutter bar. The reel speed index is the ratio of the peripheral speed of the reel to the forward speed of the machine. It must be greater than 1 so that the reel bats move backwards relative to the crop, and a value of about 1.25 to 1.5 does this without shattering grain from the heads.

Ratios of 2 or more would strike the crop too hard and cause grain loss, so the higher ranges are not used.

Answer: C

The keyed reach height is 4 m.

A tractor drawn hydraulically operated platform is an orchard aid that carries workers on a platform lifted by the tractor's hydraulic system so that they can prune, thin, spray or harvest tree crops without ladders. To serve ordinary fruit trees it has to lift the worker several metres: the tractor-drawn orchard platforms reported in the literature work at about 3 to 4.5 m, and one designed for litchi and longan orchards has a working height of 4.0 m.

The other options, 1 m, 1.5 m and 2.5 m, are heights a person can reach by standing on the ground or on a low stool, so they would not justify a hydraulic platform at all. The question gives only the printed value and no source, so the answer rests on the key and on the typical working height of these machines, not on a derivation.