Question

A mower has driven wheel of 60 cm diameter. The crank of mower makes 550 rpm, when it is driven by a tractor at a speed of 2 km/h. If speed ratio between the crank wheel and land wheel is changed to 27:1, calculate the increase in speed of mower to maintain the same speed of crank.

(a) 0.20 km/h

(b) 0.304 km/h

(c) 1.402 km/h

(d) 1.36 km/h

This question was posed to me in an interview for job.

Enquiry is from Harvesting Equipments topic in portion Harvesting Equipments of Farm Machinery

Answer 1

Right option is (b) 0.304 km/h

For explanation: \(\frac{Nc}{Nl}=\frac{27}{1} \)

Nl=\(\frac{Nc}{27}=\frac{550}{27}\) = 20.38 rpm

Linear speed of mower, V = \(\frac{πDNc}{60} = \frac{π*0.6*20.38}{60}\) = 0.640 = \(\frac{0.640*3600}{1000}\) = 2.304 km/h

Increase in speed = V2 – V1 = 2.304-2 = 0.304 km/h.