• #### Engine Gear Box

Gear box is for power transmission, then why cant we give a small gear box for big engine and vice versa?

#### kanthasami

• Aug 3rd, 2009

Gear boxes are not only meant for Power Transmission, but also get the different speeds and torques according to the requirement. For example, while starting a vehicle, we need less speed and more tor...

• #### Thermal Efficiency

Why the thermal efficiency of the engine decreases at part load?

#### deemech

• Jul 11th, 2010

Due to the practical irreversibilty and some losses

#### kanthasami

• Jul 26th, 2009

There are always some mechanical losses in the engine while running. These losses are more or less same at all the speeds. When the speed decreases, the output will obviously decreases. But, the losses remain same. So, the overall efficiency also decrease.

• #### Speed and Torque

What is the practical difference Speed and Torque?

#### shank

• Dec 7th, 2013

The first cyclist gives his force alone but, the second cyclist gives his force with addition to the rider behind him.so, the second cyclist have the tendency to give more torque than first cyclist.

#### bhargavmech

• Aug 20th, 2009

speed is the distance traversed per unit time.. it is a scalar quantity. torque is the vector product of distance and force..it is a vector quantity. torque= r * F where r is distance between point of...

• #### Torsion- Shafts

Why do we use solid shafts for transfer of power in case of pumps/ turbines & other machines why we use a hollow shaft (pipe) in universal joints of automobiles; although the rated load and twist is approx. the same.

#### Arun Govind Neelan

• Feb 27th, 2012

In automobile application we have to consider weight in addition to torque and strength. Hollow shaft has high torque transmitting capacity per unit mass compared to solid shaft. If you consider bending stress diagram for hollow it is min at centre so material requirement is minimum at centre.

#### ravindra sariya

• Feb 16th, 2012

In case of turbine and pump there is an axial component of force present so solid shaft can deal better than hollow shaft...and in automobile only pure torsion is present and also hollow shaft have le...