A break is a device by means of which artificial frictional resistance is applied to a moving machine member in order to retard or stop the motion of a machine .

prony brake

a simplest form of an absorption type dynamometer is a prony brake dynamometer .as shown fig. It consist of two wooden blocks placed around a pulley fixed to the shaft of an engine whose power is required to be measured .The blocks are clamped by means of two bolts and nuts , as show in fig. A helical spring is provided between the nut & the upper block to adjust the pressure on the pulley to control its speed .The upper block has a long lever attached to it and carries a weight W at its outer end. A counter weight is placed at the other end of the lever which balances the brake when unloaded .The stops S,S are provided to limit the motion of the lever.
When the brake is to be put in operation the long end of the lever is loaded with suitable weights W & the nuts are tightened until the engine shaft runs at a constant speed and the lever is in horizontal position .Under these conditions the moment due to the weight W must balance the moment of the frictional resistance between the blocks and the pulley .
This artical was taken by Theory of machine (R.s. khurmi & j.k. gupta )


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