The Technical Stuff
When power sweeping the brush head expands through centrifugal force to suite the flue being swept.
Because it is not a traditional brush there is no surface tension being created in the sweeping process as the head adjusts to fit the flue.
The force of the sweeping action is increased by the speed of rotation and this has the effect of stiffening the brushing action.
For older style chimneys a low speed is used. For a heavily built up clay / steel flue then faster speeds give an unbelievable cleaning action.
In short, this system cleans chimneys more effectively whilst causing less strain on the structure of the flue.