Merlin Roughness Indicating Machine (modified)

Merlin Roughness Indicating Machine (modified)

Merlin Roughness Indicating Machine (modified)
measures displacement to less than a millimetre
CodeBM615
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  • Easy to use
  • Self-calibrating
  • Robust
  • Easily maintained
  • No complex calculations
This modified roughness indicating machine can be used for either direct measurement or for calibrating other instruments such as a vehicle mounted bump integrator. 

The machine consists of a metal frame 1.8 metres long with a wheel at the front and a metal foot at the rear. Above the rear foot are handles used for moving the machine. Midway between the wheel and the foot is a probe which is attached to a weighted arm to hold it onto the road surface.

At the other end of the arm is a pointer which moves over a prepared chart consisting of a series of 5mm wide columns.

The arms is pivoted close to the probe so that a vertical displacement of the probe of 1mm produces an equivalent displacement of the pointer by 1cm.

The position of the pointer on the chart therefore gives an accurate indication of the position of the probe with respect to an imaginary line, joining the bottom of the wheel and rear foot.

If the position of the pointer is noted at a number of places along a road, then the rougher the road, the greater the spread of readings. It has been shown that the spread correlates well with road roughness as measured on standard roughness scales.