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Hardness Test

Ra├║l Bragado Alcaraz
Ra├║l Bragado Alcaraz
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Table of contents: Hardness Test

The hardness test is closely related to the health of the players.

The management of the hardness The condition of sports surfaces requires correct maintenance, as well as monitoring of the values that they present. Approximately 15% of concussions in football are the result of poor management of this parameter.

The hardness is measured in gravity values "g", by means of the so-called "hardness".Clegg's hammer"The maximum value reached in the hardness test the so-called "Gmax". This is a numerical value representing the hardness of the surface.

The NFL conducts this test before every game and all playing areas must have values below 100 Gmax.

Factors that influence this physical characteristic of the terrain are VWC and the frequency of field use. Aeration operations also contribute to the decrease of this Gmax value.

The correct test for measuring hardness on sports surfaces is shown below.

  • Purpose and field of applicationHardness determination on sports surfaces.
  • Principle of the methodA cylindrical mass is released from a standardised height above the sport surface to be tested and the peak deceleration produced on impact is recorded.
There are different manufacturers for this type of equipment.
Clegg's hammer
Clegg's hammer
  • Description of equipment:
  • Test mass. A solid metal cylinder, flat-ended, with an accelerometer protected in a safety housing, attached to a BNC connector.
  • Coaxial cable. Used to connect the test ground to the recording device.
  • Recording device. Capable of reading and displaying the peak test deceleration due to mass impact with the surface. It shall filter the frequency to a limit of less than 7 KHz and the deceleration shall be displayed in units of gravity (g).
  • Guide tube. It is used to control the lowering height and must allow the test mass to fall freely. It should have a diameter of 54+- 10 mm from the base of the tube. The guide tube normally has a circular flange at the base of approximately 150 mm to allow the tube to be held vertically.
The most important thing to know the hardness is to perform the test correctly and always in the same way.
  • Operating procedureSecure the guide tube by holding it vertically and release the impact mass inside the tube; in the case of football the height shall be 550 +- 10 mm. After the impact of the mass on the surface, the peak deceleration is recorded in gravities (g). After each test, the guide tube is removed so that the test mass does not impact twice on the same point on the surface. Ten readings shall be taken at random points in each of the goal, touch and centre zones.
  • Calculation and expression of resultsThe results are expressed in gravities. The average is calculated for each area.
  • Report testUNE 41959-1:2002 IN must be followed; The essential points for the correct report are: Surface identification, location, area and previous history; mean hardness value, Individual test results if required, details of any deviations from the procedure.

At Tiloom we can determine the hardness of your field or offer you the perfect measuring instrument for you.

You can purchase each of the versions of Clegg's hammer in the following links:

Ask us if you have any questions!


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