Test procedure to evaluate impact and holding forces at the shaft of manual operated concrete floating machines

Status:

completed 01/2002

Aims:

When operating a concrete floating machine there is a risk of accidental injuries while the shaft after it is released unintendedly turns around and hits the operator who may not be able to leave the danger zone in time. Therefore safety devices are required which decrease the remaining energy of the system to a permissable value. To evaluate whether machines in the market fulfil these general requirements, it is asked for a test method, which is adequate to determine the forces occuring at the shaft during the impact. Additionally the determination of the holding forces during the running up phasis gives a hint about the more or less ergonomic kind of handling of the machine.

Activities/Methods:

After determining the physical units and estimated values of the data to be measured the test-rig was developed and provided with the relating measuring equipment. With inclosure of actual test-orders in some cases, measurements with in the market usual machines of different types were carried out. Meanwhile the permissable values had to be determined by using relevant publications in biomechanics of the human body.Those publications were found in most cases in automobil-related papers, therefore an adjustment according to the actual boundary conditions had to be done.

Results:

A test-rig was constructed and furnished according to the draft of the test methods' description. Practical tests and forthcoming routines had been already carried out there. With the results obtained and on the basis of relating knowledge found in publications, the in general relevant actions: kinetic energy of action, peak value of load, local load distribution, increase of the loads' value and time interval of action could be concentrated to the ruling criterion, the kinetic energy of the action. The critical value is supposed to be at 25 Joule, regarding the existing knowledge for the time being. Looking at the holding force a critical value of 350 N should be assumed, following the regulations for physical strenght of man. In spite of this, the sensoric tests show that it should be recommended to reduce this value to 250 N, in case of impact loads.

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