How to build a rein tension meter
Abstract: A large part of the interactions between horse and rider during horseback riding takes place through the reins and the bit and devices for measuring the tension on the reins, rein tension meters, has fairly recently been developed. To safeguard the welfare of the ridden horse riders need to be aware of the rein tension they apply and actively work to decrease it. Furthermore, there is a need to develop the study of rein tension through new techniques and refined analysis procedures. A good-quality rein tension meter should be small in size, sensitive, durable and as accurate for light rein tension as for strong forces. Rein tension meters used in research on horse and rider interaction commonly depend on strain gauge technique for generating rein tension data. Strain gauges are electrical resistances and when subjected to tension or compression the resistance change. By connecting the strain gauges in a Wheatstone bridge circuit the sensitivity of the measure is increased and the circuit is compensated for temperature changes. The aim of this project was to create a durable rein tension meter at a low cost that would be as accurate for high loads as for small changes of tension. The rein tension meter was made from bent stainless spring steel, strain gauges, a custom made amplifier and electric cable. Three different sizes of steel, 140'40'1 mm (large), 110'35'1 mm (medium) and 90'30'1.5 mm (small) and two different types of strain gauges, pairs of parallel strain gauges and pairs of perpendicular strain gauges, were tested. Power and logging of data was supplied through an Inertial Measurement Unit. The rein tension meters were calibrated by lifting known weights and were tested at local riding schools as well as with privately owned horses. The maximum force the steel could withstand was calculated and the stability of the output voltage to the same weight was tested. A polynomial regression calculation was used to convert the voltage output received from the ridden tests into rein tension in kilograms. The results show that the pairs of parallel strain gauges were most appropriate to use, the small size meter was most durable due to being thickest and the small size meter also had the most appropriate measuring range of 285 g to >30 kg. Repeated calibrations of the small rein tension meter with the same weight yielded similar values. The mean of the mean rein tension received from the school horses were 1.2 kg for the left rein and 1.11 kg for the right rein. The maximum rein tension registered was with a horse that was difficult for the rider to control and would run off frequently during the ride and its highest rein tension peak reached 31.58 kg. In conclusion, the rein tension meters created were found to be both durable and accurate and well suited for rein tension measurements and the small size rein tension meter with a measuring range of >30 kg is likely enough to register rein tension in most horses and riders. This rein tension meter can also potentially synchronize the rein tension data with the stride cycle. To safeguard the welfare of the horse, training techniques and rider performance need to be measured and evaluated and a tool like this rein tension meter makes it possible to monitor, at least in part, the interactions taking place between horse and rider.
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