Jar Lids: Effect of Diameter, Gripping Materials and Knurling

Abstract

In Exp. 1 , 10 female subjects each twisted six jar lids vs a torque meter with a bare hand, rubber gripper and a cotton cloth. The torques of 3.17 Nm f o r the 48 mm dia, 5.02 for the 67 mm dia, and 6.04 for the 86 mm dia lids differed significantly. Torques of 4.04 f o r the cotton cloth in the hand, 4.85 for the bare hand and 5.36 for the rubber gripper also varied significantly. The 4.66 Nm for non-knurled was not significantly different from the 4.84 for knurled.Exp. 2 replicated Exp. 1 with 5 of the 6 lids for 29 visitors to a University Open House. The results were compatible with Experiment 1. Torque exertable on a lid can be predicted well from grip strength, lid radius and the gripping material (rubber, bare hand o r cloth).

Modelling wrist-twisting strength of the elderly

“…The presence of an optimum diameter for wrist-twisting strength went unnoticed by previous researchers for more than one reason. There was no significant difference between the mean rough and smooth torque values (table 2) at any of the three smallest diameters (3 1,55 and 74 mm), an observation also made by Nagashima and Konz (1986) for lids in the diameter range 48-86 mm. This implies that the presence of knurls and threads (roughness), as they appeared on commercially available lids, did not enhance torque producing capabilities -a flaw in the surface finish design.…”

“…However, between 31' and 74 mm, a straight-line fit was a good approximation, indicating that the mechanism of torque generation within this range was different than that above it. Linear trends were also evident in the data of Rohles et al (1983) and Nagashima and Konz (1986). For smooth lids, the torque-diameter trend between 3 1-74 mm was also linear but there was a sharp decline in torque for the largest lid (figure 3).…”

“…These two studies, though providing useful data on cumulative distributions of torques, did not examine the biomechanical aspects of wrist-twisting strength nor interactions among lid variables. Imrhan and Loo (1986), in a preliminary analysis of the data of this study, and Nagashima and Konz (1986), expressed the idea that lid height and diameter could affect hand grip, and tried to control grip by restricting lid height to a narrow range.…”

The effect of torque direction and cylindrical handle diameter on the coupling between the hand and a cylindrical handle

“…Grip force is better represented this way, since contact force varies over the surface of a grasped object (Aldien et al, 2005;Amis, 1987;Fellows and Freivalds, 1989;Gurram et al, 1993;Gurram et al, 1995;Hall, 1997;Kinoshita et al, 1996;Kong and Lowe, 2005;Lee and Rim, 1991;Radhakrishnan and Nagaravindra, 1993;Yun et al, 1992). Third, each contact segment can have a different friction coefficient depending on material (Nagashima and Konz, 1986), surface texture (Bobjer et al, 1993;O'Meara and Smith, 2001), and normal force (Bobjer et al, 1993;Buchholz et al, 1988;Bullinger et al, 1979;Comaish and Bottoms, 1971;Seo et al, 2005).…”

“…Previous studies have shown that handle diameter (Adams and Peterson, 1988;Cochran and Riley, 1986;Crawford et al, 2002;Imrhan and Loo, 1988;Nagashima and Konz, 1986;Pheasant and O'Neill, 1975), grip force (Crawford et al, 2002;Imrhan and Loo, 1988;Nagashima and Konz, 1986;Rohles et al, 1983), and friction coefficient (Nagashima and Konz, 1986) are associated with hand torque. These previous studies support the early model by Pheasant and O'Neill (1975) that predicts torque as a product of the handle diameter, friction coefficient and grip force (see Fig.…”