SATRA’s Pedatron test machine

Further developments on the industry-leading whole-shoe test machine which simulates actual walking.

by Peter Allen

It is important for all companies involved in the footwear supply chain to know how well a product will actually stand up to use. Premature failure of soling, for example, can prove costly in terms of complaints, refunds, complete product recalls and loss of reputation.

SATRA developed the STM 528 Pedatron to provide an alternative to user wear trials over an extended period of time for soling wear assessment. However, with the benefit of SATRA’s ongoing research programme, extensive Pedatron testing experience and developments in the machine, it is now also used to assess more features of footwear in addition to soling wear. The SATRA STM 528 machine has also proved to be an effective means of assessing the wear characteristics of flooring surfaces and flooring hardware, such as stair nosings. This article describes the Pedatron and the developments which have been included in its latest, recently released version.

Realistic gait

In order to achieve a realistic wear assessment, Pedatron has been developed to closely replicate the action of walking, with parameters determined from biomechanical studies of walking gaits. One of the improvements to the new machine has been the introduction of improved artificial foot forms. These have been produced to give a closer correlation with underfoot pressures measured from actual walking gaits. In addition, these new foot forms reproduce wear characteristics on internal footwear components typical of those found in products due to user wear.

The SATRA Pedatron test is a whole shoe test. It reproduces the flexing, shear loads, compression shock and turning motions which occur in footwear use. Under the influence of these loading conditions, the effect of the shoe construction on the soling wear can be demonstrated. The repeatable nature of a Pedatron test allows for the assessment of how alternative constructions – for example, in the upper or the method of assembly – influence soling wear.

A standard textured flooring surface is used for footwear testing, allowing for consistent results to be obtained. In addition, a wide range of flooring surfaces can be installed in the Pedatron, and used for specific footwear to flooring interface testing. These include sports floorings specific to the type of footwear under evaluation. An enhancement to the latest Pedatron model is the addition of a motor-driven floor surface lift, to improve the process and reduce the time taken to set the footwear to floor height at the start of a test.

Extended scope

SATRA Pedatron has been found to be an effective test machine when used in conjunction with other test machines to assess footwear over a simulated lifetime of use. For instance, a slip test can be carried out on a new footwear sample using the SATRA STM 603 test machine, and then repeated at intervals during or at the end of a period of Pedatron wear testing. This allows the effect of soling wear and other damage (such as compression set and/or spread) on the footwear’s slip resistance to be assessed. Another example is combining Pedatron wear testing with water resistance tests. Conducting a water resistance test – for example, using a SATRA STM 505 test machine before and after Pedatron testing – allows for an assessment of the effects of wear on the water resistance of the footwear.

SATRA has also developed an artificial ageing protocol, which combines cycles of Pedatron testing with the introduction of heat and moisture into the footwear – with controlled drying cycles. This has been found to be an effective way of simulating a wear trial (but in a significantly shorter time), and with the consistency and repeatability of a mechanised process. Artificial ageing can be used to evaluate complete footwear or a component within the footwear. This protocol can be used for the verification of new products and the comparison between variants of complete footwear. It can also be a means of verifying evolutionary changes to a footwear component during product development and an aid to quality auditing subsequent production batches.

The Pedatron test machine incorporates a robust drive system, which combines mechanical and pneumatic systems to ensure that the footwear is subjected to realistic angles of contact, applied vertical, shear and torsion loads and induced flexing – as found in walking. The machine is designed to be responsive to the mechanised walking action. It allows soling rebound and footwear to flooring slip (on low friction surfaces), which can occur in actual walking.

A number of machines are in use on a daily basis in SATRA’s test laboratories, and have accumulated many millions of step cycles. Due to the demand for Pedatron testing, SATRA test laboratories are currently installing two additional Pedatron test machines.

In addition to the changes already discussed, the latest Pedatron has been redesigned to improve the simplicity of build, reduce the operational noise, extend component life and simplify machine maintenance. It has also improved the process of set-up and visibility within the working area.

Click here for comprehensive information on SATRA's range of test equipment.

Publishing Data

This article was originally published on page 36 of the May 2012 issue of SATRA Bulletin.

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