STD-TE 73 TWO ROLLER MACHINE

Background

The TE 73 family of machines dates back to original Plint and Partners Ltd designs from the 1960s. These machines are all to the “overhung” roller design in which test rollers are mounted on the end of spindles and in which the spindle housings are mounted adjacent to each other. This arrangement has the obvious benefit of making the rollers much more accessible than in other configurations. There is, however, one significant consequence of this arrangement and that is that, with equal sized rollers, the roller diameter must obviously be greater than the spindle housing diameter. In other words, the diameters of the spindle housings fix the minimum shaft centre distance and thus determine the minimum diameter of roller that can be accommodated. This configuration is thus only suitable for experiments using quite large diameter rollers, the consequences of which are:

The larger the diameter, the greater the torque generated, for a given load and traction coefficient.

The larger the diameter, the more expensive the rollers become to manufacture.

Despite these caveats, it is of course worth noting that there are known scale effects with two roller or twin disc tests, so in some circumstances, adequate correlation can only sensibly be achieved when performing tests with rollers of sufficient size. For obvious reasons, tests demanding high surface speeds are best achieved with larger diameter rollers, likewise tests requiring a long hertzian contact length. Finally, if large amounts of frictional heat are to be dissipated in the contact, the larger the roller, the larger the thermal mass and surface area and the better the heat dissipation. Small rollers can become unrepresentatively hot!

The early TE 73 machines were primarily used for the study of highly loaded lubricated power transmitting contacts and rolling contact fatigue of materials. The successful operation of machine elements such as gears, rolling bearings, cam/follower systems and traction drives is vital to industry. The common feature to all these is that fact that power or motion is transmitted through highly loaded lubricated contacts with rolling or combined rolling and sliding motion.

In the TE 73. the two rollers are driven at different speeds to give varying amounts of slip in the contact and therefore to transmit increasing amounts of traction. The maximum traction coefficient is obtained at a particular value of slip and this is a characteristic of an individual fluid.

In modern variable ratio gear systems there is an additional complication. It is an inherent property of this kind of mechanism that there is a velocity gradient across the width of the contact zone in a direction perpendicular to the rolling direction. In other words there is spin in the contact zone. The effect of spin is to modify the traction slip characteristic. The distinction between the high and low slip regions is lost and instead there is a more gradual growth in traction as slip increases. This phenomenon can be studied in the TE 73 by introducing a third disc between the two rollers, that is free to rotate about a perpendicular axis.

Technical Specifications

Technical Specifications – TE 73S

Technical Specifications – TE 73H