Dimensions / Weight: The base of all models is 0.25 inch thick aluminum plate. It is 16" deep for all models, 16" long for all D5, D7, D8, D9 & D10 Models and 22" long for all other models. One-half of the depth of the machine supports all functional mechanisms and their housing. The front half of the base provides the working surface or area for product testing. The base is supported on one-half inch high feet to provide clearance for clamping test products at both ends and along the entire front edge of the base. Net Weight: (Approx. 40-50 pounds)

All functional elements are mounted above the normal level for product testing and therefore are not subject to damage by accidental liquid spills.

Heavy gage brushed aluminum houses all functional components with only the drive fork bracket extending forward to carry the drive fork over the test area. Access to the component area is by removal of only two screws from the lid of the housing. All controls and indicators are mounted on the front surface of this housing. The housing is eight inches high on fixed speed models and ten inches high on variable speed models.

The drive fork is fabricated from 1/16" stainless steel. It is held in place by a bracket of the same material which is secured to linear bearings carried on accurately spaced parallel bars. Reciprocation of the drive fork assembly on the parallel bars is by a unique double chain and sprocket arrangement. There are no belts, cables, springs or other such mechanisms in the drive chain requiring service or maintenance.

Absolute linearity is obtained with unique drive system. Acceleration and deceleration is sinusoidal providing for the smoothest possible change in direction at the end of each stroke.

The drive fork is adjustable vertically with respect to its drive bracket. In its lowermost position it is less than one-half inch above the test surface with the tray and glass plate in place. This relative low position minimizes the tendency of the carried surface to tilt in the direction of travel. The fork can be raised in half inch steps, inverted and further raised to accommodate test specimens up to two and a half inches thick without losing close proximity to the test surface.

Design of the drive fork cradles accessories used in the test and permits them to simply be lifted free. There are, therefore, no rotational or other unbalancing forces imposed on such auxiliaries. They are "Free Floating" and self-leveling.

There are three equally spaced holes in each of the tines of the drive fork. A test auxiliary can be placed in either of the three pairs of holes to accommodate positioning of the test specimen. The spacing also permits simultaneous cradling of three brush boxes, two abrasion boats or two sponge boxes for multiple specimen testing.

Electric drives used in fixed speed models are right angle gearhead motors are totally enclosed, non-ventilated permanent split capacitor type. These ball bearing motors are rated for 115 volts, 60/50 Hz, continuous duty with a temperature rise of 40°C (104°F). (Machine cycle rate is based on 60 Hz operation.) The gear case is zinc alloy, grease filled, hardened steel worm with phenolic output gear and ball bearing output shaft. Electric drives used in variable speed models are right handle gearhead motors of totally enclosed non-ventilated 90 volt permanent magnet type. These ball bearing motors are rated for continuous duty with a maximum temperature rise of 40°C (104°F). The 115 volt motor speed controller is solid state, with constant torque speed regulation and a motor speed range of 10/1. The motor gear case is die cast aluminum, oil filled with hardened steel worm and bronze output gear.

The cycle counter is electrical and is energized through a switch from the drive linkage. The desired number of cycles is set by hand on thumb wheels behind a protective door. There are four of these thumb wheels for a maximum setting of 9,999. On start of operation, the exposed dial counts upward to the preset value and turns off the machine. The counter then may be manually reset to run the same count or the count may be changed.

All electrical components of single rate model are fused for 2 amps while all variable rate model are fused for 3 amps. The fuse holder is located on the right side of the housing. An electrical diagram is located under the lid of each machine.

Furnished with each machine is an instruction manual covering operation and maintenance. Included is an electrical diagram and for variable cycle rate machines a graph for the setting of cycle rate dial and instructions for changing the minimum and maximum rate settings for variable rate machines.

Velocity of the drive fork is a function of stroke length as well as cycle rate. The following graph relating rate dial setting to cycles per minute and drive fork velocity in inches per second is representative of Models D10V, D10VF and D10VFI. The relationship for other models is similar except for the cycle rate - velocity ratio.

• It varies with respect to the nature of the surfaces.
  
• It varies directly with pressure between the surfaces.
  
• It is independent, within limits, of surface contact area.
  
• It is independent, within limits, of rate of motion.
  
• Static (starting or break-away) friction is always greater than kinetic (sliding or motion) friction.
  
• Coefficient of friction is defined as the force required to move one surface over another divided by the weight on the surface. The coefficient of friction has a wide range. For example: greased metallic surfaces may be as low as 0.05, wet leather on metal 0.36 and dry leather on metal 0.56.

In order to measure friction between any two surfaces, one surface must be moved with respect to the other. The pressure or loading between the surfaces must be fixed and known. The force required to start the motion and to retain it in steady state must be determined.

Gardco linear motion test equipment with force measurement capabilities are ideally suited for measuring friction. Models with cut-out bases are designed for making measurements not only on prepared samples but also directly on the surface supporting the machine. The variable rate features of these models permit operating at a sufficiently low velocity so that kinetic energy and momentum factors may be neglected. A velocity of three to five inches per second is suggested when working with most surfaces. The force recorder is highly recommended for use in this measurement even though there is force indication on the machine panel. The recorder provides greater sensitivity and a high response record of force resistance throughout the machine cycle and for repeat cycles.

In order to provide a wide range of different surfaces and the loading on these surfaces, Gardco has produced an auxiliary weight for the abrasion boat and a modified sponge box to carry a much heavier weight. Both of these items are directly cradled by either the standard fork or extended machine drive fork.