In-Club Testing Results

The Bronze Self-lubricating Bushings were installed in my two clubs in March 2003.  After installation, many of the members asked if new equipment was purchased because the machines felt tighter.  Since installation, the bronze bushings have performed flawlessly.  No lubrication has been applied.  The machines operate like new and members do not complain about the machines "feeling loose" or sloppy.  In addition, there is no grease residue that might get on members clothing.

This pictures shows a machine axle with plenty of lubrication as a result of the self-lubricating properties of these bushings.

All axles checked in actual operating machines showed similar lubrication.

Machine Simulator

Due to the fact that clubs vary in the number of members and therefore the amount of usage on the machines, I decided to build a machine simulator in an attempt to wear out the bronze bushing.  The goal of this simulator was to operate in a similar manner to the exercise machines and to overload the bushings in order to determine how long they would perform before requiring replacement.

The pictures show the simulator machine I developed in my shop.  Each two foot arm is loaded with 65 pounds of weight.  One arm has plastic bushings and the other arm has bronze self-lubricating bushing. The size of the receptor tube holding the bushings is the same length as one of the Curves machines.  A motor moves the arms back and forth 12 times a minute in a quarter of a circle.

The picture to the upper left shows the plastic bushings installed with plenty of grease.  The lower left picture shows the bronze self-lubricating bushings installed without any lubrication.

After 75 days of continuous movement, the bronze bushing arm is removed to show the amount of lubrication on the axle - this is without any lubrication being applied.

Test Results

After 7 days of continuous operation (24 hours a day 7 days a week) the plastic bushings were worn to a point that they needed replacement.  After 10 days of continuous operation the plastic bushings were almost destroyed and definitely needed to be replaced.  This wear was observed even though the plastic bushing had been well greased.  The arm with the plastic bushing allowed movement in excess of 1/4 inch up and down.  That movement was on a 24 inch arm.  In an exercise machine, the movement would be considerably more as the arms are much longer than 24 inches on most of the machines.  The arm with the bronze bushing, in the same about of time, did not allow significant movement.

After 120 days of continuous operation, the bronze bushing show little wear.  The bushing was under a constant load much greater than would be expected in the normal operation of an exercise machine.

Based on this 120 day simulator test, the bronze self-lubricating bushings in the exercise machine application appear to have a long term wear characteristic that can be measured in years.