In Club Testing Results

The Self-lubricating Bronze Bushings were installed in our two clubs in March 2003. After installation many of our members asked if we had gotten new equipment as the machines felt tighter. Since installation the bronze bushings have performed flawlessly. Absolutely no lubrication. 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 show 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 manor similar to the exercise machines and to overload the bushings to determine how long they would perform before needing replacement.

The pictures show the, not real pretty, simulator machine. Each two foot arm is loaded with 65 pounds of weight. One arm has plastic bushings and the other arm has self-lubricating bronze bushings. 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 through about a 90 degree range.

Shown here are the plastic bushings installed with plenty of grease and the self-lubricating bronze bushings installed without any lubrication.

After 75 days the bronze bushing arm removed to show the amount of lubrication on the axle.

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 was well greased. The arm with the plastic bushings 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 bushings, in the same about of time, did not allow significant movement.

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

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