I am often asked about 'the way the paper moves across the tracker bar'. Customers tell me about 'jerky motion', sluggishness and generally uneven movement. These problems are becoming way too familiar and indicate a common trend that is shortening the usable life of many player pianos. So, I have devised a Simple Test that anyone can use to determine if the air-motor is suffering from 'stiffness' due to idleness. This page also has information about other problems like Sluggishness, Unevenness, Vacuum Leaks and one method to Reduce or Delay the effect of Stiffness due to Idleness

1.) Remove the Front Panel, exposing the air-motor.
2.) Remove the ladder chain from the gear at the end of the air-motor crankshaft.
3.) Turn the gear by hand a little bit. If it tries to move back to where it just was, you have a problem (click here). If the gear stays where you put it, turn it a little bit more. Keep turning and stopping until you have moved the gear through 360 degrees of rotation. And then do it again, turning lesser or greater amounts. If, at any time, the gear tries to move backward (or forward) all by itself, (click here). If the gear stays anywhere you put it, the air- motor does NOT have a 'stiffness' problem but it DOES have a problem.
4.) Reconnect the ladder chain and replace cover boards.

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If your air motor is running unevenly, sluggishly or sounds like it's leaking, and you have passed the '360 Test', click on the KeyWords....... Uneven....... Sluggish....... Leaking

Your problem is Stiffness. The only total cure for this ailment is the replacement of the pneumatic (or bellows) cloth. You can Do-It-Yourself or Send It To Us.

Stiffness can be caused by only Three things. Time, Environment and/or Idleness. Of the three, Time is the only one that cannot be interfered with or changed. All pneumatic (or bellows) cloth looses it's suppleness as it ages and nothing has as yet been devised to stop the process. It's effect can, however, be delayed, to a degree.

Environmental conditions in your home play an important role in determining the life expectancy of all the cloth (and felt) in any pneumatically operated device. Information on this (and other) aspect/s of Player Piano Care can be found on The Rules Page.

The last factor, which too often reduces the usable life and the performance of the air-motor (and most other pneumatic devices), is Idleness. The USER alone determines this factor but the effects of idleness can be delayed. Unfortunately, it is often too late to start using delay tactics and the air-motor must be rebuilt.

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The fact that the air-motor exhibits the symptom known as 'fly-back' or 'backlash', indicates a problem. However, there are only Three possible explanations for this problem. First, it is entirely possible that the motor is entering the first stage of stiffness due to idleness. At this point, you should feel the cloth. It should be supple like a cotton shirt. If the cloth is relatively supple, employing a delay tactic may greatly reduce or even eliminate the fly-back. Second, if the cloth feels like a starched shirt, it is getting old and should probably be rebuilt. However, it may have years of life left in it and I only recommend rebuilding if the unevenness adversely effects the quality of the music. Third, something is impeding the movement of at least one bellow. Remove the air-motor from the player and, while holding the sliding valves in place, turn it upside-down and listen for any foreign debris moving around inside. If any noise is detected, you may be able to remove it by removing the sliding valve for that bellows and then 'shaking' it out. If the debris is firmly lodged in the bellows, it will have to be rebuilt. The debris is most likely stuck in the hinge and it is unlikely that it can be removed, but you can try.

Below is a video that shows how you can use your lungs to check various devices in a player piano.

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Most simply put, the best tactic to delay to the problems associated with idleness is:

The 180 Degree Repair Technique

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The easiest way to test an air motor for leaks is to disconnect the vacuum supply hose that's connected to the motor and then seal the connector with a piece of duct or masking tape. Then, turn the drive gear in the opposite direction (or backwards) of the way the gear normally turns. If there is leakage in the motor, turning the gear backwards will be very easy. If there is no leakage, turning the gear backwards will be very difficult.

There are numerous types of leaks that can adversely effect the operation of virtually any air-motor. The most common type of leak occurs at the stress points (or folds) in the bellows cloth. If these small holes are readily visible to the naked eye, gluing small circles of thin pouch leather may significantly improve the torque and reduce sluggishness and/or unevenness. However, all repairs made to the cloth (with the exception of loose glue joints or unnatural cuts) should be considered temporary repairs.
The second most common leak occurs in the sliding valves. Over time, either the sliding valve and/or the main block can become warped. Warpage generally occurs as a result of extreme changes in the environmental conditions effecting the piano and the only preventative measure is to maintain the correct environment. Warpage can only be removed by dismantling the motor and carefully sanding the 'sliders' and the 'block' with very fine sandpaper on an extremely flat surface. It is recommended that you hire a professional for this job.
The third most common leak occurs when dust and/or debris is allowed to build up on the sliding surface. Since the air- motor works on vacuum, it has a natural tendency to 'suck in' the dust. However, the dust must pass over the sliding surfaces and often becomes 'embedded' or 'stuck' to those surfaces. Over time, this build-up will scratch the block, leading to a minor leak. Regular cleaning by a qualified technician can greatly reduce the possibility of this problem but the owner can also clean off dust build-up. Simply blowing off the dust is usually enough but using a feather duster also does a great job.
The least common problem is cracking. Cracks can develop in any piece of wood. Repairing the cracks in an air-motor should generally be left to a qualified technician especially if they are present in the sliding valve surface. Cracks around the vacuum supply fitting and the air-motor mounting hardware can be filled with almost any type of filler, but it's unlikely that those cracks are responsible for poor motor operation.

The easiest, most durable and most positive way to eliminate leakage inside the main air channel is to seal off all valve holes with a good tape (like duct tape) and pour in a healthy amount of Phenoseal right in the main supply flange. Slosh it around for a minute or so and then pour out the excess and let it dry for 24 hours. It's best to remove the tape about twenty minutes after you pour out the excess to aid the drying process. Also, be sure to clean around the holes in case any of the sealer got under the tape and onto the face of the block.

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Uneven rotation/movement of an air-motor can only occur when the bellows are not all working with the same efficiency. To determine the cause of the problem, start by performing the Simple Test at the beginning of this page. It the air-motor passes all the tests and procedures then the problem is most likely located in the drive train or the transmission.

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Basically speaking, sluggishness in an air-motor is the result of leaks or some form of contamination. Air-motors can become contaminated by a variety of things but the most common contaminates are TAR, OIL and GREASE. Unfortunately, novice technicians and owners think that applying oil and/or grease to the metal and/or felt bearing surfaces will improve the operation of the air-motor. Nothing could be further from the truth.

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Comments or Questions to: John A Tuttle (Site Owner)