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I have owned a Computrainer stationary trainer for 20 years and recently had the flywheel shatter, sending shrapnel through the walls and ceiling of my basement, as well as into my hamstring. Should flywheels on stationary trainers be replaced on a regular basis to avoid fatigue-induced failures? How often should a flywheel be replaced?

Broken flywheel Plywood shattered by flywheel shrapnel

  • 1
    possible duplicate of Magnetic trainer failure – mattnz Aug 10 '15 at 23:22
  • Is that really a question? Or a warning? – brendan Aug 12 '15 at 1:18
  • I think replacing the whole trainer is likely a more economical option than replacing just the flywheel – Batman Dec 25 '15 at 2:51
  • You should definitely replace the flywheel after that incident, yes. I've only broken one flywheel in all my nearly 15 minutes of use, and that put me right off the whole idea. Although admittedly the magnetic trainer that seized up did more damage (not to me, fortunately), destroying the rear wheel as well as the trainer. I think there are too many silly claims made, because people both sit on the trainers for hours and do intervals, so many of them do lots of revolutions as well as seeing bursts over 1kW on a regular basis. – Móż Dec 25 '15 at 3:39
  • The flywheel replacement from Computrainer is free. Replacing the flywheel is definitely a more economical option. – R. Chung Dec 25 '15 at 14:51
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Apparently you are not the first victim of this problem: http://www.saferproducts.gov/ViewIncident/1237585

I suggest you should also submit an incident report to the CPSC (assuming you are in the US). Since you were injured you may also want to talk to a personal injury lawyer. RacerMate's website claims they offer an "indestructable build".

The manufacturer should provide guidance on the safe use and maintenance of their products. I'm sure they are aware of this type of failure.

Update: the currently shipping Computrainer flywheel is apparently made of copper. That sounds like it would be less prone to shatter.

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This is not an answer to your question but rather an update. Racermate has announced a recall for all "blue" flywheels, and they are replacing them. Here is the announcement and a form to get the replacement: http://www.racermateinc.com/blue-flywheel-recall/

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Should flywheels on stationary trainers be replaced on a regular basis to avoid fatigue-induced failures? How often should a flywheel be replaced?

It seems to me that a better solution is some sort of bulletproof housing.

Periodic replacement seems impractical in real life. For one, the replacement interval is not consistent and will depend on a number of environmental factors. Two, it might not be possible for a consumer to replace the part; it might be made worse.

The description on the accident is horrifying.

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