Rubber engine mounts are a 5 year rubber replacement item. They can go bad like you said just due to time, but also if excessive heat gets to them or chemicals like oil, fuel. solvents and just the weight of the engine over time. Some get harder, but some get softer to. I'm doing a rubber replacement on a Flight Design CTSW today and the rubber engine mounts get replaced.
Roger Lee LSRM-A & Rotax Instructor & Rotax IRC Tucson, AZ Ryan Airfield (KRYN) 520-349-7056 Cell
It seems to me that the rubbers doesn´t last 5 years in good conditions depending on the installation and exposition to heat and chemicals like you said. They visually appear OK but, in fact, they lose their efficiency causing the transference of vibrations to the plane structure.
My experience is that after 2 to 3 years they start to significantly lose their anti-vibration capabilities.
The examination of the gearbox indicated several areas of wear. As a result virtually everything inside the housing was replaced.
Since re-installation, I have flown about 2.5 hours at various airspeeds and power settings. So far I haven't experienced the vibration.
Gentlemen: I am one of the many with a Rotax 912IS engine who has to get my gearbox rebuild every 100 hours because of excessive noise and vibration. After rebuild the noise and vibration is gone, but it doesn't last long. I know many with ULS engines who never have issues with a gearbox, but everyone has issues with a 912IS.. There is something wrong with the 912IS gearboxes which Rotax has not been able to solve.
I attended a seminar at EAA-Oshkosh this summer taught by one of the Rotax experts. Among many topics discussed was the 912IS gearbox. He said they have been very unreliable and Rotax is quite aware of the issue and has been trying to improve the situation. He said the new 2017 gearboxes for the 912IS are a definite improvement. Of course, we all have 2014, 2015 and 2016 gearboxes, which are being rebuild every 100 hours or so, so it doesn't help up. Replacing parts in a poor design does not help a bit. Just gets us another 100 hours.
I would like to hear from ROTAX on this issue. My question is can I purchase a brand new gearbox of 2017 design, which would solve the problem? Of course, another $5000 down the drain, but I would pay almost anything to get this issue solved. I would need to know above what serial number would improve the situation. One cannot just purchase a new gearbox because there is no way of knowing when the manufacture data for the components might have been. Does ANYONE have insight on this issue?
We owners do not need to hear anymore about how it is our fault and it is because there are other problems with our airplane. This is a Rotax issue and can only be solved by Rotax. I am not asking for warranty or for any freebies. I am more than willing to spend the big bucks to get this problem solved before it kills me. It is just so difficult to get reliable and knowledgable information on the subject.
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