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Thread: Tachometers

  1. #1
    Junior Member
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    Default Tachometers

    Has anbody (else) been having trouble with the mechanical (Superior Labs, Inc.) tachometer in Carbon Cubs or Sport Cubs? Since 2006 I've flown many SC's and now own #132 Carbon Cub; which just experieced a (final) tach failure today. Of the several demo Sport Cubs I flew from 2006 through 2009, I had two tach issues that required replacement of the instrument in different SC's. Now, with the recent failure, it seems to be a reliability issue, especially since the tachs that failed had only about 110 hours of time indicated. I've confirmed that it's not a cable issue, having inspected and lubed it well and confirmed that it is securely attached at both ends (the cable appears "as new" when removed and lubed).

    After communicating with Jason today at CubCrafters, he indicated that there is no record of a persistent tach problem, although he indicates that records may be incompete. Perhaps this general inquiry will reveal whether owners have had significant problems.

    From new, the tachs seem to me to be unstable - ie. the needle fluctuates wildly at certain rpm, generally in the 1500-2000 range. Mine did that on the Carbon Cub from the get go and I recall the other Sport Cub tachs had similar issues at various rpm. Today the problem with the Carbon Cub tach indicated "0" upon engine start up and then only seemed to register "reasonable rpm indications") after many minutes (20-30 minutes of flying). This problem with my Carbon Cub tach has gone on for about 30 days now (it started by having obviously inaccurate readings upon engine start, and then sorting itself out over several minutes of operation); and finally today, the readings became unreliable at start, during flight and at landing .... during a one hour flight.

    My web search suggests that the SLI tach is pretty well established and should be good, they claim a two year warranty, and has an FAA TSO "rating". I would expect more than 110 hours of reliability, wouldn't you think? My thinking is that if not a cable problem and the engine is obviously fine and running smoothly; it can only be the instrument itself.

    Any other tach problems out there that might help me (and CC) figure this out?

    Thanks,

    Doug

  2. #2
    Senior Member chipallen's Avatar
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    Default Re: Tachometers

    Hi, Doug;

    I can recall replacing three tachs over the past several years; two on Sport Cubs, and one on a Carbon Cub. After replacement, they all performed beautifully, with no further problems. (FYI, the Carbon Cub was #96, so don't think it's related to the age of the airplane).

    I don't have any further thoughts on the matter, I just assumed in each case it was a "bad" tach.

    Chip

    Chip Allen

    SWT Aviation, Inc.
    Cubcrafters Southeast Sales Center
    Marietta, GA

  3. #3
    Senior Member
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    Default Re: Tachometers

    My tachometer just quit recording at 400.0 hrs. It still shows RPM with no problem, but tach hours are stuck.....anyone one else had theirs fail this way? Can it be repaired or does it mean a new tach?
    Jon
    Sport Cub S2

  4. #4
    Administrator Pete D's Avatar
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    Default Re: Tachometers

    I don't believe they can be repaired, at least not economically. The few that I have seen fail in this manner were just replaced.
    Pete Dougherty
    Customer Support Manager
    Cub Crafters Inc

  5. #5
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    Default Re: Tachometers

    Mine did the exact thing at 349hrs. I took mine apart and noticed a loose screw that was preventing the worm gear from contacting a gear that drives the hrs. I bet that's what is wrong.

  6. #6
    Senior Member couleeone's Avatar
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    Default Re: Tachometers

    I just balanced my prop and discovered my tach was reading 130-150 rpms fast..any ideas other than replacement?
    Geo
    Piper Cub J3
    www.cubdriving.com

  7. #7
    Administrator Pete D's Avatar
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    Default Re: Tachometers

    Quote Originally Posted by couleeone View Post
    I just balanced my prop and discovered my tach was reading 130-150 rpms fast..any ideas other than replacement?
    I don't know for sure but you MIGHT be able to do a placard? Something like "Tachometer reads 150 RPM high" or something like that. Ask your mechanic...
    Pete Dougherty
    Customer Support Manager
    Cub Crafters Inc

  8. #8
    Senior Member randylervold's Avatar
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    Default Re: Tachometers

    Mechanical tachs, all of them, are notoriously inaccurate, always have been, that's why the electronic variety are preferred if accuracy is the objective. Still, once you know your mechanical tach is off then you can compensate accordingly. You can get an optical tach from an R/C store, set it on your glare shield, and know your exact rpm if you want.
    Randy Lervold

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