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Thread: Check your Tach

  1. #1
    akflyer's Avatar
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    Default Check your Tach

    I have been playing with props on multiple planes and charting the differences. Static RPM, take off time, climb rate, cruise speed, max RPM straight and level, max speed etc.

    I have been starting with the metal prop and charting the numbers then swap to the sensenich ground adjustable prop and run the tests again at various pitch settings.

    After the 4th airplane we did this on and comparing numbers it was beginning to look like I had the worlds strongest 160 HP 0320 or the guys with 180 HP engines were "sick". I ordered the trutach optical tach and checked it out. Turns out the tach in the plane was reading almost 250 RPM low on the high end so when I thought I was cruising at 2450 I was much closer to 2200. I thought I was turning 2700 on take off but was much closer to 2450 (with the borer prop). It also explains why it felt like I was cruising slow and had to fly tail low to maintain altitude.

    At RPMs under 1100 the mechanical tach is dead on with the optical tach but it rapidly goes astray at higher RPM.

    I am going to run all the tests again and see what I get turning "rated" RPM.

  2. #2
    tnowak's Avatar
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    Default Re: Check your Tach

    Did you buy the TruTach II, as available from Aircraft Spruce?
    I have tried other models without too much success or with me needing to be really close to the prop.
    I would really like to be able to use a device like this from inside the cockpit.
    I assume this is how you used your optical tach?
    TonyN

  3. #3

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    Default Re: Check your Tach

    I've used the simple RC prop tach from inside the cockpit and it works great. Really cheap, $27.

    Hangar 9 Micro Digital Tachometer, HAN156 on Amazon

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

  4. #4
    andya's Avatar
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    Default Re: Check your Tach

    Have used similar device from ACS (don't recall the brand name).
    worked better when I put some reflective tape on back of one blade and
    flew with sun behind me. they work fine
    "Progress is our most important problem"

  5. #5
    tnowak's Avatar
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    Default Re: Check your Tach

    Thanks for your replies. Will get one of these.

    TonyN

  6. #6
    Alessandro's Avatar
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    Default Re: Check your Tach

    As suggested yesterday I test my tachometer, with 2 instrument, the “micro digital hangar 9” and a certified instrument, same result.

    Here the differences in the static test:

    Indicated 1000, real 950
    Indicated 1500, real 1440
    Indicated 2000, real 1930
    Indicated 2500, real 2420

    Do you know if in level flight, WOT, with 58” propeller, at 2000 ft, the 160 hp can reach 2800 (real) rpm ??

    Thank you.



    Inviato dal mio iPhone utilizzando ShortWingPipers.Org

  7. #7
    Gilbert Pierce's Avatar
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    Default Re: Check your Tach

    Mine will just barely. Electronic EI tach.

  8. #8
    Alessandro's Avatar
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    Default Re: Check your Tach

    Quote Originally Posted by Gilbert Pierce View Post
    Mine will. Electronic EI tach.
    Ok, thank you.


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  9. #9
    Glen Geller's Avatar
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    Default Re: Check your Tach

    Reviving an old thread...
    I was thinking about tach accuracy in our aged airplanes, and using the trusty old hand-held laser model airplane tach to verify accuracy, but really don't care for the "ya gotta futz with it" nature of that gadget.
    Came across a number of self-contained, panel mounted, inductive digital tachometers with hour counter, countdown timer, programmable for type of engine and number of cylinders, and cheap enough to experiment with.
    Here's an example:
    https://www.amazon.com/Tachometer-Ge...8CXKV7HF&psc=1
    It runs on an internal CR2450 battery, has a 5' lead with two wires: one wraps on an ignition (spark plug) wire for signal, the other to engine ground.
    It can be programmed to start operating when the engine is running, track hours of operation, max RPM, and programmable countdown timer (set for 25 hrs and when it reaches zero schedule an oil change!)
    I think this will be useful for seeing if your tach is accurate, and when running in a new engine, tracking some operational values.
    Since it is not wired to the plane it is a portable device like a USB charger or a Garmin aera GPS, and could be considered a reference instrument.
    Mount to the panel near the mechanical tach with dbl-stick tape.

    Here's the user's guide from the OEM, who sells this thing for ~$55. http://www.enmco.com/pdf/PT14-Engine-Monitor.pdf
    The rebranded unit seen on Amazon is ~$15.
    I'm going to get one and test it on my lawncopter and then try it on the Tri-Pacer.

    Cheers,
    GG
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    Glen Geller
    1955 PA22-150 "One For Papa!"

  10. #10
    akflyer's Avatar
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    Default Re: Check your Tach

    Quote Originally Posted by Glen Geller View Post
    Reviving an old thread...
    I was thinking about tach accuracy in our aged airplanes, and using the trusty old hand-held laser model airplane tach to verify accuracy, but really don't care for the "ya gotta futz with it" nature of that gadget.
    Came across a number of self-contained, panel mounted, inductive digital tachometers with hour counter, countdown timer, programmable for type of engine and number of cylinders, and cheap enough to experiment with.
    Here's an example:
    https://www.amazon.com/Tachometer-Ge...8CXKV7HF&psc=1
    It runs on an internal CR2450 battery, has a 5' lead with two wires: one wraps on an ignition (spark plug) wire for signal, the other to engine ground.
    It can be programmed to start operating when the engine is running, track hours of operation, max RPM, and programmable countdown timer (set for 25 hrs and when it reaches zero schedule an oil change!)
    I think this will be useful for seeing if your tach is accurate, and when running in a new engine, tracking some operational values.
    Since it is not wired to the plane it is a portable device like a USB charger or a Garmin aera GPS, and could be considered a reference instrument.
    Mount to the panel near the mechanical tach with dbl-stick tape.

    Here's the user's guide from the OEM, who sells this thing for ~$55. http://www.enmco.com/pdf/PT14-Engine-Monitor.pdf
    The rebranded unit seen on Amazon is ~$15.
    I'm going to get one and test it on my lawncopter and then try it on the Tri-Pacer.

    Cheers,
    GG

    They work great on 2 strokes and regular plug wires. They won't read off our shielded wires on the planes though. I have tried a couple different ones that I had on hand none of them would read on the shielded plug wires, hence me going to the optical tach prior to the engine analyzer that has a digital tach in it driven off the mag.

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