Pulley clearance 1/8" cable

Discussion in 'Tube and Fabric' started by Little Scrapper, Jun 14, 2019.

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  1. Jun 14, 2019 #1

    Little Scrapper

    Little Scrapper

    Little Scrapper

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    Imagine a torque tube (control stick) and two steel fittings welded on it. A 2" pulley goes between them. The cable is 1/8" and does a 180° turn on the pulley itself. Clearly it's for the elevator.

    Anything written or documented that would explain the maximum/minimum allowable clearance from the phenolic body of the pulley to the inside of the steel fitting? Attached is a drawing I made to explain it.

    If no documents exist what is the standard practice?

    Thanks

    IMG_20190614_092705207.jpg
     
  2. Jun 14, 2019 #2

    Little Scrapper

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    Here's a quick side shot of the assembly. Regardless of the actual assembly I'd imagine most control pulleys in most airplanes using cable have minimum and maximum allowable clearance right?

    IMG_20190614_093943062.jpg
     
  3. Jun 14, 2019 #3

    TFF

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    I think it’s all about keeping the pulley free. Essentially pulley bearing width or with washer spacers if needed. Space needs to be maintenance friendly at most. You would be adding fences to keep the cable from jumping track so no worry is needed if cable jumps, you have to make it so it can’t.
     
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  4. Jun 14, 2019 #4

    TFF

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    94546A7B-E45A-482A-A0C9-0E0C4425AAEE.jpeg
     
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  5. Jun 14, 2019 #5

    Little Scrapper

    Little Scrapper

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    Ok. So no washers. The bearing clearance by itself with no washers, so the difference between the body and the bearing race is .031"

    IMG_20190614_101343517.jpg IMG_20190614_101343517.jpg
     
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  6. Jun 14, 2019 #6

    FritzW

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    There's no min/max gap guidance. 43-13 even talks about *clamping the inner race of the pulley bearing.

    *They (self locking nuts) may be used with anti-friction
    bearings and control pulleys, provided the in-
    ner race of the bearing is secured to the sup-
    porting structure by the nut and bolt.
     
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  7. Jun 14, 2019 #7

    Little Scrapper

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    Thank you.
     
  8. Jun 14, 2019 #8

    wsimpso1

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    The standard inner race thickness is the spacing you should have. That prevents the cable from falling into the gap while rigging. Then a cable guard will keep the cable on the groove.

    Billski
     
  9. Jun 15, 2019 #9

    CharlieN

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    One question with this application, a 2" pulley utilized with 1/8 cable is recommended for no more than 15° bend. In your application can you utilize a larger pulley with the cable return run through the torque tube? The 2¾ or larger pulley allows for a considerably more natural bend for the cable. This would offer less chance of the cable to either take a set or try to climb out of the sheave.
     
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  10. Jun 15, 2019 #10

    Little Scrapper

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    The 15° they mention is the deflection angle or perpendicular to the body not the 180°direction.

    In this application the angle will be less than 2° I'm guessing.
     
  11. Jun 16, 2019 #11

    ultralajt

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    I found this in book Aircraft detail design manual: ADDM.jpg
     

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