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Author Topic: PA .75 Information  (Read 1237 times)

Offline Dan McEntee

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PA .75 Information
« on: June 14, 2021, 09:21:23 AM »
   I'm asking for a friend who needs some information. We would like to know what the torque value is for the head bolts on a PA-75. I think they are a 4-40 but I'm not sure. He has one of those small tools for setting such fasteners, just has never needed to use it before.

    Also, what are the thicknesses of the head shims that most PA-75 operators use? I have the tools and materials to make them but would lie to know what thicknesses are typical.

    Just posting this here as he is busier than a one legged man at a butt kicking contest trying to get things straightened away for the NATS and I'm trying to help him out.

  Thanks in advance,
   Dan McEntee
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Offline Brett Buck

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Re: PA .75 Information
« Reply #1 on: June 14, 2021, 10:07:36 AM »
   I'm asking for a friend who needs some information. We would like to know what the torque value is for the head bolts on a PA-75. I think they are a 4-40 but I'm not sure. He has one of those small tools for setting such fasteners, just has never needed to use it before.

     That is a Randy question for sure, but a little research and I found a typical range of around 10-11 in-lb. That appears to be based on how much elongation/tension you get in the bolt. Sounds a little high to me for tapped aluminum - I would certainly not exceed that. Part of the tension is going to be supplied by deflecting the head, since there is some unsupported length.

   
Quote
Also, what are the thicknesses of the head shims that most PA-75 operators use? I have the tools and materials to make them but would lie to know what thicknesses are typical.

    .003, .005, and .008 are typical shim dimensions, you want more, stack them. As to what you need, it depends on how you set up everything else. We should be out at the field on Sunday, hit David up for that.

    David's airplane will be in my van Wednesday afternoon, I will remove the head and measure it for you., and maybe "help" him out by adjusting it...   

   Just kidding, of course.

     Brett

Online Dennis Nunes

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Re: PA .75 Information
« Reply #2 on: June 14, 2021, 11:51:19 AM »
    David's airplane will be in my van Wednesday afternoon, I will remove the head and measure it for you., and maybe "help" him out by adjusting it...   

   Just kidding, of course.

     Brett
Remove the head and tell David that it somehow fell off during the 2400 mile trek to Muncie.  ;D ;D ;D

Dennis

Offline frank mccune

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Re: PA .75 Information
« Reply #3 on: June 14, 2021, 04:12:06 PM »
      Hi:

      Eleven inch pounds is correct for a 4-40 screw and an aluminum hole.

      Good luck,

      Frank

Offline Air Ministry .

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Re: PA .75 Information
« Reply #4 on: June 14, 2021, 09:30:39 PM »
Inch Pounds or Inch OUNCES !   Id say In. Ounce . about 1/4 or 1/3rd of  a full  fingertip push ! Farmers fingers . Bout 1/2 a city fingertip push . S?P H^^

Offline RandySmith

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Re: PA .75 Information
« Reply #5 on: June 14, 2021, 11:55:02 PM »
   I'm asking for a friend who needs some information. We would like to know what the torque value is for the head bolts on a PA-75. I think they are a 4-40 but I'm not sure. He has one of those small tools for setting such fasteners, just has never needed to use it before.

    Also, what are the thicknesses of the head shims that most PA-75 operators use? I have the tools and materials to make them but would lie to know what thicknesses are typical.

    Just posting this here as he is busier than a one legged man at a butt kicking contest trying to get things straightened away for the NATS and I'm trying to help him out.

Hi Dan

Use  10 in lbs  for the  head, and about  8 for the  backplate,  the  shims  should  start at  15 thousands, that is  the stock setup. The head bolts  are  4-40 x 5/8  and need to be a high strength  bolt, please do not  use  stainless  as some  have
The PA has a T flange  sleeve  so there is  no bending  of the  lip of the sleeve
any other questions  just ask or email

Randy

  Thanks in advance,
   Dan McEntee

Offline Brett Buck

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Re: PA .75 Information
« Reply #6 on: June 15, 2021, 09:24:56 AM »
Inch Pounds or Inch OUNCES !   Id say In. Ounce . about 1/4 or 1/3rd of  a full  fingertip push ! Farmers fingers . Bout 1/2 a city fingertip push . S?P H^^

  Inch-pounds

    Brett


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