PA 61 CRANKSHAFT THREAD?

[Claudio Chacon]

Hello guys,
Can anyone help me with this?
Need to know which is the thread...have to buy a tap to make a brass prop nut.

Thanks in advance....

[Brett Buck]

Hello guys,
Can anyone help me with this?
Need to know which is the thread...have to buy a tap to make a brass prop nut.

  5/16-24.

   *Brass* prop nut?

    Brett

[Claudio Chacon]

  5/16-24.

   *Brass* prop nut?

    Brett

Thanks Brett.
Brass, yes...or bronze if you will, arenīt both correct terms to name the same material?
English is not my native language, so I may be wrong...

[Brett Buck]

Thanks Brett.
Brass, yes...or bronze if you will, arenīt both correct terms to name the same material?
English is not my native language, so I may be wrong...

 Your English is infinitely better than my Portugese.

    It depends on who you talk to. Brass and Bronze aren't that specific, there are many grades of each. "Red Brass" typically means one of a wide variety of bronze, some people use brass and bronze almost interchangeably, although they are greatly different materials.

   However, I the real question was more why you want a brass or bronze prop nut, i.e. something other than steel.

     Brett

[Claudio Chacon]

Your English is infinitely better than my Portugese.

    It depends on who you talk to. Brass and Bronze aren't that specific, there are many grades of each. "Red Brass" typically means one of a wide variety of bronze, some people use brass and bronze almost interchangeably, although they are greatly different materials.

   However, I the real question was more why you want a brass or bronze prop nut, i.e. something other than steel.

     Brett

Oh! Good for you! My Portuguese is non-existent! I speak Spanish  !

Concerning the Brass/Bronce term, I thought you did not understand whay I meant with "Brass".
I choose brass just because it's as heavy as plain steel and I like the looks when you polish it, thatīs all.

Thanks again, Brett!

[Brett Buck]

Oh! Good for you! My Portuguese is non-existent! I speak Spanish  !

 

   My apologies, I thought you were from Brazil! My Spanish is only slightly better than my Portuguese...

Concerning the Brass/Bronce term, I thought you did not understand whay I meant with "Brass".
I choose brass just because it's as heavy as plain steel and I like the looks when you polish it, thatīs all.

Marine bronze/red brass, gunmetal bronze, seem like OK choices. I would probably not use conventional soft brass just of the strength/durability, unless it has a lot more than standard engagement.

     Brett

[Claudio Chacon]

   My apologies, I thought you were from Brazil! My Spanish is only slightly better than my Portuguese...

Marine bronze/red brass, gunmetal bronze, seem like OK choices. I would probably not use conventional soft brass just of the strength/durability, unless it has a lot more than standard engagement.

     Brett

Nothing to apologize for, Brett!

Lauri Malila mentioned in other post that keeping the rotating mass as low as possible can be a good practice, this is something I didnīt thought about!
What's your opinion on this subject? (I mean, using a heavier prop nut to re-establish the CG)

[Brett Buck]

Nothing to apologize for, Brett!

Lauri Malila mentioned in other post that keeping the rotating mass as low as possible can be a good practice, this is something I didnīt thought about!
What's your opinion on this subject? (I mean, using a heavier prop nut to re-establish the CG)

   Makes no difference to first approximation. It may stress the crankshaft but the difference in prop spin-axis inertia and therefore the angular momentum and precessional torque is negligible. It won't have consequential trim effects, other than moving the CG as you expected.

     Brett

[Brett Buck]

Not everything is about mathematical aproximation.
If you can keep it light, then it's better to do it that way. Period.
Small streams make a river, and when you eliminate all possible stupidities, you'll start seeing the point. One of those things is rotating masses.
Another thing is that such screw-nut connection is rarely a precision fit. It will introduce more inbalance into the system, which may or may not disappear into the noise. But it will introduce an inpredictable inbalance which will have its effect on the fragile harmony of stunt engine.
That's how I see it. When I don't know much, I try to make the fundamental things right. That's surprisingly lot in the final result.
Of course, you can pump 5 times more fuel than it's necessary through the engine and back it up with a pipe, then you have enough noise to hide many things. But is that elegant? L

     And Howard claims Paul and I are afflicted with "The Princess and the Pea" syndrome.

   Calculate the radius of gyration of a prop nut, then the radius of gyration of a propeller, divide one into the other, and square it. I did that assuming a 12" prop and a 3/4" heavy prop nut, and I get 11%. If anyone thinks they are trimming well enough to detected an 11% difference in an already small effect, then more power to them. That's the equivalent of the torque you get from moving the leadouts something like 3/32".

    Brett

[Claudio Chacon]

Thank you Brett an Lauri VERY MUCH for your input.
You both have been very kind...