Lose prop in the roost

[Sonnyj]

Mornin Ya'll
I've got a 50x26 woodin prop on a 72hp Mac. How much tourque do I apply to the nuts and how often if ever should I loosen them?

[Chuck Irby]

Sonny, don't you have the spring washers between the nuts and the prop also?

[Sonnyj]

Mornin Chuck
Yes there are 6 washers under each nut.

[Chuck Irby]

Hey Sonny, I was thinking they were more than just washers, more like a spring that would keep tension against the prop. At any rate, Mike Gaspard or one of the guys who flies a Mac would be your best bet for the best answer to your question, IMO.

[Jonvee]

A wooden prop on a MAC should be using Belleville washers. You stack them to oppose each other and they create a spring to help keep tension on the prop as it swells and shrinks with moisture. I don't remember the torque settings. Here is a website for Belleville washers. http://www.keybellevilles.com/belleville_washers.html

[gyromike]

Sonny,

Right off the top of my head, I can't remember what I used for torque values. I think it's 25 ft.lbs.

I'll have to check my books when I get to the hangar.

You may want to contact Tennessee Props to make sure.

I also use the Belleville (spring) washers.

[Sonnyj]

Well I just had another look and yes they are Belleville washers,and they are stacked in the proper oder,but the nuts are only finger tight,and it got me to wondering if I should loosin them during long periods of storage,and how tight should they be. I do appreaciate any info you have.
Thanx Sonny

[gyromike]

Sonny,

You won't have to loosen them, but you'll want to check the torque periodically. I do mine at each annual condition inspection.

The Belleville washers seem to do a good job of keeping the right amount of pressure on the crushplate, even if the wood expands and contracts.

I haven't seen mine change any, but it stays in a closed hangar.