Propeller Torque

[blueflyer]

I just noticed a torque table on my wooden Colin Walker prop for 3/8" bolts.
It says for 3/8" bolts:
200 in-lbs/20 ft-lbs

Now, I'm no math major, buts thats not a conversion between foot-lbs and inch-lbs. What gives here? What torque value should I use?

I feel like I'm missing something very obvious here......

 

[elippse]

When the torque value is given for a propeller bolt, it is to apply a certain amount of tension to the bolt to provide enough clamping force, since a fixed-pitch prop is driven by the friction between the hup and the flange and the crush plate. You'd be better off to get the information on the use of Belleville spring washers which has been on the forum and use them under the bolt heads. They will also take up any expansion-contraction which takes place on wood props to make sure that the prop doesn't come loose. If your prop shrinks and you lose the clamping force, no amount of safety wire will keep the bolts, and the prop, from coming off!

 

[664781]

Torque

My Aymer-Deymouth called for 20 Ft. Lbs. 24 was the max.

 

[blueflyer]

I understand why I need a certain torque value, but I am at a loss for what torque value to apply. Since 200in-lbs (or 16.67 ft-lbs) does not directly convert to 20 ft-lbs (240 inch-lbs), I am skeptical of either value.

 

[DanH]

Is the subject propeller maple, yellow birch, or mahogany?

200 in-lbs is typical for yellow birch, given an SAE2 hub and 3/8"bolts. Maple can be squeezed harder, while mahogany is softer.

BTW, in this case the crush plate transmits no torque.

 

[blueflyer]

Turns out....

Well, I just called Frank over at Performance Propellers who was more than happy to discuss this quandry while he was at Wal-Mart no less. Anway, he told me to use the 20ft-lbs of torque, go fly for an hour and recheck the torque. If they are loose, tighten them down to 25 ft-lbs and go fly some more. I appreciate all the input.