Thanks for your reply Mark, just curious, do you ever have to, or take the time to see if your torque values have changed with weather changes? I have no idea if tractor verses pusher types make any difference. I wouldn't think they would but I do not know. Rutan insists on rechecking torque values at least every 25 hours of flight time, probably as a safety exercise. The pusher types do receive extra air oscillations from the strakes, exhaust and landing gear. Typically on a factory built airplane that uses a certified engine such as a Lyc or Cont, the nuts are fixed to the prop hub, they usually have a flange on the back side that keeps from pulling the nut through the holes. The bolt heads are on the front side of the prop. The bolt heads are the drilled type and usually are safety wired just to keep them from backing out if they were to have that tendency. The prop hub recessed nuts may or maynot be locking type but over many years of on and off they may loose the torqueing ability if they were to begin with, so the safety wire on them is probably a good practice. In your case where you are using regular metal locking nuts then I probably would not use safety wire either. Larry H.
My Purchase of KR-2 in Iowa! - Wood Prop Questions Larry H. wrote: > I am curious if any of you ever have to re-torque, or if any of you ever > check the torque values of your wooden props. > One more question would be, what is your torque values on your props. The exact wood species that the prop is made of would make a difference, so I'd say the first place to ask that question would be the manufacturer. Having said that, Sensenich recommends something like 15-20 ft-lbs (it's on their website somewhere) but when I torqued mine to 15 ft-lbs I hear wood "cracking", so I don't torque it that tight. I have to qualify that, because I use metal locknuts, which have a "running torque" (the torque it takes just to rotate the nut due to friction) of 5 pounds (determined with inch pound torque wrench and bolt clamped in a vice). That means when I torque my prop I set my inch pound wrench (which is more accurate since this is at about 75% or its range) to 180 inch pounds (10 prop + 5 locknut) and torque the nuts in alternating fashion. That means my prop bolts are actually torqued to 10 foot pounds. It doesn't change much past the second torquing after initial installation, but I do retorque it every 50-100 hours or so just for good measure. [12 inch pounds = 1 foot pound.] Yes, I do have a crush plate and my torque wrench is accurate and calbrated. And no, I don't use safety wire. Safety wire to me is a great excuse to never torque a prop, or whatever else is wired into submission. I don't believe in the stuff, and the only piece of safety wire on my plane is a 6" piece that I wrapped around the heat muff as a lightweight clamp. If I'm really worried about a bolt backing out or a nut coming off (like the ones that hold my prop hub to my crankshaft) I'll use red Loctite on them...- Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net
