Hi Pops, you are up early. Ultra-prop hubs has slots, "8mm or 5/16" wide". Ivorptop says not safety wire, not loctite, no Ny-loc or castle nuts. Nothing to prevent re-torquing, regularly.The Rotax 503 prop hub has 6 threaded holes for 5/16" prop bolts. Should locking nuts be used behind the hub , or should castle nuts be used with holes on the bolts for safety wire?
Perhaps, but constantly checking the torque on the bolts on a wooden prop can gradually crush it. The prop hub will expand and contract with atmospheric moisture changes, and if you retorque the bolts when it's dry you'll turn them in a little. When the prop expands again it gets crushed a little. Standard practice with wooden props on Conts/Lycs is to check them yearly, at annual time.But 2-stroke engines have vibration and TV issues that are different than "real" airplanes. There may be a valid reason why they are always trying to encourage you to re-torque the prop bolts on a 2-stroke?
Yes. I got that picture off the 'net. I always ran the wire around to the next hole to get a positive pull in the clockwise direction on the bolt head. And pulled the wire tight. When it comes to lockwiring you'll often see installations that are nearly useless at preventing rotation. I've found it done backwards a few times, and inadvertently did it myself more than once.BTW, Dan, I'm not too thrilled about the angles of 2 of the wires in the above photo. Such may not have been acceptable when I worked on US Army helicopters.
I'd seen this before - didn't associate the name attached to the work until now. Here is the web page:I seem to recall Mark Zeitlin doing some successful experiments with Belleville washers and a wooden prop.
Also interesting is that with Belleville washers, the safety wire is actually accomplishing something. Craig Catto (who now ships bellevilles with every prop, to my understanding) has done experiments showing that even if safety wire is installed well on prop bolt heads, it's possible for the bolt head to turn up to 60 degrees (one flat), which is MORE than enough to lose almost all if not all compression on a non-belleville install wood core hub propeller. So with the ability of the prop hub to shrink out from under the compression, and the ability to turn the head substantially even with safety wire, the SW isn't doing a whole hell of a lot unless bellevilles are installed.Note, though, that the belleville washer thing only maintains the proper clamping pressure without having to retorque periodically; the bolts still need to be safety wired.
My original goal was to be able to tighten the bolts just by counting the # of turns (or partial turns) of the prop bolt - I figured that while not everyone knows how to use a torque wrench correctly, most of us can count. That turned out to have a lot of variability in it due to confounding factors. So then I went to measured washer deflection, and that was better, but pretty hard to do, and also had a few confounding factors that made it somewhat inaccurate.I suspect that, with Belleville washers, you could determine the clamping force by measuring deflection, without having to move or re-torque anything. I don't recall if this was in the article, and for all I know it's a flawed idea.