Brodhead Pietenpol Association

Original Posted By: lshutks(at)webtv.net (Leon Stefan)
Graham wrote->I particularly wanted the torque spec of the main nut on the prop flange.Well, I'll have to admit defeat on this one. I checked the Flying & Glider Manuals, Pietenpol's narratives on converting the Model A, and the Pietenpol manual and plans. No info on this particular bit of information. As a matter of fact, I came away even more puzzled than before because I've never actually seen a Model A prop flange or hardware so I can't visualize how the piece of axle that is used as a centering shaft for the prop is actually attached to the flywheel flange or crankshaft.It appears to me, however, that the large center nut that holds the prop onto the flange, would carry no more torque than the prop bolts if the prop is wood. Most prop bolts are torqued to something less than 20 ft.-lbs, and I wouldn't think that the large nut would be any different. For example, my Tennessee Props wood prop, with AN6 bolts, calls for 200 in.-lb. (16.7 ft.-lb.)I'll have to defer to the Model A guys out there. Anybody?Oscar ZunigaSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________ ETAsAhQow8MuTU+T/IBy+gkSqkrOwXzctAIUNXhpnIH6UwkczBAufy2La1j68Vo=

Original Posted By: "Oscar Zuniga"
Howdy again, low 'n' slow fliers; I got an excellent email from Delton Perry regarding the prop bolt issue. Here's the info he sent me, including his qualifications. I've rearranged and edited it a bit:======================I am a EAA technical counselor and Power Plant rated. I am retired and building an RV6A. I am somewhat familar with the Pietenpol and A Ford engine.I will try to describe the arrangement of the prop hub make up according tothe drawing that I have. The plans that I have were drawn by Orrin Hoopman forBernie Pietenpol. The flanged shaft that you refer to is an input shaft from aModel T transmission. There is also a five inch plate made from 12 gauge steelthat goes next to the propeller. This plate is larger than the flange so as tosupport the back of the prop.There are four 7/16" studs for attaching the prop.I will describe the stack of pieces starting at the crankshaft flange. The "T"transmission shaft goes first, the 12 gauge plate next. The four 7/16" studs gothru the plate, T shaft flange and screwed into the crankshaft flange. The studshave jam nuts that tighten this stack to the crank flange. The prop goes onnext, the crush plate next, then retaining nuts. The drawing is a littleconfusing. When you look at the drawing, it appears to have a nut on the largeshaft. A closer look at the drawing actually shows the 7/16" nuts. The alignmentof the nuts on the drawing makes it apperar that the large shaft has a nut. Ihave seen several Pietenpols with this basic arrangement. I not seen a large nuton the shaft. This may or may not agree with your drawing.Actually a nut on the end of the of the "T" shaft would serve no purpose,according to the drawing I have. If the 7/16" studs happened to break, the "T"shaft, prop and all would separate together from the crankshaft flange.As general rule, the torque on wood props will run from around 12 ft/lbs to16 ft/lbs. Much more than this will begin crushing the wood fibers. I don't knowthat I have seen a published torque value on the four 7/16" prop nuts. Assumingthat the studs have a National Fine thread, I would suggest no more than 16ft/lbs.As a side note, I have seen some that have made a shaft/flange assemblywith a five bolt pattern for cub prop. I assume that these were machine shopmade as the Continental prop hub would not be easy to modify to fit the Model Acrankshaft flange.The corvair engined Pietenpol does have the center shaft with a castle nutthat is cotter pinned. The crank flange on the corvair is pressed on to thecrankshaft. The procedure is to cut an internal 1" thread into the end ofcrankshaft. You then make a shaft to screw into the end of the crankshaft. Thisshaft serves as safety shaft to prevent the crankshaft flange from separatingfrom the crankshaft. There is another way to accomplish this, but the safetyshaft arrangement is what you usually see on the corvair engined planes.==============================Thanks, Delton. I'm learning something new here practically every day.Oscar ZunigaSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________