Brodhead Pietenpol Association

Original Posted By: "Christian Bobka"
Subject: Pietenpol-List: Alternate Woods-UpdateThe wings have really been a pleasure to work on, even if there is a multitude of parts. I built the tailfeathers first, then the fuse, then the CenterSection, finally the wings. Maybe if I built another Piet, I would do the wingsat the beginning.We have a 35 Piet on the airport, which is non-flyable, but interesting. Ithas a two-piece wing, which I am beginning to think is superior to the Vi Kapler design, since the aileron control cables can be run directly to each wing.Im still a little bit perplexed about how one connects the control cables through the Center Section in such a way that they can be easily re-connected.Im amazed at the difference the drag and anti-drag wires make to the rigidity of the wing. I put in some temporary hardware store wires to stiffen thewing while finishing it.The fellow next to me is building a scaled Jenny, and has installed 3/32 cables for the drag and anti-drag braces. He uses Cable Bushings rather than turnbuckles, twisting the cable to achieve the correct tension, after pulling thecable tightly around the Bushing. It is easy to adjust the tension, each half twist tightening the cable by about ten pounds. His spec. calls for 35# tension, a figure I think that I will use. I made a set of turnbuckles early on,so cost is not a factor, rather the weight saving and simpler hardware seems to me to be worthwhile.I bought the folded trailing edge at AS&S. Planning to clean the aluminum carefully, then to Epoxy the T.E. to the ends of the ribs with T-88.Looking forward to meeting again andtalking with all of you at Brodhead this year.Carl L @ Compton Airport.________________________________________________________________________________

Original Posted By: "Michael D Cuy"
Mike,You never should have the need to shim the relief valve so forget aboutthat. That is not a cure. The problem you indicate is one of excessiveclearances within the engine. The excess clearance allows oil in when,let's say a conrod is going down the barrel and then it compresses the oilin the same space as the rod is going up the barrel. This compresses theoil and compression heats. That is why the oil heats up. As the oil heatsup, the viscosity drops, which causes more friction elsewhere which causesthe oil to thin out even more, etc. My first guess is that there is animminent conrod failure due to a bearing that is failing. Excessiveclearance due to a bearing failure also allows an internal oil leak of greatmagnitude which reults in zero oil pressure. Zero oil pressure cuases otherbearings to fail. Remember, this is the symptom. The real question now iswhy the rod bearing or whatever is failing?I have said it once or more times before or more on this list that anotherpoint of failure in these engine is the from cam journal where oil passesfrom the left oil gallery across an annulus in the front cam journal to theright oil gallery. It is common that there is excessive wear here due totoo little bearing surface area for the loads imposed. The oil leaks out ofthe oil system at his point excessively, causing low or no oil pressure andexcessive compression causes heating of the oil as the valve springs forcethe cam to and fro. Unfortunately for us, the case aluminum is the bearingmaterial for the cam and the excessive wear at this journal mandatesexpensive solutions.One is to line bore the case for oversize cam journals and then buy areplacement cam with OS journals. Big $$. Another fix for an experimentalis to have a known good cam's journals plated oversize with hard chrome andthen ground for trueness to an OS to match the case which has been lineboredto cleanup the mess at the front journal. Another fix is another case but,how do you know the other case is good? It might have the same problem. Itis very difficult to measure the fron cam journal because it is virtuallyinaccessible when the case halves are together which is the conditionrequired for measurement.Let me know what you find.Chris----- Original Message -----

Original Posted By: Doc Mosher
Subject: Re: Pietenpol-List: Cont. 85 hp low oil pressure questionIn a message dated 6/9/04 9:05:52 PM Central Daylight Time, sbobka(at)charter.net writes:>Chris,Your assessment is right on.When I assembled my engine, I did a clean and dry fit of the cam and crank (with new main bearings), using plasti-gage across the journals, assembled andtorqued all hardware, being very careful not to allow the crank or cam to turn,or it will smear the plasti-gage. Then disassemble, and recorded all the measurements. I was relieved to find that all clearances were within spec.Chuck G.________________________________________________________________________________Date: Wed, 09 Jun 2004 23:49:14 -0500