Billet Cranks Made In The USA


Dan Weseman, the man behind the Wicked Cleanex, The BTA 5th bearing, and the Panther project,  the second winner of the Cherry Grove Trophy,  is working his way toward a new goal is the land of Corvair powered flight. He is developing a made in the USA, true billet crank for Corvair flight engines. Follow this post and get an inside take on his motivation and the challenges involved.

Above, Dan in his new 12’x50′ climate controlled workshop built inside his hangar. He built the space to facilitate the development of and the eventual production of “Florida Panther” aircraft. In the photo are a fuselage side for the steel tube sub frame and an aluminum wing rib. Although the plane is intended to be an LSA legal, fun flying plane, Dan is building in enough strength for some advanced aerobatic work.

Dan Weseman has a well earned reputation in the world of flying Corvairs as a get it done kind of guy. Outside of aviation, people are impressed by people who get a lot done in a day. Inside aviation, accomplishments are done on a longer time scale. Building a plane has an element of  “What can you get done in the next 4 hours?” to it that is very important.  But it also has the requirement of stringing together a long series of these work sessions. Lasting accomplishments are built of this type of sustained efforts.

Dan often takes a modest tone on the outside, saying things like “we will see how this works” in discussing projects, but knowing him for many years, I have come to see that such comments are really to keep discussion low, and they address the fact that many new arrivals in experimental aviation are yet to see the sustained effort required to bring anything good to physical reality. Downplaying the discussion side of his efforts is a way that keeps Dan operating the project on his schedule, not on anyone elese’s expectation.

This has proven to work well in the long run. Dan, in joint effort with his father Jim, have now delivered more than 200 of their 5th bearings to Corvair builders. The bearing story is one of careful development and testing followed by steady customer support. Same goes for Dan’s efforts making “Cleanex” Corvair installation packages available to people building Sonex airframes. After building and flying his own aircraft and refining the installation, Dan moved to making the parts available. His installation components are compatible with all of our engine components. We even developed some parts, like the Reverse Gold Oil Filter Housing and the Universal #1 Exhaust specifically for Cleanex installations. The engine installation has been a steady success story. When I visited Dan’s shop there were 5 more Cleanex mounts in process being finished by master welder Vernon Stevenson.

Dan is now turning this approach to the subject of billet crankshafts. While other people have thought of this before, and Corvair race car guys have had a handful of them made by crank specialty shops over the years, they have not shown up in experimental aircraft.  Here is where Dan’s unique background comes in. For a day job, he installs CNC machining equipment in industrial production shops in the southeastern U.S. His company deals with the transportation and installation, so he gets to work with all types and brands of machinery. He has been inside more machine shops than any other person I have ever met. He fully understands which type of modern equipment is best suited for making a run of billet cranks for high stress Corvair engines. Combine this with his background as a builder and a flyer, and the experience he has in bringing parts to the market and supporting them, and you have the makings of a success story.

A billet crank is made from a piece of round stock, typically in the case of the Corvair, a cylinder 6″ in diameter and two feet long. This material is most often 4340 alloy steel made under exacting conditions. This cylinder itself is a forged piece of material, not cast. Professional race car engine builders specify that these blanks be made in the U.S. with a paperwork trail that demonstrates their pedigree. Because 80% of the material in the blank is going to be removed to make the crank, it must be guaranteed to be homogeneous throughout the blank.

Hand making these cranks in a crankshaft shop is one of the reasons why they typically cost $3000. The material removal takes a long time on traditional equipment. Many crankshaft shops only have the reserve manpower to make a few of these a year. Dan is looking into a different approach, where he is going to have 98% of the material removed by very powerful CNC equipment, bar feeding lathes that can work from a 20 foot long billet. As a second step he wants to take them in groups to a crankshaft specific shop like Moldex, where those craftsmen will be able to put the finish grind and balance on the part. He is working toward driving down the price toward $2000-$2500 with a new gear installed.

Such a crankshaft can be made stronger than the original GM forged crank. Contrary to what many people think, billet cranks are not inherently stronger than forged ones. The grain of a forged crank actually makes it stronger than a billet in direct comparison. However, automotive cranks do not have large radiuses in the fillets. In cars they are not required. Purpose built aircraft cranks have much larger radiuses, reducing the potential for a stress riser. Billet cranks can be built with large radiuses, and this allows them to potentially withstand extreme forces better than a forged crank with smaller radiuses. At times, discussion on crankshafts is driven by people who don’t have a grasp on concepts like this. Productive understanding starts with a practical look at how the concepts are applied to our specific engine. Commentary without this isn’t worth serious consideration. People will always throw around statements like “they are 20% stronger.” No statement like that makes sense without addressing tension, torsion, bending or fatigue life. The real discussion is a far greater in depth, while focused on a far narrower scope.

A number of people think that the genesis of Dan’s billet crank project was when Mark Langford broke the back end of his KR-2s crank in November. In reality, Dan had long been planning on having a billet crank as an  experiment in his new aircraft, the Panther. In his own style of letting the project set the timetable, not public discussion, he was working quietly on the topic, developing the plan as he worked in a number of different CNC shops that have the equipment that would make the project economically viable. After Mark’s comments, some builders started asking about billet cranks, including Chinese ones. In an effort to let people know that he was working on a U.S. made one, Dan mentioned this, and has a small email list of people who are following his progress. Mark Langford is one of the people who has said he will use one of Dan’s cranks in the next incarnation of his engine. To be clear, Dan’s interest in the development was driven by the fact that he is going to set up his personal Panther for some very hardcore aerobatics. He has told me he wants to use the Precision mechanical fuel injection we have for testing, and he is even considering an inverted oil system. In his 3,100cc Cleanex, Dan flew a tremendous amount of sportsman aerobatics on a stock GM crank. He did a lot of this without a 5th bearing. After he developed his bearing he retrofitted it on the same engine/crank and kept going. Over several hundred hours of hard flying he has not had a crank issue with either the nitrided crank by itself nor his 5th bearing. When it comes to flying like that, most people recognize that it makes sense to have a 5th bearing. Likewise, now that Dan is moving up a notch in the stress department, going to a large radius billet crank is just part of his plan to make sure that he has 200% of the strength he needs, not 99%.

The most common question that people have about these cranks is “Do I need one?” My primary answer for this is that the vast majority of builders do not need one of these. That is my opinion based on the big picture of statistical evidence we have from being at the center of the Corvair movement. I have seen Dan fly hard aerobatics at wide open throttle in his Cleanex for 30 minutes at a time on a stock GM crank. We have pilots like Andy Elliot who have flown hundreds of hours on a 3,100 without a 5th bearing. Mark Petz overhauled the engine in Bernard Pietenpol’s Last Original last summer. It had 800 hours and the crank was perfect, in spite of never having been nitrided and not having a 5th bearing. We have a lot of pilots with several hundred hours on non-nitrided cranks and no 5th bearings. It is all a matter of personal choice. Very seriously, I am not, and do not wish to be, in charge of anyone eles’s building, flying or life. The primary attraction to me of flying is freedom, and the root of this is being able to decide things for myself. I am not here to take that away from anyone. I take presenting the facts very seriously. I take countering disinformation seriously. I take the task of explaining the risks very seriously. I want builders to know the big picture. But I fundamentally trust that anyone who is rational enough to fly a plane can make the correct decision for themselves, given factual, accurate information presented without emotion. If I came out and said, you have to have a nitrided crank, a 5th bearing, or a billet crank, or I will not work with you, then I am dictating that our accumulated knowledge will only be shared with some people. I make strong recommendations, demonstrate that I believe in these recommendations by building engines that match them and flying behind them. But, in the final measure, builders are going to make their own decisions.

New people will often say, “Just tell me what to do” in homebuilding. This is ok when you’re getting started in homebuilding. Most of these people get off to a good start by replicating the engines that we build in our shop. Over time, this same person needs to transition to the mindset where they are analyzing the available information and making the decision for themselves. I want builders over time to understand the logic of all of the choices we make in our work. They are not required to agree with the choice, but it is not a sign of conformity if two people look at a set of facts and come to the same conclusion. Making choices for yourself is what being in command is all about. This is how you prepare for being aloft, especially with another person in your plane. It is the great reward of flying. Self reliance and earned self confidence also happen to be your best line of defense in any flying situation.

In modern life, people are less and less in charge of important decisions that count.  On many fronts, society is trying to prevent you from hurting yourself, and the method they choose is most often taking away the ability to do so, not educating you and letting you choose the path. Flying, and homebuilding in particular, is the polar opposite of this. You have to have a really negative view of individuals to buy into a system that tries to prevent people from having the means to hurt themselves…The queen and the hive dictate to the worker bee his limited task, and when he has fulfilled it, he is no longer of any common good, and he is expected to die quietly because the hive programmed him to do so… In my book, humans are individuals, not insects. Any person who chooses do something simply because he wants to is affirming this. Any person who picks up a tool and sets out on a journey to create something of his choosing, a goal that does not serve the hive of society, can expect both the disdain of  the hive and the warm welcome of other individuals.



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