To read an updated on this story please click on this link:
Chinese Crankshafts for Corvairs, update 2/17/13.
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Friends,
Every now and then the subject of having a new crank made comes up. With a little reasearch on the Net, people find out that new cranks have been made for Corvairs. These fall into two groups: Billet cranks made in the U.S. for Corvair race cars, and cranks made in China.
In this post, I am going to speak about the latter. First, let me say that a lot of people make comments or hold very stong opinions about things they have never seen. Most people are guilty of this in one way or another, and it’s mostly harmless. However, when the subject of airplane building is at hand, I always want to listen to a guy who has first hand knowledge, because in aviation, the results of poor information isn’t always harmless. When I speak on the same subject, I am very careful to make sure that the person reading or listening is getting an accurate picture, and that they also understand the parameters of the discussion. On the subject of Chinese crankshafts for Corvairs, I think that I have a particularly informed opinion, not because I understand the engine, but because I have also seen the Chinese cranks in person, I know the guy who had them made, was present when they were inspected, followed their issues, and I know the only guy who has flown one. Follow through this story with me and get an insider’s look at these cranks, and then decide for yourself how you would feel about flying behind one.
The story starts with Brady McCormick of Washington state, about 2006. Brady is a good guy, and a heck of a good craftsman, but he isn’t an engine guy nor has he ever had any kind of aviation training. He likes the Corvair for his own aircraft, a 701 he is slowly building from plans. He buys a lot of core engines, which all turn out to be early models which have short stroke cranks. Over several months he hatches a plan to have new cranks made. He starts looking around the U.S. and finds that billet cranks cost $2500 to $3000. He finds a Web directory run by the Chinese government to direct foreign buyers to Chinese manufacturers. By contacting an agent in Taiwan, Brady finds out that new forged cranks can be made for about $1000. Brady was going to use these to build engines and also resell them to builders. Quite a plan for a guy who had never built a running Corvair engine of any kind.
The catch on the plan came up quickly. The Taiwan agent stated that she needed $30,000 to have new forging dies made, before the cranks could be made on the mainland. To get started, she offered to have 5 cranks made from billets. These could be done without having dies because billets are just machined from round stock. Brady sent a sample crank, money for 5 billets, and a large deposit on making the forging dies. At this point he honestly thought that everything was going to work out, and that he was making a regular business arrangement, just as if he were dealing with a U.S. based company. Although I had not met him in person at that point, I regularly spoke to Brady on the phone, and as I listened to his great plan, I honestly thought his money was gone and he was never going to get anything. Something worse happened. They sent him the 5 billet cranks. Encouraged by this small first transaction, Brady borrowed $30K from his father’s retirement savings and sent it to pay for the forging dies. On that day he felt he had just made a move that would make his fledgling business “Magnificent Machine,” a major player in the experimental market. The long run would show something very different had taken place.
When Brady first announced his new cranks and put pictures on the Web, it started an Internet flap because they didn’t look like normal billet cranks, and Brady was prone to making statements about them that he couldn’t back up, like “they are 2.5 times stronger than GM cranks.” This was just stuff that he read on Web sites and wanted to believe. When he encountered people who actually had a university background in strength of materials, he was reluctant to admit he might be wrong. It was a rocky introduction.
I met Brady in person at the Arlington airshow shortly after. He was very different in person than what he projected on the Web. He was modest and much younger than I expected. In 30 minutes I decided I liked him and even though I am not a fan of things imported from China, I was moved by his desire above all else to return his father’s investment. I counseled him to change his Web site and online claims, and act more like his in-person self. I invited him to Corvair College #13 and he showed his stuff to our builders. At this show, Roy from RoysGarage.com was also a technical guest of mine. Roy took Brady aside quietly and showed him that the cranks were of marginal accuracy, and Brady should tell his source that the concentricity needed to be a lot better. Brady had two cranks that were 3.00″ stroke (instead if the stock 2.94″), Two that were 3.125″ and one that was 3.25.” To give you an idea of how much planning was missing, a 3.25″ stroke crank had the connecting rod actually hit the cam lobe on rotation. Brady had enthusiasm but not experience.
The first guy to buy a crank from Brady was Steve Makish, a friend of ours and a well known KR pilot of great experience. Steve understood that this crank was unproven, something of a test. He felt like he was a good guy for the job of test pilot. He bought a 3.00″ crank for his engine. After the short block was assembled at Dan Weseman’s with one of his bearings, Steve took it home to finish it. This is when he discovered that the rod throws on the crank were ground almost 1/8″ too wide. If assembled, it would have marginal oil pressure. Brady was informed, and he went out of his way to fix it; the best solution was having a custom made set of connecting rods. This took many weeks.
When the engine was assembled and run, Steve did his usual extensive ground run. After a long time, something didn’t seem right. Compression dropped off, and an inspection showed that the exhaust valves were bent. Usually the only thing that can do this is putting the cam in several teeth off, something a lifelong motorhead like Steve isn’t likely to do. After some time, it was noted that the keys on the back of the crank didn’t match the ones on the flange. A careful inspection revealed the following photos. The crank had been made undersize at the factory, and instead of scrapping it, they had made a hidden repair that had failed. Very luckily, this happened on the ground.
Above is the sleeve that was put on the crank. The stock crank has the same diameter as the outside of the sleeve. In this case, the Chinese had all the crank forces going through the thin section with threading on the inside.