Fly low, fly fast, turn left

I'm a big fan of engineering on the wrong side of the edge. I've been taking a couple of days of vacation to hang out at the Reno Air Races. People take airplanes of all sorts, hot-rod them, and get crazy in the air. Lots of wierd geeky engineering to slap together amazing craft. People race all kinds of craft: little Pitts Special biplanes, Czech L39s, homebuilts, and everyone's favorite, the "unlimited" class. In the unlimited class, there is one limit: it must use pistons. Anything else is fair game. Most of the planes are hot-rodded WWII era craft, and to have any hope of the big trophy, you have to be able to hit at least 500 miles an hour.


There's something particularly insane about hot-rodding a Rolls Royce Merlin engine (which is a pretty common thing to do at these races). At these kinds of excessive abuse, they frequently come to bad ends. About half a dozen have bit the dust this week. The picture on the left is one that broke a piston rod on Wednesday. The picture on the right is a close up (click on the picture for a large version). The broken piston rod spun around and almost sawed the engine in half. This happened in flight. It takes a good pilot to land one of these things with no engine. Ouch.

Comments:

We've had similar problems with engine tuning for years. You can relatively easily gain a bit more power and torque with a simple ECU remap albeit with less fuel efficiency and maybe a need to change spark plugs more often.

But once you get into the more serious stuff, one of the more routine upgrades is to strengthen the rods, seals etc. Any Nissan Skyline tuner can tell you all about this....they take a 280bhp engine and get them out to 700bhp or more but there's significant attention paid to all aspects of engine tuning even the "trivial" things like balancing.

Posted by Dan Creswell on September 17, 2006 at 05:54 PM PDT #

A friend of mine encountered a similar connecting rod failure (and similar damage) to his VW Squareback engine. We dropped it in hopes of eventually replacing it, but that never happened.

A couple of years ago, I got a detailed tour of a running diesel-electric locomotive. The power plant was a 10 cylinder monster which was also used in WWII submarines. I am told that individual cylinders in those engines can be serviced while the engine is running! Don't ask me how.

For raw power to weight ratio, it's hard to beat a turbine. I can sort of understand why the Reno unlimited class is limited to pistons. Turbines can easily produce twice as much power for a given weight. More importantly, I don't think there's much you can do to hot-rod a turbine, other than metallurgy. At the end of the day, materials are the limiting factor.

Turbine failure is not as spectacular as with reciprocating engines. It basically overheats and spits output wheel chips in the exhaust. I had a chance to see the damage of a hot start a few months ago.

Then there was the case of the turbomolecular pump that suffered bearing failure. It made a loud howling noise until we put it out of its misery. The shaft never turned again.

Posted by Madhu Siddalingaiah on September 19, 2006 at 09:51 AM PDT #

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