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Suggestions to Preston Briggs
This site was last updated on February 15, 2008.
Here's how to get a reliable one-flip start for your Nelson. The technique can probably be adapted to other engines, but you'll have to do your own experimenting. I'll try to be precise, but beginners will certainly want someone to demonstrate.
The key to this approach is getting the engine ready to start. That is, whenever you need a perfect start, you'll go through a little ritual to prepare the engine, then start it. So, let's begin by considering how we get ready for a match.
We begin by carrying the plane and equipment out to the circle. We fill the bladder, prime the engine, start it, set the needle, and shut it down (perhaps with the shutoff, as part of an official shutoff demonstration). Next we top off the bladder, reprime, and we're ready to go for the real thing. The point is that there are two separate starts, where the first simply a low-pressure warm-up for the second.
For the first start, when the engine is cold, prime the engine by filling the exhaust port about 1/8 full, or a bit less (usually one pitman will hold the plane upside down while the other applies the prime with a syringe). Trap the prime in the cylinder and turn the plane right side up. Connect the glow driver, pinch the fuel line, cock the shutoff, warn the guy holding the plane, and hit the prop.
This "hit the prop" step deserves more explanation. The process of trapping the prime is simply turning the prop counter-clockwise (when viewed from the front) so that the piston comes up and closes off the exhaust port. After turning the plane upright, make sure the prop is pushed counter-clockwise up "against" the compression. You'll want the prop to be level at this point; if it isn't, fix it. To actually start the engine, we flip it (wack it!) backwards (clockwise). The prop will turn freely for about 180 degrees, bounce off the compression, and the engine will start.
Be sure to use some sort of finger shield or chicken stick! In addition, be sure the crew holding the plane is ready for the engine to start. Always following the same starting ritual will help avoid surprises.
As the engine starts, release your pinch on the fuel line and set the needle. If you need to demonstrate the shutoff, do so. In any case, shut down the engine.
Now we're ready for the match. Top up the fuel, if necessary. Attach the glow driver and repeatedly burp out any remaining fuel. That is: holding the plane carefully, flip the engine forward, letting it run off any fuel left in the engine. The idea here is to get the engine into a known, repeatable state. Remove the glow driver and prime at the exhaust port, but this time using only 5 drops of fuel.
If the engine cools too much, then this prime is not enough. You'll need to measure the time to know how long you've got. An easier way is to run the engine in prime-sized bursts to keep it warm. You may notice some pit men doing this when they have a longer-than-expected wait. In some cases, you'll see a once-ready pit crew who has been waiting for the "other guy" to get ready suddenly say "No!" and run their engine again. This is what is happening - they are warming it back up again.
Just like anything done right, it takes practice. The greatest issue with the "pro start" is the priming bottle or lack of it. A syringe is not adequate for consistent starts. Give your pit crew a chance - get the right equipment and use it.
Thanks to Ken Burdick who contributed most of these details.
