Speed Secrets – Volume 3

Moving backwards from the prop, lets take a look at that glow plug. Hmmm, I wonder how long that thing has been in there? Well, maybe its time to check. On race day, I like to put a new glow plug in my O.S. and Nelson engines before I test fly at the beginning of a day prior to the 1st heat. This lets you get the needle set perfectly, for that specific glow plug. After the test flight, and after ALL subsequent race heats I like to take the glow plug out and take a look at the element and the color of the base of the plug. There are a lot of signs that can be read from looking at the glow plug. First and foremost in my opinion is the color. There are basically 3 categories that I use to rate the color. The first would be little to no discoloration at all; in other words it still looks basically new. In this case, you are probably running the engine on the rich side, and can lean it out somewhat. The second category would be a very nice “light” shade of brown (or tan). In this case you are very close to the optimum needle setting for the engine. The third category would be a dark brown or black color, which means you are running too lean and you should richen up the engine for the next heat. When I am examining the plug after the heat, I put my glow igniter on it and take a good look as it starts to glow. What I am looking for is any deformity to the shape of the coil, or if it is no longer centered in the plug as it lights. If it’s not pretty close to perfect, I will replace it, and put the used plug away and use in my sport planes. My favorite glow plug for our local races is the K&B HP plug; however, they have been tough to find lately. I’ve been using the McCoy #9’s, and the K&B 1L quite a bit also, and they are pretty good. At Hobby Warehouse, I believe you have to ask the car guys for the McCoy plugs. At times I have played with running a short plug, or even doubling up on the glow plug gaskets, but have not come to a definitive conclusion that it has actually helped.

Now that we have the prop and glow plug covered, are you doing anything with that OS Muffler? Historically, these mufflers have been prone to come apart during a heat, which forces you to throttle back, and most often causes a loss of points in that heat (not to mention the cost of a new muffler). There are a lot of ways to prevent this from happening, but I’ll share what I have been doing with pretty good success. When I buy a new engine, I immediately take the muffler apart and toss the baffle so I don’t forget. I then toss the cheap “Chinese” pot metal rod and nuts in the garbage. I replace the rod with a piece of 6/32-threaded rod; you will need to slightly drill out the ends so that the rod will fit. I clean up the muffler joint with a little acetone, and dry well. I then mix up a small batch of JB Weld. I apply a small amount of JB Weld on the flange that inserts in the back muffler half and slide the two halves together gently and wipe up the spooge that comes out. Insert the threaded rod and attach a nylon lock nut on the front and back. Or, you can double up a couple of 6/32 nuts, which works fine also. At this point, I take the excess JB Weld I mixed and place a blob on the front of the nuts on both the front and back holding everything together and let dry. At this point, you should be in pretty good shape. My only word of caution, is do not tighten the nuts as tight as you can go. Get them slightly tighter than snug, and that will be fine. If you over tighten the nuts, you will put a lot of strain on the threaded rod as it expands less under heat than the aluminum muffler. One last means of safety, if you don’t mind the look (and drag), is to take a piece of baling wire, and wrap it around the muffler, holding it in place in case of a breakage.

That’s it for Volume #3, stay tuned, more “Speed Secrets” to come.