Barnyard Buzzards Newsletter March 2009 Page 4

Buzzard Droppings March 2009

Text Box: Saturday was a really nice day... not too cold not too hot, very little wind. Even the E-guys were having fun. When there is lot of flyers out, please use the pilot stations! If they are full, wait your turn. We have a 4 plane in the air limit and guess what - we have 4 pilot stations. If you’re not on one of the stations and the others are full, guess who is in the wrong. It is that time of year when the weather is getting a little warmer, but not hot by any means. There is not too much chance of sun stroke or frost bite. What can get us in trouble is the life blood of our hobby. No, not the fuel, but the batteries. I hear all the time “I’ve used these batteries for 27 seasons and they are just fine”. Well they may not be just fine for the 28th season. With all the neat stuff we have to test the condition of the batteries, there is no excuse not to test the batteries and determine what life is left in them. I personally discard battery packs when they get down to about 75% of their new life. The new life is not necessarily the number that is stamped on the label. Remember the manufacturer of the battery

Text Box: rates their batteries at much lower current drain than we typically use, hence, there may be a delta right from the get go. Keeping good records will go along way to not getting to the field with dead batteries. The worst thing is that they are usually all right for the first or second flight and give out in next flight. You can guess what happens when the batteries give out. Let’s all make the commitment to check our batteries, and be a little safer. Don’t forget the transmitter battery. While you are working in your aircraft, check the condition of the wiring. We don’t want to see wiring where the insulation is in bad shape or connectors that are loose and worn. Remember the connectors we use will corrode, some more than others. If you have a choice, always use the gold plated type. You should also check the fuel tubing and tank for leaks. 72 Mhz guys - put your antenna up, 2.4Ghz guys - leave yours down. UNTIL NEXT TIME, BE SAFE BE COURTEOUS

Last month we talked. about muffler design and that many just

redirect the exhaust away from the model. Some designs actually cause

high back pressure and essentially reduce the engines performance.

Some have asked how the tuned pipe works. This animation is from

http://en.wikipedia.org/wiki/Two-stroke_cycle

This is a “tuned pipe” design. The idea of a tuned pipe is to pull some of the fresh fuel and air into the header while the exhaust port of the engine is open, and then ram this fresh fuel and air back into the cylinder before the exhaust port closes. The size, shape of the muffler, and outlet size create a sonic shockwave that performs this ramming function. This effectively supercharges an engine. With the right geometry , the exhaust system can reduce the noise and add power to your engine. We will conclude this discussion and provide some examples of effective mufflers next month.

By Ron Swift

Vince Bell, Safety Officer