Ray's has asked me to write up a short article on the power set-up of a Speed 400 sailplane, so here I go.
The motor has to be a stock Speed 400 can motor. These come in various voltages running from 7.2 volt to 4.8 volt. The standard motor used in this class is either the 6 volt or the Rocket 400 race. These motors are available from many different sources, I get mine from Hobby Lobby: http://www.hobby-lobby.com/speed400.htm There is not much you can do with these motors to increase performance other than break the motor in. There are various ways to break in the motors. I like to hook up two alkaline C cells and run the motor with out prop or gearbox until the cells are drained.
99 % of the guys run a gearbox. The favored gearing is 4.5-1. There are a few gearbox that are used. The favorites are a Cosmotec 4.5-1, and the one I use, it is a Mini AC 4.64-1. The Cosmotec is hard the fine, the AC is available from Hobby Lobby: http://www.hobby-lobby.com/gear400.htm There a are other gearboxes that will work, MP Jet and Graupner also makes a nice one that works fine. The big thing is finding one that fits your plane, and how much you are willing to spend.
There are many different sizes of folding props that will work. Anywhere for a 11 X 7 to 12 X 10 or larger will work. The big thing is to make sure you don't over prop and run too many amps through the motor. It's best to keep it under 12 amps or so. There is no one perfect prop for everyone, The best thing to do is try many different props to see what works best with your plane. On my WindDancer I use a 11.5 X 7, it works best for that airframe. Hobby Lobby and Esprit Models has a good selection of folding props and hubs to chose from.
There not that many brushed ESC's to chose from these days as most are for brushless motors. Castle Creations makes nice one, and Dymond Modelsport has a nice one as well. One thing to look out for is the BEC function. Most ESC's have a BEC of 1 amp which is good for only up to three servos. If you are going with a full house plane with 5 servos or more you should go with a separate battery pack to run your servos, or use a separate BEC to run the servos, Castle makes a nice one: https://www.tanicpacks.com/product_info.php?cPath=114_81&products_id=856&osCsid=03fd95463bab5156784f8ce7786661f8 Tanic sells all the Castle line of ESC's as well.
You are limited to 8.4 volt battery packs. So you are limited to a 7 cell NiCad or NiHM pack or a 2 cell Li-Po pack. Most 7 cell packs are in the 1100 to 1500 ma size and weigh in about 5.5oz. You can use a 900-1500 Li-Po pack and save 2oz or so. I like Tanic for all my Li-Po needs: http://www.tanicpacks.com/ CheapBattery Packs is a good source for NiCd and NiMH packs. http://www.cheapbatterypacks.com/main.asp?sid=565424&
Sky Bench Aerotech
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