Hey,

I am on a team designing an unmanned aerial vehicle for competition. Due to the power requirements of the equipment, we are going to use a generator to supply the main power (backup batteries will be available). Basically it will be a brushless motor driven by the engine. Any suggestions on how we could use the engine to drive the generator? (ex. adding a pulley behind the propellor to drive a belt, etc) I'm not sure exactly which engine we will be using. Some kind of gas engine ~50cc hopefully.

Thanks

first of all a belt is the best way to go, because you will get less vibration with a belt, and if the crank extends out the back of the motor the back would be the best place to connect it, as for the front if there is room you could have a groove machined in the prop hub (to be used as a pulley), if there is no room for a groove you could have a new prop hub made to accommodate a groove,,,

there is another way, if the crank extends out the back of the motor you could connect the generator directly to the crank with a rubber coupling,,,

another thing, if there is not enough room in the plane up front, you could us a flex shaft and mount the generator back farther.

check-out the link for all the parts you will ever need for a project lik this.

https://sdp-si.com/index.asp


Jim

can also be done without any belts, gears or couplers: [link]http://www.sullivanproducts.com/GenesysCustomMainFrame.htm[/link]


dave

I used to own an Aeronica Champ that had a generator mounted on the bottom of the fuselage between the landing gear legs, the generator had a propeller on it and was powered by wind. The generator would begin charging before I was airborne due to the wind from the propeller while taxing. I believe the generator would put out about 4 amps and 14 volts. It was enough to keep my 7 amp battery charged while I used the radio and the position lights at night. I think that this would be fairly simple to copy on a model airplane.

Looks like i'll have to go with belt drive from front. Maybe adding a pulley behind propellor. Looks like it'll push it out at most an inch. Hopefully that will be ok. A sullivan generator would be nice, but we are dealing with a budget here. Don't think a custom generator would be cheap. The generator is going to have to put out a great deal of power to support all our stuff. We decided that a driven brushless motor was our best bet. Engine driven is best to reduce drag. Looks like some crafty engineering is in order. Thanks for the website Jim, I was just about to go searching for one.

Thanks for the suggestions.

I think the Fuji 50 flywheel is far enough away from the case to put a thin tooth belt behind it..It will be interesting to see if there's enough power for both the generator and the prop...

You may already know this. A driven DC motor is a generator, whereas a driven brushless motor is essentially an alternator. This means in addition to a regulator, you will have to carry a rectifier to convert the AC to DC first.

Yea, we've got the regulator figured in. Got some guys in the ECE dept here at MS State working on it.

If you can find one out there somewhere, the old Byrons used to sell their "Mustang" 50 (It was a Fuji 50 before GP started importing the line into the US) with a built-in generator. I never had one, but understood they worked well. It might keep you from having to "re-invent the wheel"...so to speak!

Lee

A lot of engines have a shaft coming out of the back. It will be less expensive and less complex to pick an engine with a rear shaft. Driving auxiliary equipment from behind the prop is a BAD engineering decision. It will lead to many difficult to solve problems later.

An engineer’s opinion.

Any of the small motorcycles or scooters have ready made, well proven alternators with regulators, rectifiers etc. all sussed out and ready for use, - should be easy to adapt one of those to fit the rear shaft, - I would have thought!

I definately agree with using the shaft coming out of the back. Sorry, still new to gas engines. Being right by the propellor would worry me quite a bit. I'm still trying to pick an engine. We had a Saito 180 we had hoped to use, but newly calculated power requirements persuaded us to go bigger. So, who wants to suggest an engine. Let me first mention that we blew our budget long time ago. This plane as going to be really expensive (>$10k I could easily see). We have equipment left over from last years attempt plus $2k more. Therefore if propulsions group (me) wants a new engine we are going to have to figure out how to get a new engine. Plus I'll have to figure out how to get money to pay for it. So basically I need cheap, but not cheap enough to risk the plane crashing. Right now Fuji bt-64a is looking good. I believe that one has a shaft in back. By the way, our plane is about 30lb with a 9-ft wingspan. Anyways, thanks for the info

-Mark

Take a Honda EU1000 generator and use the engine and generator assembly out of it to power the plane. It has a 50cc engine and the generator is built into the flywheel.
Charlie

While unfamiliar with the Honda EU1000 generator, 50cc should fly 30lb with ease.

Bill

I don't think my definition of "ease" would apply to a 30 lb airplane powered by a 50cc engine..

Well I have a 35lb airplane with a 56cc industrial engine and 8’ wingspan and it fly’s well. In spite of the ridiculous high wing loading it flies and lands like a trainer and has a remarkable amount of vertical.

Mark’s description of intended use was of a flying experimental platform for a school project. My comment was based on experience and the description of intended use.

.

Bills,
What is the wing loading on your plane? - I was worried about my 1/3 scale Super Decathlon ( 89 inch span ) and weighing 18 lbs!

'Big Ugly' is a Stick 21” by 96” span with symmetrical wing and dihedral at 33 to 35lb.
40oz/sq. ft.
Someone found it in a farmer’s barn and gave it to me about 12 years ago. I have flown it with a 25cc, 56cc and 69cc engines. 25cc was very dangerous.

Mark...can you post a photo of the plane you are working on? Or a photo of a plane you may modify...for this project? Thanks Capt,n

Don't have pics quite yet. Here's a link to a website i'm messing around with. [link]http://www.msstate.edu/~mvd8[/link] I hope to keep it updated fairly well (pics, etc). I don't have much webspace, so we'll see how much I can post.