Hi guys,

I am student in Ireland who is carrying out a final year project in the design and building of a light weight generator. In the project I will have to incorporate an engine to power the unit.

Unfortunately am kinda back to square one as regards the choice of engine for my project.
(See previous thread:
http://www.rcuniverse.com/showthread...75&forumid=145 )

I went down to my local supplier of model engines and he told me that the OS model airplane engines would not be at all suitable for my needs. The reason for this is that there will be almost no load on the engine, ( it only has to turn a shaft in a dc motor), and so it would burn out very quickly. Therefore he suggested that I use a marine engine that is water cooled:

Irvine 46 ABC Marine Engine, ( this is the one he recomended as he said it was the most reliable and not too tempremental to use. However he also just happened to have it in stock as well!!)

OS 21 RG-M Marine Engine, ( he said this one was more tempremental if it is not run at 30,000 revs. However i only want 10,000 rpm output from my engine so may have to investigate gearing down, etc.)

However now I am really lost and becoming frustrated in my search. All threads seem to indicate that the OS engines are the most reliable but my dealer says the opposite!! (BTW He is a most unfriendly and unhelpful guy!!!) Also I am designing a light weight engine yet the weight of these water cooled engines seem to be a small bit excessive when compared to the airplane engines.

What I am basically asking you is what engine would you recommend me to use. It must be:
- light and reliable
- not liable to burn out due to lack of any real load.

I know these are unusual questions but you are my only real source of information. I need your views as i think my dealer only wants my money!!!

Thanks for any help you can give.

UCCC

How about a weed whacker ?

1- has it's own cooling
2- plenty of torque
3- has it's own fuel tank
4- easy to put a pulley on the output shaft
5- has it's own pull starter
6- cheap, about 100 bucks
7- reliable, low PRM

Just strip it down, and figure a way to mount it.

Dave.

The man at the Local Hobby Shop told you the truth. He may have been more helpful and attentive than you thought?

Some other options you may have is to put a fan on the engine to keep it cool and to give it some load but I wouldn't want to be around a homemade fan that is turning 30,000 rpm.

You could also put some electrical load on your generator. That in turn, will load your engine some.

Enjoy,

Jim

You are barking up the wrong tree! First you shouldn't use a glow 2 stroke engine because of the fuel consumption and high RPM. Recommend using either a glow engine converted to gas or a desiel engine. You need the carbarator because the power output will vary with electrical load, you need to hook the carb to a governor that will give a constant speed, unfortunately a straight venturi will not give a constant speed as the load will cause an RPM change. You will probably not be able to get many HP charts. Model Airplane news did some about a year or so ago, you might contact them, but of course if you convert them to gas you can throw the charts out the window. Suggest you take the glow engine curves and convert the torque to a reduced amount based on the differance in glow and gasoline. With a less powerfull fuel running at say 6,000 rpm for 200 watts plus inefficiencies I think you will be in the .40 range. After using this method to select your engine you could buy an inexpensiver dynometer to make your own curve. I think I recall one made of wood that cost less than $200 US.

BTW. Here is a usefull link

http://www.powereqpts.com/calculator.htm

Another option might be a Helicopter engine with the fan and ductwork. Ihave a purpose built AC generator with a Quadra motor on it. Uses an air vane governor on it Somewhat like the old Briggs lawnmower governors. Keeps a constant RPM for 120 volts output. 200 watts.

Actually a WATER cooled 4 stroke would be more efficient than a two stroke. Spark ignition on gasoline.A water cooled engine may be hard to find. If you are allowed mods you could jacket the cylinder and head. Use a lightweight thermo siphon to move the water under its own thermal differential. A small aluminum radiator would be easy to fab and lightweight. This would minimize power used to provide cooling. Air fans consume power = higher fuel consumption. Another good choice would be a diesel for economy . The water cooling allows a better use of the engines ultimate power. Engines are most efficient at peak pressure. A governor would not be needed to regulate the output ,the generator should be sized to have the right output at full engine power. Use the smallest engine that will deliver the needed power wide open. If you can locate some neodymium rare earth magnets they would make an excellent rotating magnet ,some proper impedance coils on the stator would eliminate brush drag. You can use some low loss diodes to rectify the 3 phase AC if DC is required.

Just a few rambling thoughts. I'll stay tuned or you can PM me. Good Luck !

Here is a pic of one. I have a couple of these Gannet 15cc marine engines. Total loss oiling, magneto, spark advance...circa 1958~1964, made in England.



These are not for sale, but thought LF might get a kick out of it.

As for the project...get some soft copper tubing and wrap around the cylinder of the engine, and circulate water via an electic fuel pump you power off the generator..might work, but hey! it's an experiment, right?? Best of luck.

I know ChuckAuger will like it....

"The reason for this is that there will be almost no load on the engine, ( it only has to turn a shaft in a dc motor), and so it would burn out very quickly. Therefore he suggested that I use a marine engine that is water cooled:"

You will have never no load. Even when not generating electricity the magnets in the generator will have some load. When generating electricity you will have plenty of load. Almost .3 HP of it. The torque required depends on the speed of the generator and how it is geared. Does it have to be a DC generator? An alternator would self regulate the speed somewhat. With a generator you will have to have a crude Governor, just enough to pick the engine up from a high idle to full power when you have a load. It need only to keep the RPM within a couple thousand RPM. The helicopter engine and 4 stroke LF mentioned are good ideas. But the prof said it had to be a two stroke? Does he know about the small 4 strokes that are available, or did he assume that such a small engine had to be a two stroke?

Well, you should have a fridge for ice..LOL

Did you ever get the aluminum baseball bat??

....you think I forgot ? ( heh heh heh ). The tiny
fridge plugs into the inverter. The lamp is just
to have some light when your'e grabbin' a cold
one at night. :stupid:

Add an electric razor, and the plane chargin'
stuff....you can fly all summer, even at night,
and never have to leave the field. In Ireland...
you have to make hay while the sun is shinin'.

( Yes I got the bat today, thanks bro. )