Instructables

How to cool an outboard motor without using water?

I am wanting to build a personal ultralight helicopter. First issue here is to find a suitable engine. Outboard motors have the 40+ horsepower I need and can be found pretty cheaply on places like craigslist.

One thing I know about these engines is that they use a water pump to suck up water and cool the engine. It is important that this water is present and can the engine can be wrecked if it is run without water for more than a minute or two.

Short of including a water tank on this helicopter, do any of you have any practical solutions to keep an engine like this cool?

(Just so you know, an "ultralight" helicopter must weigh under 249 pounds without the passenger. In the US, you can fly ultralights without a pilots' license. 40hp outboard motors weigh around 160lbs so I don't have a lot of room for heavy water.)

Re-design4 years ago
What type motor do they specify on your plans?

How many horsepower do they suggest?

Are these plans for a true helicopter or is it a gyrocopter?

There is no way to cool an outboard of 40 hp without some liquid flowing thru it putting the excess heat thru a radiator.  They just arent' meant to be cooled any other way.  They have almost no surface area designed for air cooling.  Why would they they are sitting in this huge body of cool water so they use that.
1up (author)  Re-design4 years ago
I am not going by any plans but building something completely from scratch. It is a true helicopter, not a gyrocopter.
Re-design 1up4 years ago
Then I feel completely justified in my next statement.

ARE YOU NUTS?

A perfectly designed, built and maintained (by professionals) helicopter is just a bunch of parts all trying to come apart at the same time.

This is not hacking a computer or psp.  How far are you willing to fall?  Unless you've got some experience in building some actual full scale flying aircraft I give this project less than 1/10 % chance of working.

Please, please, please if you do this, make sure that it is well documented especially the first flight so we can see it on youtube.
1up (author)  Re-design4 years ago
I 100% expected a response like that. ;)

Please don't worry, I am not some "lolcomputerhacker" or whatever. I have a lot of experience in engineering and (pretty much) know what I am doing. Besides, I am not planning on soaring to 50 feet on the first flight (or ever, for that matter). There will be extensive testing and safety measures before any "serious" flying will ever take place.

And I know you're not going to like my next statement, but if a helicopter can be built like this, which is basically an engine on sticks, I don't think it'll be too hard to build something similar.
Re-design 1up4 years ago
It's a little more that a "motor on sticks".

How do you plan on managing contra-rotating props?

What does you engineering experience tell you about how to attach fins to turn a water cooled engine into an air cooled engine and keep it from seizing up?

Don't get me wrong, I'm not trying to dissuade you from doing this I just think you should be aware of some of the problems you're going to have to over come.

You should look into using a different engine.  Start looking for an air cooled utility engine.  Converting the outboard it going to be a huge engineering problem that will just waste you time and money.
> ... going to be a huge engineering problem that will just waste you[r] time and money.
.  That pretty well sums it up. Just because it's possible (and I'm not sure the conversion is even possible) doesn't mean it's desirable to do so.
I guess my computer is running low on "r"s, I missed two of them in my post.
.  Here. Have some of mine. I have plenty
rrrrrrrrrrrrrrrrrrrr
.  And a few caps, just for good measure
RRR
1up (author)  NachoMahma4 years ago
Nacho, I desire to. ;) Re-Design, I've realized the disadvantages of an outboard motor. While cheap, it is not a great choice for something like this. I am looking for something more like a Wankel engine (or rotary engine). I know contra-rotating propellers would be a major challenge. I was planning more on using a single prop with a tail rotor as well. Hopefully, once I get enough money I will be able to work on this and have it work well. Or maybe it won't. Either way, it's still going up here. ;)
Have you ever flown in a helicopter before?
Its just not something you pick up in a weekend.
I would be very curious to see you keep this in a ultralight format...under 249lbs..
I guess it could be done, but not likely.
The other problem you will involve is the airspeed restriction of 60mph and fuel load of 5gal max.
The FAA has done its research as well to control us as well, "clipped wings" if you will.
MAD-1 Re-design3 years ago
this might be somthing close to what you want
http://www.youtube.com/watch?v=61VAxd-J9U8&feature=related
Well yes and no. There are reasons why gyrocopters have rotax and other engines. If you want to use a water cooled engine, I would suggest a radiator. Also anit freeze and possibly a cooling fan electric. Now a ultra lite needs to be under 249lbs. Also dont forget you will hurt yourself or worse by taking short cuts. Go with what has been tested unless you are a licensed pilot and mechanic. There are a lot engines designed as I said before. Look into powered parasailers the engines are a rotary style , 40 hp, about 75 lbs, and the vibrations are reduced by the style of the rotary engine.

Remember what is at stake when you take short cuts!!!!!
Well yes and no. There are reasons why gyrocopters have rotax and other engines. If you want to use a water cooled engine, I would suggest a radiator. Also anit freeze and possibly a cooling fan electric. Now a ultra lite needs to be under 249lbs. Also dont forget you will hurt yourself or worse by taking short cuts. Go with what has been tested unless you are a licensed pilot and mechanic. There are a lot engines designed as I said before. Look into powered parasailers the engines are a rotary style , 40 hp, about 75 lbs, and the vibrations are reduced by the style of the rotary engine.

Remember what is at stake when you take short cuts!!!!!
redsoup4 years ago
You can't unless you want the moniter to be scrap in 30 seconds if not less
Arbitror4 years ago
Don't go with an outboard motor, use something like a large lawn mower motor, or something else to the like.
1up (author)  Arbitror4 years ago
For something like this, a generalization is that for each 10 pounds you want to lift, you need 1 hp. I am looking for at least 40hp and I don't think there's any lawnmowers that big. ;)
You only need enough water to go round the engine and through a radiator. There are piston engined aircraft designed this way, but for lightness and simplicity you might think of aircooling. There used to be a lot of cars that were air cooled. Apparently the Porche 911 was air cooled at one time, although this amazes me. I know many VWs were. It is less popular for cars now but there it still makes sense for motorbikes since the engine is exposed and you can just put fins on the outside of the engine block and the air flows over proportionate to speed, which is roughly proportionate to power output. It cuts out a lot of extra equipment making the bike cheaper and lighter. Outboards are designed with the fact that they are going to be very near a ready supply of water in mind i.e. with water cooling, and you don't even have to carry the water around with you. Converting one 'captured water' cooling or to air cooling might be a rather tough job, especially as there have to be thousands, if not millions, of second hand motorbikes kicking around. Here's some info I found from a random google: http://www.bajajusa.com/air%20cooled%20-%20water%20cooled.htm One thing to take away is that it wouldn't make sense to try to squeeze more power out of the engine than it is designed to produce over an extended period. It is one thing having a catastrophic engine failure when you are on a road, but having one in mid air! If you do build an ultralight, you MUST post it here, it sounds like a great (if loony) project!
1up (author)  Cabbages and Kings4 years ago
You gave me an idea. Perhaps I could attach enough fins that the air flowing from the rotor could cool the engine. Like you said, the air flow would be roughly proportional to the engine speed. Also, that link is interesting. Thanks! And when I get around to having enough money to build this, I will make an Instructable. :)
orksecurity4 years ago
Coolant loop through a radiator, just like in a car.
You've got ~40 kW of heat to lose from the engine. I can't see you lifting a radiator big enough with it.
Depends on what the coolant is, I suppose... but I don't think there's any other answer except finding another (air-cooled?) engine.