How to cool an outboard motor without using water?

[Mario]

Here I go again with the helicopter idea. I'm a little smarter now, though.
5 hp lawn mower engine, pff, yeah right.

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.)

 

[samjc3]

Boy I dont know, short of running liquid nitrogen. Those outboard are way oversized for their cooling, because moving in water is such good cooling. Air doesnt work as well. Get an RX7 wenkel engine instead.

 

[βeta]

Wankel*


Nah, just stick a small radiator on it. Will need a fan since it won't be moving at speed really.

 

[bic]

You might be better off with a motorcycle engine. Those buzzy rice burners are relatively light, can make decent power at high revs, and they'll either be air-cooled or will come with a closed circuit liquid cooling system.

 

[epicelite]

Mineral oil?

 

[ShockSlayer]

mini car battery+ mini inverter + mini mini fridge.

SS

 

[Antome]

mini car battery+ mini inverter + mini mini fridge.

SS

Peltier unit, try find one (They're used in most fridges, cars stuff etc big or small, I believe. Pretty much anything that somewhat heats up/cools stuff (Most soldering iron's dont apparrently)Correct me If i'm wrong)
You could make one, but it'd probably end up more costly. Just dont consider trying.
It's a wafer type of thing usually attached to a heatsink That can both heat up or cool... stuff when a voltage is applied.

Basically these are applied to SS's suggestions.



Crap, I think i'm doing something useful.

 

[XCVG]

Peltier units can be found on car fridges and some heatsinks and wartercooling setups, but you're probably better off getting some from a surplus site. They wouldn't provide enough cooling and would consume too much power for your setup, though.

And at 160lbs without a passenger you're already too heavy. I think.

 

[Mario]

Peltier units can be found on car fridges and some heatsinks and wartercooling setups, but you're probably better off getting some from a surplus site. They wouldn't provide enough cooling and would consume too much power for your setup, though.

And at 160lbs without a passenger you're already too heavy. I think.

(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.)

And bic, thanks for the idea. Only problem is finding one cheaply enough. I don't have $2000 to spend on this, although I suppose I will if I absolutely have to.

 

[Valium]

I find it pretty amusing that you're building a helicopter with a boat motor.

 

[βeta]

Bic is right about little motorcycle engines.

 

[Mario]

Yes, I am thinking that is the best choice, if I can get one cheaply. Also looking for a Wankel, Robin, or Rotax engine for relatively cheaply. Any one of these, if it's at least 40hp, should work just fine.

 

[samjc3]

Curios: Are you going to build a true helicopter, or a gyrocopter?

 

[βeta]

Why do you want some crazy engine type?

 

[samjc3]

because the power to weight ratios are so much better. normal engines are heavier than crap.

 

[βeta]

Good reason.

 

[Mario]

True helicopter, something a lot like this:
http://www.youtube.com/watch?v=7D31WGnKTUE

 

[PalmerTech]

Yeah, an outboard motor is a bad idea. Those suckers weigh a lot compared to normal engines, because they are made with marine-grade parts. Rust resistant, yes, light, no. Plus the whole water cooling issue.

And 40hp outboard engines are gonna cost a good bit of money, too.

 

[jleemero]

Palmer's absolutely right.


Go for a true light-aircraft engine.
A small Wankel will do you nicely.

In fact, you could even use a Volkswagen Aircooled engine.
Back in the day, there were planes that used these guys.
The late model 1600cc Dual Port engines put out just about 50 horsepower, and weigh less than 240lbs.
And, of course, THEY'RE AIRCOOLED!
These engines are simple as Heck, BARELY a step up from Lawnmower engines, as far as I'm concerned.

You could even go for a later (Post 1974) model and get a fuel-injected one, though unless you go bigger than the 1600cc, you won't really gain a noticeable amount of power.

There are simple variants, like the engine that was put in the VW Bus, Karmann Ghia, and the Safari, all are incredibly similar, just with small differences in layout, fanshrouds, etc.
However, they're all heavier than the good ol' Type 1 VW Engine. Albeit, only just.

You want one, you can buy a crate motor, and then you know you have a new, good engine, that's Dang near guaranteed to not have problems.
You COULD buy a VW Beetle, anything from 1971 to 1979.
However, if it's newer than 1973, it'll be fuel-injected.
An unnecessary complication in my opinion.


If you really wanted to, you can pack on a few extra pounds for HUGE performance gains.
A 1600cc Dual Port puts out around 50HP stock, and can be done up to pull about 65HP, but going beyond requires measures I'm not in favor of.
You can modify, or buy an already modified engine, that can be much larger in size, even a 1776cc can pull 75HP + with relative ease, and the larger engines, think, 2032cc, can well exceed 100HP, while still maintaining a weight of under 300lbs.