heating problems
 

hi all...

i've got a pusher form paraglider with an O.S FX 46 and a 10X6 pusher prop on.
the problem is that the engine gets really hot after 2 or 3 minutes to a point where it can no longer
work

is there anything i can do to make it better????

thnks
yoav.

RE: heating problems
 

10x6 seams a bit on the small side. It will run a 11x6 Have you tried riching it up a couple of clicks. I run 12.25x3.75APC props on my 46FXs.

Cheers.

RE: heating problems
 

1st guess is that it is running too lean. Other things to check are that all screws are tight. Don't be embarrassed if you find a loose screw on something. It's not uncommon.

RE: heating problems
 

Well, I don't see how to increase airflow.


So you will have to increase surface area. Try a heli head or some homemade heat sink fins. You must add cooling surface.

RE: heating problems
 

Keep in mind that the difference in pressure over the head of that engine will be about the same in a pusher config as in a pull config. The air has to come from somewhere. I like your thinking on surface area, that is a good one!

RE: heating problems
 

first of all thankl you all for your help.
now...
homemade heat sink fins... sounds interesting!
have you tryed it yourself???

RE: heating problems
 

you may want to try baffles to direct the air over the head. Have had to do that and it works fine. Richen it up a bit too. My Long EZ had the same problem. Had to use a naca duct with a channel that directed the air.

RE: heating problems
 

any pusher motor will overheat on the ground. there isn't sufficient airflow over the head that is present on puller configurations. SInce aircraft fuel uses less oil usually in lesser grades than say rc cars the engines are more suseptable to overheating. Richen the engine up and get it in the air asap. If you have a long taxi way you may consider taking the starting equipment with you and start it near the runway.

RE: heating problems
 

Hi!
You are just simply running it to lean!
Just open up the highspeed needle and your engine will work OK.
No additional heatsink or heli head is required. Remember our small glow engines are getting the most cooling from the methanol in the fuel not by the air itself.They are so to speak semi liquid cooled. So don't run it too lean. And don't use more than 5%-10% nitro.
10x6 is to small prop...put on a 11x6 APC.
Regards!
Jan K
Sweden

RE: heating problems
 

Well, I think the darn thing just flys to slowly to provide adequate airflow.. its like it is always taxiing.

Alluminum motor mounts would help draw some heat from the case. And then you could have sheet brass or alluminum bolted in between the engine and mount to increase the area even more.

There are fuels with more oil, that might help some. The answer will most likely come form the shotgun approach. try everything !!

Run it as rich as you can, for sure.

RE: heating problems
 

The bottom half of the two stroke motor runs pretty cool while the fuel and air are being sucked thru. The heat transfer there happens after the motor has shut down. running toward the rich side helps rather than tweaking it to the max prior to takeoff. sometimes a scoop that picks up undisturbed air and directs it straight to the cylinder head will do the trick. Usually a heat sink cylinder head is the most reliable.
If you want to go wild you might try making a venturi cooling system using the exhaust gas flow to suck cooling air past the cylinder like the old Aerocommander 720s had. It was the only plane that I ever flew in where you increased the engine rpm while standing still to improve the cooling flow thru the cowling.