My Thunder tiger Pro 46 keeps blowing or melting glow plugs. I use 10% nitro with a 11*4 prop. I started with the OS no.8 glowplug, but that lasted about three flights. Then I switched to the OS A3 which worked great for a while, but this past sunday the first one which lasted about 10 flights was dead and the next one only lasted one flight! Luckily I had a spare no. 8, and got two flights out of that. I KNOW my engine is not lean, its actually a bit on the rich side.(used a tachometer)other than that the engine is really running very smooth and reliable. Does anyone know what the problem might be? Any suggestions what other types of glowplugs I can use?

thanx!

Hi!
Sorry! But it's a simple fact that when an engine blows plugs it's too lean!
You cannot trust a tachometer reading only...it says nothing! You have too listen to how the engine sounds and draw your conqlusions from that. OS 8 or Enya 3 is good plugs that each one should last for years...if engine is set correctly.
And 11x4 is awfully small prop if you fly at sea level. A much better size for general sport flying is a 11x6 (APC) or 12x4 if you fly a high winged trainer or slow flying model with lots of wing area.


Regards!
Jan K

Yes. What Jan said.

This almost seems to be a tank problem. Runs great on the ground, then in the air it starts foaming up, or the clunk line has a hole in it that "un ports" halfway through a flight...sends the motor smoking lean and pop goes the plug.

Re-do your fuel system. New fuel line throughout, and be sure it's well padded. It can touch nothing but foam or you're asking for these sorts of problems.

Or just richen it up some more. All engines lean out as it unloads. Some more than others, you can't go by a certain RPM drop for all engines. Just changing the prop will change how much it leans out in the air. No hard and fast rule on how much to richen it on the ground. Regardless of how you set it, tach, infrared gun, or ear.

There is one other possibility but with todays glow drivers, remote. If you have too high a voltage the plug life will go to poop. It should glow a nice cherry red to orange, If it's white it's too hot.

Look very closely at the exhaust residue. If there are little sparklies in it that is an indication that something is wearing inside the engine. Those metal particles are murder on a glow plug.

However 99% of short lived plugs is too lean, or to much nitro.

Another unfortunate possibility. You have a bad main bearing sending tiny bits of metal through the engine and distroying your plugs amoung other things. TT uses good japanese bearings but the ball retainers can break and when they do they often rub against the crank and send tiny bits of retainer through the motor. Examine the exhaust residue and the slight glitter will be telltail.

Denis

thanx for all the advice guys.did open up my engine and saw nothing wrong,had my instructor take a look as well.as far as I can see the bearing case is fine,no cracks or anything, it still looks brand new as it is suppose to be, engine is now only three months old.the whole tank is wrapped in 1/2 inch thick foam, so I don't think its a fuel problem.exhaust residue is clear and shiny but no glitter at all. the plane is a Hangar 9 Ultra stick .40 and the elevation of Potchefstroom(where I'm flying) is round about - 5000ft. i'll richen it a bit and will let u know what happened,going flying again this weekend.
cheers!
spik