spik

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!

JPMacG

My Feedback: (2)

Check your rear bearing. I had a TT Pro 46 that destroyed several glow plugs. Turned out the rear bearing cage was breaking apart and metal fragments were impacting the glow plug coil. If you catch it early before a big piece breaks off and damages your cylinder or liner you might be able to save the engine.

JPMacG

My Feedback: (2)

To check the bearing take the back plate off and look inside. The balls should be equally spaced around the circumference of the bearing, not clustered together. Look for metal fragments in the crank case. Inspect as best you can (hard to see) the bearing cage for missing metal. Also take the glow plug off (to eliminate compression) and turn the drive shaft by hand. It should not feel rough.

If you need to replace the bearing you can get lots of how-to help on the engine forum. Just ask.

spik

is it possible even if the engine is new?engine is now three months old!

JPMacG

My Feedback: (2)

Seems unlikely, maybe the problem is not the bearing but metal chips left in the crankcase at the factory. In either case I think you should open up the back plate and see whats happening in there. I can't think of another reason for your glow plug troubles. An OS A3 or 8 glow plug should last a very long time in that engine on 10% fuel. I mean several years or more.

The good news is since your engine is new you can have it repaired under warranty.

Missileman

Is it possible that your glow ignitor is running too hot and there is nothing at all wrong with your engine?

Jim C.

Ive seen it happen. even with the battery ones.

very possible. I didnt open up my heli engine (os. 50) ran good the first start, then it wouldnt start back up. take out the plug and there is pieces of FUEL TUBING in it! wasnt the kind I use so I know it wasnt me. but I always check a new engine first just didnt on that one.

jaka

Hi!
If your engine is OK the most likely thing is that you run your engine too lean!
Simple as that!

Second..a 11x4 prop is awfully small for a .46 engine. A much better prop size would be a 11x6 (APC, RAM or Graupner Cam-prop) for general sport flying or a 12x4 for 3D hovering manuvers.
A 9x7 APC could be used for Q-500 pylonracing type models.
Why run so much nitro? The TT .46 run as good on just 5% nitro!
The OS 8 or Enya 3 glowplug is what I recommend. There are others too but these are the "old stand byes".

Regards!
Jan K

aerowoof

only three things that I know about will burn out a glow plug
1.heat-running too lean or no cooling air over the head
2.metal particles coming in cotact with the element,especially aluminum,also will show up as a black residue in the exhusted oil.
3.too much voltage applied while starting-this will burn out the plug when connected not after it is runnig and disconnected.

da Rock

If you're using an igniter that's wired to a flightbox panel that has a rheostat on the plug circuit, check the voltage it's tuned to. There should be a meter that shows what voltage is going to the plug. Since the plugs are going out in the air, this probably isn't going to show a lot of voltage if it's the cause. Most times, when it's the cause it happens on the ground. And a lot of times, it's when the plug wire is connected to the starter connectors. And that'll blow the plug RIGHT NOW.

There is also a minor possibility that the engine has somehow wound up with too much compression from the factory. If they usually have a head gasket, maybe it was left out on assembly. Some manufacturers used to fit up engines with a varying number of gaskets to get the design compression rating from parts that had maxed tolerances. You'd see one engine with one head gasket, and might see another with three.

da Rock

I agree with the advice that the 11x4' are pushing the envelope.

All of my 46 engines responded to 11x5s like they were too easy to spin. I wound up wanting the 5 pitch enough to cut down 12x5s to 11.25" diameter to put enough load on those engines that they would be happy with the shallow pitch. And truth is, I think a couple of my 46s would like it if I made some 11.5x5s for them.

spik

thanx for all the advice guys.did open my engine yesterday,saw nothing wrong,no metal paritcles or any particles for that matter at all.I use a battery glow driver, think its a 1.2V, can that be the problem?how do I check if it is too hot? oil residue on plane is colourless,might have a very light brown tint to it.what prop must I use if not the 11*4 for good vertical power?my plane is a Hangar 9 Stick

bkdavy

My Feedback: (1)

Put an APC 12x4 on it. Its the perfect prop for the TT Pro 46. It should end up turning around 12,800 rpm on the ground, and you'll end up with unlimited vertical. Its the way I've been running my TT Pro 46 for three years. I also run an OS A3 glow plug with Omega 15.

As for the bearings, take off the back plate and inspect the rear bearing. You should be able to see it without removing anything else. If the cage is starting to fail, it will be very obvious. You may not have any visible particles in the piston, but small particles will cause premature failure of the glow element. The first indication I had of imminent bearing failure a month ago was two burned out glow plugs in two flights.

Brad