khodges

My Feedback: (1)

I've got a 40 size "Texas taildragger" with a OS .50SX. It eats glow plugs, I can't get one to last more than three or four flights. I run Cool Power 15%, and I don't think I'm too lean, the engine runs great, no problems with overheating. generally, you can hold your hand on the head after landing (Uncomfortably). What gives?

I've tried OS #8 and the Fox "Miracle plug", Both last about the same.

The Ghost

What prop and max rpm's(no gessing) are you getting. You may be overreving and burning up the plug.

Cheers

TexasAirBoss

My Feedback: (22)

I love that engine. Got one on my new Bonanza. In the past, I have had problems with that engine eating plugs, Fox RC Longs. And then I had a OS 61 that did it. Now they don't. I don't know why. It just stopped .

jaka

Hi!
First: When an engine "eat" glow plug its usually due to a too lean setting! Simple as that!
Second. heat and vibrations is the glow plugs worst enemy. So use a fuel with less nitro...Why use 15% nitro when all engines run as well on just 5-10%..!? Too much nitro and a lean needle setting is a sure way of getting blown glow plugs (and destroying engines).
A good plug for all sport engines running on 0-15% nitro is an OS 8 or Enya 3 glow plug.
Prop it right!
10x8,10x9, 11x6, 11,5x6, 12x4, 12x5 ,12x6,13x4,13x5 all APC is what I would use...different props for different purposes.Smaller for faster smaller airplanes and larger for slow flying airplanes.

BillS

I have an OS .50 and maybe change plugs once a year at most. I use 15% fuel and a 10 X 8 prop. If the element burns out the engine is too lean.

Tune for 300 to 500 rpm less than maximum, no engine sag on a long up line, check for floating trash at the carb inlet occasionally and plugs seem to last forever.

Bill

Steve Collins

My Feedback: (8)

Another possibility is that something is coming apart inside the engine. Have you removed the head to see if you can detect any foreign particles? Tiny metal particles will take a plug out!

In the past, when I had problems with an engine eating plugs, I found that the bearings were going bad and there were tiny bits of metal from the bearing retainer inside the combustion chamber.

Open up your engine and inspect it carefully to at least eliminate this as a probable cause.

khodges

My Feedback: (1)

Nothing wrong with the engine, bearings good, no metal bits anywhere. As far as too lean goes, I don't think so. I have a good smoke trail, and I'm running it about 1000-1500 rpm below peaked out (which was 12,200 when I tached it) I have a 12-6 MA prop on it. I bought the plane and engine used, but basically new, the engine has maybe 20-25 tanksful through it (12 oz). Half of those are since I bought it, and whatever the plug was that was in it when I got it lasted for the first 10-12 tanksful. Then it started quitting when I'd remove the glow ignitor. Change the plug, it was fine for a couple of tanks, or maybe more, then the same thing. Change the plug, get about 4 or 5 flights, same thing. I'm not a needle twiddler, once it's running good, no reason to screw with it, weather hasn't changed enough to warrant retuning, rpm's stay about 10K, which certainly isn't overrevving it. Engine is mounted sideways, for whatever it's worth.

I'm not changing fuel, all but one other of my engines are 4-strokes (Saitos, + one Supertigre .61) and they all run fine on 15%, and glow fuel is getting too dang expensive to have two or three kinds sitting around sucking up atmospheric moisture. I don't think the fuel is contaminated, I opened the jug a month ago, keep it capped, and none of my other engines have had any problems.

garys

I'd go down in prop size and see what happens. Running too big of a prop and lugging the rpm's down will cause more heat and is harder on the engine and glow plugs than a lighter prop turning more rpm's.

Rcpilot

My Feedback: (78)

Agreed. 12x6 is a .60 size prop.

With the .50, you're basically running a "hot" .46 engine. I'd run an 11x6 for sport or a 12.25x3.75 APC if you want to 3D with it (I'm not familiar with the plane)

I think you are using too much prop and too much nitro. 15% is for guys who are competing in pattern, IMAC or pylon. I run 5% in all my glow engines and they work fine. 5% is cheaper too. Around here, it's a LOT cheaper.

Also, you're using the dreaded Cool (Cruel) Power. I like Omega. Made by the same company. It has 30% synthetic and 70% castor. 17% total oil content I think. Never had an engine gummed up or overheated from using that fuel.

I know it's not what you want to hear, but you did ask. Try a smaller prop first. If that doesn't do it, then change to either lower nitro or something with some castor in it.

BillS

A 12 X 6 is more prop than I care to run on an OS .50.

Bill

Gray Beard

My Feedback: (-1)

15% nitro too much??? That's A new one on me but live and learn.
You really are lugging that engine down with that big of A prop. Just for grins try an 11X6 or 4 then grab up A 10X8 and give that A zing and see what you think.
The 10X8 is the number one APC prop in our smaller racing classes with engines from .46 to .55 and the APC 11 inchers are what A lot of sport pilots are using.
Going through glow plugs that fast is really odd, are you sure there aren't little metal pieces floating around inside your engine??
Just wondering?

Steve Collins

My Feedback: (8)

That engine would be much happier with a 10X7 prop.

I raced pylon for many years, flew ducted fans a few years and now fly turbine jets. The very best plug, used extensively in all of them, is the McCoy MC9. Stands up to a lot of punishment and keeps going. Pylon racing and ducted fans really punish a plug.

This plug is also marketed by Hangar 9 but it is still called an MC9. Try one and see if your situation improves.