rednekk58

Hey All,
My first nitro heli, a Venture .30 with a OS .37., about two gallons of 15% nitro through it. My glow plug fell out at about 15 to 20 feet high. Luckily nothing damaged. Installed same plug. (It was still in remote igniter) Next flight it did it again. First time I thought the idiot who installed it didn't tighten it enough. Second time I know I did. Little damage this time, got it fixed, put a NEW plug and gasket with a hint of blue loctite. Lasted about four or five? flights. Just came out again. Don't think I've damaged anything. Not in the mood to look closely yet.
In my over thirty years of glow engine experience (all airplanes) , I've never seen or had this happen. I have some high heat red loctite, but using that is just a band aid. I want to fix it. From "feel" the threads arent stripped. I could tighten it normally. Could the head be expanding enough to lose it's grip on the plug? Both were OS plugs.
Anyone have this happen to them? Any ideas before I go looking?
Just another challenge.
Thanks for Ya's Help

Update:Finally went to the truck and dragged into the basement. one landing gear mount, everything else looks Ok. Won't know till I can check tracking.
THreads in the engine look fine. Same with the plug. Could running this too rich case this? I run very rich, as I don't need the power for my capabilities. Just grabbing at straws and trying to get my gears turning. (My age they need a lil oil)

P.S. This was right after my boy came in second at his cub scout packs Pinewood Derby for the second year in a row!!!
He was videoing the heli when you could here the engine die, then the camera points to the snow immediately. He must have wanted to watch!!!

Gorgok

Wow. I have never had that happen either... and i've had plenty of nitro experience. I have run plenty of engines rich, usually though i do avoid it... i'd rather burn my fuel than drip it out the exhaust.

Liquids do act as solids though, you know water hammer effects and all. I guess if you had enough liquid, with little gasses, in the engine it could run out of stuff to compress and basically smash right into the plug. I would think this would violently blow the plug out though, and maybe blow up, not just unscrew it... And even for this you would need alot of liquid in the engine... not just a little flooded, i mean liquid. If at speed the engine suddenly did get a surge of liquid i bet it would look pretty nasty... and instantly stop turning over...

BarracudaHockey

My Feedback: (11)

I've seen it happen once where a 50 shot a plug out but its not the norm. Wonder if you have a vibration issue, can you see the fuel tank on the venture while you are hovering? If so check and see if the fuel is foaming, that would indicate a high speed vibration.

chickenx5

it would have to be blowing out, it couldnt unscrew, try hovering then landign and checking it and see if it ever gets loose. Thats pretty wierd.

rednekk58

Hi all,
Thanks for all the help.
It's definately not blowining out. Threads are perfect on the head and the plug.
I double checked before this reply. Tried to take pix, that didn't work.
Plug was still hanging in the remote plug Thingy. (brain Fart)
I don't recall the fuel foaming. I'll pay more attention to that next weekend, weather permitting. The engine ran great, right up until it quit. Didn't notice any loss of power.
Light just went on. If the plug was backing out, wouldn't the engine start going lean?
I've used the trick of starting flooded small engines by removing plug(s). Cranking the engine over to clear it out. Then installing the plugs back hand tight, and then I back them out about a turn. Put the wires back on. Start it an LET it suck air till it's warm.
The liquids from real rich hammering on the plug has me wondering now too.
Guess I'll start by tuning it correctly this weekend too. Burning the fuel, rather than wasting it is a smart idea. Just been lazy. That will eliminate that.
I was thinking of putting the same plug in without Loc Tite and hover in the yard, and checking it every few minutes to see if it's loose.
If ya have any other suggestions I'd appreciate it. Thanks!

Guess I'll have to spend more time on the sim with autos.
I figure a couple more flame outs and we'll have this problem licked!

Gorgok

When the glow plug is backing out you would at most lose compression slowly turn by turn. Since you are making the volume in the chamber larger. Until it gets far enough out when it would draw air in the glow plug as well, then it would probably run lean. But by that time i would think its so far out that falling out would happen plenty soon.

I've never had any loctite or anything on my glow plugs... they always stay tight until i unscrew them.

Since its obviously not violently coming out, i'd have to agree that vibration is the only thing. Maybe the threads on your head, while in perfect appearance, are a little too large? It might feel the same putting it in, and cranking down on it, but under vibration its not tight enough to hold it in... I don't really see how this could be a new problem though... If it were like this i would think it always was like this.

BarracudaHockey

My Feedback: (11)

Locktite liquifies when it gets hot so thats not going to help you too much.

I'm going to assume that you are using the brass washer that comes with the plug.

No need to run an engine slobbering rich, it doesnt do much besides waste fuel.

rednekk58

Up date. Yup, one that comes with the plug. Got to fly about a tank today, plug didn't loosen at all. I tightened the plug with a rachet this time. for a better feel. I haven't had time to play with the needle yet. The loctite I have is part # 27240, high temp, high torque. Forgot to take it out of my tool box when I was a machine tech at Sylvania. Lotta heat around those machines that melt and form those 400 watt lamps.
From what I remember it's good stuff. I don't use it much cause it's a pain in the butt if you have to get it back out. How hot does the head get, or should be. I have IR temp gauge. (Different job and tool box)
I'll still do a few more hovering tanks before the last resort. Should be able to find time Thursday morning.
BTW, no foaming that I could see. (can't believe I remembered to look for it AND write about it)
Like Always, Thanks.
I'll pass on what I find.

jsenicka

My Feedback: (79)

Weird.
My dad had an SK80 motor in a Ultra Sport 60 last summer that dead sticked about 6 times from spitting the plug out.
Finally changed brands or something and problem quit.
I know he runs Thunderbolt plus now, but not sure what he had at time of problem.
Seemed he was placing plenty of torque on the plug.
if you figure it out, I would sure like to know what can cause it.

rednekk58

Hey jsenicka,
Do you know how long it took before spitting the plug?