Destroying Glow Plugs

[TERMINATOR]

Mr Jetpack,

Distorted glow plugs come from either too much compression for the percent of nitro being used, too much load on the engine, or too much scavenging from the pipe like a lean condition. Its telling you it is a "timing" problem.

Hmmm, you will never kill a plug because of to high CR.

The thing that kill plugs are HEAT or a bad engine.

Find what is generating the heat and the problem solved.

Try lowering your compression, lengthening the pipe, or use a smaller prop and see what happens.

Do that but not lower the CR.....

Anders

the .12 motors dont like to lug a lot of prop, m440 is way too much, that is whats causing most of the problem..free up the boat and put a prop on that will spin easy,for 30% fuel somewhere in the 35mm range should get you going..then start shortening the pipe, .12s like to rpm..

i have also seen low timing and high CR cause this problem on the .12s with higher nitro

i dunno martin, mine would pull a cupped 1440 with ease.. it launched great and the pipe at 7 1/4 ..ab15n it was screaming. 70 percent redmax and 188 exhaust .004 clearence , and was eating plugs at first on break in then i cannot remember that last time i changed one in it.. not trying to be funny here but it was a long time before i could get it to go on that and seen high 50's all the time out.

tk

 

[mtruex]

Mr Jetpack,

Distorted glow plugs come from either too much compression for the percent of nitro being used, too much load on the engine, or too much scavenging from the pipe like a lean condition. Its telling you it is a "timing" problem.

Hmmm, you will never kill a plug because of to high CR.

The thing that kill plugs are HEAT or a bad engine.

Find what is generating the heat and the problem solved.

Try lowering your compression, lengthening the pipe, or use a smaller prop and see what happens.

Do that but not lower the CR.....

Anders

the .12 motors dont like to lug a lot of prop, m440 is way too much, that is whats causing most of the problem..free up the boat and put a prop on that will spin easy,for 30% fuel somewhere in the 35mm range should get you going..then start shortening the pipe, .12s like to rpm..

i have also seen low timing and high CR cause this problem on the .12s with higher nitro

i dunno martin, mine would pull a cupped 1440 with ease.. it launched great and the pipe at 7 1/4 ..ab15n it was screaming. 70 percent redmax and 188 exhaust .004 clearence , and was eating plugs at first on break in then i cannot remember that last time i changed one in it.. not trying to be funny here but it was a long time before i could get it to go on that and seen high 50's all the time out.

tk

he has low timing and 30% nitro...a smaller prop will HELP eliminate the glow plug problems, isnt that what he asked for help on ps i can run cupped 1440s into the upper 60s on 65% but there not 40mm

 

[TERMINATOR]

Mr Jetpack,

Distorted glow plugs come from either too much compression for the percent of nitro being used, too much load on the engine, or too much scavenging from the pipe like a lean condition. Its telling you it is a "timing" problem.

Hmmm, you will never kill a plug because of to high CR.

The thing that kill plugs are HEAT or a bad engine.

Find what is generating the heat and the problem solved.

Try lowering your compression, lengthening the pipe, or use a smaller prop and see what happens.

Do that but not lower the CR.....

Anders

the .12 motors dont like to lug a lot of prop, m440 is way too much, that is whats causing most of the problem..free up the boat and put a prop on that will spin easy,for 30% fuel somewhere in the 35mm range should get you going..then start shortening the pipe, .12s like to rpm..

i have also seen low timing and high CR cause this problem on the .12s with higher nitro

i dunno martin, mine would pull a cupped 1440 with ease.. it launched great and the pipe at 7 1/4 ..ab15n it was screaming. 70 percent redmax and 188 exhaust .004 clearence , and was eating plugs at first on break in then i cannot remember that last time i changed one in it.. not trying to be funny here but it was a long time before i could get it to go on that and seen high 50's all the time out.

tk

he has low timing and 30% nitro...a smaller prop will HELP eliminate the glow plug problems, isnt that what he asked for help on ps i can run cupped 1440s into the upper 60s on 65% but there not 40mm

i see there feller.. i was not trying to answer why, i was just stating that i run this and have no trouble killing plugs.. and pulling a 1440 that is almost 36 mm ..lol

terry

 

[nitrotwin]

WOW !!!!

 

[Rick Sowell]

Wow is right, I didn't mean to start a heated topic, but I have recieved some great help, I hope this wont get too out of hand. I measured head clearence and it is .006, I agree with the comments that I am probably pulling too big of prop load and I will try some other props next time out. Mtruex stated that a 1440 was around 36mm my propchart shows it as 39.9mm are you cutting it down? I have a 36/55, a 38/55 a 38/63 and a Y 535, and a X435, that I can try, I jiust haven't had alot of run time on this boat since I bought it. I was told that it used to run a 215 or a V937/3, the 215 has more pitch than I am running and still a 40mm dia. so I can't think that this is the way to go. I agree that it looks like too much load as it slows in the corners when you are on the rudder. I have had good luck with K&B glow plugs so far and was recomended by some fellow boat racers, Mark Anderson and Eric Bourlet, for all the championships that they have won I don't think they are wrong.

I will reply to several PM's separately from this thread, thanks so much for the help. Rick

 

[nitrotwin]

You say it is aircooled have you cut the fins on the head to get a proper operating temp?

 

[Rick Sowell]

Yes the head has been cut to two fins above the two fins that house the head button, so four fins total, doesn't seem too hot when you bring it in after a run. I don't think it is over heating, I believe that it is like the others have said too much prop load.

 

[Ron Olson]

What I told you last night was from my experience from the Hammerhead .12 'rigger as I ran what I believe is the same motor that you've got.

I found the P-215 made it a very driveable boat but the V-937/3 needed everything well tuned to turn it so I'd dial it in first before putting one of those puppies on it.

For those that don't know what he's got, it's a Picco .12, not really a bad motor for when it was made and what it was supposed to be dropped into. My only other mod to it was a Nova Rossi .21 carb that had been turned down at the base to fit in the block. Possibly the new Nova Rossi carb would really wake it up as the carb bore looks really close to the .21's. I also whacked off the top 3 heat sink fins and even on 65% nitro it still runs cool.

Start conservatively with something like a X-437, X-637 or X-438 and she what she likes. None of my .12's liked the M-440. They would spin it but really strained to do so.

 

[Rick Sowell]

Ron: the picco has an OS 10M carb on it as well, so it probably will be real close to what you had. How come a 215 will work and the M440 wont? the 215 is 40.64mm and 2.48in of pitch, and the M440 is 39.90mm and 2.19in of pitch, it seems to me the 215 is the larger of the two props or am I missing something?

 

[Ron Olson]

Weird, isn't it?

From what I've learned, the Prather props have a constant pitch whereas the Octura's have a progressive pitch. I've found this out on other sizes and boats. My .21 mono could spin a P-220 but an M-445 has almost identical numbers but the boat didn't like it.

We're in the chatroom if you want to stop by.

 

[Kris Flynn]

Where to get O'Donnel plugs from??

 

[Ron Olson]

Where to get O'Donnel plugs from??

Kris, I don't know about where to find them in Oz but Tower Hobbies has them.

 

[Chris Wood]

Ron: the picco has an OS 10M carb on it as well, so it probably will be real close to what you had. How come a 215 will work and the M440 wont? the 215 is 40.64mm and 2.48in of pitch, and the M440 is 39.90mm and 2.19in of pitch, it seems to me the 215 is the larger of the two props or am I missing something?

the m440 is the same prop as the x440 but the tongues are cut off.. when you cut the tongues off they are a little harder to launch than with them. that also brings the pitch progression closer together.

also the pitch progression from leading edge to trailing edge might be different and that maybe where you are seeing a harder time pulling the prop.

chris

 

[kcvnd]

Platinum which is either coated to the coil wire, or the coil completely made from platinum (the better kind) can glow through catalytic reaction with methanol vapor, even with no other ignition source.
Castor oil, synthetic oil, nitromethane, ect cannot generate this reaction with platinum. Methanol vapor is unique in this respect with platinum, it is what enables glow plugs to work.

The closer you get to running 100% nitro, methanol content becomes less and less until your glow plug stops working or blows out gets destroyed. At this point, glow power isn't the right method of ignition, and you have to switch to a spark ignition system to make it happen.

This is actually true. Platinum is widely used as a catalyst. The reaction of methanol vapor CH3OH on platinum is a combustion reaction that heats the plug to cause it to glow red hot and also actually produces formaldehyde CH2O. Here is a picture of the process where a platinum spiral is heated shortly under a gas flame. Then it is positioned one cm above the surface of metanol. After a few seconds the spiral glows like on the picture, and can continue to glow like this for a long time as long as the methanol vapor is present.

The reaction occurs with the vapor only and not raw fuel. I believe this is why idle bars are present on some plugs to block the raw fuel from making contact with the platinum wire. The difference between a Hot and Cold plug as I understand it is the amount of platinum catalytic surface area that is created in the plug to allow this reaction to occur. That is Hot plugs have a smaller surface area and are used when the nitromethane content is low as there is more methanol vapor to catalyze in the reaction. Vise versa, Cold Plugs have a larger surface area and are used when the nitromethane content is high as there is less methanol vapor to catalyze in the reaction so you want to trap it over a larger surface area.

Sorry for my two cents, this is a result of too much Organic Chemistry in college!!!!!!!!!!!!

 

[Terry Keeley]

What about running fuel like we do at the Record Trials with no methanol?

 

[Mark Leyde]

Rick and everyone else. This was my .12 rigger until Rick bought it from me. I will give you the low down on it. First Rick get your self some 60% nitro and use it. it will make a big difference. I set that motor up for it and only burnt one plug all year long. It ran great with OS A5 plugs. Don't ask me why but it did and the are not exspensive. Next run a stock P215 prop it worked the best for me. Yes I could make it pull faster props but only when the air conditions where pefect. I also ran that rigg with a AB15N pipe. It pulled it through the turns better but it was Much harder to get a good lounch with it.

 

[kcvnd]

What about running fuel like we do at the Record Trials with no methanol?

I have never been to the record trials. Do you run straight, 100%, nitromethane? Hmm I have to think a bit on that one and get back to you.

I guess I should have kept my 2 cents in my pocket.

 

[Charles Perdue]

What about running fuel like we do at the Record Trials with no methanol?

No methanol or platinum?

I just had to put my 2 cents worth in the pile.

Also there are some of the major glow plug manufactures that DO NOT use platinum wire or platinum coatings on the wire at all.

Maybe the wire stays hot from the last combustion cycle. This happens at 500 times a second at 30,000 RPM. Not much time for the wire to cool off.

Not just a thought, this is the opinion of most of the engineers that specalize in glow ignition technology.

I am quite sure that this is what Jack O'Donnell was referring to.

Maybe 3 cents worth.

Charles

 

[Terry Keeley]

No methanol at all.

A popular C/L speed mix back in the day was (apparently) 80-10-10, that's 10% prope & 10% oil. I've personally run that mix (in boats) but haven't found it any better than 70% with a little alcohol.

Guess the prope helps keep the fire lit. :lol:

Anyone try just nitro and oil?

 

[Ron Olson]

Terry, I remember Andy Brown talking about trying 90% nitro and 10% oil once. He mentioned having to use a squirt of lighter fluid to get it to fire up initially.