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Author Topic: Taters  (Read 1322 times)

Offline Dave Harmon

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Taters
« on: July 24, 2021, 09:32:54 AM »
Does anyone know for sure what causes 'taters' on glow plugs??
This plug is a Thunderbolt long idlebar and as can be seen....there is a huge deposit on the wire.
The engine is a Brodak 40....fuel is 20N 15Synth 5Castor.
No Armorall, no acetone or propylene oxide.

Offline Dennis Toth

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Re: Taters
« Reply #1 on: July 24, 2021, 09:49:56 AM »
Dave,
One of the causes for taters is pre-ignition. This is caused by over load on the engine or two lean a run for the temperature/humidity conditions. You can tell if its pre-igniting as you will hear crackling in the engine note. I have had this on my OTS FOX 35 ships that have a muffler installed. For me the easiest change was to go from a 10x6 prop to at 9 1/2 x 6. It seems to occur once the temperature is in the 90's with 70%+ humidity (common here in FL). Others have switched to a colder plug or added a head gasket but for me the prop change was simplest.

Looking at the photo is looks like it could be fused aluminum, this usually comes from conrod or backplate rub and too low oil content or all synthetic oil in an engine that is pre-igniting and too lean.

Best,   DennisT
« Last Edit: July 24, 2021, 11:04:20 AM by Dennis Toth »

Offline Brett Buck

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Re: Taters
« Reply #2 on: July 24, 2021, 12:41:29 PM »
Does anyone know for sure what causes 'taters' on glow plugs??
This plug is a Thunderbolt long idlebar and as can be seen....there is a huge deposit on the wire.
The engine is a Brodak 40....fuel is 20N 15Synth 5Castor.
No Armorall, no acetone or propylene oxide.

    That is it, alright, although they are usually smooth rather than that rough.

      SIG?

     Brett

Offline Dan McEntee

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Re: Taters
« Reply #3 on: July 24, 2021, 01:06:02 PM »
   I'm not really religious on checking my plugs on a regular basis but if I am having some sort of issue I will look at the element just to check things out. I have seen some of mine and some other club members with plugs that were in use for really long periods of time and have carbon build up on the idle bar ( one of the reasons I use idle bar plugs) but the element was always clean. I don't believe I have ever seen any "taters. " Distorted elements or broken elements,  yes, but never seen anything on the element. I find the phenomenon interesting and always read these posts about it, and I as curious as anyone on what causes it. It might happen to me some day and I want to know what causes it and what to do about it. I think I read at one time you can take a pint or new xacto knife and knock the taters off?  If it comes off, it makes me wonder if it's some kind of ash??
  Type at you later,
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Offline Brett Buck

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Re: Taters
« Reply #4 on: July 24, 2021, 01:20:49 PM »
I find the phenomenon interesting and always read these posts about it, and I as curious as anyone on what causes it. It might happen to me some day and I want to know what causes it and what to do about it. I think I read at one time you can take a pint or new xacto knife and knock the taters off?  If it comes off, it makes me wonder if it's some kind of ash??

    They are usually smooth black lumps. Scrape them, and the black is just on the surface, and underneath is solid tan mass, like melted tan plastic. They can be scraped and broken off the wire, then the plug "works" again.

     We never had this issue until we got PA61s and larger. It varies from engine to engine, one engine might start losing significant power after as little as 15-20 flights, others might go 50, even with exactly the same setup. This seems to do with just the size of the engine and the fact that it runs much hotter as it gets bigger, not particularly an issue with PAs. I would expect the same if I switched to SIG on the Jett engine.

     We solved this by switching from SIG to Powermaster. We have never had a significant tater with Powermaster fuel of any variety. Randy says the problem is in the castor oil. I don't know for sure, but I was concerned about the "anti-foaming" ingredients in the SIG, which I presume is silicone. Bottom line, don't use SIG on your 61 and up stunt plane, or buy a lot of glow plugs.

    Brett

Offline Reptoid

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Re: Taters
« Reply #5 on: July 24, 2021, 02:32:06 PM »
I've never seen a tator on a glow plug that big or with that kind of texture/color. The worst I've seen used to grow on flat coil racing/speed "Glow Bee" type plugs running higher Nitro and castor. I would be very suspicious of whatever ingredients you're running for fuel. Does 20N 15 syn 5 castor mean 20% Nitro? That's pretty high nitro for a Stock Brodak 40 unless you've raised the head. My glow plugs in my Stunt engines never look that carboned up after a year of use and running more castor (50C-50S) Make sure that it is not aluminum or bushing material although that usually causes a hot spot and burns through the element almost immediately. Extreme heat retention will exacerbate the problem (tuned pipe, restrictive muffler, etc.) If you're mixing your own fuel; make sure your ingredients are pure; M-1 for methanol (not M-2 thru M5 because they have additives you don't want or need) pure castor and a decent synthetic like klotz, MA-731, or Motul Micro-2T. I have also seen tators on plugs flown in very dusty conditions repeatedly.
Regards,
       Don
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Offline Steve Helmick

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Re: Taters
« Reply #6 on: July 24, 2021, 05:12:27 PM »
The bit about the heat from restrictive mufflers made me remember that early B.40 mufflers were less restrictive than 2nd batch, leading me to ask our OP about that. IDK if Brodak had the mufflers revised or not, or who is making Brodak engines these days. I know they were originally made by the Two Star guys in Moldova.  D>K Steve

PS: I haven't ever noticed a "tater" on any glowplug of mine. It's been awhile since I've run anything other than the PA .51 or AAC .46VF.  I always run a T-bolt 4-cycle in those...no idle bar...and not sure if that helps or hinders the tater situation. I was also wondering if perhaps there is a chemical treatment that might remove taters in a kinder, gentler way?   
"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline BillLee

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Re: Taters
« Reply #7 on: July 24, 2021, 07:16:38 PM »
I've never seen a tator on a glow plug that big or with that kind of texture/color. The worst I've seen used to grow on flat coil racing/speed "Glow Bee" type plugs running higher Nitro and castor. ....
The "taters" that we used to see on the flat coil GloBee plugs were caused by the material (ceramic of some sort) that was used as the seal. Under the stress of the high nitro, the ceramic would essentially "boil" and would collect on the element. The taters looked like small white beads on the element. Nothing like the big black glob in the OP's picture.
Bill Lee
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Offline Dave Harmon

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Re: Taters
« Reply #8 on: July 24, 2021, 08:39:48 PM »
I'll try to answer everyone without making a bunch of 'reply' posts.

Before Armorall came along I remember the older guys in Tulsa using photographic film developer emulsion fluid to stop the fuel from foaming.
I don't know what was in that stuff and I never used it.
I don't remember much of a tater growing on my plugs in the decades since then and like other guys have said....THIS tater is humongous I've never seen anything like it.

If I remember correctly....Armorall causes a glass-like coating with some globs on the plug wire overall which when gets bad enough coats the wire and prevents the platinum from reacting with the methanol when the battery is removed. Just the other day....a guy started his engine and when the battery was removed....it instantly quit like he threw a rag in the prop.
Never has happened to me because I don't use Armorall....ever.

Mufflers....I use a Big Art chip muffler on the B-40 engines....seems to work very well.
I have a couple of RSM chip mufflers too.

The color of the tater and color of the plug body in my pix is misleading because of the lighting.
I had to use flash to get it to show up. The plug body looks dark because it is the typical black body T-Bolt plug....but...it DOES look like it's goobered up with lots of castor goop.
I should have cleaned it before the pix. I would say it is pretty normal.
I too have often wondered about the idle bar contributing to the problem. I don't have any indications either way.
Fuel.....Last year in a conversation with Clarence Lee....I asked him about K&B X2c synthetic oil K&B had used all those years ago.
I still have several gallons left and have use it in every engine without any problems.
Clarence said that X2c oil is all synthetic and is actually UCON 1145.
He also mentioned that it is good oil for our use but it has a 430 degree flash temp which is somewhat lower than KLOTZ KL-200. Otherwise he said it is ok to use but add some castor and try not to run too lean.
The castor I am using is Morgan castor....the bottle says it has "CP-1" in it....don't have any idea what it is.
Gotta be some kind of slickener though....I hope it doesn't have any silicone in it.
The methanol is from the local race shop....there is a good drag strip here with lots of racers.
I don't know what grade it is but I know the owner from waaaay back so I'll ask him.
Just to be totally clear.....I mix my own fuel. It's just too damn hard to get fuel anymore but the ingredients are readily available here.

Dennis points out what likely is the problem.
First....there is no metal sparkelys on the plug or on top of the piston which would indicate the engine is making metal.
Usually it is bearing material but of course the B-40 is plain bearing.
There is no evidence otherwise that there is any other problem with the engine.
The last couple of flying sessions with Joe have gone well but the weather was hot....about 90 and 65% humidity AND I had leaned the engine a bit to a fat 2 cycle.
There was no detonation crackle.

I was able to remove some of the tater but of course....I broke the &^%$#% wire.
I wanted to use the plug until it caused a operational problem with the engine....dang it.
Next time out I'll fatten it up some and start over.

Hopefully I have responded to most of the comments.
Don't stop with the comments just because Randy moved the thread....keep the comments coming!



Offline Steve Helmick

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Re: Taters
« Reply #9 on: July 25, 2021, 10:49:40 AM »
It would be interesting if somebody...perhaps a college chemistry student or chemical engineer...could take a few tatered up glowplugs, crush the individual taters and do a chemical analysis. We used to do tests like that in HS chemistry class, but of course, the teacher knew what the samples were, and it was up to us to figure it out. If you know somebody....

They did some sort of spectrum analysis on steel samples in the metalurgy lab at Jorgensen Steel. Something altogether different, but same objective. IIRC, the test involved vaporizing the sample. The resulting color spectrum gave the answer about chemical composition.

I'm also wondering if the chemical composition of the glowplug wire might be a factor in the "tater or no tater" results. Is one brand of glowplug more prone to getting taters than another?  D>K Steve

 
"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Dave Harmon

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Re: Taters
« Reply #10 on: July 25, 2021, 04:23:34 PM »
IIRC, the test involved vaporizing the sample. The resulting color spectrum gave the answer about chemical composition.

I'm also wondering if the chemical composition of the glowplug wire might be a factor in the "tater or no tater" results. Is one brand of glowplug more prone to getting taters than another?  D>K Steve


Good idea Steve.
Unfortunately I don't know anyone in industry anymore who has access to a spectrometer/graph/whatever.

Back in 90' when I was working with Irwin Ohlsson developing the Enya 3 clone now known at the T-Bolt 3, I provided a couple of new Enya 3 plugs in the pkg to him for analysis.
He cut one of them in half to observe the internal dimensions and pulled the wire out of the other plug and had it vaporized. He told me that the reason why the Enya 3 worked so well is because the wire had more platinum than any other plug he had seen since 1950.
The top of the E3 unscrews so a ring terminal can be fitted to the plug stem, then the top put back on.
This comes in very handy for engines that are deep in a cowl and need a remote start connector.




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