problems with metal particals in exhaust oil.

Krzy Fri May 31, 2013 7:45 pm

OK so I've got a bit of an issue with all the cox engines I have. Every time I run an engine I'm finding ultra fine metallic particles in the left over exhaust oil (usually a dark grey color). What troubles me is that this is across 5 engines of which I have tried new and old crank cases, cranks, cylinders, spring vs non-spring, 6 different props all balanced, and 5 nose screws/spinners in every combination I could with no luck in removing the problem. The amount of oil left is literally puddles around my test stand so I can't think it's a lack of oil content.

I have tried both Hobbico 1/2A fuel you get at the typical Hobbytown shops, and a custom mix of Traxxas 33% top fuel that from tests done is shown to have 20% oil that I have added 3oz of Sig caster oil to the main gallon for my car engines. Then from there I mix 3 oz at a time with an additional 12ml for my cox engines. the current value from the cox fuel calculator xml for this mix is below.

New Blend (oz) 3.4
Percent Nitro 29.4
Percent Oil 32.4
Syn/Castor ratio 45 (note ratio is set to 20 on input field of calculator)
Nitro (oz) 1.0
Total Oil (oz) 1.1
Castor Oil (oz) 0.5
Total Castor (%) 14.7

The fuel guide PDF says you can run as low as 5% (though with short engine life) and typically want 20% so I don't think a castor amount of 14.7 percent with all the extra synthetic would be the cause.

Any way I'm am completely baffled by this and wondering am I worrying over nothing or is it a concern. Will run another short test and get photos Tomorrow of the oil and particles.

Krzy Fri May 31, 2013 7:50 pm

Forgot to state It's 3oz of the fuel with castor oil in it and add an additional 12ml of castor oil. Just wanted to add this in case people were confused.

pkrankow Fri May 31, 2013 8:03 pm

Which exact engines are you running? .049 reed? TeeDee or medallion? something bigger than .049?

Did particulate get into these engines. Sand, excessive dust, clean fuel equipment?

Are you running them excessively lean attempting to eek maximum RPM out of them?

How many runs in from reconfiguring the engine, particularly piston/cylinder changes?

What prop(s) are you running or what RPM range are you in?

Phil

Krzy Fri May 31, 2013 8:36 pm

Mainly .049 reeds and today I tested a used but good conditioned .051 Tee Dee that I tore apart and cleaned up last night. The Tee Dee showed the same issue and the crank and case are solid with no side to side slop.

All engines are clean of particulate before and after runs so that isn't the issue.

As for leaning the engines I usually take them to the point where they don't gain any more RPM then back them off to where they just start to drop a little RPM, All ways done it this way and never had an issue with overheating or burnt oil nor metal particles.

2 of the cylinders are actually old ones that are broken in all ready and never had this issue with. It really depended on how much grey there was coming out, I did do one for 5 tanks and ended up throwing parts of it away cause the cylinder/piston lost all compression while the crank had buff marks on it and the case bushing oval-ed. I probably could run them a few more but I'm afraid of damaging parts again, hence the asking here.

All props are cox originals, I've used 6x3, 5x4, 5x3 all balanced and all but the 5x4 in both grey and black. RPM depends on the engine, on the reeds I get around 17K to 17.5K max. the Tee Dee today I had at 19K to 19.5K with a 5x3 prop.

I know some of the metal can be from the new parts breaking in, issue is like I said above, I did one for 5 tanks (used but excellent condition cylinder, new heavy duty crank and extruded casing) and it was trashed so I've been reluctant to go past 3 tanks if it's still spewing grey (amount of metal in oil does not taper off with each tank either).

I'll take some photos Tonight of my engines both built and torn down so you can see what I'm working with and maybe help diagnose my issue.

**Cribbs74** Fri May 31, 2013 8:59 pm

Something is not right, your mixes may be suspect, but sound ok. If it's happening with all 5 engines find the common denominator. Fuel is one.

Are these old ressurected engines or new builds?

Ron

Krzy Fri May 31, 2013 9:58 pm

For the reeds one was a NIB Babe Bee I had laying around from the early 90s, the one I trashed was from a x-wing control line plane I had back in HS, one is new cox international, and another is a mix of old and new parts.

The Tee Dees are used from ebay I got 2 days ago one is a .049 and the other is a .051, I took the best of the parts to make a good one and a alright one. I have yet to run the .049 Tee Dee and frankly I probably need to replace the cylinder since it's a old #1 open exhaust Black Widow that has a lot of rust inside it, before I even try running it.

I would agree with the fuel mix issue other then even 1/2A fuel gives the same issue, unless of course the Hibbico 1/2A fuel is utter crap, which wouldn't surprise me.

When I fine my camera I'll take some up close picture of all the parts I have.

One thing I notice is with all of them I get some fuel and oil seepage from the front of the engine between the engine case and prop back plate. I can only assume some of this is normal since it happens on all of them.

I know I've throw a lot of info out tonight so for now I'll leave it at this, and Tomorrow weather permitting I'll run a few of the engines, mark the RPM and Props used, and try to get some photos with my tablet of the oil and seepage so you guys and see what I'm dealing with and tell me I'm just being paranoid about it all.

Surfer_kris Fri May 31, 2013 11:44 pm

Yes, there should be oil coming out in the front and it can be a little dark. Are you using any spring starters? They can also grind a little on the outside of case (from vibrations) and make the oil residues dark.

**RknRusty** Sat Jun 01, 2013 2:57 am

Surfer_kris wrote:Yes, there should be oil coming out in the front and it can be a little dark. Are you using any spring starters? They can also grind a little on the outside of case (from vibrations) and make the oil residues dark.

That's true, it scared me once until I realized the gray was coming from the spring touching the drive plate. It's not unusual for an engine to have a bit of a nosebleed, maybe more so on older engines.

Krzy Sat Jun 01, 2013 8:20 am

OK that's good to hear about the nosebleed issue. Color wise it's all ways grey no matter if I use a spring or not, I can only guess it's the drive place and case rubbing together at times. Weather looks to be doing all right (knock on wood) so hopefully in a few hours I'll have some photos of the oil.

dinsdale Sat Jun 01, 2013 9:32 am

Are you sure it's metal particles and not carbon particles from the combustion?

**RknRusty** Sat Jun 01, 2013 9:43 am

I'd recommend ordering a quart of Sig Champion 25 or some equivalent and see if it still bleeds gray. If you order this weekend you should have it by Wednesday. Better find some more items to get your order up to $25 so you get a $5 discount on shipping. That's the only thing I hate about Sig. Their shipping is a ripoff for small purchases.

Krzy Sat Jun 01, 2013 11:34 am

Well I feel a bit stupid right now. Embarassed

The issue I found out today wasn't my fuel mixture, it was a cracked prop screw. I found this out when I was running up my custom reedy that was a mix of a Cox International TD cylinder, Killer Bee Back plate, KB/Diesel Crank, and Type "A" Head Conversion with Hot plug insert. Hit about 17.5k RPM when all of a sudden the prop and nose cone go flying off and the engine screams up to 30K+ RPM before quitting Shocked

. Luckily the cylinder, piston and crank are fine, the Casing though is trashed do to ovaling of the bushing (up and down slop with the crank in), and the drive plate was striped out inside by the crank.

I can only guess is that since this was the same screw and cone on the engine I destroyed last year. It caused a balance issue due to a the prop and drive plate slipping, that led to the case bushing ovaling and eventual failure. Because of said failure I probably was a bit paranoid

about the grey oil with metal for the other engines on break in and not running them enough times. Also was probably caused by swapping out said screw between all the engines trying to hunt down the issue.

I put the cylinder from my custom Killer Bee onto the .049 Tee Dee I had yet to run and got it up to 19k on the 3rd cycle and completely clean oil.

So in all this head ache of mine was over a damn $0.25 part. Think I'll go to the hardware today and buy some hardened hex cap screws so I don't have to worry about this again.

So Big thanks to all of you trying to help and sorry it ended up being some thing so stupid. *insert epic face palm here*

**RknRusty** Sat Jun 01, 2013 12:29 pm

Hey, an o-ring brought the Challenger and seven souls down. Don't sweat it, that's mechanics. Your persistence paid off in the end.

**Cribbs74** Sat Jun 01, 2013 12:46 pm

Yeah man, no big deal. We have all been there. The important part is you found and fixed it.

I see you are a guest, have you considered placing membership? We would be glad to have you.

Ron

**Admin** Sat Jun 01, 2013 12:47 pm

Yeah, its easy and FREE to join the forum!

KrzyInuYasha Sat Jun 01, 2013 1:20 pm

Yup, happy I found a good fuel mixture that works and those Tee Dees I got work wonderfully. Just gotta build that Bridi Quickest 200 I have and mount one of them on it.

Yea was just lazy at the point in time to register as you can see though I finally did.

**RknRusty** Sat Jun 01, 2013 1:21 pm

Glad to have you with us, Krzy.

andrew Sat Jun 01, 2013 1:53 pm

Krzy wrote: Think I'll go to the hardware today and buy some hardened hex cap screws so I don't have to worry about this again.

Unless your hardware store is an unusually well stocked store, they will not likely have the prop screw ---- the size is 5-40.

I buy mine in bulk from McMaster-Carr and a little long so I can cut them to length. I usually try to size the screw so that it tightens up just before it bottoms out. This gives the maximum thread contact and helps support the crank where it has been drilled out. If you want only a few, COX International has them, as does several of the custom vendors, i.e., Microfasteners, RTL, etc.

gcb Sat Jun 01, 2013 1:58 pm

Krzy,

What about your cleaning process? Are you using a polishing compound? Some of the symptoms you state can be caused by residual polishing compound or a bit of undetected rust...which is iron oxide, a polishing compound.

I would suggest both a thorough cleaning with a solvent plus a slobbering rich first run after reassembly.

When you get replacement prop screws remember they are 5x40, not 4x40.

Good luck and welcome aboard the board. :-)

George

KrzyInuYasha Sat Jun 01, 2013 2:56 pm

yea my ace hardware is pretty well stocked. As for cleaning I use non-chlorinated brake cleaner (basically acetone in a spray can) after each run on the out side to clean all the oil off, wipe with a paper towel, then put a little after run oil into the cylinder ports and air intake ports, crank by hand a few times.

**RknRusty** Sat Jun 01, 2013 3:35 pm

I would recommend lint free rags(like t-shirt rags) instead of paper towels for anything near the fuel system. If you look at it under a magnifying glass after using paper towels you'll be amazed at how many loose fibers are left behind. And I'm with you on Brake Parts Cleaner, great stuff. I don't know how I ever lived without it. Just don't let it blow back in your face.

I'd like to emphasize what Andrew said about the prop screw length. It's important to use a screw that goes as deep as possible without bottoming out. It will prevent the splined nose of the crank from busting off on high RPM engines. I like the black oxide hex screws too.

dinsdale Sun Jun 02, 2013 9:54 am

Krzy wrote:Well I feel a bit stupid right now. The issue I found out today wasn't my fuel mixture, it was a cracked prop screw. I found this out when I was running up my custom reedy that was a mix of a Cox International TD cylinder, Killer Bee Back plate, KB/Diesel Crank, and Type "A" Head Conversion with Hot plug insert. Hit about 17.5k RPM when all of a sudden the prop and nose cone go flying off and the engine screams up to 30K+ RPM before quitting . Luckily the cylinder, piston and crank are fine, the Casing though is trashed do to ovaling of the bushing (up and down slop with the crank in), and the drive plate was striped out inside by the crank.

I can only guess is that since this was the same screw and cone on the engine I destroyed last year. It caused a balance issue due to a the prop and drive plate slipping, that led to the case bushing ovaling and eventual failure. Because of said failure I probably was a bit paranoid about the grey oil with metal for the other engines on break in and not running them enough times. Also was probably caused by swapping out said screw between all the engines trying to hunt down the issue.

I put the cylinder from my custom Killer Bee onto the .049 Tee Dee I had yet to run and got it up to 19k on the 3rd cycle and completely clean oil.

So in all this head ache of mine was over a damn $0.25 part. Think I'll go to the hardware today and buy some hardened hex cap screws so I don't have to worry about this again.

So Big thanks to all of you trying to help and sorry it ended up being some thing so stupid. *insert epic face palm here*

I'm still a little perplexed. This might be the solution for one engine, but you said that you were having the exact same problem with multiple engines. sounds a bit too coincidental for my liking. How could the same, somewhat odd series of errors occur in ALL of your engines at the same time? If I were you I'd still be looking for the cause of the discoloured oil. I'd also still be suspecting that it's mostly carbon from the combustion.

KrzyInuYasha Sun Jun 02, 2013 11:46 am

Like I stated it was a mix of paranoia after destroying one engine and probably not running the others long enough for new parts to wear in. Also using said screw across all engines at some point in time when trying to hunt down the issue probably was apart of the cause. Could of also been my fuel mixture from last fall to this spring has changed and I wasn't using enough oil like I am now. All I know is that after the screw went and I replaced it things are clean now.

Also doubt it's carbon, I could literally see metallic particles on my finger after running it through the oil.

I'll keep an eye on things and see what happens once I rebuild my custom and break it in again. Biggest concern I had that started this thread was one of the Tee Dees was showing this issue and I was afraid of damaging the crank and crank casing like I have with my bees.

Honestly I would love to see Bernie and Matt make castings and dies for new manufactured .049 Tee Dees. Even if the engines were to cost $100-$150 each, I would gladly buy them knowing I would get brand new engines then risk buying a supposedly NIB from ebay for the same money.

GUS THE I.A. Mon Jun 10, 2013 1:19 pm

No doubt! I would love to see new Tee Dees, and put an end to the hoarding and holiness that is associated with them. These babies were meant to run, and if there is a demand for them, they would sell! Look at how they're listed, and priced, when the originals do come up for sale. It's ridiculous.

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