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Author Topic: Oils aint oils !  (Read 1687 times)
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« on: August 03, 2016, 01:29:06 AM »

Reading the forum reminded me that perhaps not everyone understands the need to lubricate a engine ( Running an engine )

One of the most misunderstood aspects of model engines is how much oil do I need ?
And this depends very much on the use of said model engine ( be it marine , car , plane - what ever )
Too many engines have been destroyed due to under lubrication .
And what I mean by that , is sometimes we cant get a perfect tune , or the tune may vary depending on how much fuel is in the tank .
A lean run basically means that the engine is starved of fuel , and because the fuel contains the lubrication for the engine , the engine is also starved of the lube .
This can have a profound affect on a engine ..
Less lube means more friction between moving parts , leading to more heat , more expansion ( piston ) which may lead to more friction , more expansion , more friction and we end up with a worn out engine in one run .
This is a extreme example , but I have been there and done that . 

Back to oil :
Castor oil is the oil of choice for model engines ( Glow Diesel ) ..
For two reasons , superior lubrication as well as castor helps to remove some heat from the engine ..

How much oil ... 
This depends very much on the engine and materials used for the piston cylinder assembly ...
You generally have a cast iron piston in a steel cylinder
You have aluminum pistons with a piston ring in a steel cylinder
You have cast iron pistons with rings in steel cylinders
You have cast iron in chromed steel cylinders
Aluminium pistons in chromed brass cylinders
Aluminium pistons in chemically plated cylinders ( is it some sort of nickle mix ? )
And the Aluminium in Aluminium cylinders
And do you have ceramic coated cylinders now ?

For you high tech materials 20% castor is a safe bet ..
For your older tech materials 25% is a safe bet ..
And for really old engines you may wish to run 30% to stretch their service life ...

Low oil for racing ...

This is where things get interesting ...
I remember when PAW came out with the Twin BB engines for more power ..
In the UK one team was running 10% synthetic oil in their engine and winning all the Goodyear races in that class ( PAW 2.49 BB )
Now what a lot of people dont seem to understand :
The cylinder of that engine was chromed , and the piston had been set up to run low oil ..
So what happened was the piston did not expand as much when the engine warmed up ..
So rather than the piston cyl being matched for expansion ( maintaining relative fits ) , the cyl actually expanded a little more than the piston for a slightly more lose fit ..
Hence this engine could tolerate less oil under high load ...

Now a lot of people did not understand this , and trying to emulate this team , they kept PAW in the money for a while ( Spare parts sales ) , as people wore out their engines .
So obviously the team that was able to do this ( run low oil ) understood what it took to make it so .

So , if you want to do very high tec stuff , you need the skill , knowledge , and understanding to do so .. Simply switching to lower oil content - Im sorry to say is just silly ...

Story time :

  At the time PAW brought out the Twin BB engines , well I just had to have one ..
When I got it home , I thought .... This is very average ..
I blue printed the engine , timed the engine ( to my specs ) and ran it in very carefully ..
Oh boy was it a nice engine ...

But it was then dis allowed for Vintage A , so I sold it ..
Now the person that bought it saw what was happening in England ( 10% oil ) an promptly wore out that PAW ... ( Oh dear ) running 10% oil ...

I was down at Moorabbin  ( Flying Field ) , quite some time ago ( Decades )
And some one from somewhere was using a diesel Nelson in Goodyear ...
I thought it a good idea , engine certainly produced some power ...
But the engine just would not hold a tune ...
It started of really really strong and then slowly died ( grinding to a halt )

A lot of the experts were crowded around this engine trying to work out what the problem was ..
Now after watching and listening for a while I asked the owner how much oil he was running ?
I think you know the answer , 10% oil ....
HuhHuhHuh?/  Seriously , a high powered , high RPM engine with 10% wait for it ------ Synthetic ...

I suggested that he should perhaps try adding 10% castor to that mix so the engine could hold a tune ...
Hmmm , the response was a hissy fit along the lines that other people were running 10% so he should be able to as well ....
Yeah I walked away thinking I had just communicated with an idiot ... 

Seriously , some people have the money to buy good gear .. Perhaps even more money to replace it after they have destroyed it ..
Bit they just dont understand , that perhaps it takes a little more effort than just lowering the oil content of the fuel ..
Perhaps it also requires engine re work to adjust how the moving parts relate to each other under load , and with less lubricant ...

So here is a clue ...

Never run less than 20% unless you are a genuine expert ( I dont care what some expert told you )
If you dont know , use 25%
If you have a valuable old engine , just go 30%

If you have to push the envelope , do so slowly .. Drop the oil 2% at a time ...
When the engine runs like crap , you have gone too far ...
If you dont know how to set up an engine ( running fits ) , dont even try running low oil ..
Unless of course you have more money than you know what to do with , and destroying engines means nothing to you .. 

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« Reply #1 on: August 05, 2016, 04:36:14 PM »

Excellent comments!

Only one slight quibble... Some modern engines are designed for a certain type of run, and use of synthetic oils. These are expensive, generally, but the recently introduced Evolution CL Stunt engines seem to be an exception. They are reasonably priced, too. (At least here in the USA.) Comments on a few sites mentioned problems with the EVO 36s. Discussion surfaced the fact that the oil used was improper for the engine, and that problems were solved with a fuel with a higher fraction of total oil being synthetic.

These technological advances are not, apparently, extremely expensive to produce. Inexpensive 2-cycle IC engine powered weed-whackers are "fitted' to run on a 1 in 50 oil mix! Somewhat special oil, or at least one marketed for that use.

There are costly, highly developed CL stunt engines in which materials and clearances cannot tolerate classic castor varnish buildup. Cooling and operating temperature clearances are, apparently, compromised. Just as with good ABC (or other like combinations), clearances at working temperatures are critical. A slow, oily, 4-cycle break-in doesn't let the p&c reach design temperatures. Fit expansions are not achieved or maintained. Lubrication has to deal with greater friction than if the engine is run at the proper temperature range. ...On a lighter load and for briefer periods initially, of course, but at RPMs typical for flying conditions.   

Appreciate your thorough and clear comments. Again - Thanks! 


« Reply #2 on: August 05, 2016, 09:31:52 PM »

I think some of the engines you mentioned may have had other issues .. ( Model airplane )

As for other two stroke engines ( Weed Whacker / or motor cycle engines ) Yes they generally run less oil , due to several reason ...
One is better control over tolerances and expansion rates , the other is the use of piston rings ..
Piston rings have gotten rather high tech these days ..

 As for Weed whackers , I dare say a lot get destroyed ( engines ) rather quickly ...
I think I ran 20:1 a long time ago when I had a two stroke motor bike ( Decades ago ) ... ( And how many of these are damaged from low oil ? )
Honestly , 2 strokes wear out faster than 4 strokes ( Motor bikes and weed whackers ) Which is why most weed whackers are 4 stroke these days .. ( I dont think I have seen a 2 stroke at Bunnings )

I haven't used synthetic oil ( except in my car ) in possibly 20 years , so one would hope its better now ( really I would ) which is why I have not really mentioned it .

This entire tale is one of caution , and one of empowering the reader to understand that they are the last line of ( ?? something ) when it comes to protecting their investment .
And not to blindly follow what others do or say they do ...
The old saying of , better safe than sorry comes to mind ..
+ This was not really about Castor VS Synthetic ...
I am sure there are some synthetic experts some where , and hopefully they wont mind sharing ...
I think I still have a bottle of synthetic that I used , ( oh I used synthetic ) but Im not sure its still manufactured ..
It was a motor bike blend , was high tech at the time , and it worked well ..
Hell I still used 20% in my fuel mix , ......  But the blend was much lighter than castor and I think I picked up a decent amount of RPM without sacrificing safety ( of my engine ) ....
And that oil would tolerate a hard run ( Diesel ) and not damage the engine ..  ( And to me , that was very important )


« Reply #3 on: August 06, 2016, 07:51:26 AM »

Wow !  Shocked

 I just had to take a look , yes ... There are lots of two stroke line trimmers ( The cheap ones ) ...
And yes they seem to run a 50:1 mix ..  I dont think I would run that , not 50:1  ...
I would be more tempted to run 30:1 or even 20:1  ..

Perhaps 20:1 to run it in with , first few tanks .. then drop the oil slowly .. 
I would not be overly comfortable with a 2% oil content ( Two stroke line trimmer ) ....
Especially if you got one that runs a little lean .... 
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« Reply #4 on: August 06, 2016, 03:31:32 PM »

Granted and generally agreed.

Synthetic oils for model aircraft use have improved greatly over the past few decades. An on-line buddy in the US, a retired lubricants 'expert' assures us that in many of the crucial requirements, they are better than good castor oils. Film strength, load capacity, "lubricity" and a few others...

However, castor likely remains better in temperature tolerance. A study by Dave Gierke in Flying Models (a US mag) the 1970's reported his "course" in engines and power production, measurement and refining. He was at the time a high school sciences teacher, and a World Class CL PA champion. The course is very good. Part of his testing included temperature tolerance of (then available) synthetic oils, castor oils and if I recall, a few other bean oils.

Castor "hung in there" to a bit above 500°F, whereas the synthetics burned away below that temperature. The heated castor, as you pointed out, carries the heat out the exhaust; burned synthetic oil cannot do that, and even adds a bit to the heat to be rejected.

Haven't seen any later decent studies in this line.

Even in chromed cylinders, castor can form a varnish-like goo that bakes into any porosity on the piston surface. The modern engines I mentioned can't continue to perform as designed with even a very slight dimensional change, AND with a metal surface characteristics change as a likely retarding barrier to heat transmission effect on operating fits at design operating loads and temperatures.

The non-ferrous engine working parts need to be used as they require. Manufacturing precision these days requires a minimum of 'buffing in' of surfaces, but does rely heavily on NOT running them far out of the design RPM, load and heating parameters. Or so I've heard from acquaintances who are much more into long-enduring consistency of operation. (CLPA is a fine example of such use, and those truly expert fliers, who have not gone to electric power, demand and get incredible consistency from their non-ferrous glow engines... over hundreds of contest and practice flights.)


« Reply #5 on: August 06, 2016, 09:34:48 PM »

These days , it might pay to see what the car buggy guys are doing with lube ..
Since I think they are and have been at the fore front of engine development for some time ..  + The operational environment for the engine may be more harsh ...
Having said that , the car buggy folk also seem to destroy a hell of a lot of engines as well ... So perhaps a little care is warranted as to where to seek information from ( ? )

Aaaaah , varnish build up ......  Another kettle of fish

Again comes down to how an engine is set up ( if you know how to do this )
Yes varnish build up can definitely slow down an engine , and whilst I never indulged ( Much ) , in de_carbon_ing or de_varnishing an engine , it was common practice to do so with racers .
I even saw people pull engines apart on the flying field to de_carbon and de_varnish ... ( FAI Team Race )

If there are any old or "new even" FAI team racer's who would like to share the process ...
I would expect the methods to be many and varied depending on the materials used for the Piston cylinder ..

« Reply #6 on: August 07, 2016, 04:22:04 AM »

Here is a DIY guide !


Personal Note :

I would try and avoid cleaning agents / water .. Rather use WD40 / RP7  or other lube based cleaner ...

« Reply #7 on: August 07, 2016, 05:12:46 AM »

Re oil :

From COX :

 A model airplane fuel consisting of 15-25% nitro (35% for racing) and a
minimum of 20% oil (at least 1/2 of that 20% has to be Castor oil).

From Traxx :

1. The fuel must contain both castor and synthetic
oils with a total oil content of 12 to 18%
2. 3-5% castor oil must be present in a synthetic/castor
blend fuel.

Synthetic-only fuels are not designed for
ABC engines and can permanently damage
your engine. If you have any questions
about fuels call us toll-free

Best 2 stroke oil ? :


http://www.challengers101.com/EngineOils.html  Very interesting ...

http://www.modelairplanenews.com/blog/2013/05/14/what-fuel-is-best-for-your-engine/ very interesting read ...

http://www.rcmodelreviews.com/goodoil2.shtml  More good reading

« Last Edit: August 07, 2016, 05:52:59 AM by old4570 » Logged

« Reply #8 on: August 07, 2016, 08:18:37 AM »

Must read !

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« Reply #9 on: August 11, 2016, 04:18:13 AM »


Working my way through your links... THANKS for them! The Model Aircraft News item does not 'come in' on my system. Has it expired?

The Challengers item is very good, BUT notice it is intended for 2-cycle engines for ultra-light, people carrying, aircraft. Gasoline burners, IOW. Timed spark ignition. I expect that the bean oils, castor as their premier, are excluded by reason of cost. Perhaps also as a result of keeping a good mixture of available gasolines with castor... Alcohol as a fuel for ultra-lights? I haven't heard of that, have you? 

A while back, I was a tangential part of an effort to develop an extremely fuel efficient engine-power system for high endurance, with minimized fuel-flammability risk for storage and provision to the engine. (A parallel example - US Navy lost several vessels during WW2 to fire caused by enemy action with AVGAS stored aboard.) Even some specs of current diesel (kerosene) fuels are, by intention, far less fire hazard than any gasoline formulation... That was not the purpose for which I did my few things, but is similar enough to explain the thinking.

Until very recently, we model fliers have used either glow fired alcohol pre-mix fuels, or less often, compression-ignited premix "diesel" fuels. Yes. timed-spark fired engines are now appearing...

According to some SAE papers I looked at, alcohol fuels have a combustion flame front speed that defies measure with the lab equipment then available. Gasoline and "kerosene' were measurable, hence slower. These were at near-stoichiometric fuel-air ratios where complete-burn conditions existed (ALL the available fuel burned, using all the available oxygen in the available air.)

We don't have such conditions. We modify the mixture by load, throttle and fuel to make it controllable far below ultimate. MOST of us are not looking for the ultimate the engine can generate, but rather a slice of its performance envelope matched to our needs in (model) flight. For those who can't grasp this: If our car has a tach, does that indicate we are pulling the engine's max power at, say 3,000 RPM on a high-speed road which allows us to 'dial-off' max to a smaller fraction of ultimate output for that RPM.

Thanks again for the links! More soon, if more seems indicated.



« Reply #10 on: August 11, 2016, 07:58:41 AM »

Hmmm , Ultralights !

 For a while there I used to read KIT PLANES , fantastic magazine ...

And one thing became very clear to me .. For some strange reasons the engines for ultralights seemed to suffer a lot of failure = Some times resulting in death !
Now for motor bikes this is possibly not so dramatic , but still relevant .
So I included the Rotax thing because I would think that people who's lives depend on the oil , might have a clue ( ? )

 If there is one thing I have learned is not to discount information , but rather gather it up , analyze it , and see where it leads ..
+ A lot of the oils will mix both ways , petrol and alcohol ( Methanol ) ...

I mean , you take away what you take away , that's human nature ..

Just checked and all seem to be working fine ...

I would have thought that people risking their very lives , might be a little more careful with the oil they feed their engine ..
But apparently not ! Since a lot of ultralight engines have seized over the years = Were they using synthetic oil ?
Yes we humans make mistakes , we are very good at that ..
Lucky for us modelers , all it might cost is an engine ...

I haven't been able to find a head to head test ( oil shoot out ) , and most articles seemed to be purposefully vague when talking about synthetic 2 stroke oils . ( Strange )
I would have thought the motor bike lads may have done an oil shoot out , but apparently not !
So , synthetic two stroke oils are a little bit of an enigma till I win the lottery ( The big one ) ...
Then I can afford to buy 20 or 30 engines and run them till they sequel and die ....

hehehehe !
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« Reply #11 on: August 13, 2016, 02:27:35 AM »

Old, love your phrasing and choice of words!

We have differing understandings because - surprise! - we have had different experiences. Which is less valid? Yours, of course! Just as mine are less valid in your experiences... Opinions which confirm our individual positions, which some other person phrases differently.

That aside, until just this Summer, I'd subscribed to KITPLANES since the Rutan Voyager cover edition. ...which commemorated the globe circling non-stop flight of Dick Rutan and Jeana Yeager in Burt Rutan's strange, effective aircraft. (Also a fine, human book, if you haven't  yet...)

At over 76 1/2, now, with sea level sinuses although I live at ~5000' above MSL, I don't contemplate building my own people-carrier. RobRucha  and Barnaby Wainfan sustained my subscription interest if nothing else.

Example - Aircraft engines are over-designed for their purposes. UNDER-designing them is not acceptable when human lives are involved: just never mind the lives lost to faulty assumptions about realities.

Model aviators don't risk their lives INSIDE their  aircraft - a real difference. It is an advantage...

KITPLANES has only recently started back to basic airframe construction and maintenance "lessons," which I had in a great secondary school, 60+ years ago. The courses were adequate that if I'd wanted to, I could have tested for an Airframe and Engine ticket(then: an A&E license.). Other than more metrics, and a few minor changes in material ID nomenclature, bolts and nuts, ferrous and alumin(i)um and its alloys, remain much the same. Basic stress analysis method articles are familiar.

I AM glad that the 'open the lid and the internet is waiting for your command' generations are being exposed to some of what they expect their 'devices' to have done without pestering them about what is actually involved. (If no one had bothered to upload what you need, you are SOL. (Military expression, the kindest translation may be, "(excrement) outta luck.")

Anyway, I've read-studied-tested much that supports my comments to my satisfaction. as I am sure you've done, as well. We can learn from sharing these, moreso where there are differences. I'm game to keep on, learning as we go. you too, I hope? Others, beyond AND between our ideas may benefit, too.


« Reply #12 on: August 13, 2016, 04:10:18 AM »

Well ...

Homebuilds run all sorts of engines ... 

From rebuilt re purposed car engines , to small chainsaw type engines pushing powered hang gliders and powered parachutes ..
I do like the idea of powered parachutes ... 
As well the rest ..  I guess the fun of home builds ... You never know what you are going to see ...
And people being people , you must factor in human nature ...


« Reply #13 on: August 13, 2016, 06:22:45 AM »

http://www.trikepilot.com/magazine/read/rotax-two-stroke-reliability-reveled_876.html   Good read ...

http://curedcomposites.com/twostroke.html  Interesting read

http://www.ultralightnews.com/engineinfo/coldseizure.htm   Hmmmm , reliable Huh  Seems to be a lot of coldseizure going on , so dont know if that is = to reliability ... 


Anyhow , some interesting reading ...   
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« Reply #14 on: November 12, 2017, 01:05:54 AM »

Old 4570,

Sorry to break your bubble, but modern synthetic oils are not only as good as any vegetable oil, but better in all respects: lubricity, film strength, viscosity stability, detergency, oxidation resistance, and varnish formation being among the advantages. They allow much tighter fits and better sealing, along with lower wear and lower friction. They do not develop varnish at higher temps and burn cleanly . High temp stability is considerably better, and they are stable to higher temps than any vegetable oil such as castor.

The above is based on scientific evidence not on empirical or anecdotal evidence from model magazines.  It's also from data developed in our Reynolds Metals Co. lab on actual engines and industry standard lab tests.

As an avid modeler, these tests had a secondary interest for me. I have always blended my own fuel, and this seemed like a real leap forward. It was. Since 1958 I've used nothing but synthetic oils in my engines. I still have most of them. I wouldn't hesitate today, to pull any one of them from it's box and fly it.

  I'm attaching one of my old business cards not to brag, but to show I do know a little of what I speak.

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Re: Oils aint oils !
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« Reply #15 on: February 19, 2018, 02:23:22 AM »

I agree fully - the synthetic lubricants have made the stunt engine world better since early seventies. They became known to us through stunt people who went to international competitions. Syntethic -yes - top lubricating and anti-wear qualities etc. However, I stick (literally, especially at freezing temperatures) to castor oil where I can. There are FAI-classes with "castor only", also tether car juniors are limited to use castor oil.
I use pre-owned two-stroke engines and fly with my youngest son. Castor is in my understanding, less toxic, or should one say non-toxic, compared to synthetic exhaust fumes. Also, cleaning your plane after a day flying is less toxic as castor can be wiped off with ordinary kitchen cleaning water-based solutions for ordinary households. A splendid quantity of castor in glow fuel ends up to your hands and face converting you to a happy, soft handed man with nice suntan.
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« Reply #16 on: February 19, 2018, 11:35:43 AM »

Although this doesn't have much to do with 2 cycle oils it is another data point on synthetic oils.  40 years ago I worked for a company that made roll over car washes.  The side brushes used a 60 to 1 gear box designed for 1/2 or 3/4 HP and as the brushes got larger that was no longer sufficient.  When I was working on these devices we were using 2 HP motors but the same gearbox.  The sheet metal limited the gear box size that would fit.  We were running some tests where the washer was set on an endless loop and a junk car was washed over and over.  The gearbox would get so hot that you could not touch it even for a moment as you would be burned.  I was tasked to see if there was a solution other than a complete redesign of that part of the washer.  Mobil had just come out with a pure synthetic gear oil and I called a rep and got a gallon of that as a sample.  I stopped the test and changed out the gearbox oil and after running the washer through 50 or so cycles you could rest your hand on the gearbox.  It did not get anything other than warm!  I have never ran anything other than synthetic oil in any of my cars since.  I had a VW 1.8T golf years ago and it used a 5w - 40 Castrol oil that was $7 a quart and was not sold anywhere but the dealer.  They screwed up one time and replaced that oil with regular oil and my fuel economy went down about 1.5 miles per gallon.  That more than paid for the additional cost of the oil.  I sold that car to a guy at work with 130,000 miles and it would burn about 1 pint of oil in 5000 miles.  He commuted a large distance and the last time I talked with him it had 200,000 miles and still burned only 1 pint every 5000 miles.

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