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Synthetic instead of caster oil?

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Don Fry18/01/2020 20:27:51
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Posted by paul d on 18/01/2020 20:20:42:

Sorry forgot to add: In response to John's original post, just ask the engineers at old warden to abandon castor in favour of modern synthetics in there vintage rotarys etc....castor still has a place imho..... tin hat firmly applied.....

Tolerances of half an inch perhaps, gum has uses.

paul d18/01/2020 21:32:03
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Don, having worked extensively on the clerget radial fitted to the Brooklands museums sopwith Camel ( replica airframe, original engine) amongst many other full size engines I can assure you the tolerances are extremely tight..... A very interesting subject for a sensible discussion.

Don Fry19/01/2020 07:09:08
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Sorry Paul, being facetious. But I still can't see the relevance of 100 year old oil and engine technology, on machines that got through the thick end of a gallon of oil an hour at half throttle. Might as well start a lecture on the efficiencies of biplane wing arrangements and ask modern designers to take note.

paul d19/01/2020 08:22:54
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Totally relevant Don....'our' engines like the rotarys of yesteryear both relie on total loss lubrication..enjoy your Sunday

Former Member19/01/2020 08:46:49
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[This posting has been removed]

Don Fry19/01/2020 09:45:30
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Posted by paul d on 19/01/2020 08:22:54:

Totally relevant Don....'our' engines like the rotarys of yesteryear both relie on total loss lubrication..enjoy your Sunday

You forgot to add, they are both made from metal. And also in caster oil, the fatty acids estified onto the glycol base work in very similar ways to modern oils in how and why they adhere to said metal. The way they break down under heat is very different however, so a hundred years of science has some uses. Not a great Sunday, sunny, but too much wind.

David Davis19/01/2020 10:08:14
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Among the afficianados of Enya engines are people who insist that you should use fuel containing 20% castor oil. I use Southern Modelcraft 10% nitro synthetic based fuel in everything, except Cox 049s and HP VTs. This fuel contains 15% ML70 and 2% castor. I have never had a problem with any of my Enyas or any other engine while using this fuel. This much loved Enya 50 continues to provide sterling service in the nose of my Boomerang trainer.

enya 50 in the boomerang.jpg

Engine Doctor19/01/2020 10:38:33
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Posted by John Wagg on 15/01/2020 20:33:07:

I have always used caster based fuels. Both 2 stroke and 4. Just ordered some Laser 5% which is synthetic. Now on full size engines it was considered not good to change oil types (mineral to synthetic). Is there any problems switching between lube' oils on my engines?

Let's get back to the O/P and answer the question for John .

No problem changing John . With model engines as so much fuel goes through them that any residue will be flushed out provided it hasn't been in storage for ages and set like varnish. If your engines are old / vintage engines then continue to use castor based fuel with a high castor content . This is preferred as old engines generally have poorer working tolerances and were often made from poorer quality materials needing higher oil content and higher viscosity oil ,hence Castor oil was used. Modern engines are a different breed , generate more power hence more heat ancestor oil simply turns to varnish and causes engine damage at worst . At the least it will bake onto the external cases and you shiny new engine ends up looking like a chip pan !

Model diesel engines use castor based fuel as they generally have a cast iron piston and steel liner and the quantity of fuel/ oil that passes through them protects the moving parts well and the rescue from the paraffin keeps the castor from baking on and is easily wiped away. Cox engines are similar having steel liners and pistons and run ell on any decent castor based fuel.

There are exceptions and a few diesel use ABC piston liner technology so I'll probably benefit from synthetic based fuel.

Modern synthetic oil is extremely good . I have used it in all types of engine including YS and it's brilliant.

So modern engines use modern ( synthetic) fuel .

Jon - Laser Engines19/01/2020 10:41:24
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Posted by paul d on 18/01/2020 20:02:06:

Jon, I must pick you up on a couple of points, you say the oil contributes nothing to combustion, of course it does! it's present in the combustion chamber when ignition takes place and a proportion of it burns which takes me to my second point.

You also say oils lean run protection properties is folk lore, you fail to mention the secondary function of the oil, it dissipates heat, oil that doesn't get burnt exits the exhaust taking heat away.

The slowing/stopping/ prop throwing has nothing to do with there being insufficient fuel to maintain combustion it's due to the engine suffering a partial seizure.

I do seem to remember reading of your trouble with a paw 60 diesel and your attempt at a cure with poor running, you drilled a hole in the cylinder head when it was quiet obvious it had a worn bore allowing the products of combustion past the contra piston!

I know it sounds like I'm "having a pop", I'm not I'm just giving you my opinion having spent 25 years working in F1, now those engines do operate at the limits of what's possible when it comes to cooling and lubricating.

As a aside and it may be of interest to some but 'we' once used a modified laser engine as a air pump back in Ayrton Sennas days with the Honda engine ( you may need to ask Neil about that!).

Hi Paul

This is always the problem with these threads. I have to leave stuff out to make the post less than 3 pages long.

To clarify, in the context of the conversation of klotz vs ml70 the oil contributes nothing to combustion and makes no difference to engine smoothness. Yes you are right about it taking up space and all that, but in terms of X% of oil A vs X% of oil B there can be no difference in engine performance assuming there are no additives in the fuel which will stabilise combustion or have some other effect....like Ferrari and their oil leaking turbo

Oil as coolant, yes it will throw some heat out of the exhaust but the effect is very small and has no effect on engines of this size. While i have not measured it i have not noticed any difference in engine temperature between my engines run on 15% oil and 5% oil. Again though, my point about lean run folk lore is that the engine will stop long before the heat dissipation of the oil or its tolerance to heat becomes relevant.

Throwing the prop has nothing to do with seizure. As was pointed out increased cylinder temperature advances ignition and in the case i was mentioning this advance gets so far ahead of itself that the engine fires very early and stops dead. This kicks the prop off the front, and can do internal damage, but the engine has not seized.

The PAW 60, yes i drilled the hole as i suspected pressure was building above the contra piston and this was my test to see if i was right. I was, and its still in bits waiting for some love. Not sure how that is relevant though ?

Old Warden. Yes, those engines use castor, they also use alot of it, and were designed for it with materials that are not anywhere near as good as the ones we use today. Admittedly i have not checked this, but i suspect very few Merlin engines are running on the sorts of oil they used in the war. Certainly they run on 100LL low lead fuel as the older stuff is no longer available. I would also agree with Don in that they are less relevant to our engines. A modern hedge cutter would be a closer match. Its engine is total loss oil as well but it uses synthetic, and not much of it. Not to mention that many hedge cutter engines now have props on them!

David, im a big fan of enya engines and their blurb has always said 15-20% oil synthetic or castor. At least, all the ones i have say that anyway. All on my Enya's run on the 5/15 nitro/oil laser 5 fuel and run happy as anything. My OS15fp states 20% castor else it'l blow! 15% synthetic and its never run better.

Jon - Laser Engines19/01/2020 10:43:00
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Posted by Engine Doctor on 19/01/2020 10:38:33:
Posted by John Wagg on 15/01/2020 20:33:07:

I have always used caster based fuels. Both 2 stroke and 4. Just ordered some Laser 5% which is synthetic. Now on full size engines it was considered not good to change oil types (mineral to synthetic). Is there any problems switching between lube' oils on my engines?

Let's get back to the O/P and answer the question for John .

Sorry, my bad embarrassed

John Wagg19/01/2020 13:00:32
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Hi all, Got my question answered thank you.

Enjoyed the other information and discussions regarding "oils".

Still waiting for the Laser fuel to be delivered as have to buy it on-line theses days. No local shops now.

Will finish using up the rest of my castor fuel in the 2 strokes but will use the Laser in my 4 strokes.

Cheers,

Hopefully see some of you at Old Warden etc.

Edited By John Wagg on 19/01/2020 13:01:26

Peter Christy19/01/2020 13:07:22
1877 forum posts

I see a number of people here differentiating between "old" and "new" engines, when specifying which oil to use. I think we need to be careful here. If by "old" you mean "vintage" (Frog 500s and the like), then there may be a case for some castor - but I'm not convinced.

To give an example, I'm running a pre-Blackhead Webra 61 dating from late 67 / early 68 (can't remember exactly when I bought it, but it was around then!) on Bekra - pure synthetic - with no issues at all. Similarly I'm running an old OS Max 40 from around 1973 on it. No problems at all. And then there's all the Cox .049s.

Basically, my experience is that anything made in the last 55 years is fine on full synthetic! And I wouldn't dream of allowing castor anywhere near them, nowadays!

--

Pete

paul d19/01/2020 19:47:49
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Nice discussion chaps, I for one meant no offence or malice just offered my thoughts etc, I will however beg to differ with Jon with his comment about the presence of oil adding nothing to combustion ( it does....) also we need to remember however advanced we have become in meteorology the engines we use in models are still incredibly crude devices compared to even modest commercial engines ( most 2 stroke chainsaw engines, out board motors etc run on 100/1 oil/ petrol....try that with your laser ( substituting methonal obviously) just for fun have a look at the current range of 'Stihl' agricultural range of products....2 strokes that run on the 4 stroke cycle, fuel injected blah blah blah and guess what,the recomended fuel/oil premix is vegetable based.

Jon - Laser Engines19/01/2020 20:30:03
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Posted by paul d on 19/01/2020 19:47:49:

I will however beg to differ with Jon with his comment about the presence of oil adding nothing to combustion ( it does....)

No im with you. Oil makes a difference, just not in the context of the conversation here.

15% of castor, ML70, Klotz..it wont make any meaningful difference which oil you use. RPM might change slightly due to viscosity and lubricity factors, but unless there are combustion enhancing additives, like the model technics SICAL, it wont matter at all.

As you rightly say model engines are extremely crude in real terms which is again why i say it will make no difference as i am trying to keep the conversation within the scope of model engines and their operation as opposed to the ultimate tuning guide for internal combustion.

As a side note, i accept your challenge i have some methanol and i have some oil. All it will cost me is a conrod so i will fire up a laser on 100:1. I know they work on 50:1 on petrol, and i use petrol at half the rate of glow fuel so... i have reasonable confidence it will be ok. I already flew two of our engines on 5% oil for a year with no ill effects and we are looking to introduce 7% oil fuel as our standard. It will be an interesting test

Frank Skilbeck19/01/2020 20:52:07
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And of course if you say halved the oil content from 20% to 10% then you'd actually be reducing the oil flow to the engine by around 55%, not 50%, as you'd have to reduce the mixture flow to keep the fuel flow the same. And you should get around 12% more runtime on the same tank.

Been running my Laser 150 on 10% oil, has almost a gallon through it, no ill effects so far and removing the rocker cover shows these very well lubricated.

Jon - Laser Engines20/01/2020 08:41:30
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Posted by Frank Skilbeck on 19/01/2020 20:52:07:

And of course if you say halved the oil content from 20% to 10% then you'd actually be reducing the oil flow to the engine by around 55%, not 50%, as you'd have to reduce the mixture flow to keep the fuel flow the same. And you should get around 12% more runtime on the same tank.

Been running my Laser 150 on 10% oil, has almost a gallon through it, no ill effects so far and removing the rocker cover shows these very well lubricated.

quite right. The leaner mix will reduce overall consumption and the fuel will be cheaper as its the oil and nitro that are the expensive parts.

If mixing yourself you can drop oil to 7% if you want. Which oil are you using anyway?

Edited By Jon - Laser Engines on 20/01/2020 08:41:46

Chris Freeman 320/01/2020 09:37:09
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A old flying buddy of mine has just hung up his TX as he has developed shaky hands so he can no longer fly and work on him machines. He was a master machinist who for 30 years made most of the metal bits that I needed for my aircraft. He gave me all his oil that he still had and this is about 15l of Castrol M and about 15l of Castrol MSSR.

We normally used a mix of 10% MSSR and 5 % M for our engines and 12% oil in the larger Super Tigre's. How good was MSSR?

I have been using klotz with M for the last 6 years with no issues.

Nigel R20/01/2020 09:38:41
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" 100/1 oil/ petrol....try that with your laser ( substituting methonal obviously)"

how much lubrication does the petrol itself count for?

methanol isn't lubricating at all, is it?

so would presume any glow fuel will always need more oil than an equivalent petrol engine?

Jon - Laser Engines20/01/2020 10:19:17
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Posted by Nigel R on 20/01/2020 09:38:41:

" 100/1 oil/ petrol....try that with your laser ( substituting methonal obviously)"

how much lubrication does the petrol itself count for?

methanol isn't lubricating at all, is it?

so would presume any glow fuel will always need more oil than an equivalent petrol engine?

In a 2 stroke there is an argument for the lubricity of petrol helping out a bit but not in a 4 stroke you burn it all off and only have oil in the crankcase.

All that said, petrol is a pants lubricant anyway.

Nigel R20/01/2020 10:30:44
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ok - thanks for clarifying jon

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