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Castor oil in 4 stroke engines

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J D 817/03/2019 10:53:33
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I DID IT, put some castor in the old mowers fuel tank. Lovely.smiley reminded me of grass track racing days in the 70's when the aroma of castor hung ovet the track.

I raced in a 1100 rear wheel drive class in which only very limited mods were alowed. [ polishing the ports,bigger carb but no fancy cams or anything like that.] Looking for an edge I decided to try a synthetic oil that was becoming available at consirable cost.

Man did that 1100 crossflow go, it would rev something silly off the line. I was more than once accused of having some hot tuning in the engine but it was just the oil that gave the edge. John.

Frank Skilbeck17/03/2019 11:04:42
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Slightly off topic, I have a couple of 30+ year old Lasers a 61 and 75 which were run on castor fuels when they were new (and did lots of running), they are still running (on the original bearings too), but they are now running on fuels that are synthetic (with maybe 2% castor), does changing to a synthetic on an engines that have previously on run castor fuels have any advantages or disadvantages.

Next time I stock up on fuel I will get the Laser mix with no castor.

Levanter17/03/2019 11:26:30
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Posted by brokenenglish on 16/03/2019 14:54:08:

I shall probably be a minority of one, but I disagree with some of the statements above.

CNC machining, etc. is obviously excellent for modern engines, but I don't think it gives better fits than hand-lapping, and suggesting that vintage hand-lapped P/L assemblies had poor fits and depended on using very viscous (thick) lubricant to run, is very untrue, ridiculous even.

Maybe I've misunderstood the above posts, but does anyone really think that all the ED Bees, Babies and Hunters, all the Mills engines, the Kalpers and all John Oliver's production ran superbly (which they all did and still do) with poor P/L fits?

Edited By brokenenglish on 16/03/2019 14:55:26

Maybe minority of two now but probably more. How on earth did we manage to make things with extraordinarily fine tolerances before the 70s when CNC started to be introduced? Although a fantastic development I think the applications of CNC are often misunderstood. Some amazing stuff was produced on automatic machines with air logic controls and I used to run a Conomatic six spindle auto lathe (a beast) that turned out parts - well, six times faster than a CNC lathe (I hade those as well) One of the big differences is the reduced levels of skill required for tool setting. Lots of things changed with CNC but not everything.

Levanter

Cuban817/03/2019 12:14:28
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Just on the oil content percentages....I know Laser Jon has experimented with much lower oil content with glow fuel (5% IIRC) and reducing from my usual 18% synthetic to 15% Laser mix has been a complete success in my ASP and OS fourstrokes. Why are we still stuffing such high oil content fuel through our engines?

Peter Christy17/03/2019 12:23:52
1375 forum posts

Frank: Switching to pure synthetic does seem to slowly remove castor varnish from inside the engine, so I would rank that as an advantage. In time, it may remove it from the outside too, but that will depend on how much the oil gets thrown around, I guess!

Cuban8: For some applications (think helis, or closely cowled engines) the oil is not just acting as a lubricant. It also acts as a coolant, carrying heat away in the oil globules in the exhaust. Not a problem if there is plenty of cooling air, but heat build up can be a problem in some applications, which excess oil can mitigate.

--

Pete

David Davis17/03/2019 13:08:11
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Our club offers its own fuel blend. Initially we only used 11% high quality synthetic oil in the fuel but after two or three brand new OS 46 AXs suffered serious damage we increased the oil percentage to 15% and that seemed to cure the problem. Mind you I'm not sure how well any of these engines were run in.

I am currently using Southern Modelcraft 10% nitro 15% oil in all of my engines without adverse effect. The oil content includes 2% castor. I will use straight synthetic once stocks are used up.

Cuban817/03/2019 13:13:52
2444 forum posts
10 photos

Pete, I concur with your points, but petrol motors run on a fraction of the oil content of glow fuel and rely on air cooling given the minimal residue from their exhausts. For general sport flying (not helis) where we're usually not at the max performance end of the envelope and for some scale models with good air cooling, I'd guess that most of us could reduce to something of the order of 10% oil with no problems and much cleaner models at the end of the flying session.

I like the simplicity of glow power, but I don't appreciate the oil over my nice clean models. Petrol is cleaner, but petrol fourstrokes are very expensive and have the added complexity of ignition systems, and from what I've seen, carburettors that due to their complexity, do give much more trouble compared to relatively simple glow types.

Ron Gray17/03/2019 13:27:41
1407 forum posts
358 photos

@Cuban8 - the complexity of ingnition systems is only a matter of having an additional battery to power them and connecting the cut out to a spare RX channel. Of course you have to route the cables but once done.........Similarly the carbs, once set, tend to be forget thereafter, in fact with the Walbro ones I’ve experienced it’s been a question of minor tweaks and then leave alone. Ditto Laser carbs (very similar to their glow carbs although even less tweaking!!!).

Peter Christy17/03/2019 15:52:07
1375 forum posts

I've only got one petrol engine, in a large scale heli. For the power output, it is massively heavier than the glow equivalent - and that's before you add in the ignition batteries. Its also quite noisy - it has a real bark to it!

Setting up the Walbro carb is quite fiddly - the needles are very sensitive - and you can't afford to get it wrong in a heli!

Yes, it does run cleaner, but most of my helis have exhaust systems that throw the oil clear of the airframe anyway. On my fixed wing models, I find a wipe down after each flight minimises the amount of cleaning at the end of the day.

Most of my models would be regarded as "large" by 1960s standards (around 5ft span, or smaller), but probably "small" by 21st century standards! But in that range, you can't beat glow for power to weight ratio - unless you go electric!

It always amuses me when I go to the nationals or similar events and see everyone commenting on how quiet and efficient the electric models are - over the sound of all the Honda generators chugging away charging the batteries! cheeky

--

Pete

GrahamWh17/03/2019 16:22:40
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The castor issue seems to be a bit like the car oil situation. Going to Halfords for a can of oil for the next oil change, there are a range of oils available. There are silly price synthetics, better priced fully synthetics, part synthetics and mineral oils. The modern high performance cars need the fully synthetics, but really old fashion cars can have the mineral oils. All to do with finer tolerances in the latest car engines.

Would anyone put mineral oil in a new Audi?

Edited By GrahamWh on 17/03/2019 16:23:14

Doc Marten17/03/2019 16:29:16
233 forum posts
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Posted by GrahamWh on 17/03/2019 16:22:40:

The castor issue seems to be a bit like the car oil situation. Going to Halfords for a can of oil for the next oil change, there are a range of oils available. There are silly price synthetics, better priced fully synthetics, part synthetics and mineral oils. The modern high performance cars need the fully synthetics, but really old fashion cars can have the mineral oils. All to do with finer tolerances in the latest car engines.

Would anyone put mineral oil in a new Audi?

Edited By GrahamWh on 17/03/2019 16:23:14

You would if it had hydraulic suspension....Citreon and Roycers still use it.

Edited By Doc Marten on 17/03/2019 16:30:10

GrahamWh17/03/2019 16:51:52
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smiley

But not for their engines - they use fully synthetic!

Jon - Laser Engines17/03/2019 16:52:20
4569 forum posts
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Switching away from castor in an engine that has always used it should not present any problems. I have done it a bunch of times and it was always fine.

The comments about oil and cooling are valid but its the methanol itself that has a far greater cooling effect than the oil. Spill methanol on your hand and you get frost bite almost straight away. Methanol evaporating in a crankcase or cylinder head does the same which is why high nitro engines run cooler as they run a richer mix. This cooler temperature can be bad for reliability but that is another story.

The oil % story is another issue as well and while i am sure that most modern engines will be happy on 10% synth or less i dont recommend it for general use as i dont want to hear about it if it goes wrong. Also 5% top quality oil will work much better than 15% chip fat and when it comes to home brewing, a great many go for the cheapest gear they can.

ASH.17/03/2019 20:17:12
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269 forum posts

Old timers swear by Castor - it has a higher flash point than synthetic and so protects the engine in case of accidental lean runs.

As to oil content,, I'm now using 12% Klotz (2%castor) reduced from 18%, 6.6% nitro. To my surprise I find a significant increase in power which I can only put down to reduced drag from oil friction something I had previously been highly sceptical of.. However, I have found the Saito 72 runs hotter especially when flown at WOT. The engine is tuned to optimum on both needles and so there is very little oil residue to clean up from fuselage underside.

How does Klotz Technipate compare with ML70 apart from huge price difference..? I have heard European oils are more superior to the American stuff which is ester based PAG or POE..!??

I am concerned about the carbon build up on exhaust valve/ chamber. I will have to find some way to clean it off when I come to do the bearings. Anyone know the best way to do this without completely dismantling the valves,rockers etc. I was thinking of getting an UltraSonic cleaner.

I know I know, I probably need therapy but I'm hooked on the aroma of burning castor.

 

Edited By ASH. on 17/03/2019 20:27:37

GrahamWh17/03/2019 21:16:21
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355 forum posts
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I've tried an ultra sonic jewellery cleaner on a sooty exhaust - didn't really do much.

J D 817/03/2019 22:38:53
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1119 forum posts
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ASH, You found as I did in my grasstrack racer 40 years ago that using synthetic oil gave more power. I thought at the time that at the start of a race [ grasstrack races were short] cars on castrol R were slower off the line because the oil was still a bit stiff so to speak.

Jon - Laser Engines17/03/2019 23:24:12
4569 forum posts
168 photos
Posted by ASH. on 17/03/2019 20:17:12:

Old timers swear by Castor - it has a higher flash point than synthetic and so protects the engine in case of accidental lean runs.or.

Edited By ASH. on 17/03/2019 20:27:37

No, it wont. This is a myth

The whole 'lean run' protection claim is flawed as the engine will not run in a lean condition. Lean mixture is a mixture beyond optimum performance and results in an rpm drop and then rapid overheating, followed by a flameout. A lean engine will rarely run more than a few seconds before it stops.

The root cause of this misunderstanding is that a perfectly tuned engine may overheat and stop due to poor cowling design or the use of high power for a long time. This overheating is misdiagnosed as lean due to the high engine temperature and deadstick.

So if we ignore the lean part and focus on the overheating part, castor is very good at holding on at high temperature. It was better than synthetics available in the past and so it gained this reputation. Unfortunately, as was previously discussed earlier in the thread, while the castor might have prevented your engine seizing in the old days it also took payment for that service by laying a coat of varnish on the piston. This varnish is sticky and created friction causing more load, more heat, and more chance of this engine overheating again. It would also bake onto the fins, which got dust and debris on them, resulting in a nice insulating blanket over the engine. None of this is good for the engine.

Since then synthetic oil has come a very long way and its tolerance to heat is such that castor really offers no advantages. If you run your engine so hot that a decent synthetic oil burns off then you deserve whatever you get

Klotz regular techniplate is fully synthetic if memory serves, its the super techniplate that adds the castor. The regular flavour is fine for use in pretty much everything at 15% and would most likely be fine as low as 8 or 10%. If you want to play safe then 12-15% will be fine im sure.

Tom Sharp 217/03/2019 23:40:58
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3350 forum posts
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Not model related but. Does Castrol oil no longer contain castor oil?

Peter Christy18/03/2019 07:56:09
1375 forum posts

Jon is right, regular Klotz Techniplate contains no castor - its the super Techniplate that has a trace of castor (about 2% IIRC).

My son and I were involved in testing when Bekra heli fuel was being developed. Originally the oil content was 15%, and it was fine. It only got increased to 18% because OS said anything less would void their warranty. The only difference it made was a very slight power drop and a much oilier model!

Tom: Castrol used to supply castor oil in two types "R" for petrol engines and "M" for methanol. The "R" does not dissolve well in methanol, and vice versa! I don't think they've used it in motor oils since the first world war, when it was used for rotary engines!

Back in the late 60s and early 70s I used to race karts - the serious kind, with 200cc engines and 4-speed gearboxes! In our group we had four karts, each with three members sharing a kart. All the other teams were running on Castor based fuels (these were Villiers 2-strokes). Our team leader insisted we run on molybdenum disulphide based oil. We were the only team to regularly complete a season on the same piston! The castor teams used to get through two or maybe three.......

--

Pete

Jon - Laser Engines18/03/2019 08:45:12
4569 forum posts
168 photos
Posted by Peter Christy on 18/03/2019 07:56:09:

Originally the oil content was 15%, and it was fine. It only got increased to 18% because OS said anything less would void their warranty. The only difference it made was a very slight power drop and a much oilier model!

yup. My 8th scale nitro car runs a 21 2 stroke at up to somewhere near 40,000rpm. It uses 16% nitro 12% synthetic oil fuel without issue. Given the general torture of being a car engine in terms of heat and revs is far beyond anything a fixed wing engine will see. If 12% is good enough for that the its good enough for the rest of us!

As for OS, my 15fp was designed for 20% castor but it runs much better on 15% synthetic. Model technics did testing some years ago and found the critical point was actually somewhere down around 2 or 3% oil so im pretty sure we use way too much oil in glow fuel. But that might be worth another whole thread!

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