Oils for use in diesel fuel
12-28-2015, 01:24 AM
#26
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My understanding of Castor flowing towards the heat is that it's an indication of the viscosity reducing with heat. That is, if you heat a puddle of Castor on one side then that side will become thinner and start to flow quicker than the other side. (I'm talking about temperatures lower than that required to make the Castor thicken in to varnish). It would normally be deemed an advantage for a lubricating oil not to do this, but to maintain its viscosity as the temperature rises instead. Obviousely the Castor is still viscous enough at higher temperatures for our purposes.
In any case the tendency of Castor to 'flow towards the heat' is probably fairly irrelevant in our engines. I would imagine the oil being flung around and smeared by the moving parts would be the main way the oil is moved around.
Castor oil is used in rotary aero engines because it doesn't mix with petrol not because of any superior lubrication properties, in fact the oil gums the engines up quite badly (opposite problem to the pilot). Castor oil and fuel is introduced into the engine through the crankshaft, the oil follows the same path as the fuel mixture through the engine and out the exhaust lubricating as it goes. If the oil mixed with the fuel it would lose viscosity and have a reduced ability to lubricate.
Dave H
In any case the tendency of Castor to 'flow towards the heat' is probably fairly irrelevant in our engines. I would imagine the oil being flung around and smeared by the moving parts would be the main way the oil is moved around.
Castor oil is used in rotary aero engines because it doesn't mix with petrol not because of any superior lubrication properties, in fact the oil gums the engines up quite badly (opposite problem to the pilot). Castor oil and fuel is introduced into the engine through the crankshaft, the oil follows the same path as the fuel mixture through the engine and out the exhaust lubricating as it goes. If the oil mixed with the fuel it would lose viscosity and have a reduced ability to lubricate.
Dave H
Last edited by gerryndennis; 12-28-2015 at 01:33 AM.
12-28-2015, 01:44 PM
#27
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Hi Dave,
I just look at my BBQ plate every time that I add oil.
Starts off hot and dry, add some fluid (say water to steam clean) and it readily absorbs the heat and converts to a gas - running away from heat.
Then when hot and dry again, add some vegetable oil and it too readily absorbs heat and wants to convert to a gas - running away from heat.
No fluid wants to stay a fluid when heat is applied as it converts to its gaseous stage - unless there is some funky rare kind out there(?)
It wants to expand away from the source of heat and energy and then condense back to its natural state when it can.
This applies to castor oil with the odd proviso that once the lighter fractions start to boil off what is left also starts to polymerize into longer chains.
But there must be certain stages where it can be quite solid and waxy at low temperatures, gaining liquidity as an 'oil' at its usable range and reverting back to a solid and charred varnish at high temperatures.
Cheers.
I just look at my BBQ plate every time that I add oil.
Starts off hot and dry, add some fluid (say water to steam clean) and it readily absorbs the heat and converts to a gas - running away from heat.
Then when hot and dry again, add some vegetable oil and it too readily absorbs heat and wants to convert to a gas - running away from heat.
No fluid wants to stay a fluid when heat is applied as it converts to its gaseous stage - unless there is some funky rare kind out there(?)
It wants to expand away from the source of heat and energy and then condense back to its natural state when it can.
This applies to castor oil with the odd proviso that once the lighter fractions start to boil off what is left also starts to polymerize into longer chains.
But there must be certain stages where it can be quite solid and waxy at low temperatures, gaining liquidity as an 'oil' at its usable range and reverting back to a solid and charred varnish at high temperatures.
Cheers.
12-29-2015, 10:35 AM
#28
Agreed Chris and Dennis...
The petroleum-base oils definitely withdraw from the heat and may also char quickly. Castor stands up to high temperatures well, relevant?
My son gave me a copy of Bill Gunston's Piston Aero Engines for Christmas, (1993, PSLtd, UK). Gunston also discussed castor used in rotary engines, and the practice of cutting it with kerosene after running to prevent gumming... The book is excellent, mostly stuff I knew, but presented in a more chronological manner. That links available materials, technology and manufacturing abilities in a "new" way, making sense of some of the horrors we've seen and heard of that were used to pull or push aircraft around the sky before 'jets' entered the picture.
My boy knows what I like!
The petroleum-base oils definitely withdraw from the heat and may also char quickly. Castor stands up to high temperatures well, relevant?
My son gave me a copy of Bill Gunston's Piston Aero Engines for Christmas, (1993, PSLtd, UK). Gunston also discussed castor used in rotary engines, and the practice of cutting it with kerosene after running to prevent gumming... The book is excellent, mostly stuff I knew, but presented in a more chronological manner. That links available materials, technology and manufacturing abilities in a "new" way, making sense of some of the horrors we've seen and heard of that were used to pull or push aircraft around the sky before 'jets' entered the picture.
My boy knows what I like!
12-30-2015, 12:08 AM
#29
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I used 20/50 motor oil for years in plain bearing PAW 2.5 and AM25 with no problems whatsoever. These were used all the time and and had gallons of fuel through them. Some of the commercial diesel fuels in England used motor oil and there was no complaints at the time. As long as the oil content is high enough - I use 25% in plain bearing engines, you won't have a problem. Glows are a different kettle of fish with the higher operating temps.
Cheers
Doug
Cheers
Doug
12-30-2015, 05:04 PM
#31
Thread Starter
I'm gonna stick with castor for the most part myself.. I have some PAG synthetic in a few different viscosities that I might use up in my ABC and AAC diesels. I have one iron/steelie that I'll use just castor in although it's pretty beat up with a gouged up piston. All the rest of my diesels are ringed or ABC/AAC.
12-30-2015, 07:37 PM
#32
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If you look at the way zinc additive protects , by forming a phosphate glass coat in the pores it should be a good thing for the big end , which is the reason they put it in automobiles.
but only took it out because its bad for catalytic converters
seeing Im not running a catalytic converter on my plane , or even in my car for that matter , the zinc must be a good thing
but only took it out because its bad for catalytic converters
seeing Im not running a catalytic converter on my plane , or even in my car for that matter , the zinc must be a good thing
01-10-2016, 05:56 PM
#33
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Once more
If you look at the way zinc additive protects , by forming a phosphate glass coat in the pores it should be a good thing for the big end , which is the reason they put it in automobiles.
but only took it out because its bad for catalytic converters
seeing Im not running a catalytic converter on my plane , or even in my car for that matter , the zinc must be a good thing
but only took it out because its bad for catalytic converters
seeing Im not running a catalytic converter on my plane , or even in my car for that matter , the zinc must be a good thing
I dont think I would try it
it may kill combustion , and I dont want that ,
my stuff is hard enough to start as it is
Some of my engine parts are made pretty rough , so its touch and go ,
As one of my flying colleagues use to say
Oh dear , There she goes again
