On Thu, 10 Aug 2006 21:57:54 -0300, "jtaylor"
><[email protected]> wrote in message
>> Castor bean oil was essential to rotary engine planes in the First
>> World War. It's still hard to beat for 2-cycle engines, if you can
>> stand the smell.
>It's not that hard to beat any more, especially if you consider that few
>motor-cycle owners are willing to take their cylinder heads apart at the
>frequent intervals required to decarbonise the pistons and rings; castor oil
>is notorious for gum formation.
>Modern tribology has better solutions.
True, castor oil has its problems, but it still seems to be essential
in radio-control miniature aircraft engines:
"Two-stroke fuel has three major ingredients: methanol, castor oil,
and nitromenthane (nitro). Methanol comprises 60%-75% of most fuels.
It burns completely and adds to the fuel’s total energy output."
"The lubricating oil comprises roughly 20% of the fuel. Most
two-stroke fuels contain two types of oil; 4%-8% is usually castor and
the remaining 12%-16% is a synthetic that varies by manufacturer. Oils
typically do not burn completely, and what small percentage of the oil
that does burn does so at lower energy levels than methanol."
"Castor oil is used because it maintains a lubricating film at higher
temperatures than most synthetic oils do. If the engine’s high-speed
fuel/air ratio is too lean—too much air—the engine will run at high
temperatures. Castor oil will maintain lubrication in an overheated
engine; most synthetic oils burn away."
"Castor oil also helps remove heat from the combustion chamber better
than most synthetics. Castor oil leaves a film residue in the engine
that offers some rust protection. Most synthetic oils do not."
"However, too much castor oil causes excessive residue buildup that
can diminish an engine’s performance. Because castor oil does not
burn, it reduces the fuel’s total energy output. For these reasons,
the castor oil percentage is usually kept at less than 8%."
"Synthetic oils do burn, but not well or completely. Little synthetic
oil residue is left inside an engine. Synthetics also offer excellent
engine lubrication when operating at normal engine temperatures."
"Because high oil content detracts from the fuel’s total energy
output, the easiest way to increase an engine’s apparent power output
is to reduce the fuel’s oil content. However, oil contents much less
than 18% can cause long-term wear problems in .40-.60 sport engines."
"Fuel manufacturers are studying new oils that produce more power and
offer better protection with quantities as low as 16%. But for now,
consider using fuels with 18%-20% oil content in newer or
sophisticated (expensive?) .40-.60 engines."
"The third fuel component is nitromethane. It burns at a higher energy
level than methanol. However, it also produces higher
combustion-chamber temperatures and therefore needs to be limited.
Most sport fuels contain 5%-25% nitro. It prolongs the combustion
event. The burning process takes longer, and that also produces more
I doubt that I'd smell castor oil at a modern motorcycle observed
trials event, as I did back in the '70's, but you can still smell the
castor stink at R/C strips.
Just as you can't turn a cat into a vegetarian, you can't run those
waspish little glow-plug engines very well without castor oil.