Fuel and lubricating oil

[MikeN]

I am building the Bentley BR2 rotary/radial engine to the L K Blackmore design.
With this design, Petrol is drawn in from the carburettor through the hollow crankshaft in to the crankcase where it mixes with the oil  to lubricate the working parts before being transferred to the cylinders for combustion.
The book of instructions says to run the engine on lead free fuel that contains no methanol ( I'm guessing ethanol as well?).
Lubricate with castor oil . Castrol R30.
My question is:
As an alternative, Can I run it using 2 stroke oil and any pump fuel?
I feel this would be more convenient as I recall reading somewhere in the past that Castrol R is a bit messy and leaves unwanted deposits ( but smells lovely!).
Thanks Mike

[Roger B]

Methanol and ethanol containing fuels tend to absorb water which can cause corrosion problems, especially when they are distributed through the engine.

[Admiral_dk]

Ethanol is part of Normal Pump Fuel 

A good alternative is Alkylate Gasoline - sold under a number of names all over the World and often in DIY and Garten centres - for Generators, Lawnmowers, Trimmers and Chainsaws.

Per     

[MikeN]

Thanks for the replies.
It seems I can buy ethanol free fuel from a nearby boat marina.
However my main question was, can I run this engine with 2 stroke oil instead of castor oil ( Castrol R)?
Thanks

[Vixen]

Don't get over concerned about ethanol free. Standard pump petrol will run most engines.

Castrol R will eventually gum up most engines, but it smells great. Use a low sulphur synthetic car engine oil or 2 stroke oil instead.

Mike

[AlexS]

Couple of months ago questions send on Castrol technical about use of mineral or synthetic oil on old two strokes. His answer there is difference on viscosity, mineral is 2 times thicker cold and get much thinner when hot. Synthetic stays stable and reach critical places faster when engines are cold too. But synthetic oils contains esther, what could cause hardening and cracking of crankshaft seals if they are older or lower quality. Modern mineral I guess would be better mixing with A/F and reducing residue than what used in 50 years ago. Also tolerance old or model engines are larger. See Elf has a lot of different two stroke oils and mineral is "pre mix" is cheapest compared to castrol power RS.

[Vixen]

The OP (MikeN) wants to run his Bentley BR2 rotary/radial engine built to the L K Blackmore design. This is a four stroke engine with a total loss, pumped lubrication oil system. It is not a two stroke requiring pre-mix fuel.

The Bentley BR2 should run well on standard pump petrol and any good quality lubricating oil. Modern synthetic engine oils or 2 stroke oil will both burn cleanly, leaving minimum ash or other deposits within the engine.

Castor oil was used back in the days before modern lubricating oils were developed. Castor oil was and still is an excellent lubricant but unfortunately leaves gummy deposits when burned. The gummy deposits cause the piston rings to stick in the piston grooves as well as coking up the combustion chamber.

Mike

[MikeN]

That's what I was hoping to hear Vixen, thank you.
The engines not finished yet although almost everything is made now. I'm hopefully about to start the final assembly .
I've been turning it over on the lathe for a couple of hours to run it in a bit  (Blackmore recommends 8 hours on the lathe!!).
I've spent the day dismantling and degreasing it (yet again) so wanted to know what oil to assemble it with.
With 9 , 18 or 36 of everything it takes hours every time I take it apart to make an adjustment then reassemble it!

[Vixen]

I've spent the day dismantling and degreasing it (yet again) so wanted to know what oil to assemble it with.

Use the same oil you intend to run it on. I would go for a modern synthetic car engine oil.

Mike

[petertha]

I am building the Bentley BR2 rotary/radial engine to the L K Blackmore design.

I have the Blackmore book & looked up the compression ratio out of selfish interest. Its stated as 5.6:1. In my inline-6 thread I was wondering out loud about CR for gasoline specifically because it also has horizontal side entry spark plugs. This orientation can limit piston height at TDC (crossing over the hole) & thus CR. I was of the understanding our engines 'needed' 7:1 - 8:1 as a target & that lower CR was more reserved for low RPM stationary or hit & miss class. But this Bentley CR is a data point that contradicts the rule of thumb.

Sorry for the side tangent MikeN but did you use the same (1/4" nominal) sized spark plug bodies?

Just to throw my 2-bits into the oil discussion, even though methanol/glow engines seem to be receding in popularity for a number of reasons, castor was giving way to synthetic for quite some time. In some of the more demanding applications, fully synthetic was thought to perform better. Some blends had some castor but majority synthetic. Of course, different opinions. Sometimes its what the market wants. I also heard it had an indirect benefit of assisting miscibility, but this was above my pay grade. Everyone agrees castor it creates unwelcome varnish inside the engine which is PITA to remove.

[AlexS]

excuse I read the message wrong

[Charles Lamont]

I have the Blackmore book & looked up the compression ratio out of selfish interest. Its stated as 5.6:1. In my inline-6 thread I was wondering out loud about CR for gasoline specifically because it also has horizontal side entry spark plugs. This orientation can limit piston height at TDC (crossing over the hole) & thus CR. I was of the understanding our engines 'needed' 7:1 - 8:1 as a target & that lower CR was more reserved for low RPM stationary or hit & miss class. But this Bentley CR is a data point that contradicts the rule of thumb.

ET Westbury side valve engine designs, Whippet, Seal, Seagull etc have a considerably lower CR than that. Somewhere around 4:1 for the Seagull.

[LANTAIN1982]

H

[LANTAIN1982]

HI MIkeN.
I have been running my BR2 for some years now.    Use 91 octane ex the pump,  lubricate with Medical grade Caster oil with a dash of metho in the tank to thin it down.     Engine is now longer shiny, but starts on the first swing after priming, but the smell when running is something to make it all worth while.
All the best with the engine.

[petertha]

ET Westbury side valve engine designs, Whippet, Seal, Seagull etc have a considerably lower CR than that. Somewhere around 4:1 for the Seagull.

Thanks Charles. Wow I did not realize that. Here my thread if you are interested & so I don't tangle this one up any more than necessary.
https://www.modelenginemaker.com/index.php/topic,12594.45.html

[GordonL]

Not to infringe on another's post but I have been using naphtha with miracle oil but I have just been adding a bit to the bottle and cannot remember what the ratio is supposed to be. Anyone know what the recommended ratio should be? Maybe I should try castor oil. I have never used it.