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Fuel for Cox .049


gowen
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This is my first time posting here, so apologies if I'm treading old ground.  I did a search and the only thread that comes close is "Techpower 5 v Optimax".

 

Since restarting the hobby, I have only flown electric.  I recently came into possession of a Cox .049 Queen Bee and I though I'd put it in a vintage style airframe. 

 

Researching the fuel requirements for this engine, It seems I need 20% to 30% nitro, and 20% lubricant of which, at least 10% must be castor (https://www.mh-aerotools.de/airfoils/documents/cox_049_operation_and_troubleshooting_guide.pdf)

 

Model Technics GN-25 or GX-25 would have been ideal, but is no longer available and I can't find direct alternative.  I contacted Den's model supplies, as a seller of Cox engines and he recommended buying Big Bang 25% and adding 10% castor oil.  The problem is that Model Technics Castorlube is out of stock everywhere is all can sizes.

 

So the question (finally), Does anyone:

 

1. Know where I can buy some castorlube.

2. Suggest and alternative brand of castor oil.

3. Suggest an alternative fuel that is available.

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Gowen, welcome.

My opinion, caster oil smells nice, will clear yer pipes right quick if you haven’t been eating enough fiber, and makes a nice tahini. But it’s ancient technology, and has been replaced by modern synthetic oils, and has no place in a fuel. 
I would use a 20 to 30 % nitro methane fuel, and whatever synthetic oil it comes with, but to be cautious, I think I would want 15% plus in there.

The Big Bang is good to go as it is.


 

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The fuel of choice for Cox engines back in the day was Nitrex 15. They seemed quite happy on this mixture, I'm not sure about the lubricant, it had 15% nitro which seemed enough. Fuel with 30% nitro needs an explosives licence in the UK and they are thinking of lowering it to 16%. I met a guy in the states who was using 45% nitro in his but this was excessive and unnecessary.

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Yamada Mix (Model Technics) is 20% nitro plus 23% Klotz synthetic but do not know if Optimax will continue it. Southern do a 20% nitro plus 20% synthetic but a gallon of either would last several lifetimes in a Cox. As has been said above, 15% nitro is plenty, other than on the Cox 010.

Must fly my Queen Bee sometime. It is in a Mini Blitz.

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Back in the 1960s, when Cox .049 engines were everywhere, we used Nitrex 15. 

This had 15% nitro, and the little engines happily screamed into life with their instantly recognisable,  high-pitched note. 

 

From recollection, they were quite fussy about fuel.  They didn't run well on anything less than 15% nitro. 

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Just found this.

IMO, there's some confusion in the OP.

A Cox Queen Bee is an .074, not an .049, so which are we discussing? Is your engine a Queen Bee or is it an .049?

Whichever engine it is, and in spite of the dogmatic remarks made above, IMO, you'll need some castor in the fuel.

IIRC, KK Nitrex (in the UK) and the original Cox fuels (in the US) both used castor.

Edited by brokenenglish
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BTW I had the same engine bought around the 1980's, I used it, mounted inverted, to power Henry a small motor glider. As related below & contrary to perceived wisdom the engine ran happily on straight (zero nitro) 80/20 fuel most of the time I owned it until I sold it.

It was my habit to pop Henry in the car to have a few flights after flying my larger models, if the wind wasn't too strong. I generally used straight fuel (zero nitro) for the larger models & carried a small can of 10% nitro for Henry. As sod's law would have it one thermal promising day I got Henry out only to discover that I'd forgotten the 10% fuel can. With nothing to loose I filled Henry's tank with zero nitro fuel then was surprised when the little Cox started quite easily & ran well. There was little if any noticeable difference in the power so from then on the engine drank straight fuel. 

 

Henry.thumb.jpg.3d8f7c1f0d879926271cfc7ca806a4a7.jpg

 

Henry in later life converted to a civilised power unit - 400 can motor with 7 nicads.

 

Incidentally, I believe KK Nitrex 15 fuel didn't actually contain 15% nitromethane. IIRC, either Ron Waring or Peter Chinn wrote that it had about 5% nitromethane plus an unnamed substance that gave it the claimed equivalent of 15% nitromethane. The name was a marketing title.

Edited by PatMc
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2 hours ago, Martin Harris - Moderator said:

I was wondering about the perceived wisdom of high nitro requirement for these engines - ISTR running the Cox .049 on a power pod attached to my Graupner Amigo (perfect for full power touch and goes) on normal straight (castor) fuel back in the 70s - and I  don’t recall any starting or running problems…

They will run on  low nitromethane fuel. If the operator is capable of running it in a smaller window of success. It’s just easier to run it with a lot of nitromethane. Runs cooler, less fussy on the needle.

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2 hours ago, Don Fry said:

They will run on  low nitromethane fuel. If the operator is capable of running it in a smaller window of success. 

What's the heck's that supposed to mean ?

Use the same start process as with high nitro fuel, adjust the needle in the same way & it works. Couldn't be easier.

Edited by PatMc
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9 hours ago, PatMc said:

What's the heck's that supposed to mean ?

Use the same start process as with high nitro fuel, adjust the needle in the same way & it works. Couldn't be easier.

I love you Pat. Needle valve settings are less critical with more nitromethane. Nitro methane also helps cooling. All a help if your ear, or experience is suboptimal.

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On 18/07/2022 at 11:34, Andy Stephenson said:

The fuel of choice for Cox engines back in the day was Nitrex 15. They seemed quite happy on this mixture, I'm not sure about the lubricant, it had 15% nitro which seemed enough. Fuel with 30% nitro needs an explosives licence in the UK and they are thinking of lowering it to 16%. I met a guy in the states who was using 45% nitro in his but this was excessive and unnecessary.

Explosives precursor and poisons licence is what you need ,not an explosives license which is something totally different, very different in how they are acquired and renewed. The explosives license has a Firearms officer come and do an interview and the EPP is acquired though the Home Office. Both are relatively easy to acquire if you have nothing to hide.

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