stunthanger.com
Engine basics => Engine set up tips => Topic started by: rob biddle on December 30, 2011, 11:36:05 PM
-
Hi all,
I wasn't sure if I would be better off posting this in the 1/2a section or not but I was just wondering what is considered the best "standard" fuel brew for a cox 0.020?
I picked up a new unrun 0.020 off junk-bay cheap a few years ago and my new place has enough room to fly it in the front yard. 8)
Cheers, Rob..
-
Yup. Lots-o-nitro, lots-o-oil. You don't need 25% nitro -- while it's been years since I've fired up my pee-wee, I remember it running just fine on 15%. 25% oil wouldn't be a bad idea, though.
-
Thanks Guys,
Would I be right in assuming the oil content should be mostly castor?
Rob..
-
Rob, I run 1/2 A all the time and 1/4 A. I'm a big fan of Sig Champion fuels. I use 35% nitro for all my 1/2 A needs. They do make 25% as well. This fuel keeps these engines running beautifully. It keeps them clean as well. I can let them sit months and no stuck reeds usually. The blend is 50/50 Klotz and castor oil 20% total content. It works better than any fuel I ever used. This can be purchased by the quart through Sig. I receive it in the mail a few days later. Ken
-
When you use 35% fuel and call Sig and ask them what to do so it won't melt your Sig dope finish, they'll tell you to use 20% nitro fuel -- and that it'll work fine in a Cox engine (the fuel, not their dope).
Just sayin' (from experience).
-
Just for the record, no dope finish is impervious to our fuels. Sig holds up the best and their Lite-Coat in my opinion is the best as far as fuel resistance. 10% fuel if not immediately wiped up will cause discoloration. If your in search for a finish that will hold the test of high nitro, www.nelsonhobby.com will provide you with the paint that will do so. I use it with 40% nitro using their crosslinker and it eventually fails but this takes a good while. The water based polyurethane finish stands up to 10% without using the crosslinker. For higher nitro it is a must to use the crosslinker. Yes these engines will run on low nitro but funny thing start to happen. Engines aren't as reliable, needling can be finicky as well. True I would certainly opt for the lowest nitro to suit your needs due to the fact plugs aren't cheap. High nitro doesn't require high compression therefore the engine may require several head gaskets. The state of the engine will also indicate what nitro you may need. Until I was familiar on how to tune these engines, I would virtually rip the filament out of the plugs and this was with 25% nitro. Cox plugs work but they certainly don't have a long life span. The Cox .020 heads are also now available again through Xenalook. Like all glow plugs currently, they bring a higher price than what you probably remember paying for them. Cox standard fuel was 25%. The racing fuel was 30%. Many factors dictate what nitro is needed. I was just stating that Sig is readily available and you certainly are getting what you pay for. Hobby shops in these parts are quite scarce. The last time I recall a hobby shop in this area even having fuel for Cox engines it was quite expensive for the 8oz. bottle. Those days are far gone and the internet seems to be our hobby shop for most of us. Ken
-
I run my 1/2A, 1/4A, and 1/8A engines on 25% Nitro, 25% Castor Oil fuel. Works great, except it can glue down reeds if the fuel system is not flushed with a bit of Alcohol after the running is done for the day. H^^
Pat
-
Thanks Guys,
The local toy shops (I'm a bit loathe to call them hobby shops) here don't stock anything suitable. Unfortunately it's all about plastic clad arf r/c trainers and 3d models or r/c buggies.
With all the hazmat rubbish associated with australia post it's easier to mix my own from scratch.
Cheers, Rob.
-
If they cater to the nitro-power RC buggy trade at all get a bottle of that stuff and doctor it up with enough castor to bring the oil content up past 22%. That fuel will tend to lots of nitro and not much oil, so after you finish putting in enough castor you'll definitely have more fuel than you started with. My understanding is that you really want "de-gummed" castor, but drug-store castor has worked for me.
The better quality of motorcycle racing shop will have castor oil, at lower prices than the drugstore. You can tell if a motorcycle racing shop is of the better sort by asking them if they have castor oil -- if they say yes...
In the US, Sig has castor for $23/gallon, and I don't believe that it gets charged a hazmat fee. But I have no idea what the situation is in Oz.
-
Rob, didn't realise you were an Aussie. Castrol M castor is fairly readily available but price can vary widely so shop around. The best bet if you want 5 litres is from this ad that I've copied from the Vic Stunt newsletter with some non essential stuff deleted.
Highest quality first pressing de gummed.
$45 for 5 litres
(including container) + P&H
$10 in Victoria
Ph Ken 03 9398 8244
Email: combtkid @ hotmail.com
Although I've never flown a model with a Cox engine, I ran 3 .049's (two reedies and a Tee Dee) on the bench just so I could say I've started a Cox and all gave one flick starts and were quite easy to tune with 80/20 fuel. I'll admit though that I didn't run my new Tee Dee .020 so I can't say how it'd run with no nitro. Worth a try though :).
-
Thanks Brian,
That'd be Ken Maier (sp?), I've met him a few times at knox. Nice bloke, a couple of the local boys have used his castor.
Seems like good stuff.
Cheers, Rob.
-
The best fuel that I used that was cheap enough is Byron 45% add oil to suit. There is no such thing as too much nitro in small engines they run too cold. we used to use up to 70% in TD's at one time. It was fun and sometimes you blow one up. Rev up 4/7 was the prop of choice.
Dennis
-
There is no such thing as too much nitro in small engines they run too cold.
Can you explain what's meant by running too cold? I'd read that when using too little (or zero) nitro the plug would go out from lack of heat and that was one of the things that got me curious enough to try running my .049's with my usual 80/20 fuel. One flick starts, no rev drop when power was disconnected, runs rich in a 4 stroke with no signs of the plug fading away. In other words, to me they seem to handle just like any other much larger engine. Naturally you'll get more power (revs) with nitro but that applies to all engines.
-
Brian. Yes, you can run a 1/2A on low nitro fuel and it will start and run but it isn't fun as the power is not there. Nitro also made getting a setting much easier. Also consider if you one who uses a 6/3 prop on a 1/2A it doesn't hurt to give the little critter a bit of help.
Cox fuel when I was young was 25% nitro for sport and the Red can was 30%. Cox didn't sell those percentages capriciously. They wanted to make sure that you got maximun enjoyment and easy starting with their product
-
Brian. Yes, you can run a 1/2A on low nitro fuel and it will start and run but it isn't fun as the power is not there. Nitro also made getting a setting much easier. Also consider if you one who uses a 6/3 prop on a 1/2A it doesn't hurt to give the little critter a bit of help.
Cox fuel when I was young was 25% nitro for sport and the Red can was 30%. Cox didn't sell those percentages capriciously. They wanted to make sure that you got maximun enjoyment and easy starting with their product
I agree with Dennis, I run 25% to 30% nitro and they run real nice. I never had any fuel for them that was higher then 30% or I would have used it. IIRC, the Cox fuels had 18% castor. I would add a couple ounces of Klottz to a quart to help keep things clean. Now that I understand Randy's fuel recommendations, I see the need for synthetic and castor with the total oil content being the key.
BIG Bear
RNMM/AMM
-
Thanks Guys,
I'm gonna try mixing some up with 25% nitro, 25% oil (50/50) and see how it goes.
I just remembered about 25 years ago we used to buy 125ml bottles of 'Blast Off - Rocket Fuel' we used to run our reed valve .049's on it.
From memory I think it was 25% nitro and 25% all castor, had totally slipped my mind until I was discussing it with 1 of my old high school mates yesterday. :)
Cheers, Rob..