RE: Cox Reed Valve FAQ

RE: Cox Reed Valve FAQ
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RE: Cox Reed Valve FAQ - 5/14/2007 10:23:11 PM

liquidice

Posts: 2
Joined: 1/8/2007
From: Apopka, FL, USA
Status: offline

I just came across two new cox cylinders/pistons/crankcases to use as spares with my current engines. I noticed the fuel ports are similar to the picture of the venom cylinder at: http://www.mh-aerotools.de/airfoils/cox_venom.htm

I've placed a picture of my cylinder below(hopefully, this is my first time uploading pics). Is this a high performance cylinder?

Also, I've had a hard time finding 1/2a fuel locally so I have been using O'Donnell 30% nitro RTR. They say it has a high percentage of synthetic and castor, but won't tell me the ratios or total percentage. My question is whether this fuel will destroy my engine or is it ok to use?

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(in reply to aeomaster32)

Post #: 51

RE: Cox Reed Valve FAQ - 5/15/2007 1:26:09 AM

aeomaster32

Posts: 101
Joined: 11/4/2006
From: Maroochy River, AUSTRALIA
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First, about the fuel. I have run on as little as 5% Nitro, but settle in 10% for Texaco competitions. (Higher nitro increases fuel consumption.) As for oil, I use 20% Synthetic, but make no claims, other than to say it has worked for me so far. Unlike caster oil, you are less likely to end up with gummed up reed valves and pipes.

From your picture, I can only see one inlet port; some later engines, and hotter versions have two ports. Once again, for my purposes, one port is likely more fuel efficient than the more powerful two porter.

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Post #: 52

RE: Cox Reed Valve FAQ - 5/24/2007 7:35:24 PM

drayegon

Posts: 29
Joined: 1/15/2003
From: Redding, CA, USA
Status: offline

If the cylinder has the large opening for the exhaust take the slotted end of the wrench and after turning the prop so the piston is out of the way insert the wrench in the port and turn the cylinder off. Let me guess the cylinder is the one with the twin narrow slits. take you exacto knife and with the handle on the #11 blade insert it in the slit like you would the wrench and turn it off. You might break a blade but out of the thousand or so I have built rebuilt I never have. Course I try to make sure that I get the blade all the way from one side of the cylinder to the other. I also try to make sure that I hold far enough down the crankcase not to cut my hand off either. Do this gently as if it is cross threaded it is taking some of the aluminum from the crankcase with it already. take care dray GOSH did I say thousand motors? it may have been more than that. I quick count says I have over two hundred on my work bench right now. Hmmmmmmm

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Post #: 53

RE: Cox Reed Valve FAQ - 5/24/2007 8:01:46 PM

Tim Wiltse-RCU

Posts: 2463
Joined: 5/2/2003
From: Concord, NC,
Status: offline

liquidice,

What you have is a common Cox Sure Start engine cylinder. I can see the twin exhaust slits in it's sides. Now it's a little hard to tell from the angle in the picture but if the bottom slit on each side of the cylinder is bigger than the top slit then you would have a Killer Bee cylinder. As for the bypass porting(ports inside the cylinder) the Sure Start shares the same bypass porting with the Venom, Killer Bee and late model TeeDee .049/.051's. The difference the Sure Start has is the exhaust porting lacks sub piston induction that the others have resulting in a slower running engine. I hope this helps.

LAter,
Tim

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Post #: 54

RE: Cox Reed Valve FAQ - 5/24/2007 8:39:14 PM

MJD

Posts: 1701
Joined: 5/27/2003
From: Orangeville, ON, CANADA
Status: offline

quote:

ORIGINAL: liquidice

I just came across two new cox cylinders/pistons/crankcases to use as spares with my current engines. I noticed the fuel ports are similar to the picture of the venom cylinder at: http://www.mh-aerotools.de/airfoils/cox_venom.htm

I've placed a picture of my cylinder below(hopefully, this is my first time uploading pics). Is this a high performance cylinder?

Also, I've had a hard time finding 1/2a fuel locally so I have been using O'Donnell 30% nitro RTR. They say it has a high percentage of synthetic and castor, but won't tell me the ratios or total percentage. My question is whether this fuel will destroy my engine or is it ok to use?

Any company that won't tell you the total oil content and basic makeup (i.e. 35/65 castor/synthetic for example) is a loser IMHO. "High" oil content in car fuel terminology is not necessarily the same as our definition of the term. In which case the oil might be low for 1/2a use. If so, the engine might forgive you for a while but it is intuitive to say that the wear rate would be higher than normal. The ball and socket joint will likely suffer the most but overall the engine will be wishing it had more and will repay that thirst with shorter service life. How much shorter, 10, 20, 50%? No idea, never tried to wreck one myself (well, not intentionally).

For sport 1/2A se 15% nitromethane minimum, 20-30% better. 10% makes for finicky running in most cases. They burn so little why be chintzy on nitro content? 1/2A's drink nitromethane like milk. Sig Champion fuel with 20% oil is a good alternative if you can find that. Cox 1/2A fuels are 22% oil or so IIRC. In any case, 18% oil is sort of okay and many people use it as I have when faced with no other choice, 20% is more better and personally I would generally be content with it, 22%-ish recommended by Cox and others and I agree.

There's gotta be a hobby shop somewhere around you that carries decent fuel for 1/2A's. Or.. by any chance does this same hobby shop have a bottle if SIG castor oil? If so get some. I don't know what oil percentage this fuel you have is, but if it is 16% like some car fuels I've seen, adding 4-5% castor by volume will bump you up to 20-21%. If you find out what the oil content is by some miracle, add enough to bring it up to 21-22%.

.049/.051 sport models will fly at weights up to the low 20's in ounces - of course this depends on the design. Ther are many classic 1/2A sport models whose typical ready to fly weight was 20-22 ounces. But I cringe at those weights. For good performance you want to hit 16oz or less IMHO, and frankly with the plethora of small reliable radio gear we have off the shelf these days there is little ecuse not to hit that mark. A lot of folks here pride themselves (or at least taunt the others about it) at building sport 1/2A models at 12 ounces and less.

MJD

(in reply to liquidice)

Post #: 55

RE: Cox Reed Valve FAQ - 5/24/2007 11:16:51 PM

aeomaster32

Posts: 101
Joined: 11/4/2006
From: Maroochy River, AUSTRALIA
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Quote:For sport 1/2A se 15% nitromethane minimum, 20-30% better. 10% makes for finicky running in most cases. They burn so little why be chintzy on nitro content?

Just to be clear, in my case it is not the cost of the nitro that is the issue. It is the duration of the engine run. The longer the run, the higher you get, and in a competition, that makes a difference. Certainly for sport use, more nitro may help with better running. From what I understand, increasing nitro, inceases fuel consumption.

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Post #: 56

RE: Cox Reed Valve FAQ - 5/25/2007 2:56:34 PM

MJD

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From: Orangeville, ON, CANADA
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quote:

ORIGINAL: aeomaster32

Quote:For sport 1/2A se 15% nitromethane minimum, 20-30% better. 10% makes for finicky running in most cases. They burn so little why be chintzy on nitro content?

Just to be clear, in my case it is not the cost of the nitro that is the issue. It is the duration of the engine run. The longer the run, the higher you get, and in a competition, that makes a difference. Certainly for sport use, more nitro may help with better running. From what I understand, increasing nitro, inceases fuel consumption.

Yup, I know in your case you're talking Texaco competition which is a whole 'nother matter. My comment about being chintzy on nitro wasn't actually directed at your post or any other, it is just my general philosophy towards choosing 1/2A fuel. My comment about 10% being finicky was however intended to clarify that it isn't really a good choice for a sport Cox 1/2A fuel, in case someone got that impression. All my past experience with Coxes has taught me not to bother with anything less than 15%.

You're right, specific fuel consumption does increase with higher nitromethane content, since the correct fuel to air ratio increases.

MJD

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Post #: 57

RE: Cox Reed Valve FAQ - 5/27/2007 9:44:26 AM

bigtim

Posts: 2338
Joined: 5/31/2004
From: san francisco, CA, USA
Status: online

another question for the knowledgable any tips for repairing over drilled back plate holes,I would think that something like JB Weld would work to fill them in so they can be re-drilled, but if anyone has a better idea that would be great to hear it.
BTW, Virginia Hobby sport great people to work with got some parts for a engine and also picked up a goldberg kit for a great price nice tip.

< Message edited by bigtim -- 5/27/2007 9:48:59 AM >

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Post #: 58

RE: Cox Reed Valve FAQ - 5/27/2007 9:44:43 PM

drayegon

Posts: 29
Joined: 1/15/2003
From: Redding, CA, USA
Status: offline

Their is no big deal when you re anodize these items. First off you have to stip the old anodizing off the item. then you polish it. the you anodize it and you dye it then last you must seal it so that UV does not destroy the coloration and fuel also does not discolor the dyes used. Any commercial shop that does either rebuilding or restoring of these types of parts knows what and how to do this stuff. take care dray

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Post #: 59

RE: Cox Reed Valve FAQ - 7/19/2007 8:18:52 PM

mtntopgeo

Posts: 189
Joined: 2/21/2004
From: Superior, MT, USA
Status: offline

Hi guys, I'm new to this cox thing, so please try to tolerate my total ignorance. ... I have what i think is a "Sure Start" in a box of stuff that I got with another engine purchase. A blast of WD 40 (inside & out), a little work on the needle (straighten, taper the blunt end, & replace the spring with a piece of fuel line) and it was ready for the start-up. It came with a Thimble Drome 5.5x4 prop on it, & that is what I used with 15% nitro, 20% all-castor fuel. Started out with a max of 8,600RPMs, & after a couple of minutes, the max that I could get was 11,600 RPMs. Changed prop to a MAS 5.5x4, and the Max RPMs increased to 12,200. I looked at one of the sites, listed on this thread, (black widow test) & the RPMs were considerably higher. I searched around, but couldn't find any results for the Sure Start. .................Questions

(1) Are my numbers near average for this engine? (Seem low to me)

(2) If the numbers are low, am I using the wrong prop/fuel?

(3) If the numbers are normal, what size plane (just for sport/fun flying) would I put this engine on. I would hessitate about putting
it on a 14 oz simple series. (maybe a 11 oz 280 electric such as the Mini Sport?)

I realize that this is only a $7.00 engine, but if it could carry something in the air, I'd like to give it a try. ............... George K.

< Message edited by mtntopgeo -- 7/19/2007 8:32:11 PM >

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Post #: 60

RE: Cox Reed Valve FAQ - 7/19/2007 11:51:50 PM

aeomaster32

Posts: 101
Joined: 11/4/2006
From: Maroochy River, AUSTRALIA
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Those figures seem a bit low. I can manage near 8000 on a Master 7x4. It may be that you have a throttled effect. Somehow the air or fuel is restricted. On 5cc of fuel it is normal to go 2:30 with a 7x4. See how your fuel consumption compares.
Remember that the more wing your plane can fly on, the less it depends on engine power to keep it going.

< Message edited by aeomaster32 -- 7/19/2007 11:54:17 PM >

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Post #: 61

RE: Cox Reed Valve FAQ - 7/20/2007 6:27:16 AM

burtcs

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Joined: 12/20/2004
From: Corvallis, OR, USA
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mtntopgeo:

I bought a couple of SS's when they were availible, not a hog but for sport flying and personal use. With a Cox 5-3 prop and 35% nitro (25-35% is good) with the std. glow head I got about 17.5K ( I suspect this is the norm). I changed out the glow head for a Galbreath head and Nelson glow plug, fired it back up and got 18.5K. Your milage may vary with a nitro and a 5-4 prop but that is quite a discrepency.

regards - Steve B.

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Post #: 62

RE: Cox Reed Valve FAQ - 8/2/2007 3:07:28 PM

Yuu

Posts: 327
Joined: 9/4/2006
From: Shawano, WI, USA
Status: offline

George...15% fuel and 12,000 rpm isn't bad. That's about what I get here in WI at 800' above sea level. But up in the mountains, your mileage may vary. And it may loosen up a bit too. Fly it... it's good fun.

(in reply to burtcs)

Post #: 63

RE: Cox Reed Valve FAQ - 8/4/2007 5:05:54 AM