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Old Sep 24, 2014, 09:39 PM
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Official Cox .049 Questions Thread!

This thread will probably be ongoing for a while.

I'm getting ready to get about four Cox "Black Widow" .049 powered airplanes up in the air. The plane kits are already ordered and I'm putting together a Sig order for the needed building supplies/dope/etc.

I've got several Cox questions to run past you guys over the next while.

First question:

In the dateless past, I simply used Fox Missile Mist (20% nitro I think?) for our Cox .049 engines. (Black Widows, TD's.) Worked fine. Some thought it was too oily, but like I said, worked fine. HOWEVER (and it is a BIG however)...

Missile Mist is no longer available.

Plus, I only have about a half gallon of Missile Mist left over from "way back when". It's time to find a new .049 fuel that really starts/runs great and lubricates the little engines nicely.

SUGGESTIONS?
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Old Sep 24, 2014, 10:17 PM
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For sure this isn't going to be your final answer but a couple of years ago I decided it was about time I ran some Cox engines seeing I'd been given quite a few. I tried a Babe Bee, a product engine with the twin transfer ports and a Tee Dee. All could be started with one flick, ran perfectly smoothly and could be tuned to run anywhere from a 4 stroke to flat out. The fuel was just a plain 80/20 all castor mix. Obviously they'll give more power (revs) with nitro but they certainly don't need nitro.
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Old Sep 24, 2014, 10:49 PM
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Hi downunder!

Thanks for the input. Nitro is hard to come by 'round these parts (USA). Very tightly controlled substance. So... could be that one of these days all us Yanks will be using FAI fuel.

All:

Okay... done some research. Cox International has a fuel guide page that quotes the original Cox recommendations on nitro/oil percentages and oil type. They then go onto a amend it a bit to allow for available fuels. (See below.)

Here's the link:

http://coxengines.ca/files/FG.pdf

Bottom line: Cox recommended a fuel with at least 20% castor, and at least 20% nitro. (No wonder my use of Missile Mist worked out so good. It's might nigh perfect!)

Cox Int'l goes on to amend the above by saying that since you can't find such fuel premixed, at the least use a 20% 50/50 mix of castor/synthetic.

On their recommended fuels list is Sig Champion at 25% nitro, and 20% 50/50 oil.

I'm a little uneasy with using a fuel with blended oil. I've been a strong pro-castor oil advocate since day one. But what's a guy to do?

Anyway, on the Sig order list is a 1/2A Flight Pack that contains the above fuel along with other goodies aimed at making life easier for 1/2A flying.
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Old Sep 25, 2014, 12:09 AM
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I have found that Sig fuel works the best in Cox engines with Brodak's 1/2 A fuel second. Other fuels can be found for 1/2A cars in quite a few hobby stores that specialize in gas cars.
I would not use OLD fuel as some parts evaperate and others break down.
Larry
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Old Sep 25, 2014, 06:27 AM
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Ritches Brew sells high nitro all castor mixes, and can blend to suit.
http://www.ritchsbrew.com/pricing.html
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Old Sep 25, 2014, 08:42 AM
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Hi Fella's!

Seeing as I have s significant supply order going off to Sig soon, I figure I'll just go with Sig and be done with it for now.

As for Rich's Brew: The Cox-recommended 20%-25% nitro w/20% castor isn't offered by Ritch's, and I doubt I'll bite the bullet ($$) and get a custom mix.

I do have some Missile Mist left and I've run it in 1/2A's with good success in the past. Seeing as I will not be using it in my fleet of 36X's anymore (limiting them to 10% nitro w/castor), no need for it to just sit. So I may use it up, too. We'll see.

NEXT QUESTION:

I see that Cox Int'l offers three types of reeds: Stainless steel, Mylar, and Teflon. All of my Black Widows need to be rebuilt w/gaskets/O-rings/reeds/etc, so the next question is:

Which reed material would you go with?
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Old Sep 25, 2014, 09:45 AM
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Quote:
Originally Posted by LA Ming View Post
Hi Fella's!

Seeing as I have s significant supply order going off to Sig soon, I figure I'll just go with Sig and be done with it for now.

As for Rich's Brew: The Cox-recommended 20%-25% nitro w/20% castor isn't offered by Ritch's, and I doubt I'll bite the bullet ($$) and get a custom mix.

I do have some Missile Mist left and I've run it in 1/2A's with good success in the past. Seeing as I will not be using it in my fleet of 36X's anymore (limiting them to 10% nitro w/castor), no need for it to just sit. So I may use it up, too. We'll see.

NEXT QUESTION:

I see that Cox Int'l offers three types of reeds: Stainless steel, Mylar, and Teflon. All of my Black Widows need to be rebuilt w/gaskets/O-rings/reeds/etc, so the next question is:

Which reed material would you go with?
While the small Cox engines may run on zero nitro, they don't run well. I wouldn't (and don't) run anything less than 15% nitro and preferably 20-25%. I run the Sig fuel that is 20% oil, 1/2 castor half synthetic. I usually add a little additional castor oil.


Mike
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Old Sep 25, 2014, 01:52 PM
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Originally Posted by pmackenzie View Post
Ritches Brew sells high nitro all castor mixes, and can blend to suit.
http://www.ritchsbrew.com/pricing.html
Randy Ritch is a very accommodating guy. I've used Ritch's Brew off and on for 40 years, used to sit around Dickie's garage in Houston while he mixed it up . . Randy was in elementary then, maybe I was visiting as far back as Kindergarten. He and my kid are friends.

Give him a call, Andre, tell him I suggested you do so, and if Jeff hasn't mentioned my handle lately, you don't have to tell him it's "Kiwi " since probably won't know me that way, more likely it's "Jeff's Dad", he'll tip to. Cox engines work BETTER, in my opinion, on less castor, and a half and half lube mix keeps them a helluva lot cleaner.


Kiwi
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Old Sep 26, 2014, 04:34 AM
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I can answer your reed questions. For the style of running your looking for, I feel the stainless reed is your best bet. My best performers however used the Mylar. Problem with the Mylar is that it will try and suck down the hole in the venturi. While this sounds bad, the stainless does it as well and it to will distort. The Teflon reeds in my opinion have never worked well for me. I damaged a engine as two reeds were stuck together perfectly and I assembled thinking it was one. The circlip popped out during a run and just beat things up bad. I never have had any appreciable advantage using them so I stick with the standard.

The key to success is testing your reed prior to assembly. This means using a large syringe with the plunger withdrawn. Hook the syrings to the o-ring side of the venturi on the tank back with the reed installed. Push the syringe which will force the reed outward allowing you to expel the air. Now try and withdraw the plunger of the syringe. You shouldn't be able to do withdraw at all. No leaking what so ever should be present. If so, try another reed or flip that particular one over and try again.

Another tip is to fill in the v-groove of the tankback using a piece of dental floss. Wetting the dental floss allows it to stay in place while assembling and this provides a gasket between your tank and backplate. Once assembled, close the needle down and pressurize your tank through the filler pipes with the syringe capping the underside using your thumb. This will tell you if the o-ring is leaking and or tank/ neeedle valve/ and backplate screws. If the backplate screws are leaking, a simple fix is to remove the screw in question and tear off a piece of Q-tip, roll the cotton in your fingers into a thin strip and wrap onto the screw threads. This will serve as packing and is also service removeable unlike gasket maker. Ken
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Old Sep 26, 2014, 09:43 AM
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Thanks Mike and Kiwi!

For now I'll use the stuff that Sig is sending me in my measly little $180.00 order. (And that's only parts and supplies! They have a lot of cool stuff in their catalog... way too easy to spend the loot. )

This just in: A C/L friend says he's got a can of fresh Cox Racing Fuel he'll give me when I get to the Tulsa Gluedobbers contest tomorrow. Now how cool is that?

Ken:

Thank you very much for sharing your excellent experiential advice. I think I will purchase both the stainless steel and Mylar and piddle to see which seems best for my engines.

NEXT QUESTION:

Some of my Black Widow cylinders have unobstructed exhaust ports. Others have "slits".

Which is preferred? Can I just slap on some Tee Dee pistons/cylinders and be done with it? Or, would the limiting ability of a vibrating reed make any extra transfer port depths/volume negated and so just stick with the Black Widow piston/sleeves?

My goal is to have all of the batch of engines perform reasonably close to one another with no "one offs".

EDIT: I note at the Cox Intl' site that there are cylinders with "Sub Port Induction" that are also available. ??? Is this better than the basic Black Widow cylinder for the reed equipped Black Widow engines?
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Old Sep 26, 2014, 04:53 PM
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The Cox slit style cylinders that are sold by Cox International is the left over Cox inventory prior to Cox going defunct. These cylinders were referred to as Sure Starts. I'm a personal fan of the earlier versions from the 70's and 80's. These were the open port cylinders you mentioned. Cox did however make the slit cylinders in the 80's and I have one of them in my collection. Bernie from Cox International now offers the slit style cylinders with the slits removed. This sometimes needs a little attention and de burring. As for the performance, they can really turn up nicely.

The Sure Start cylinder however does have a transfer port alongside of the
bypass. This particular porting in similar to a TD. While not exactly TD performance, they can be pretty close. One major problem with the Black Widow is the crankcase itself. I've worn out many cases . My solution was to bush the case similar to the cases Kustom Kraftmanship offered. If you were to install a TD cylinder onto the Black Widow, I would make sure it's already run in a bit. Essentially, your asking to do what the mouse racing crowd has already done.

Performance and reliability can be further enhanced by using a Merlin plug setup or my choice which is the Nelson/ Galbreath head. You can purchase 3 Merlin plugs and the head clamp for $15. A Galbreath head is around the same but you would need the plugs . Ken
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Old Sep 26, 2014, 06:53 PM
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The ones with no sub piston induction work better with a muffler. I have one black widow with the two slits, and oddly enough, it seems to go pretty good. I haven't tached it to compare. I think the slits were to stop brush fires?
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Old Sep 26, 2014, 08:19 PM
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Hi Ken.

Thanks again for your detailed and knowledgeable reply.

All the different cylinders have me a bit confused.

My goal is to have all the Black Widows on equal footing in case we want to tie on some little 1/2" x 6' streamers and play combat. I have three complete BW's and the front end assembly of another (which would need a tank assembly). All of my BW's are from the Cox era. Some purchased in the very early 80's, one in the mid-later 80's. Those purchased in the early 80s have open exhausts and cast metal back plates. The late 80s purchase has the open exhaust and composite back plate. I have one BW case that has the slit sleeve on it... but I think that was a replacement cylinder. I have about three or four slit sleeve cylinders w/pistons in a parts bin drawer, all of them used. I haven't a clue what I used those for.

Anyway, perhaps it would be best to purchase these for the BW's needing a piston/sleeve:

http://coxengines.ca/cox-.049-sub-in...iston-spi.html

And then as the others need replacement, switch to these for them as well? I'll either go this way or simply run the two best of the group "as is" and put TD piston/sleeves on the other two. When the other two wear out, replace theirs with TD piston/sleeves too.

aspeed:

Thanks for your input. I was uneasy about the slit sleeves, but that may be the way I go. Either that or TD pistons/sleeves. (See above!)
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Old Sep 27, 2014, 02:47 AM
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One thing to keep in mind with the cylinder you provided the link for. Note in the description that this piston has been shortened and lightened. I have one of these and it really goes well. Early on when these were provided, the pistons were shortened too much with resulted in to much SPI (sub port induction) and the cylinder required a shim underneath. Only a few thou is required and I usually keep around .006" clearance under the skirt. That being said the newer ones unlike the older ones have the proper clearance.

So many factors can dictate change from one engine to the other. Overall, these engines are easy to swap and a few flights will yield which ones are on par with each other. I prefer the 1980's open slit Black Widow with the plastic backplate as I always found these to run virtually the best out of my collection. Screws don't leak but one needs to be extremely careful with the plastic backplates. The molded lugs would crack internally yielding poor runs and leaks.
This can happen from over tightening and crashing. Don't think your out of the woods if you have metal tank backs either. I've had many with cracks in the same place as I mentioned which only showed themselves when I pressurized the tank. Like I mentioned before, closing down the needle all the way and pressurizing the tank will certainly show you first hand the air leaks I mentioned. This is what causes poor runs and poor fuel draw with these engines.

Keeping the piston ball socket in check is a must so having the proper tool to reset and resetting correctly is required to keep top performance. If this isn't done, the rod will pop a hole in the top of the piston over time. Another performance robbing threat to the engine is congealed castor oil in the crankcase and oil groove within the case. I disassemble the crank by pressing off the prop drive. I chuck the shaft into my drill press and sand the shaft with 400 witching to 600 and finishing with 1000. I then get all of the varnish out of the case itself. If this is left in there, it can rob a lot of rpm's when the engine tries to peak.

My point to all this is that many many factors dictate engine condition and this isn't always due to cylinder configurations. I had one Black Widow that essentially felt like it had NO compression but ran over the top compared to my others. Ken
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Old Sep 27, 2014, 10:30 PM
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Thanks once more Ken for some very good info. All of your information is going to be very useful.

I think it's been decades since we've flown Black Widow powered airplanes. I've forgotten quite a bit about them, such as how to disassemble the crank from the crankcase, but I'll figure it out again.

Fortunately, I still have a rod reset tool that I used back in the 80s when into Tee Dee combat, and recall using it on our Black Widows as well.

Frankly, I'm kind of looking forward to getting started on refurbishing the little BW's! Still need to decide which way to go on the cylinders, though.

I'm hoping my batch of Lil' Bat's arrive soon, so I can get started on the airplanes, at least.
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