What is the difference between new cox parts?

Heh.

I probably will have to wait till Bernie is back home won't I?

Thanks Cribbs. I want to know for sure before ordering otherwise I can just modify what I have.

Phil

I think at one time Cox made the larger tank in a couple different 'air tube' diameters, I don't think the Blackwidow tank was the same as the Golden Bee tank?

Which makes one wonder - do the racing folk ever ream out the tube? I'm sure it can be done, I suppose the best way might be to use EDM. And there's probably some limit beyond which you'll poke holes in the sides, so you have to leave some meat on the walls of the tube.

Iskandar

OOOooo good question!

What is the difference between the "Black Widow II" and the "Golden Bee II" besides the color and the starter spring?

I am pretty sure that the modification to the back plate is done with a drill bit, #44 IIRC. I am sure a reamer would be much more accurate, but it would be more expensive for the tool too. I am wondering if the TANK is drilled/reamed also.

Is the regular tank, and extended tank the same or different diameter of passage compared to the stunt tank and black widow tank?

Phil

I know that there are currently no original "stunt" backplates in production, the ones that Bernie uses are modified babe bee backplates. Not sure what Matt uses, but I would think the same.

Cox International wrote:These backplates were made by modifying Babe Bee backplates. As a result minor cosmetic imperfections may be visible where the filler holes/tubes once were.

EX Model Engines wrote:Please note the backplates are modified from our stock Babe Bee style ones and may have slight imperfections.

pkrankow wrote:OOOooo good question!

What is the difference between the "Black Widow II" and the "Golden Bee II" besides the color and the starter spring?

I am pretty sure that the modification to the back plate is done with a drill bit, #44 IIRC. I am sure a reamer would be much more accurate, but it would be more expensive for the tool too. I am wondering if the TANK is drilled/reamed also.

Is the regular tank, and extended tank the same or different diameter of passage compared to the stunt tank and black widow tank?

Phil

Other than the drive plate and starter spring type, they are the same, only the color is different. If you bought an engine and found the backplate air inlet and the venturi inlet to be smaller than .082"(the old Black Widow size) it's a very simple modification. You can test the size by probing with a drill bit. Here are a couple of quotes about this from an earlier thread that may be helpful:

andrew wrote:Start smaller --- you can always make it larger. Here's an excerpt from Paul Gibeault's Mouse Race Guide:

With the tank and tank back together, check that the venturi size is .082" I.D. If not, drill out
the tank and tank back inlet venturi to .082”, (this is what the record holding engine used).
Drilling out the venturi larger than .082” sometimes produces an rpm gain, but often your
engine won't run as steady and your range will be less. To me, it's just not worth it.

RknRusty wrote:If you enlarge the venturi on an un-modified Babe Bee, you have to open up the backplate air inlet and the venturi tube. I have a small standard set of bits. I finger twist a 5/64 bit, the closest I can come, and the hole is .0078". I finger-spin it enough to make it a loose fit. It is indistinguishable, performance wise and probably about .082 anyway. Don't use a power drill, it goes through almost as soon as you give it the slightest twist with your fingers. Keep in mind, a Babe tank has a smaller venturi outlet behind the reed than the screamer Bees. Like Bernie said, a Black Widow tank and backplate (and probably all 8cc stunt tanks) is bored to the larger specs.

With the tank back off, it's about a 5 second modification. The bit finger twists through so easily it'll surprise you when it pops through, and you're done. Clean out the shavings and put it back together.

More good reading here:
https://www.coxengineforum.com/t753-the-revised-2011-gibeault-mouse-race-program

I think a new "Golden Bee II" is in my future for the new year! I don't like the starter on the "Black Widow II" and modifying an old engine with new parts adds up to the cost of a new engine!

I like that fuel hose and pickup tube modifications too, even though I am not racing, I want the best/most power I can get on at least one plane.

Phil

Phil, when you get your new engine, go ahead and check the pickup tube position. Bernie said recently, when I asked him about a tank mounted "backwards" on the new Blue Bullet, that he hadn't considered control line needs when assembling engines. Never being a control line flyer, it hadn't occurred to him that we needed a certain position.

See what I mean. This engine pictured on his site now has the vents on the other side.

WingingIt74 wrote:I know that there are currently no original "stunt" backplates in production, the ones that Bernie uses are modified babe bee backplates. Not sure what Matt uses, but I would think the same.

Cox International wrote:These backplates were made by modifying Babe Bee backplates. As a result minor cosmetic imperfections may be visible where the filler holes/tubes once were.

EX Model Engines wrote:Please note the backplates are modified from our stock Babe Bee style ones and may have slight imperfections.

Yes, all the stunt backplates are modified from the Babe Bee backplates that we have available. Some of the raw backplates had the smaller venturi (Babe Bee) and some larger (Black Widow). What we do, on all of our backplates, is bore them out to the larger, Black Widow size of 0.082" if they are not already like this. The reason for this is I have found that this size results in a more consistent running engine across the board.

To answer the original question about the silver stunt tank assembly vs. the Black Widow one, the only difference in OURS is the color. All of our tanks have the press-fit filler tube design.

Best Regards, Matt

Rusty, I will be sure to check that out.

I already ordered a BW tank assembly from Exmodelengines.com since it was the description I was looking for and a similar price. I also ordered a metal BW back plate since it was there. (Thanks for the explanation Matt)

I then added up everything I spent and realized that parts to this hopped up thing I am building (and have already run on a extended non-stunt tank) cost more than a new engine!

It runs really well, but I need longer lines than 35 ft, and it won't do inverted very well. I was doing overhead 8's with my jumping bean because I was ready to fall over! I hope the zingers I am building run a little slower circle, they are a tad larger than the jumping bean. I have other, less powerful engines, so swapping is no problem.

Phil

I used a pre-'96 Black Widow for most of my Jumpin' Bean's first life. It really ran well, but if I wanted to fly inverted for any distance, I made sure to do it when the tank was still almost full. Nothing you can do about that. But those tanks do let you do loops right up until the end. Mine usually ran out of fuel upside down at the top of a loop with no glide speed. You just have to get your aerobatics in quickly because with 8cc, the fun light flickers out pretty soon.

I fixed the LE on my jumping bean, the outboard wing cracked at the wing root yesterday on the 2nd or 3rd flight of several more than that. (lol) I compared the zinger and jumping bean and they are very similar in dimensions. Now I really need that yellow Monokote!

I have always flown previously with a baby bee on my jumping bean, but I think the plane has always been tail heavy. I ended up strapping a nut under the engine with some wire (about the 3rd or 4th flight). It has always been twitchy, and lost the landing gear long time ago. It became a lot less twitchy with the extra weight.

If I end up TOO hopped up I can put the baby bee on, that is a strong healthy engine too. I made up some lines that should be 42 ft long, which is about the longest I can fly in my side yard.

Phil

The landing gear provided important balancing weight to my Brodak Bean. So if they were missing it probably was tail heavy, wanting to zoom up or zoom down with no cooperation in between. If you wish,I can look at my plans and tell you exactly where the CG is supposed to be.

I always flew mine on 35' lines. I did fine with that, but since I used that plane to learn aerobatics, it did a lot of ground pounding. When the bellcrank busted loose and demolished the inboard ribs in mid flight, I had a Medallion on it. I'm resurrecting it now. My build thread is called the Refried Bean if you want to take a look. In its new life it will have a Norvel .061.

That would be helpful Rusty. I have read that thread with interest. Since wheels are not going back on this one, I was planning on driving a largish screw into the wood just behind the plywood motor mount. I really should order a Brodak version, I feel kinda bad about bashing with my childhood planes.

Phil

Mark Boesen wrote:I think at one time Cox made the larger tank in a couple different 'air tube' diameters, I don't think the Blackwidow tank was the same as the Golden Bee tank?

yep

Now that picture is what I am trying to avoid with my initial question.

Phil

It almost looks like a third version? I'm guessing that all the tanks Bernie sells are the same I.D. for stunt you'd want a smaller diameter anyway and if you wanted HP you could easily bore it out.

EXModelEngines wrote:Yes, all the stunt backplates are modified from the Babe Bee backplates that we have available. Some of the raw backplates had the smaller venturi (Babe Bee) and some larger (Black Widow).

How interesting!! Back when I got into models (early 70s) the Black Widows were advertised as having more power.. an additional "xxx RPM with a given prop" (my friends and I agued for a long time over what "a given prop" was...). I always assumed the difference was due to the twin bypass cylinder, but maybe that wasn't the whole story! I don't recall mine being more powerful than Babe Bees or Golden Bees my friends owned - there probably was a lot of variation.

Iskandar

If you can fit the butt end of a 5/64 bit in it, then it could be bored larger. Like I said in the quote above, just a quick finger twist will do the job. I usually make it a loose fit so it's probably around .082". It would be nice if I had the exact sized bit or ream. Also the hole at the outlet end behind the reed was smaller on some tanks and backplates, but I never tried changing that since it's a tapered tube. Getting carried away and over-boring will make an uncooperative engine.

Mid twenties percentage nitromethane fuel seems to agree with these bees the best. More nitro is faster and so is wear and tear. Less is more difficult to needle. Glowplugboy Rocket 24 runs better in my engines than any other brand including Sig. I add 1.3 ounces of castor to each quart to get it up to 20% oil.

I'll get that CG location to you by this afternoon. As for the big screw, I would worry about creating a weak point in the wood. I suggest dropping by the tire store if you don't habe an LHS and ask them to give you a couple of stick-on lead weights. I remove the tape with acetone, bore a small hole in it, epoxy it on and then run a small wood screw through it.

I've got my Blue Bullet in front of me, was there something you guys wanted a photo of?
J

Does it have the vents on the inboard side like it should? All of Bernie's new pictures show it the right way. How about an intake screen?

Hells yeah, show us the goods!

There you go Rusty.

Huh. That is an obvious blue ring inside that intake...Is the air passage supposed to be that much smaller than the hole in the back plate (venturi?)

*

I am running Omega 15% with 8 oz of castor added to the gallon, filled most of the head space in the jug. My spreadsheet says that translates to 14% nitro, 22% total oil (51% synthetic, 49% castor) I just wrote a very simple spreadsheet to take given percentages of a fixed volume to volume of the components, then volume added and calculate new percentages.

My bigger engines love this stuff (Fox 15BB RC, and OS 40LA) but I have only bench tested those. I fear breaking RC planes...I am rebuilding a Tower40 trainer into a franken-SPAD (spadtothebone.net) since I have a good wing and a fuselage that fits in a quart ziplock.

I want to try higher nitro fuels, but bought for my bigger engines before I got back into 1/2a's. My Cox engines seem to like this mix, but I have no doubt there is better. I run 1 gasket shim, and have thought of considering to try 2, but I lack a spare currently.

I have also run home blended methanol/castor sans nitro. Yellow HEET fuel additive is methanol, and castor from the pharmacy. The Cox 049 engines run OK on it (not great), and my bigger engines act satisfied but mellow.

Phil