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Author Topic: Golden Bee wont run inverted  (Read 608 times)

Offline John Skukalek

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Golden Bee wont run inverted
« on: January 23, 2022, 05:14:11 PM »
Based on what I have been reading here it seems like a Golden Bee should run inverted in flight. Mine cuts out in about 5 seconds after flipping the airplane upside down. Any ideas?

Online Ken Culbertson

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Re: Golden Bee wont run inverted
« Reply #1 on: January 23, 2022, 05:59:32 PM »
Based on what I have been reading here it seems like a Golden Bee should run inverted in flight. Mine cuts out in about 5 seconds after flipping the airplane upside down. Any ideas?
Check the tank.  Are there tubes on the top and bottom?  If they are you have the inverted capable tank.  I had a bunch of them as a kid and I think some had the Baby Bee fill tubes.  The pickup tube inside the tank needs to be on the side near the back.  The Baby Bee can be made to go inverted for a short time if you flip the cylinder over to the bottom and mount it sideways then cap one of the fill tubes after filling it (which is really hard) so the fuel doesn't run out.

Ken
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Offline 944_Jim

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Re: Golden Bee wont run inverted
« Reply #2 on: January 23, 2022, 06:57:04 PM »
Mr. John,
Can you confirm:
A) your backplate has zero fill nipples and zero vents
B) your 8cc tank (longer than a regular Bee) has two vent tubes, one sticking up, and one sticking down

Lastly, the pickup tube needs to be located from the internal fuel pickup nipple to the outboard edge of the tank and at about 8 o'clock as seen from inside the backplate. 9:00 would give you the same right side up/upside down run time, but gravity won't necessarily allow the fuel to sling out to the 9:00 position. The tank won't completely empty.

Normally the fill/vent tubes make it tough to align the pickup tube due to all three wanting to be in the same space within the tank. Another issue is the oring that seals the backplate to the venturi tube between the reed and the needle/air intake area on the backplate. If the oring is missing, or shrunken too much, the engine will appear to needle with significantly fewer turns out because fuel leaks past that oring...that is, until the fuel level drops below the oring which then allows for an air leak.
While the color matches the Silver Bee, this tank is representative of a Golden Bee with the integral fill/vent tubes:
https://coxengines.ca/back-end/8cc-aluminum-fuel-tank-for-cox-049-engine-stunt-version-silver.html

I can add more pictures if this doesn't make sense.
« Last Edit: January 23, 2022, 10:33:18 PM by 944_Jim »

Offline Tim Wescott

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Re: Golden Bee wont run inverted
« Reply #3 on: January 23, 2022, 06:57:37 PM »
Yup.  The key is getting the pickup tube in the right spot.  You want it on the bottom for FF and lazy RC; for CL you want it on the side toward the outside of the circle, where centrifugal force will throw the fuel.
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Offline 944_Jim

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Re: Golden Bee wont run inverted
« Reply #4 on: January 23, 2022, 07:20:19 PM »
Ok...this is a Black Widow (same tank/backplate construction as GB).
This engine was just taken apart,.most liky for the first time considering how I got it. Note the 8cc Non-stunt tank to the left...no fill/vent tubes.
Note the BW backplate has no full/vent tubes, yet the Babe Bee-style backplate does. Both backplates are shown "backwards" with respect to normal CL flight. If they get flipped over so you look at the backside/outside of both backplates, the fuel pickup is on the right, or outside. Keeping the BW/GB/SB tubes left or inboard will provide room within the tank for the pickup tube to reside in clear space. The tubes will allow for airflow as the rule slings out. Having the tubes on the outboard side will guarantee fitment issues.
« Last Edit: January 23, 2022, 07:48:42 PM by 944_Jim »

Offline John Skukalek

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Re: Golden Bee wont run inverted
« Reply #5 on: January 23, 2022, 08:26:02 PM »
Thanks for your guidance including pictures 944__Jim. My Golden Bee tank has the tubes coming out of the top and bottom of the tqnk on the inboard side. I will plan to take it apart to see what it looks like inside of the tank. One thing that I want to make sure that i understand is your comment about the fuel pickup being at 8:00 looking from behind the engine Wouldn't that put it on the inboard side?  I'm probably not following you correctly?

Also it seems like you are saying that the pickup tube end should be below the center(vertically) of the tank. I believe due to gravity. Wouldn't this result in starving the engine of fuel prematurely when it is inverted?   

Thanks again

   


Online Ken Culbertson

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Re: Golden Bee wont run inverted
« Reply #6 on: January 23, 2022, 08:52:01 PM »
Do it like the top one in Jim's picture.  Make sure the fill/vent tubes are on the opposite side of the pickup tube.  That is one dirty engine!  Mine had trouble inverted at first too, mostly from the prop not turning anymore. LL~

ken
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Offline John Skukalek

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Re: Golden Bee wont run inverted
« Reply #7 on: January 23, 2022, 09:07:33 PM »
Makes sense guys. Thank you very much.

Offline 944_Jim

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Re: Golden Bee wont run inverted
« Reply #8 on: January 23, 2022, 10:32:20 PM »
Mr.John,

Yes, leave the end a bit below horizontal...it will starve early ONLY if you are trying to fly inverted in the last 30 seconds (give or take) of flight. I recommend doing any upside down work in the first half of the tank. Having the pickup lower in the tank in the position shown traps the pickup between the rib and the screw boss. Trying to keep the pickup between the ribs (at 9:00) will.be an excersize in futility.

MM nailed it...I fixed my prior post to reflect I got backwards. And heed his warning. I've had my GB since childhood. The backplate is dimpled at the screw holes/bosses from all the times I stripped it and put it back together.
« Last Edit: January 26, 2022, 06:23:25 PM by 944_Jim »

Offline Paul Smith

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Re: Golden Bee wont run inverted
« Reply #9 on: January 24, 2022, 07:27:19 AM »
A good trick is to make fixture inside the tank to positively locate the fuel pickup.  Don't leave it to chance.
Paul Smith

Offline 944_Jim

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Re: Golden Bee wont run inverted
« Reply #10 on: January 24, 2022, 04:01:21 PM »
Mr. Paul,
Can you elaborate? I know of the aluminum pickup tube job replacing the plastic tube/spring...but this is the first time I've seen a barb fixed in the backplate.

Oh, and what about the NVA? Another new one to me.
TIA
« Last Edit: January 24, 2022, 08:11:59 PM by 944_Jim »

Offline Paul Smith

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Re: Golden Bee wont run inverted
« Reply #11 on: January 24, 2022, 07:57:47 PM »
It's just a little stub of tubing, epoxied-in to take the guess work out of the fuel pickup placement. 

Sorry, I don't recall the brand of epoxy, but it's more industrial strength glue than the usual hobby shop stuff.  Normal modeling epoxy won't take the fuel immersion.

The NVA is a Kirn Kraft fine thread unit pressed into the backplate.   These were on the market a few years ago.
Paul Smith

Online John Rist

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Re: Golden Bee wont run inverted
« Reply #12 on: January 26, 2022, 04:38:34 PM »
  Sorry, I don't recall the brand of epoxy, but it's more industrial strength glue than the usual hobby shop stuff.  Normal modeling epoxy won't take the fuel immersion.

looks like JB weld.   D>K
John Rist
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Offline kenneth cook

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Re: Golden Bee wont run inverted
« Reply #13 on: January 26, 2022, 04:56:32 PM »
             There are so many problems that can occur with these engines and a few issues have been touched on. Air leaks are the culprit of the problems. Air leaks develop around the screws and from what you mentioned, you've already distorted the back plate. Obtain a large syringe preferably a 5 oz., screw the needle valve down until it's seated but not tight enough to ruin it. Pressurize the fuel tank with the syringe. Listen carefully for air leaks. Use oil around the perimeter of the backplate to tank connection. Place oil on the crankcase to tank connection. If it's bubbling, you have found some leaks. With the backplate facing up so you can see the screwheads holding the tank back on, place oil on all 4 screws and pressurize again. You will see bubbles around the screw heads, there's another leak. Check the needle valve assembly as well with oil on the top of the backplate while pressurizing.

               You can lightly sand the crankcase back on a piece of glass using 400-600 grit with a little oil. When screwed together, the crankcase is extruded and the material tends to pull out raising a bump around the threads. Flattening this assists in sealing. Insure using a 2-56 bottom tap that your crankcase threads are chased and clean.

            You can fill the v-groove inside the perimeter of the tank with a piece of dental floss as a gasket holding it in place with some oil prior to assembly.

      Backplate screws are fillister head screws and they tend to wear out. You can obtain new stainless ones from Matt at EX Model engines or Cox International. Replacing screws can sometimes resolve leaks but I use a Q-tip. I remove the screw and tear off a little piece of Q-tip and twist it up and wrap it around the screw threads the same way you would use Teflon tape. Insure that when tightening, the cotton tightens and doesn't unwrap. This works great and is serviceable at the field if needed unlike silicone or Permatex.

 Lat but not least, when pressurizing the tank with the needle closed, if you place oil on the screen and it's bubbling when pressurizing, the O-ring is leaking. Cox O-rings totally BLOW!!. Use a real O-rings for throwing darts which you can obtain easily on EBAY or sporting good store. Yes some people can make them from fuel tubing but I've found the dart O-rings to be a very good fit over anything else I ever used.

         While this may not be a issue, ALWAYS, when the engine is disassembled, hook your syringe to the back of the venturi on the tank. Regardless if your reed is new or not, withdraw the syringe. You shouldn't be able to pull the syringe back AT ALL. You can push it forward but it shouldn't withdraw. If it even slowly withdraws, the reed isn't sealing properly. Take it out, clean everything, flip it over and try again with a little oil on it. If it still fails the suck blow test throw it out and try another.  The reed must be able to rotate under the circlip. The old copper beryllium reeds can be damaged so easy you need to be extremely careful as the slightest indent can cause it to fail. My preference is the clear Mylar reed but they have a short lifespan, however, they can be extended by flipping them over but they offer terrific performance and tend not to gum up as badly as the copper reeds which gets the green goo under them.

Online ray copeland

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Re: Golden Bee wont run inverted
« Reply #14 on: January 26, 2022, 06:11:30 PM »
Kenneth, those are some awesome tips for Cox engines!!!! y1   I am sure they have come by trial and error, good job!
Ray from Greensboro, North Carolina , six laps inverted so far with my hand held vertically!!! (forgot to mention, none level!) AMA# 902150

Offline 944_Jim

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Re: Golden Bee wont run inverted
« Reply #15 on: January 26, 2022, 06:39:44 PM »
And if you ever see the name Paul Gilbeault, know you are reading info from a genuine Cox Hot-rodder.

https://www.nclra.org/TorqueRoll/2016-12.pdf

The good stuff is several pages in.


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