Outside Loops

I have had many successful runs with integral type tanks. Unfortunately, none of them were very long. I have experienced issues in the Cox like a Fox .35 where the engine wants to load and burp on the outside maneuvers. Nothing special in my setups. I was using Black Widows from the late 80's early 90's. Over and under venting and not the plastic tank. Air leak checks are a must. This is why I'm a fan of the plastic backplate because the screws are less susceptible to leaking at the rear of the backplate, however in the years I mentioned, the backplates would fail around the internal screw bosses. Seeing that the plastic is black, the cracks are usually undetectable until you air check the tank or overtighten the screws . The placement of the pickup is critical and getting it to stay put is a real test of patience. I have drilled holes in the metal ones where the area is gated in the middle of the tank to retain the fuel tubing and wire tied the pickup. The best tubing I have ever found to work was a sample that Davis Diesel provided me with. It would hold very tight on the nipple and wouldn't harden or flare out on the ends when installed. Many times I've seen the ends all distorted and not holding tight on the nipple.

                      Inverted flights are generally ok I wouldn't give them the 2 thumbs up, I limit my time inverted because it tends to generally starve for fuel. I mix up the maneuvers a good bit and I get the best of all. Having a new glow plug is key, even if the plug is glowing bright. They're just fickle and as expensive as they may seem, it makes a difference in the engine quality run. I mostly use stock Cox but I have used the Nelson and Merlin setups as well. I used Sig 35% for years, I have since backed off and went to the new Cox 25%. I like it a lot. Some of the best runs I had was using 45% Byron castor fuel. This was old fuel but worked great. Not made any longer but Randy Ritch can match that fuel. A gallon though is going to be quite a bit of money.

The main problem I have found with my old engines is in the crank area. The old castor burnished onto the crankshaft needs to be manually removed. While I can take them out of storage and run them immediately, when I put them to the test, sagging usually results when I push them through the harder maneuvers. I feel the castor starts heating up and acting like a brake on the shaft. A good polishing in a drill press rids the shaft of this . If you want to dive deeper into this, you can lap the lower portion of the cylinder using the piston upside down in the cylinder using Mother's aluminum polish. Take a piece of K&S 3/8" tubing wrap tape around the top and insert the piston onto it with the rod dropped into the center. The tape will cause a friction fit on the piston allowing you to spin the tube. Place the piston into the cylinder upside down and using the skirt only not the crown work the polish into the cylinder. Move up and down while twirling. Essentially, your tapering the lower portion of the cylinder. This is not necessary, just something I like to do as I feel that it prevents heat buildup. Any drag is a problem and the smaller the engine, the worse it becomes.

             As your probably aware, keep the prop load light. A 3 pitch is in order to sustain drive even if the engine is running high rpm's. The Cox black 5x3 works great ( Not the safety tip) . I dislike the safety tip and found them very inefficient. Keep in mind that you can have 10 of these engines and 2 will generally stand out above the rest. They're the two your in search off. I also found the clear Mylar reed to work best, it is short lived over the others. This isn't the white Teflon reed. I like the Mylar because I can tell if it's working because it has a tendency to chirp during flipping. Not all do it, only some but most of the time it lets me know .

            Roddie makes mention of the wedge tank, not always a easy install in a Lil Satan and the tank design itself doesn't prove worthy of combat maneuvering. The fuel will run away from the pickup causing overlean runs and unpredicted shut offs. A bladder is far superior. I've toyed with the idea of making the Cox tank uniflow to improve the engine runs. That being said, it's easier and more economical to bolt a Norvel on and go fly. I do like to tinker but these can test your patience and your plane's construction or I should say destruction. Good luck, Ken

Thanks for the replies. As to why integral tank engines, I thought they would be easy. I appear to have been wrong. Two things struck me from the replies. I have also learned that glow plugs and the number of gaskets under them have a big effect on the way the engines run in general, not just the amount of power they make. I will pursue this further. Also, the specific problem I am having seems to be related to the fuel pickup in the tank. I've tried lots of things, but you've given me some new ideas to try. It will take a few weeks, but I'll report back.
Gene

The only thing I can add is my recent experience with my Tee Dee .051. It runs fast and mean upright and turns inside loops just fine. It will fly inverted if you ease it over and wait for it to recover from the burp, but any hard outside g-force like a loop will shut it off.

Its piston and cylinder is so worn out that with the super high compression Merlin head, I only use one copper gasket. I think what's happening is during outside loops it's letting fuel slip past the sides of the piston(probably right above the bypasses) and drown the plug. I plan to put a new Tee Dee .049 P/C on it before flying it again.
Rusty

HI Gene,

HMmmm! I have not noticed this phenomena on my Cox powered "Flip" model. BUT...although figure 8's are NO problem, I can't remember if I've done consecutive outside's. I think it will do it but will test this Spring. Nonetheless, the only thing that comes to mind is your venturi size. The Golden Bee's tank venturi is .062" I.D. whereas the Black Widow's venturi is .082". I'm just curious if this venturi size difference makes a difference in your particular case...
OH...and one other item. I think your engine cylinder should be UPRIGHT. I can't explain why, but engines with cylinders on the side, just don't run that stable.
That is UNLESS you convert your tank to a proper uniflow, then it will work fine & you'll have a longer run time.

Wish I lived closer to you combat guys in the NW! Good luck.

Cheers, Paul

lol, I remember my first outside loops (6th grade) using a Golden Bee on a Jimmy Walker Firebird, i thought i was really something being able to do consecutive outside loops, don't recall engine issues other then not as long of run time as i wished..

Paulgibeault wrote:HI Gene,

... I think your engine cylinder should be UPRIGHT. I can't explain why, but engines with cylinders on the side, just don't run that stable.

Yes, my thoughts on drowning the glow plug only applies to my sideways cylinder, and that wasn't a Bee either, rather a beam mounted Tee Dee. So lots of different possibilities.
Rusty

I'm working on a uniflow setup that runs on exhaust pressure. I hope to have it in the air Friday. Will keep you posted.



Jim

I won't suggest that uniflow won't work. I will say the problem with the feed is the shape of the tank. Fuel gets pinned to the side wall and many times the pickup is hard bent to the back of the backplate. This is where the problem starts. Many times racing style tanks don't have the pickup hard into the rear corner like a stunt tank. The tank feeds when it's full but it quickly becomes starved when the fuel doesn't have the pickup submerged.

Here's just one example of a reed valve tank converted to uniflow & a tire valve as an overflow vent. Works perfectly & gives superior range.
Note important sealant required to make this work properly, no leaks can be tolerated.

Cheers, Paul

Here's another way. Note:  The uniflow vent must be located next to the fuel pick up. Better range (longer engine run) & stable needle setting throughout the tank run is the reward. Of course, tank MUST be sealed. J-B Weld holds the uniflow pipe vent in place.
Should work great for stunt I would think...

Cheers, Paul

This is one easy method of keeping the fuel pick up in the proper place which is the most outboard part of the tank. 3/32" O.D. tubing seems to be quite adequate, for all uses including aerobatics. Attach fuel line (whatever you decide to use) MUST fit the pick up & backplate nipple firmly. No leak can be tolerated here.

Cheers, Paul

Here's what I came up with. I'm curious to see if it chokes on its own regurgitated castor. Should have a chance to run it tomorrow after the permatex drys.

That's pretty ingenious, Jim. Keeping the tank slightly pressurized can't hurt. Even if it's an SPI engine, I don't think it'll choke on its own sputum too badly, especially with the opposite port facing straight into the propwash. I'll be intereste to see how it runs.

Ran the Uni-FLOWBEE, good consistent runs for two tanks. Will try and fly it next week.

Jim

Excellent. No gurgling or choking on it's oily exhaust?

Cool stuff Jim bee looking for the report , i persome you are after inverted and outside loops

RknRusty wrote:Excellent. No gurgling or choking on it's oily exhaust?

It ran great after I sealed a leak, it needs gaskets where the plastic reed retainer meets the tank and at the exhaust deflector as well. It was only turning 16k so drilled the texaco tank Venturi to 5/64. Also it turns out JB weld is not fuel proof so I had to re glue the vent tube. It should be fine for test flights but the concept will need a better execution to be viable.
I'll be trying this concept on a horseshoe engine with a separate tank as well. If it works as well as I hope I may build this to fly in Old Time Stunt at the southwest regionals:

http://www.outerzone.co.uk/plan_details.asp?ID=2905

I'll start a seperate thread for the horseshoe project so I don't further hijack this thread.

Jim

Here's one from the "why didn't I think of that before" department. Instead of drilling holes in tanks and JB welding tubes you could just mount a stunt tank sideways with the vents on top. The rearward vent tube would be placed in a "close enough" uniflow position. Vent the back tube to my exhaust deflector or simply into the prop blast above the full fuel height. Block the front vent and go fly.

I have done dozens of J&B weld adaptations and so far NO experience with glow fuel up to 35% deteriorating the weld

I mix by weight on a scale

I spend a lot of time making it all same color and NONE left unmixed

I scrape or sand the accepting surface
I alcohol wash the surface
I acetone wash the surface
I wear gloves to prevent any Skin oil contamination
I always let set for a full 24 hours before even touching the parts

I have used J&B weld to recreate drilled and tapped areas that I am confident are as strong as the cast or machined area

The few times I used J&B to set a C/L carb or other Nitro/glow fuel contact area, I never experienced any deterioration of the part(s)

OK what I am saying is that ....properly measured and mixed...I find the J&B weld product to be rather Glow fuel agnostic..non reactive, and still just as secure as before any fuel contamination

I know there are many J&B products so I am talking about the TYPICAL two tube STEEL version

I agree with Fred.

I have used JB Weld countless times but would like to add that it must be mixed really well before applying.

It is also more resistant to heat than common epoxies and will survive temperatures over 200 deg C. I have used it on silencers/mufflers and it has held.

As Fred recommends, the surfaces to be "stuck" need to be spotlessly clean and given a rough and even scratched surface to help the bond.