Tank Set-up

I have two airplanes, Barnstormer and profile Oriental, and I am having trouble getting consistant 4-2-4 transitions and inverted 4 cycle runs. I have installed on both airplanes a Brodak 40 with 10-5 props. I am using 10% nitro, 23% 50/50 oil fuel. I have tried Brodak uniflow tanks, standard tanks, and currently using uniflow clunker tanks. I can get the proper 4-2-4 runs on the ground, but cannot get consistancy in the air. Plus, no set-up I have tried will give me a 4 cycle inverted flight. It's always 2 cycle. I've moved the tank up and down, but still get 2 cycle inverted runs. I have experienced the Oriental staying in 2 cycle run after a loop and remaining until I leveled after a steep dive. I'm stumped! Any suggestions?

LAST EDITED ON Oct-10-04 AT 08:49 PM (CDT)
 
Larry,

If you've already tried shimming the tank to even out your runs, you must have some other problem.

If possible, get an experienced flyer to look over your airplane. Otherwise, please post a picture of your set up.

Is your uniflow line vented so it gets some pressure? Are you sure that you aren't having a vibration issue? Do you balance your props?

With a standard metal Unaflow tank, set up in normal fashion, you shouldn't be having any problems.

Thanks for your response. I did not balance my prop and yes I do see bubbles in the tank. I have cycled my Brodak about 30 times following the prescribed guidelines. I checked and cleaned the fuel filter, but not the spraybar. I will do that. Do you know of a good prop balancer?

When you are running the engine on the ground, are there any bubbles in the fuel pick up line that runs to the Venturi?

If yes, then maybe vibration due to a unballanced prop or it may be as simple fix to add a shot of armorall to your fuel. It will keep the fuel from foaming.

How many runs do you have on your Brodak 40? Did you follow the perscribed break in?

Have you checked your fuel lines, filter and spraybar?

One other thing did you try any 5/29 fuel?

I run FP40's and I have had a few that would only run decently on 5/29 fuel, while the rest of my FP's use 10/22.

ARE YOU SURE THAT YOU HAVE PERFORMED THE REQUIRED BRODAK BREAKIN PROCEEDURES? I was just checking.

Since you have changed you complete setups a few time I would recommend that you go back to the uniflow tanks, install the tank on the profile fuse and raise it about 1/8 of a inch above the center line of the venturi, plumb it as prescribed and use muffler pressure. The fill the tank with 5/22 or 5/29 ALL CASTOR fuel and try the addition of a 11/5 or 12/5 prop, try it again.

This is a basic setup for most profile ships.

You should be able to get and idea of how your engine will perform on the ground but let it run for a while and get the engine warm. If you have a tach it would be a good time to take a rpm reading. I believe the Brodak 40 should be between 7300 - 8300 rpm on the ground.

Now the tilt the nose up and back down to level, did the rpm increase? Now tilt the nose down and go back to level, did the rpm stay about the same or drop some? Now flip it over to inverted and slightly elevate the nose, did the rpm elevated silghtly over the upright rpm?

Let us know how it works out for you.
Mike Clark

Sounds like It may require more break in. I suspect 29% oil is more than is needed in this motor. I use 22% oil.

Thanks for you suggestions. I will go back to the uniflow tank and set-up the tank as you prescribed. But, I have read pros and cons about muffler pressure. Is exhaust a good thing to be piping into your tank? I was using an APC 10/5 prop and it was settling into a 4 cycle run at approximately 10000 rpm. I will try a 11/5 prop and see if that helps to get a slower rpm (I that is good). I did tilt the nose up when I set the 2 cycle run and tilted the nose down and flipped it over to test the 4 cycle run. The engine did transition from 4-2-4 as I moved the plane from horizontal to vertical and back to horizontal. I did not check to see if the slightly elevated nose was equal in rpm in both inverted and upright positions. If they are not, do I adjust the tank center line to even the rpm? Two other responses to my request stated that I may have a vibration problem. I did not balance my prop and did see bubbles in the clunker tank. I will try all suggestions and start over trying to change/tweek one thing at a time.
Thanks again.

I have a Brodak .40 in my ARF Nobler and it took about 12 flights to get it to run almost just right. It still floods if it is pulled through 4 blades, but 3 and if it is cool and/or damp, for get quick starts. Hot and dry, it will start right now. Must be the fuel. Also it will at times go to 2 cycle and stay and this engine has been broken in. Some days it will 4-2-4 just right. Others, it goes 2 cycle and stays there. I think it may be the fuel I'm using. Lots of castor seems to help. My question is why such a big engine in a dinky Barnstormer. I have two, both with Fox .35's and that is more than enough engine. In fact my best flights have been with an old, very old K&B .32.
Me, Id toss the B.40 and install a Fox .35. Nay sayers do yo stuff.

My Dad runs a B40 on a Twister with a RC clunk tank, vent still in the up spot bubble in the tank. Prop is 11x5 fat blade, RPM is 8900(4stroke) with the tail up so that the plane is level.
It goes two strk as you let it go and comes back to 4 as it goes around .5 laps
We had problems with fuel foaming with all of the hard tanks also. The plastic tank works perfect. Fuel is 10/22. Very steady stunt run the whole tank. go figure.
MM

LAST EDITED ON Oct-11-04 AT 09:36 PM (CDT)
 
You necessarily don't need muffler pressure.

Just plumb the uniflo line, to a hard tube, that is pointed into the airstrean. You'll be in bizzness.

Muffler pressure works well with a unaflo tank. It does have an effect on the overall engine run and will tend to kill the 2/4 break. That may or may not be to your liking. Try it and see what you think.

Two or three drops of ArmorAll in a gallon of fuel will help eliminate fuel foaming. Shake your fuel jug and note how it foams. Then, add the ArmorAll and you should see the difference. It's pretty dramatic. I have added AA to my fuels for more than a decade, with good results and it will not harm your engine.

I don't know whether they still make the 'High Point' prop balancer or not but if you can find one, I think they're about the best available. It's beautifully made and will last a lifetime.

If you try all of the above without success, you may have a vibrating front end. It's usually much more of a problem with profiles and with built-up fuselages.

Remember, no matter what you read online, try various techniques and setups yourself. Then you can decide what works for you.

Hey Larry,

Your engines probably need more run in time.

A good low cost prop balancer is the "Top Flight Magnetic Balancer". About $18.00 from Tower Hobbies.
Muffler presure helps engines run consistently (Steady). They will still 4-2-4 break just fine.
Also try APC 10-4 props.