DDriver

Hi ALL,

I have set up a SuperTiger G.90 converted to gas using CH Ignition System and set up for crankcase pressure with Iron Bay Fuel Regulator with their one way valve, one tee for fuel overflow and using a Great Planes Gas Valve for filling tank.
Also have a fuel filter attached just behind the fuel regulator.

Engine is tuned in with High & low needle valves reasonably set....good idle , transition & high end all working fine.

The problem I am having is that after engines starts running, the fuel lines soon develop a lot of air bubbles which does not necessarily stop the engine from running but as soon as you move the plane from the horizontal position on the stand, and tilt the plane nose up it quickly dies.

Yesterday I took the wing off and removed the fuel tank & regulator, just letting them dangle away from the fuselage to see if excessive vibration from the fuse was the culprit. Still getting the same bubbles occuring....I even changed back to muffler pressure but same result.
All my fuel lines are new, fully engaged and secured with small fast ties. No fuel leaks in fuel lines or fitting observed and when overflow dot is removed, I get a wwhhossing sound which tells me I am getting good pressure.

What could be my problem??? I am totally baffled why the bubbles are occuring in a pressurized system like this?????

Any advice or suggestions at this stage would be most welocome.

DDriver.

w8ye

My Feedback: (16)

You need to try one of the bubbleless clunks like is used in a chain saw or weed whacker? I think sullivan sells them also?

Enjoy,

Jim

DDriver

Hi Jim,

Thanks a million for your good advice.

I talked with an old mechanical friend of mine earlier this afternoon, and described my problem.
He was of the strong opinion that the problem probably lay within the fuel tank, since no external leaks were observed.
I just decided to do a bit of research on bubble-less clunks and guess what....I may have found the perfect solution.

Check out this amazing but simple system to do away with all the troublesome bubbles.[:-]

How to Build a Turbine Pleated Paper Clunk
By Mark (Rocketman) Pokrywka & Steve Ellzey

http://www.jetpilots.org/how_to_buil..._pleated_p.htm

I am heading for my local Auto Parts Store tomorrow for the suggested part and plan on using
the - second option - suggested in the above article.

I'll post my results just as soon as I can get it set up.

I really hope this works........this may be a godsend for many RC Flyer's facing this dilemma!!!

Once again.....many thanks Jim for steering me hopefully in the right direction.

DDriver.

w8ye

My Feedback: (16)

Here's one already made

http://www2.towerhobbies.com/cgi-bin...?&I=LXXF25&P=7

Jim

w8ye

My Feedback: (16)

Here's another...

http://www2.towerhobbies.com/cgi-bin...?&I=LXD741&P=7

w8ye

My Feedback: (16)

B&B sells them for $2....

http://www.bennettbuilt.com/page5.htm

Or you can go to any small engine repair shop and get one.

I bought one at the LHS.

Jim

DDriver

Hi Jim,

Thanks for the three links.

As my system is gasoline, Just a general note observed.

The O.S. Bubbless.......because they are using a silicone O Ring - Can only be for glow fuel as stated.

Now the other Sintered Bronze Tank Filter from Dubro is just the ticket as its OK for Gas or Glow.

My only problem is we don't have a RC Hobby Shop down here, so all my RC Stuff has to be ordered from
Tower or other similiar sources shipped initially to my forwarding address in Miami, then on to my
local post office.......its like snail mail.......slooowww. Anywhere between 18 - 30 days.from order to receipt.

Nevertheless I'm off to my local auto parts store to see what I can find first!!!

Once again, thanks every so much for your T.H. links.

I'll be back later.

DDriver.

DDriver

Hi Jim, Hi All,

UPDATE ON MY PROGRESS!!

I managed to obtain the necessary parts at my local NAPA Auto Parts Store.

These parts are to build a separate header tank which also doubles as a superior fuel filter &
bubbleless engine supply to help solve my mystery bubbles in a pressurized gas setup using
an Iron Bay Fuel Regulator and crankcase pressure supply from my Supertiger G.90.

I didn't have a 2 oz fuel tank available so opted to use a 2 oz Liquitex Acrylic Enamel Plastic Bottle.

Photo #1 below shows the simple items used including K&B 1/8" Brass tubing, long set J B Weld, small
Napa 3051 Pleated Paper Fuel Filter and chromed brass clunk from a damaged 6 oz sullivan fuel tank.
I also used a soldering iron not shown.
Fuel Filter came with a little rubber/plastic check valve inserted in one end.
Its not needed, so I simply pulled it out and discarded it.

Photo #2 Shows the Liquitex bottle cleaned out, cover cap cut off & small center hole drilled for real tight fit
for 1/8" brass tube in screw on cover.
Brass tubes cut to length & inlet tube slightly bent to clear centered filter.
Also I decided to use a discarded clunk and slightly tapered it so that it can be partially inserted into open
end of fuel filter with tight fit.

Photo #3 Shows a close up of the taper i made to the clunk....notice the chrome plating has gone and
now you have a nice surface to solder with.

Photo #4 Shows the 1 1/4" long brass tube soldered to the clunk and clunk in turn soldered to the filter.
All parts were roughtened with sandpaper & alchol cleaned before soldering.

In my next post, I will move on with more how to & associated photos.

DDriver.

DDriver

Hi Jim, Hi All,

FURTHER UPDATE ON MY PROGRESS!!

Photo #5 below shows the basic Header Tank components ready for assembly.
2 oz Liquitex Plastic tank bottle, filter & 1/8" brass inlet & outlet tubes.

Photo #6 shows the components trial fitted together.
Here you can clearly observe how the bent inlet tube clears the centrally located filter.

Photo #7 shows completed Assembly using Slow Set JB Weld.
JB Weld was first applied around the tubes on the inside of the cover, then on the outside as shown.
Doing this ensures that the pipes are held secure from pressure applied when attaching or removing the
tygon flexible fuel lines.

The header tank will be installed upright in fuselage with inlet/outlet tubes exiting out of the bottom.
The inlet shall be connected to the adjacent main fuel tank.
The outlet from the centrally located pleated paper fuel filter shall be connected to Great Planes Gas
Valve Fueler, then on to the Iron Bay Fuel Regulator, then on to the nearby carb.

Hopefully after the JB Weld fully sets up, I can then plumb the fuel tanks all up in the fuselage above
wing C.G. position.

After installation, I will post my initial results, hopefully I will now have a pressurized system without
the mystery bubbles and the header tank will serve an additional purpose as it has a super fuel filter of
15 ~25 microns........far better than the regular fuel filters used to remove trash.

DDriver.

DDriver

Hi Jim, Hi All,

FURTHER UPDATE - INITIAL RESULTS!!

The good news is that the header tank has now been installed and tested.

Guess what!!!!......All the mysterious air bubbles have totally vanished from the pressurized fuel system.
So the header tank project seems to have been well worth the effort.

Photo #8 below shows a close up view of the newly introduced Header Tank installed in fuselage.
I didn't quite have enough height in the fuse, so the header tank is installed slightly leaned over.

Photo #9 shows the whole wing saddle area with main tank located just behind header tank near C.G.

In my next post, I will discuss one final problem I was still facing and what I did to fix it.

DDriver.

DDriver

Hi Jim and all interested,

I sure feels good to get rid of the air bubbles after trying just about everything I could think of...the header tank did the trick!!!

Nevertheless in my first post I mentioned that along with the air bubbles, as soon as I moved the plane from the horizontal position on the stand and tilted the nose up, it also quickly leaned out & died.

Well this problem was still occurring to a lesser degree but bad enough to say - You can'y fly just yet!!!
Still needs fixing.

I still had the Iron Bay Fuel Regulator in the fuselage behind the firewall approx. 6"~ 7" behind the Super Tiger 90 carburetor.

After some time looking at the problem & thinking about the mechanics of the fuel regulated system,
I came to this conclusion:

The regulator stops the flow of fuel until the carb demands some.
The carb applies suction that pulls on the regulators diaphragm opening it.
Fuel then flows through supplying the carb with just the right amount it needs.
What I didn't initially realize, was that the fuel between the regulator and the carb nipple isn't pressurized.
Remember that the regulator only supplies what the carb asks for, so it's not been force fed (like a perry pump).


Now when the plane is horizontal and wot applied........engines runs great.
Tilt the nose up...not sooo good. why??
I began thinking just maybe the long fuel line from the regulator to carb was having gravity working against it!!??!!
So I relocated the Iron Bay Fuel Regulator to a closer position just behind the carb.
BINGO....Problem Solved.
Once you have the Hi-speed & Idle carb needles set just right, any attitude is now a non issue!!

Photos 10, 11 & 12 below shows my SuperTiger G.90 converted to run on gas with CH ignition & repositioned Iron Bay Fuel Regulator near carb.

Had 2 flights earlier this afternoon between rain showers...engine now works like a GEM!!!

Cheers.

DDriver.

Evil Homer

Hi DDriver
Would not mind going down this road myself and modifing an s90K which i have doing nothing, couple of questions:
1. Cost - how much was it to do the conversion
2. Oil content - how much oil mix do you use in the gas
3. Running - using the standard carb are the needle very sensitive
4. Prop sizes - I normal run a 13x8 on my glow S90K, what size props does this carry and what kind of RPM do you get.

Thanks
EH