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Author Topic: Uniflow tank not working?  (Read 2268 times)

Offline frank mccune

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Uniflow tank not working?
« on: August 08, 2020, 12:21:53 PM »
     Howdy:

     What would cause a Uniflow tank to prohibit the engine from being adjusted to a more rich mixture? The tank in question is a 5.5 oz. wedge that is built into a Ringmater Imperial.

     I pulled to tank and removed the end cap to apprise the internal plumbing.  All looked perfect.  The pickup was soldered to the wedge near the end far enough away to permit easy access to the fuel. The Uniflow tube was soldered to the pick up tube one half of an inch short of the end of pickup tube.  The Uniflow vent was facing into the airstream  The overflow was in the front left corner of tank and sealed while in use.

     There are no air leaks in the system.  There are no blockages in the plumbing.  The engine is a first flip starter albeit it can not be made to run richer.  The needle may be turned out until it falls out but there is no change in the rpm.  The engine was run on a test stand with a different tank.  It performed perfectly.

      Any suggestions and/or comments.?  I have run Uniflow tanks in the past and they all worked flawlessly.

      Tia,

      Frank McCune
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Online Brett Buck

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Re: Uniflow tank not working?
« Reply #1 on: August 08, 2020, 12:41:55 PM »
Quote from: frank mccune on August 08, 2020, 12:21:53 PM
What would cause a Uniflow tank to prohibit the engine from being adjusted to a more rich mixture? The tank in question is a 5.5 oz. wedge that is built into a Ringmater Imperial.

     I pulled to tank and removed the end cap to apprise the internal plumbing.  All looked perfect.  The pickup was soldered to the wedge near the end far enough away to permit easy access to the fuel. The Uniflow tube was soldered to the pick up tube one half of an inch short of the end of pickup tube.  The Uniflow vent was facing into the airstream  The overflow was in the front left corner of tank and sealed while in use.

     There are no air leaks in the system.  There are no blockages in the plumbing.  The engine is a first flip starter albeit it can not be made to run richer.  The needle may be turned out until it falls out but there is no change in the rpm.  The engine was run on a test stand with a different tank.  It performed perfectly.

  You probably have a flow restriction somewhere, hard to say where. And just to be clear, this is *not* the engine that has the gigantic venturi, right?

    I doubt that this has anything to do with uniflow, unless the uniflow vent is blocked severely. Remove the overflow cap while it is running, see if it richens up.

     Brett
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Online Dennis Nunes

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Re: Uniflow tank not working?
« Reply #2 on: August 08, 2020, 12:54:33 PM »
Quote from: frank mccune on August 08, 2020, 12:21:53 PM
     Howdy:

     What would cause a Uniflow tank to prohibit the engine from being adjusted to a more rich mixture? The tank in question is a 5.5 oz. wedge that is built into a Ringmater Imperial.

     I pulled to tank and removed the end cap to apprise the internal plumbing.  All looked perfect.  The pickup was soldered to the wedge near the end far enough away to permit easy access to the fuel. The Uniflow tube was soldered to the pick up tube one half of an inch short of the end of pickup tube.  The Uniflow vent was facing into the airstream  The overflow was in the front left corner of tank and sealed while in use.

     There are no air leaks in the system.  There are no blockages in the plumbing.  The engine is a first flip starter albeit it can not be made to run richer.  The needle may be turned out until it falls out but there is no change in the rpm.  The engine was run on a test stand with a different tank.  It performed perfectly.

      Any suggestions and/or comments.?  I have run Uniflow tanks in the past and they all worked flawlessly.

      Tia,

      Frank McCune

Hi Frank,

What happens when you start the engine and plug the uniflow vent with your finger? Does the engine speed up or stay the same? If not, you have a leak somewhere in the system.

Have you cleaned out the spraybar and needle valve assembly really well? Checked fuel lines? Could it be pinched?

FWIW, and this may seem strange but have you tried another glow plug? I beat my brains out for a couple of week trying to figure out why my engine was running strange. Changed the plug and presto-chango it solved my issue.


Dennis
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Online Steve Helmick

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Re: Uniflow tank not working?
« Reply #3 on: September 29, 2020, 11:08:38 PM »
I would wonder if there is a fuel filter in this Ringmaster Imperial? Could it be clogged or installed backwards? Yes, they can be.

I would also wonder if there is a kink in the fuel line where it turns into the spraybar. It happens. Gouge out enough wood to get a gentle turn into the spraybar or solder a 90 degree brass fitting onto the spraybar. With some planning during building, a slot in the fuselage side would be ideal, camouflaged by a blister or scoop as suits your aesthetic desires.   D>K Steve
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Offline frank mccune

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Re: Uniflow tank not working?
« Reply #4 on: September 30, 2020, 08:17:28 AM »
     Hello:

     Thanks for all of the replies!

     I checked all of the suggestions listed above to no avail.  I removed the rear of the tank and observed the plumbing.  All was well.  I painted a large ? mark on the tank and set it aside for future entertainment. Lol

     It worked as designed when fuel was pulled via a syringe.  The plumbing was one eighth inch copper tubing that was unobstructed.

     The Venturi has .281 bore with lan Enya nva.  Is this considered “huge” for a .40 or .46 size engine?

      Be well,

     

     
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Online Steve Helmick

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Re: Uniflow tank not working?
« Reply #5 on: October 02, 2020, 02:13:16 PM »
How big a diameter is an Enya spraybar? I ran as much as a .312" venturi with a .156" spraybar on a K&B .40, 11-5 Taipan prop and 10% nitro. It still didn't put out enough thrust for the Humongus, but a .46 LA was just about right, with a .285" venturi and .156" spraybar.  D>K Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Online 944_Jim

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Re: Uniflow tank not working?
« Reply #6 on: October 02, 2020, 02:53:53 PM »
Converting your decimal venturi ID to fractional looks like 9/32".
K&S makes both an aluminum tube and brass tube with that OD. I think they have different wall is thicknesses. I also noted some plastic food-grade looking tube with the same OD, but the wall thickness would be a significant choke.

How much of a job is it to sleeve the venturi down? Would the NVA be enough to keep the sleeve out of/off the crank?
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Online Steve Helmick

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Re: Uniflow tank not working?
« Reply #7 on: October 05, 2020, 05:55:00 PM »
Reviewing this thread, I would like to hear what exactly happens if the NV is opened "more". Does the engine quit, or does the NV fall out of the spraybar?

If the engine quits, it could be the glowplug. If the NV falls out, then it's a kinked fuel hose or clogged filter (which is more likely if the filter is installed backwards to the flow direction).

The reason I ask is because we had a young fellow who was gifted a thoroughly worn Fox .35 Stunt (not by me...I'm not that mean).  The glowplug was burned out, and he relied on the LHS to select the correct glowplug for him to purchase. They sold him a "short" glowplug of some sort. The engine would run, but the NV setting was on/off, with no range. I screwed in a Thunderbolt LONG idle bar and all was well. Free, I might add.   D>K  Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline frank mccune

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Re: Uniflow tank not working?
« Reply #8 on: October 06, 2020, 02:57:39 PM »
     Hello Steve:

     Great idea! As a matter of fact, I will check the plug to determine if it is a short reach plug.  Yes, I can screw the needle out until it falls from the engine and the engine will not go rich.

       
Thanks for thinking out of the box,
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Offline John Leidle

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Re: Uniflow tank not working?
« Reply #9 on: October 06, 2020, 06:36:21 PM »
  I'd consider carefully replacing the tubing... lose the fuel filter for a test run ........
     Best wishes , John L.
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Offline FLOYD CARTER

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Re: Uniflow tank not working?
« Reply #10 on: October 08, 2020, 02:40:08 PM »
I've had problems with a clunk tank (plastic) with Uniflow.  With two pieces of fuel tubing terminated on the clunk (soldered, probably), the combined stiffness of the tubing didn't permit the clunk to move much.  So it operated much like a metal tank with fixed plumbing/

Of course, the "fix" was more flexible fuel tubing.  I found tubing which was flexible and intended for clunk tanks.

BTW.  All the fuel filters I've seen are bi-directional.  There is no input/output.  It's just a  metal screen with two connectors
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Offline Dan McEntee

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Re: Uniflow tank not working?
« Reply #11 on: October 08, 2020, 05:05:35 PM »
Quote from: FLOYD CARTER on October 08, 2020, 02:40:08 PM
I've had problems with a clunk tank (plastic) with Uniflow.  With two pieces of fuel tubing terminated on the clunk (soldered, probably), the combined stiffness of the tubing didn't permit the clunk to move much.  So it operated much like a metal tank with fixed plumbing/

Of course, the "fix" was more flexible fuel tubing.  I found tubing which was flexible and intended for clunk tanks.

BTW.  All the fuel filters I've seen are bi-directional.  There is no input/output.  It's just a  metal screen with two connectors

   If you look at any fuel filter that can come apart for cleaning, you will see that there is one side that has considerably more volume than the other side. This is the side you put towards the tank. If you get an accumulation of crap, there is room for it to allow some fuel flow. If you put it the other way, it plugs up much faster and some times won't pass fuel.  Ty has already pointed out how the Crap Traps work. There is a right way and a wrong way for everything!
   Type at you later,
  Dan McEntee
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Offline FLOYD CARTER

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Re: Uniflow tank not working?
« Reply #12 on: October 08, 2020, 05:25:11 PM »
Think about it.  A fuel filter with two screens in series, whether you use it with the coarse screen or fine screen first, the end result is exactly the same.  Big pieces (of whatever the fuel has in it) will not pass.  Small pieces will not pass, either.   So it works both ways.  If it clogs up, it should clog the same amount in either direction.
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Offline Dan McEntee

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Re: Uniflow tank not working?
« Reply #13 on: October 08, 2020, 07:33:02 PM »
Quote from: FLOYD CARTER on October 08, 2020, 05:25:11 PM
Think about it.  A fuel filter with two screens in series, whether you use it with the coarse screen or fine screen first, the end result is exactly the same.  Big pieces (of whatever the fuel has in it) will not pass.  Small pieces will not pass, either.   So it works both ways.  If it clogs up, it should clog the same amount in either direction.

     Ah,. nope!  If you have ever examined one that has been in service for a while, you would see some crud in each, but fuel still flows well enough for a good engine run.  If the filter had been turned around, it would have stopped flow and another 5 or 6 bucks down on the counter at the hobby shop much, much sooner than it should have.
    Type at you later,
  Dan McEntee
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Offline FLOYD CARTER

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Re: Uniflow tank not working?
« Reply #14 on: October 09, 2020, 11:21:25 AM »
I agree that once a filter has been in use, one should never turn it around without first taking it apart for cleaning.  I use fuel filters that screw together.  I can routinely take it apart for cleaning.
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Online Brett Buck

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Re: Uniflow tank not working?
« Reply #15 on: October 09, 2020, 01:51:40 PM »
Quote from: FLOYD CARTER on October 09, 2020, 11:21:25 AM
I agree that once a filter has been in use, one should never turn it around without first taking it apart for cleaning.  I use fuel filters that screw together.  I can routinely take it apart for cleaning.

   They are definitely directional, and the direction matters. But yes, if you have it backwards, flush it out from the other direction first.

    Brett
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