Author Topic: HELP!!! lol (update) (Read 3234 times)

Dwayne · « **on:** May 05, 2011, 11:50:30 AM »

I have a Merco 40 mounted upright with a 6 oz sullivan flex tank set up with a solid tube uniflow it is halfway down the tank and pointed straight down to get even laps upright and inverted, it runs great for awhile with a great 4-2 break but it always leans out to a 2 cycle with about a minute left in the tank, I've tried everything changed all the tubes used just suction tried blocking the uniflow with presure in the overflow everything and it still leans out at the same time every time, I'm stumped

Dwayne · « **Reply #1 on:** May 06, 2011, 05:05:35 AM »

Stumped the panel did I? LOL No matter I changed the Merco for a LA 40 and I'll see how that goes.

John Miller · « **Reply #2 on:** May 06, 2011, 09:11:13 AM »

Your tank seems to be acting as a conventionally plumbed tank. The key statement that concerns me is your description of your uniflow line orientation.

The uniflow should not be going straight down, rather it should be going to the mid hieght level on the outside portion of the tank.

RandySmith · « **Reply #3 on:** May 06, 2011, 09:35:54 AM »

Quote from: Dwayne Donnelly on May 05, 2011, 11:50:30 AM

I have a Merco 40 mounted upright with a 6 oz sullivan flex tank set up with a solid tube uniflow it is halfway down the tank and pointed straight down to get even laps upright and inverted, it runs great for awhile with a great 4-2 break but it always leans out to a 2 cycle with about a minute left in the tank, I've tried everything changed all the tubes used just suction tried blocking the uniflow with presure in the overflow everything and it still leans out at the same time every time, I'm stumped

Hi the way you have it plumbed what is most likley happening is when the uniflow vent uncovers the engine then goes lean, Try making a longer uniflow vent that goes all the way to the back of the tank.

Randy

Dwayne · « **Reply #4 on:** May 06, 2011, 03:00:33 PM »

Quote from: John Miller on May 06, 2011, 09:11:13 AM

Your tank seems to be acting as a conventionally plumbed tank. The key statement that concerns me is your description of your uniflow line orientation.

The uniflow should not be going straight down, rather it should be going to the mid hieght level on the outside portion of the tank.

Yeah I thought so but the way I built the tank compartment that's the only way I get the same lap times inverted and upright.

Dwayne · « **Reply #5 on:** May 06, 2011, 03:02:10 PM »

Quote from: RandySmith on May 06, 2011, 09:35:54 AM

Hi the way you have it plumbed what is most likley happening is when the uniflow vent uncovers the engine then goes lean, Try making a longer uniflow vent that goes all the way to the back of the tank.

Randy

Thanks Randy but it goes lean on suction alone as well.

Brett Buck · « **Reply #6 on:** May 06, 2011, 04:42:26 PM »

Quote from: Dwayne Donnelly on May 06, 2011, 03:02:10 PM

Thanks Randy but it goes lean on suction alone as well.

Which, if I understand the problem, is exactly what you would expect. I couldn't quite figure it out from the above - your uniflow vent goes about halfway to the back, and all the way to the outside edge, right? Halfway back is OK, not all the way to the side = your problem.

Brett

Dwayne · « **Reply #7 on:** May 06, 2011, 05:10:30 PM »

Quote from: Brett Buck on May 06, 2011, 04:42:26 PM

Which, if I understand the problem, is exactly what you would expect. I couldn't quite figure it out from the above - your uniflow vent goes about halfway to the back, and all the way to the outside edge, right? Halfway back is OK, not all the way to the side = your problem.

Brett

Ok I'm confused is this not the way to plumb things?

Brett Buck · « **Reply #8 on:** May 06, 2011, 06:41:54 PM »

Quote from: Dwayne Donnelly on May 06, 2011, 05:10:30 PM

Ok I'm confused is this not the way to plumb things?

That looks right to me. Not going all the way to the back is not likely the problem, if the uniflow winds up on the outboard edge of the tank. That's very similar to the way I used to do it.

When you said suction, I interpret that to mean that you plugged the uniflow and left the overflow open, which would cause it to run progressively leaner during the flight. I marked up the drawing with the mounting direction and the standard interpretation of suction and uniflow.

Brett

Steve Helmick · « **Reply #9 on:** May 06, 2011, 06:57:42 PM »

Look at airplane in flight, to see if it's seriously yawing outward. If it is not, then shim the rear of the tank outboard and test fly. Moving the uniflow vent toward the rear of the tank is going to help with this.

Some may be confused by the uniflow vent pointing downward. I believe you mean the air inlet end of the uniflow tube. This seemed weird to me, when I first saw Bruce Perry's model rigged this way. He said that Randy Aero recommended it, to equalize upwind/downwind variation....one reason I like muffler pressure, ya know...

Steve

Dwayne · « **Reply #10 on:** May 06, 2011, 07:09:27 PM »

Thanks so much everyone and sorry If I'm not being clear, the bent end of the uniflow tube that is in the tank is pointed down but to the outside of the tank, Ive tried plugging the uniflow tube and run it straight suction, I've tried using preasure in the overflow with the uniflow pugged and of course the overflow plugged and uniflow preasure and all 3 ways the engine always leans out at about the same time.
Thanks again
Dwayne

Brett Buck · « **Reply #11 on:** May 06, 2011, 09:33:55 PM »

Quote from: Dwayne Donnelly on May 06, 2011, 07:09:27 PM

Thanks so much everyone and sorry If I'm not being clear, the bent end of the uniflow tube that is in the tank is pointed down but to the outside of the tank, Ive tried plugging the uniflow tube and run it straight suction, I've tried using preasure in the overflow with the uniflow pugged and of course the overflow plugged and uniflow preasure and all 3 ways the engine always leans out at about the same time.

No problem, I was not quite sure we were seeing it the same way.

The uniflow is at the bottom of the tank? Do you need that to get the upright/inverted speed right? Otherwise it should be more-or-less in the middle of the outside wall of the tank.

Brett

John Miller · « **Reply #12 on:** May 06, 2011, 10:17:21 PM »

The drawing you posted is one I drew, and the way I set up my tanks. The rules of orthographic projection require that it be draw3n this way. Note, that the object on the right is as viewed from directly above, and looking down on the top of the tank. on the left, the tank is shown in correct orthographic projection, but perhaps confusing you.

The top of the tank is represented by the right vertical line, the side of the tank next to the fuselage is represented by the bottom line. The top line is is the outside edge of the tank.

Perhaps this different view my be clearer to you.

Dwayne · « **Reply #13 on:** May 07, 2011, 06:26:04 AM »

Quote from: Brett Buck on May 06, 2011, 09:33:55 PM

The uniflow is at the bottom of the tank? Do you need that to get the upright/inverted speed right? Otherwise it should be more-or-less in the middle of the outside wall of the tank.

Brett

Yes if the tube is in the middle the engine runs faster inverted, the engine is upright and I built the tank compartment to high so if I put the tube in the middle of the tank it is a good 1/2 inch above the nva, I realy need to post some pics but I'm not at home right now I'll try later.
Thanks again
Dwayne

Dwayne · « **Reply #14 on:** May 07, 2011, 06:27:13 AM »

Quote from: John Miller on May 06, 2011, 10:17:21 PM

The drawing you posted is one I drew, and the way I set up my tanks. The rules of orthographic projection require that it be draw3n this way. Note, that the object on the right is as viewed from directly above, and looking down on the top of the tank. on the left, the tank is shown in correct orthographic projection, but perhaps confusing you.

The top of the tank is represented by the right vertical line, the side of the tank next to the fuselage is represented by the bottom line. The top line is is the outside edge of the tank.

Perhaps this different view my be clearer to you.

Thanks John that is the way I have mine plumbed.
Thanks again
Dwayne

Dwayne · « **Reply #15 on:** May 07, 2011, 09:49:56 AM »

I would like to thank everyone for their responses and input but I'm afraid it wasn't the tank, I swapped out the Merco for a LA .40 it ran perfect first flight. Equal lap times upright/inverted a little burp on outside loops but for an upright engine it wasn't to bad, but the big thing? No runaway

It ran out 3 tanks right to the end perfectly so It's the Merco sheesh wish I knew that earlier it would have saved me many head aches...lol
Anyway thanks again everyone

Dwayne

John Miller · « **Reply #16 on:** May 07, 2011, 10:21:42 AM »

Happy to hear that things are good now, with the new engine.

Dwayne · « **Reply #17 on:** May 07, 2011, 11:44:48 AM »

Quote from: John Miller on May 07, 2011, 10:21:42 AM

Happy to hear that things are good now, with the new engine.

Thanks John, now I have to figure out what's wrong with the Merco they are a very good stunt engine, maybe it doesn't like being mounted upright who knows.
Dwayne

Brett Buck · « **Reply #18 on:** May 07, 2011, 01:10:11 PM »

Quote from: Dwayne Donnelly on May 07, 2011, 11:44:48 AM

Thanks John, now I have to figure out what's wrong with the Merco they are a very good stunt engine, maybe it doesn't like being mounted upright who knows.

What variety of Merco?

Brett

Dwayne · « **Reply #19 on:** May 07, 2011, 01:40:26 PM »

Quote from: Brett Buck on May 07, 2011, 01:10:11 PM

What variety of Merco?

Brett

It's a Premier Merco 40 that I fitted wth a Brodak 40 venturi and Enya nva, the venturi was to wide for the case so I had to file it a bit to get to fit so I'm thinkig I didn't do a good job and it's sucking air.
Dwayne

Brett Buck · « **Reply #20 on:** May 07, 2011, 02:01:09 PM »

Quote from: Dwayne Donnelly on May 07, 2011, 01:40:26 PM

It's a Premier Merco 40 that I fitted wth a Brodak 40 venturi and Enya nva, the venturi was to wide for the case so I had to file it a bit to get to fit so I'm thinkig I didn't do a good job and it's sucking air.
Dwayne

This is an iron-liner engine? If so, it may be either worn out, or overheating.

Brett

Dwayne · « **Reply #21 on:** May 07, 2011, 02:37:47 PM »

Quote from: Brett Buck on May 07, 2011, 02:01:09 PM

This is an iron-liner engine? If so, it may be either worn out, or overheating.

Brett

It's either abc or abn and baffled so in theory it should be the best of both worlds a smoother running baffled engine that doesn't require a ton of castor, I'm using Omega with 8 oz. of castor added to a gallon.
Thanks Brett
Dwayne

RandySmith · « **Reply #22 on:** May 08, 2011, 09:10:35 AM »

Quote from: Dwayne Donnelly on May 06, 2011, 03:02:10 PM

Thanks Randy but it goes lean on suction alone as well.

But did you ever try what I suggested ??, some motors are much more sensitive than others to this, I had a FP 35 we worked with that you could set your watch by where the uniflow vent was,m When using the short vent it would uncover and go lean right before the sq 8. After moving it back a bit it would hold untill the hourglass, that was as far as it could be slid back so we put in a new longer tube, It then went all the way back and did not lean untill after the clover. Some people have been so tweeked by this that they ran the uniflow tube (or vent tube) like you have the overflow, and used it put in the top inside corner so it would uncover right away..keeping the run more steady and not having a point in the flight where it would just jump an few tenths all of a sudden.
Bill Werwage had a plastic tank he plumbed that way for the exact same reason.
Also if you have a worn piston and sleeve, or a leak somewhere in the system of the engine, such as the backplate gasket, that will also affect how it feeds fuel. Again some engines don't seem to care,and other are much more sensitive.

Let us know how it goes,

Regards
Randy

Dwayne · « **Reply #23 on:** May 08, 2011, 09:20:09 AM »

Quote from: RandySmith on May 08, 2011, 09:10:35 AM

But did you ever try what I suggested ??, some motors are much more sensitive than others to this, I had a FP 35 we worked with that you could set your watch by where the uniflow vent was,m When using the short vent it would uncover and go lean right before the sq 8. After moving it back a bit it would hold untill the hourglass, that was as far as it could be slid back so we put in a new longer tube, It then went all the way back and did not lean untill after the clover. Some people have been so tweeked by this that they ran the uniflow tube (or vent tube) like you have the overflow, and used it put in the top inside corner so it would uncover right away..keeping the run more steady and not having a point in the flight where it would just jump an few tenths all of a sudden.
Bill Werwage had a plastic tank he plumbed that way for the exact same reason.
Also if you have a worn piston and sleeve, or a leak somewhere in the system of the engine, such as the backplate gasket, that will also affect how it feeds fuel. Again some engines don't seem to care,and other are much more sensitive.

Let us know how it goes,

Regards
Randy

Hi Randy, no I haven't tried that yet the LA is running well so I'll stick with it for now but I'm not diving up on the Merco stay tuned and thanks for the advice.
Dwayne

Steve Helmick · « **Reply #24 on:** May 09, 2011, 02:06:37 AM »

Quote from: Dwayne Donnelly on May 07, 2011, 01:40:26 PM

It's a Premier Merco 40 that I fitted wth a Brodak 40 venturi and Enya nva, the venturi was to wide for the case so I had to file it a bit to get to fit so I'm thinkig I didn't do a good job and it's sucking air.
Dwayne

I'm wondering if the engine is a Rustler-Merco .40...the "Metamorph"....or an ABC version of the original Merco .40? I've never heard of a "Premier Merco 40", anyway. I know Ian has had ABC versions of the old .61's made, but don't know about any ABC versions of the old .40...but maybe. I think his supplier is in Ukraine, but not 100% sure.

FWIW, if it's an ABC, you can look in the exhaust stack and see brass. If it's an ABN, you just see "silver" (nickle). With the ABC, only the bore is chrome plated, but with ABN, the entire liner is plated, inside & out, flange and all.

Steve

RandySmith · « **Reply #25 on:** May 09, 2011, 01:22:06 PM »

"If it's an ABN, you just see "silver" (nickle). With the ABC, only the bore is chrome plated, but with ABN, the entire liner is plated, inside & out, flange and all. "

Hi Your correct on most motors..but not aLL you can look and see brass on some, others you will see a blue metal, still others will show a gold color metal, still others have a rainbow coloring to the sleeve. A large amount of engines that has electrolis nickle have mostly either a gold or blue coloring on the inside of the sleeve, while the one that have nickle plating look like very shiny chrome plating

Regards
Randy

Dwayne · « **Reply #26 on:** May 09, 2011, 03:54:19 PM »

Hey guys it's box stock made by Premier of England and I believe it is ABC I've had it apart and the sleeve is brass, here's a pic of the manual.
Thanks
Dwayne

Stan Bidowski · « **Reply #27 on:** May 09, 2011, 04:43:53 PM »

I'm with Randy's suggestion. When the uniflow is uncovered, the engine should
lean out. Moving the uniflow tube farther back should change when the engine
leans out as the fuel gets burnt off. Switching to the LA fixed it likely because
the correct tank setup is simply different for this engine versus the Merco ( different
fuel draw, etc. between the two engines ). If the venturi in the Merco is leaking,
that would also account for the difference as well. If you use the Merco again, please
try moving the uniflow back, and seal the venturi's fit in the crankcase and the NVA too.
Like you said, the Merco ran fine, until the last minute of the tank. This was when the
uniflow was uncovered in the tank.
Stan

John Miller · « **Reply #28 on:** May 09, 2011, 05:33:38 PM »

Some time ago, none other than Paul Walker, performed tests on uniflow termination locations. His findings were illuminating. Based on those findings, and my personal experience with literally dozens of planes using the illustrated tank, with the uniflow going to the outside, middle of the tank, I can say without hesitation that if the tank is set up as illustrated, the location of the uniflow end is not the problem.

Dwayne · « **Reply #29 on:** May 09, 2011, 05:49:13 PM »

Quote from: John Miller on May 09, 2011, 05:33:38 PM

Some time ago, none other than Paul Walker, performed tests on uniflow termination locations. His findings were illuminating. Based on those findings, and my personal experience with literally dozens of planes using the illustrated tank, with the uniflow going to the outside, middle of the tank, I can say without hesitation that if the tank is set up as illustrated, the location of the uniflow end is not the problem.

Yup I read that too, that's why I set it up the way I did but Randy is right some engines just behave differently so when I get around to it I'm going to try the merco again with the long uniflow tube and I have a feeling it'll work.

Chris Wilson · « **Reply #30 on:** May 09, 2011, 06:02:05 PM »

Some fliers may not realize that the wall of fuel in flight is not parallel to a tank's side wall or tangent to the flying circle, it in fact lies at an angle slightly towards the direction of flight.
This is the reason that tin tanks often have a wedge shape that follows the fuels angle.
Brian Eather has a treatise on this and it is illuminating.

I think that this is part of the reason why the uniflow outlet sits so well halfway along the outside wall, that plus separation distance is needed to prevent air bubbles from entering the pickup tube easily.

Cheers.

RandySmith · « **Reply #31 on:** May 09, 2011, 10:06:41 PM »

Quote from: John Miller on May 09, 2011, 05:33:38 PM

Some time ago, none other than Paul Walker, performed tests on uniflow termination locations. His findings were illuminating. Based on those findings, and my personal experience with literally dozens of planes using the illustrated tank, with the uniflow going to the outside, middle of the tank, I can say without hesitation that if the tank is set up as illustrated, the location of the uniflow end is not the problem.

And you would be FLAT wrong in saying that for some engines, and correct for others. I know this for a fact from many many setups.

Regards
Randy

John Miller · « **Reply #32 on:** May 10, 2011, 10:01:28 AM »

Quote from: RandySmith on May 09, 2011, 10:06:41 PM

And you would be FLAT wrong in saying that for some engines, and correct for others. I know this for a fact from many many setups.

Regards
Randy

OK Randy, with your experience, you are likely to be right.

I've been using this tank set up, almost exclusivly for the past 25 years. Probably only 2 or 3 metal hard tanks used during that time frame, I've used, or witnessed, this set up on Foxes, McCoys, K&B's, Thunder Tigers, Super Tigres, Magnums, Enya's, OS .35S, fp's, La's, Saitos, PA's, RO Jetts, and Stalkers. About the only one I wasn't totally happy with were the Saitos, but I'm not sure it was the tank that was the problem.

Though I'm not a neofite, I'm always open to learning. Could you please elaborate on the problems solved, and engines affected and cured by moving the end of the uniflow forward, rearward, or, as some have advocated, closing it off and using the tank as a standard vented tank?

I've come to the conclusion that there's a bit of the Alchemist in many setups, finding that a successful setup from one doesn't work worth a hoot for another. I'm trying to discover the reason why, so your help is appreciated.