Author Topic: Engine dies after two laps (Read 3473 times)

Steve Agrella · « **on:** March 23, 2015, 07:47:40 PM »

I have a LA46 in a ARF Oriental, .272 Venturi, ST needle valve, running on a Brodak uniflow 4.5 oz tank all tubes forward, engine dies after two laps.

I hooked the line up closest to the wedge to the feed, the middle tube to the muffler pressure and fill, the end tube closest to the inboard wing is overflow and plugged after filling.

I'm launching the plane in 4 stroke a bit on the rich side, getting 6 second lap times, the engine is new with 6 tanks of break in.

Any suggestions on what I might be doing wrong.

wwwarbird · « **Reply #1 on:** March 23, 2015, 08:02:01 PM »

Not sure if it actually makes a difference, but I'd put the pressure line on the overflow tube and be putting the plug on the fill tube. Beyond that the pickup tube might be plugged inside the tank, the filter could be plugged, and it's not a bad idea to change out all the fuel lines either. I've had a lot of brand new Brodak tanks with leaks too, you really should pressure check every one of them before initial use.

Don Chandler · « **Reply #2 on:** March 23, 2015, 08:04:07 PM »

I have 3 Cardinals all with LA 46 in them. The only difference I see between your setup and mine is my venturis are .280 and I don't take off as rich as it sounds like you do. Otherewise sounds like your set up is ok. Cleanliness is next to Godliness so maybe something in the system? I had that problem when I flew carrier and speed, the engine was actually running away from the fuel. I went to uniflow tanks and they worked ok.

I also have had leaky Brodak tanks, that could do it.

Don

Howard Rush · « **Reply #3 on:** March 23, 2015, 08:07:20 PM »

You might do some experiments to see if the pipes inside the tank go where they ought to go.

Scott Richlen · « **Reply #4 on:** March 23, 2015, 08:08:43 PM »

I make my own tanks and so do a lot of other guys. There are just too many poorly soldered/assembled commercial tanks out there. We will be putting on a tank-building workshop in a few weeks for our club so more guys can build their own. We put in too much work on our planes to roll the dice on most of the junk tanks that are out there.

If you insist on buying a commercial tank, buy a Brodak tank kit and finish the assembly yourself. That way you know what you've got.

Scott

bill bischoff · « **Reply #5 on:** March 23, 2015, 08:11:46 PM »

I am absolutely serious when I ask this. Is the tank in the plane upside down? Is the pickup actually on the inboard side? When installing the tank from the bottom, it's not hard to do. I watched a former NATS winner go through the motions several times before he realized what he had done.

Dave_Trible · « **Reply #6 on:** March 23, 2015, 08:37:42 PM »

Wondering if the engine is anywhere near broke in. The one LA .46 I have was extremely tight and needed nearly two hours on the bench to be friendly. Maybe a cold plug.

Dave

Steve Agrella · « **Reply #7 on:** March 23, 2015, 09:19:05 PM »

Looked at the tank installation again, crap, put the tank in backwards, thanks for the replies,made me go back and look again.

Tim Wescott · « **Reply #8 on:** March 23, 2015, 09:55:40 PM »

Quote from: bill bischoff on March 23, 2015, 08:11:46 PM

I am absolutely serious when I ask this. Is the tank in the plane upside down? Is the pickup actually on the inboard side? When installing the tank from the bottom, it's not hard to do. I watched a former NATS winner go through the motions several times before he realized what he had done.

The second to last tank that I've built was hand made to fit into a tight space -- and it was backwards. The last tank that I've built fit into the same space, only it was pointed the right way.

Keith Miller · « **Reply #9 on:** March 23, 2015, 10:07:32 PM »

Quote from: Scott Richlen on March 23, 2015, 08:08:43 PM

I make my own tanks and so do a lot of other guys. There are just too many poorly soldered/assembled commercial tanks out there. We will be putting on a tank-building workshop in a few weeks for our club so more guys can build their own. We put in too much work on our planes to roll the dice on most of the junk tanks that are out there.

If you insist on buying a commercial tank, buy a Brodak tank kit and finish the assembly yourself. That way you know what you've got.

Scott

To add to Scott, if pickup and/or uniflow tubes aren't tacked or soldered to the back of the tank, they can act as a tuning fork if the engine hits their resonant frequency. The tubes might hit resonance on your 2nd lap, start vibrating inside the tank and severely disrupting the flow going towards the engine. Try moving a straw rapidly about a fixed point between two pinched fingers and you might find that the fluid inside flows out towards the free end.

Randy Cuberly · « **Reply #10 on:** March 23, 2015, 10:57:29 PM »

Frankly it sounds like a plug problem to me. use either a Thunderbolt R/C long, or an Enya #3 and the problem will likely disappear.
If the problem was really in the tank it would likely not go two laps but would starve and quit under accelleration when launched.

Change to one of the above plugs...best choice is actually the Enya#3.

Randy Cuberly

John Rist · « **Reply #11 on:** March 24, 2015, 02:08:07 AM »

Quote from: Steve Agrella on March 23, 2015, 09:19:05 PM

Looked at the tank installation again, crap, put the tank in backwards, thanks for the replies,made me go back and look again.

Have you tried it with the tank turned around? Did it fix the problem?

Randy Ryan · « **Reply #12 on:** March 24, 2015, 07:22:02 AM »

Quote from: bill bischoff on March 23, 2015, 08:11:46 PM

I am absolutely serious when I ask this. Is the tank in the plane upside down? Is the pickup actually on the inboard side? When installing the tank from the bottom, it's not hard to do. I watched a former NATS winner go through the motions several times before he realized what he had done.

GOOD CATCH Bill!!!!! I've never done it myself, but with age creeping up on my I suspect I will at some point!

john e. holliday · « **Reply #13 on:** March 24, 2015, 01:04:29 PM »

Hey Steve, we all have done that at one time or another. Bet you pay more attention next time.

Paul Walker · « **Reply #14 on:** March 24, 2015, 02:12:11 PM »

You never mentioned which way it was quitting: rich or lean.
That answer will go a long ways to answering your question.

6.0 second lap times seem very slow to me.

dale gleason · « **Reply #15 on:** March 24, 2015, 03:49:09 PM »

To all:
Thanks, Bill, for referring to me as a "NATs winner", but, actually, I've never won the NATs. One time I came in 17th. But, having said that, tank orientation is a common problem, even among the greats. I thought it was Dougie who got my tank problem figured out for me. But, it was hot and humid that day.... like 105 and 98%. And then, later, RO. (similar conditions) Maybe you got me straightened out that time before Doug and Richard pointed out the error of me ways.

Strange...I build the tank, they show me how to use it....

Anyway, tankage is 99% of all engine problems, that last percent is not plugs, fuel, battery, precession, or stuff like that. It's a tank problem, too.

Unless you're running spark ignition. That's a whole 'nuther smoke. Then it's more like 50/50....but, I digress...

Always punch a hole in the side of the tank, wrap a few turns of copper wire to secure the feed line and uniflow in place in the inside of the tank, and solder securely, to avoid resonance/vibration difficulties, and picture the tank in a six G centrifuge. Or, better yet, use a Sullivan RST plastic tank, and life will become happy and simple.

hope this helps,
dg
(please do not ask for pictures)

bill bischoff · « **Reply #16 on:** March 24, 2015, 05:27:43 PM »

Dale, you mean YOU TOO? Another hero falls by the wayside.

wwwarbird · « **Reply #17 on:** March 24, 2015, 06:18:35 PM »

Quote from: Steve Agrella on March 23, 2015, 09:19:05 PM

Looked at the tank installation again, crap, put the tank in backwards, thanks for the replies,made me go back and look again.

That'll do it.

John Leidle · « **Reply #18 on:** March 24, 2015, 07:45:51 PM »

What prop & RPM

?

Steve Agrella · « **Reply #19 on:** March 24, 2015, 08:00:25 PM »

Thanks guys,

Yeppers tank was in backwards, won't know until Cali winds die down, couple of days it is howling out here.

100% convinced this time it's right, this s my 1st built up plane so have to think, God forbide.....lol, anyway thanks for the heads up on the tank.

I'm certainly not amune to making mistakes, seems like the older I get the worst it's getting, not life threatening so no worries, however a bit frustrating, I looked at that damn thing with acceptance ?? When I installed it.

Curare · « **Reply #20 on:** March 25, 2015, 12:18:21 AM »

hehehe I had the same thing with the first flights of my Chipmunk. Installed everything neat as a button, but called myself an idiot for plumbing the tank upside down, so resoldered it to the 'right' way.

Same problem; two laps and it'd shut off like a light switch.

Got home, I'd built the tank the right way the first time and then 'fixed' it UPSIDE DOWN!

me=idiot.

Steve Agrella · « **Reply #21 on:** March 25, 2015, 06:35:29 PM »

Went out and flew the plane today, walla it's fixed, now all I have to do is learn how to fly it.

Thanks again for you words of wisdom and kindness.

Steve

Dan McEntee · « **Reply #22 on:** March 25, 2015, 06:47:49 PM »

One thing I've learned in all my years of doing this and other life stuff, there are really no new problems, just people experiencing them for the first time! You did not invent this mistake! Like a lot of others, I been there and done that! But I didn't have the internet to lean on! Might as well take advantage of the technology and tap the limitless experience that there is here. The electric guys have been breaking new ground, but I'll bet there is a lot of repeatability in simple, honest mistakes there also. Some might be more costly! Imagine getting battery polarity wrong in a bad situation! Another diploma from The School of Hard Knocks!
Good luck and have fun,
Dan McEntee

Steve Helmick · « **Reply #23 on:** March 25, 2015, 08:06:58 PM »

Quote from: Steve Agrella on March 24, 2015, 08:00:25 PM

Thanks guys,

Yeppers tank was in backwards, won't know until Cali winds die down, couple of days it is howling out here.

100% convinced this time it's right, this s my 1st built up plane so have to think, God forbide.....lol, anyway thanks for the heads up on the tank.

I'm certainly not amune to making mistakes, seems like the older I get the worst it's getting, not life threatening so no worries, however a bit frustrating, I looked at that damn thing with acceptance ?? When I installed it.

I almost suggested that, but I've only seen it done once, and it only made 1 lap under power. A high-powered Boeing Engineer, too. No, not Paul or Howard. Certainly not me...not an engineer. Good to hear you got it figured out. I looked at the picture on the Brodak website and would have hooked up the hoses as you did. The only thing...DO NOT trust those little yellow caps. They can leak. A short piece of fuel tubing with a BB in it is probably the best way to make a cap. DO NOT stick a screw into a piece of fuel tubing. That can also leak.

Steve

Author Topic: Engine dies after two laps (Read 3473 times)

John Leidle