Author Topic: engine runs away (Read 4436 times)

Bootlegger · « **on:** February 02, 2018, 10:56:56 AM »

Got an L A 46 mounted in a full fuse model that runs away on me, pulled the engine mounted it on bench tried another tank, ran fine, pulled tank and pressure checked it, no leaks, changed flex tubing also, put it all back together, and the same thing again runs away, where do I check next? Thanks

peabody · « **Reply #1 on:** February 02, 2018, 11:08:39 AM »

Hi Gil
My experience with FP/La's is that too much pitch causes them to run away
Have fun

Brett Buck · « **Reply #2 on:** February 02, 2018, 12:02:48 PM »

Quote from: Bootlegger on February 02, 2018, 10:56:56 AM

Got an L A 46 mounted in a full fuse model that runs away on me, pulled the engine mounted it on bench tried another tank, ran fine, pulled tank and pressure checked it, no leaks, changed flex tubing also, put it all back together, and the same thing again runs away, where do I check next? Thanks

What prop are you using, and are you using the stock CL venturi, or something else? How is the tank and plumbing arranged (profile mount, how wide is teh tank, is it uniflow or suction), etc?

Brett

Randy Cuberly · « **Reply #3 on:** February 02, 2018, 12:07:46 PM »

Gil,
Could you provide a little more information please.

1. What is the airplane? How is the tank mounted. Are the engine bearers solid?

2. What prop are you running, and what fuel?

3. What RPM are you setting before it "runs away".

4. What needle valve assembly and what size venture.

5. Does the engine have the plastic back cover or an aluminum one? Is the gasket in place.

6. What glow plug are you using?

7. While FP40's frequently run away for too much prop, it's very rare for LA46's do that!

Randy Cuberly

Bootlegger · « **Reply #4 on:** February 02, 2018, 12:55:56 PM »

Prop s an apc 11.5x4, fuel is 5%N 22% oil half/half plug is a T bolt idle bar tank is a uniflow, the engine just runs at W O T at start up the model is a Dixon full fuse cardinal, in the past when I ran/flew it didn't have this problem, all the tubing in the tank as copper
That's all I can remember.. And again thanks for the help...

Randy Cuberly · « **Reply #5 on:** February 02, 2018, 02:04:18 PM »

Quote from: Bootlegger on February 02, 2018, 12:55:56 PM

Prop s an apc 11.5x4, fuel is 5%N 22% oil half/half plug is a T bolt idle bar tank is a uniflow, the engine just runs at W O T at start up the model is a Dixon full fuse cardinal, in the past when I ran/flew it didn't have this problem, all the tubing in the tank as copper
That's all I can remember.. And again thanks for the help...

What about the engine back cover...is it plastic?

What kind of needle valve assembly?

Something has to be leaking!!!

Head screws??? Plug leaking???

Since it ran OK on the other tank and not on the one in the airplane I would strongly suspect the tank. You said you checked it for leaks but there could be a problem inside like a solder ball, etc, partially blocking the pick up line or just dirt or even soldering flux. Try another tank in the airplane!

Randy Cuberly

Perry Rose · « **Reply #6 on:** February 02, 2018, 02:42:13 PM »

Vibration problem. Something is loose or not stiff enough inside the fuselage.

FLOYD CARTER · « **Reply #7 on:** February 02, 2018, 02:48:35 PM »

Randy's analysis makes the ,most sense. Take the tank apart and check that Cu tubing. They sometimes get cracks if not properly annealed beforehand. If in doubt, replace.

Bootlegger · « **Reply #8 on:** February 03, 2018, 06:40:34 AM »

Back plate is metal, venturi .282, Smith spray bar and needle, still I think that it is the tank, will pull it and check the tubing, if anbody else has suggestions please jump in with them. Thanks agaih

Bootlegger · « **Reply #9 on:** February 03, 2018, 01:46:31 PM »

Motor Man, I have run and flown this set up several times with no changes, it hung in the rack for a few months, and when I took it out that is when it went to running away, so I pulled the engine and put it on the bench and it ran fine, pulled the tank and checked fro leaks found none, put it all back together and run away again, same fuel, prop and everything else and run away again, the only other thing that I can think of is something in the tank..??
I do appreciate all the responses though..

RandySmith · « **Reply #10 on:** February 03, 2018, 05:54:44 PM »

Then you should try to replace the tank, and see how that works for you

Randy

Bootlegger · « **Reply #11 on:** February 03, 2018, 08:18:47 PM »

Thanks Randy, that is what I was thinking also..

RandySmith · « **Reply #12 on:** February 04, 2018, 02:41:25 PM »

also clean the spray bar, check the fuel filter, many have found leaky fuel filters, and replace the tubing, make sure you do not have castor slags in the fuel, or the filter, they will also cause runaway, The clear slags form more readily in cold weather

Randy

Bootlegger · « **Reply #13 on:** February 04, 2018, 07:10:31 PM »

Randy, I checked the fuel filter, it was clean, also changed all the flexable tubing. and cleaned the needle assy. Tomorrow I hope to change the tank for another..

Again thanks for all the help/advice, Gil

Dennis Moritz · « **Reply #14 on:** February 04, 2018, 09:23:01 PM »

Are engine bolts tight? Someone said could be vibration. Check for that. Might have a crack somewhere or a loosened glue joint. I'd switch out tank. Could be pick up tube or debris in tank. Are you running uniflo. Try running without uniflo. Uniflo is a plus when it works. It can, however, exaggerate bad vibes.

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Dennis Moritz · « **Reply #15 on:** February 04, 2018, 09:39:17 PM »

Quote from: Dennis Moritz on February 04, 2018, 09:23:01 PM

Are engine bolts tight? Someone said could be vibration. Check for that. Might have a crack somewhere or a loosened glue joint. I'd switch out tank. Could be pick up tube or debris in tank. Are you running uniflo. Try running without uniflo. Uniflo is a plus when it works. It can, however, exaggerate bad vibes.

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I've had planes develop issues like yours. Vibration issues happening unexpectedly with a model/engine that ran consistently for years. Taking the model off uniflo helped to tame run away.

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Brent Williams · « **Reply #16 on:** February 04, 2018, 11:06:25 PM »

I am using a very sweetly running LA46 with the OS needle valve and the FP/LA25 (.260"ish) venturi in my plane. 6oz plastic clunk tank on muffler pressure. 10/22 fuel or 15/22 fuel (the extra nitro is great at my elevation)

The 3 things which made a huge difference were:
-1- Secure engine mounting. *
-2- Sealed needle valve with fuel tubing. **
-3- TT 11x4.5 prop (magic prop) ***

*It originally had a K&B 40 so I had to re-do the brass inserts to perform the switcheroo. The maple beams were somewhat oil soaked, so the epoxy just didn't have the ability hold the insert adequately. During the first 20-30 flights or so, the engine run was decent but somewhat inconsistent. I had to re-torque the 4-40 screws several times and eventually the brass inserts started to spin in the maple. I decided to re-do the brass inserts again, and the maple splintered. !?@!&%#@!

At this point I performed battlefield surgery. I grabbed my flush cut saw and amputated the front of the plane to the first bulkhead. I then made up a 1/4" plywood firewall and installed a plastic RC mount ala the Imitation. This solid, secure mount fixed most of the run problems, which I attributed to possible fuel foaming. My plane is quite old, ~25+years old. It's not a beauty queen from many prior repairs in its previous life, so having the engine hanging out in breeze on an RC mount doesn't faze me at all. I really kinda dig it, actually. Function over form. Zero regrets.

**The next thing was to seal the needle valve with a small piece of fuel tubing, as I had a idea that there might be some air leaking around the threads. The sealed needle valve produced an immediate and dramatic improvement to the run quality. The engine run is now very stable and the needle is more responsive. Simple to change. Try it out.

*** After reading the endless positive accolades about TT props on LA46's, I bought some Thunder Tiger 11x4.5" props on ebay. I really didn't want them to be magic. But...yes, for me, they are magic. They really are. The engine just settles into nice, happy, fast 4 or wet 2 in the air and it runs awesome and totally consistent the whole flight. I launch around 10200'ish. Awesome, consistent, repeatable run.

Perry Rose · « **Reply #17 on:** February 05, 2018, 06:26:18 AM »

The only option left is to install the engine on a proven plane and see what happens. I have several.

Bootlegger · « **Reply #18 on:** February 05, 2018, 07:17:45 AM »

Fellow's I sure do appreciate all the help/suggestions, and a special thanks to Mr Rose for the loan of SEVERAL models from his Air Force. When I come get he models Perry?? LOL LOL

EddyR · « **Reply #19 on:** February 07, 2018, 08:24:48 AM »

All the above is true. BUT there is one thing that will cause your problem. It can drive you crazy. The correct glow plug. That sounds to simple. A new LONG plug. Make sure it is a long plug. On many motors a short plug will run ok most off the time. Yours sounds like the wrong plug for your setup.
EddyR

Steve Helmick · « **Reply #20 on:** February 08, 2018, 04:06:12 PM »

While we're throwing ideas out there...I'd wonder if the fuel tank mounting has loosened and is allowing the tank to vibrate. It's possible, anyway...don't ask.

Steve

ray copeland · « **Reply #21 on:** February 08, 2018, 06:38:41 PM »

My bet is on fuel foaming somehow, been there, done that. Would you please post when you get it figured out.

Bootlegger · « **Reply #22 on:** February 20, 2018, 02:13:47 PM »

It runs like it is supposed to, talked to Perry Rose, and he said that some of his were doing the same thing, so he ran them on ALL synthetic fuel, and it cleared it up.

I did the same thing using about 4 tanks of fuel, and it settled down like before, so tomorrow I'll put the set up back in the model and hope for the best..

Just wanted everyone to know what worked for me..

Again thanks for all the help/suggestions..

RandySmith · « **Reply #23 on:** February 20, 2018, 02:51:13 PM »

Quote from: Bootlegger on February 20, 2018, 02:13:47 PM

It runs like it is supposed to, talked to Perry Rose, and he said that some of his were doing the same thing, so he ran them on ALL synthetic fuel, and it cleared it up.

I did the same thing using about 4 tanks of fuel, and it settled down like before, so tomorrow I'll put the set up back in the model and hope for the best..

Just wanted everyone to know what worked for me..

Again thanks for all the help/suggestions..

What fuel were you running that is bad?

Randy

Bootlegger · « **Reply #24 on:** February 20, 2018, 03:17:12 PM »

Randy, I can't say that it is bad, it was 22% oil half/half and 5-10 % nitro, it just seemed to have a build up of castor, Perry ran into the same with his L A 46 engines and did the same thing to them. ( ran some synthetic oil in them) And it cleared my up also.. Again THANKS to every one for the help/suggestions

Steve Helmick · « **Reply #25 on:** February 20, 2018, 04:33:15 PM »

Interesting. I wouldn't expect a fuel with 11% synthetic oil to varnish up the engine at all. What brand of fuel?

My first (and only) .46LA got a gallon of PM 10-29 GMA all-castor through it before I changed to PM 10-22 GMA, and then usually ran that, with no problems. May have run some 10-18 in it, likely with a couple ounces of Randy's Aero-1 added, but I don't keep log books. Ran a lot of that in my Magnum XLS .36, and figured probably a total of 15-20 gallons consumed. The engine is now 3rd hand, since I got it from Mike Haverly, flew it for years and years, and finally gave it to Tim Wescott in the KISS! (Fancherized Twister). Tim is still using it for wifely training, and I'd bet it still runs wonderfully!

Steve

Bootlegger · « **Reply #26 on:** February 20, 2018, 04:53:16 PM »

I didn't think that a blend of oil's would do that either, the other fuel is 5-10% n and 22% oil half/half and I have run it several years in P L A 46 engines also, but this did clean up the "goofy" run's. It is now back in the model that it came from, so time will tell!... Hopefully in a few days...

Target · « **Reply #27 on:** February 20, 2018, 05:00:27 PM »

Maybe something other than the oil is the difference in the fuel?
Do other engines run well on the suspect 22%, half castor, half synth fuel?
Just curious.
Thanks

Istvan Travnik · « **Reply #28 on:** February 20, 2018, 05:16:21 PM »

Let me tell you my bet...
I observed for 30 or more years that that aluminum piston engines (mostly with baffleless, plain piston) have some desire to overcooling, and in the air getting crazy, as you say "run away". Some clever comrades of me summarized this phenomenon as: "Schnuerle engines aren't proper for stunt flying". I decided to "teach" them to the right behaviour.
Well, at first I made a knot of canvas stripe around the cylinderhead. It looked as a samurai...

Immediately started to work just like a good old FOX-35 with its baffled Meehanite cast iron piston... (Now I advise you to try it.)
Next step was to reduce cooling ability of the engine: I machined off all cooling fins from the cylinderhead.
Now (for 15 years) I fly with a piece of stainless steel (let us call it deflector) plate in the combustion chamber and I can very precisely adjust the internal temperature* of the engine, by modifying the geometry of this small plate. Bonus: glowplug is lasting at least 3-400 flights.
*temperature is easily can be estimated by the color of burned oil on the deflector: dark brown, black=cool; light gray, white=hot.

Bootlegger · « **Reply #29 on:** February 20, 2018, 06:22:44 PM »

Target, I have run this fuel In the following engines, Tower 40 O S 32, 40 FP 40, 35 Thunder Tiger 36 and various engines and it happened with some of them also. I don't unnerstan all that I know???

RandySmith · « **Reply #30 on:** February 20, 2018, 10:11:19 PM »

Quote from: Bootlegger on February 20, 2018, 06:22:44 PM

Target, I have run this fuel In the following engines, Tower 40 O S 32, 40 FP 40, 35 Thunder Tiger 36 and various engines and it happened with some of them also. I don't unnerstan all that I know???

As I have said before, come warm weather that may change the problem, into a non issue, or in cold weather castor slags happen and you cannot see them

Randy