OS LA40 re-timing

Hi,

Does anyone know the details of what needs to be done to the OS 40LA port timing to fix the darn thing so it stops running away and will do a nice 4-2 break.

I should probably just sell the piece of junk on eBay and buy a Brodak 40 and be done with it.

Warren Leadbeatter
Port Stephens - Australia
AUS-14782

>Hi,
>
>Does anyone know the details of what needs to be done to the
>OS 40LA port timing to fix the darn thing so it stops running
>away and will do a nice 4-2 break.
>
>I should probably just sell the piece of junk on eBay and buy
>a Brodak 40 and be done with it.
>
>Warren Leadbeatter
>Port Stephens - Australia
>AUS-14782


Warren-I sympathize with you. DO NOT throw the LA away. I went through the same thing and now enjoy the OS more than the Brodack .40.

There is an excellent article on how to get the LA .40 to run properly in the Flying Lines on line news letter.

Look at Dave Browns links and open that one. I followed it recently, the advice that is, and last Saturday took 5 flights on the engine and was completley satisfied.
Don Chandler
P.S. Follow the article, don't try any short cuts-it works.

OOPS-I meant Phil Browns links, not Dave Browns

Is this the link?
http://www.flyinglines.org/McClave.LA40.html

The article is by Don McClave. Thanks for pointing it out!

>Is this the link?
>http://www.flyinglines.org/McClave.LA40.html
>
>The article is by Don McClave. Thanks for pointing it out!

Not sure if that is the link. It does not say anything to retiming the engine. But I did prope the site and could not find anything else.

I did do the items in Don's artical to my LA .40 and it sure flys 100% better.
I did a standard OS NVA not the remote one. I also use a 12x4 ProZinger cut down to 11x4.

Works for me.

Paul Taylor

~I wish I knew everything you have forgotten about C/L.

Check out my Blog@
http://rootbeard.rcuniverse.com
A link to a slide show of a fun day: http://www.youtube.com/watch?v=V-_sR0ZydSQ

That's pretty much how we run FP40s in my club. Except the prop is a 101/2x41/2 apc. In the ball park. Very similar. We usually add a head gasket or two. Also we use the OS needle valve.

(snip)
>That's pretty much how we run FP40s in my club. Except the
>prop is a 101/2x41/2 apc. In the ball park. Very similar. We
>usually add a head gasket or two. Also we use the OS needle
>valve.

Remember, if you are using a standard venturi that the OS needle is .135 and the ST is .155. If you go to an ST needle you are choking the venturi down by 20 thousandths. You will need to open the venturi by the same amount to keep the same choke area.

Master C/L Link Site:

http://home.att.net/~philbrown36641s5/clhomepage.html

HI Don
Could you give me the particular link in Phil's site to click on for the LA40 info.
Thanks

http://flyinglines.org

I use the ST NV assembly -works well for me

If the LA 40 runs away it is overheating from a combination of any number of things- rpm, prop load, venturi area, muffler exhaust area, airplane size, and possibly fuel.
RPM- the peak torque is right around 10,000 rpm. If you prop it to run lower than that at a rich setting it will always be in a position to warm up and jump to an rpm over 10,000. As Brett B. has pointed out several times, if the engine is running below peak torque and rich it can also run above peak torque and way faster. Setting it up to run normally faster than the peak torque rpm gives the motor only one running setting, so it can't runaway. It may still overheat and go lean, but it won't suddenly jump 2000 rpm and go from 5.5 laps to 4.5 laps.

Prop Load- this is a 40, not a 50 or 60. It has limited torque and will not be happy turning too big a prop. A smallish prop, like an 11/4+- the APC 10.5/4.5, or a Master Airscrew 3-blade 10/7 depitched to 3-4 in. is about the max for comfortable, consistent running.

Venturi area/Exhaust area- these control the amount of air going through the engine and the peak power. They interact strongly with the prop size. Think of it as an RC carburetor. When you close the carb, the rpm drops. Nobody in their right mind would think of trying to get the wide-open peak rpm at half throttle by leaning the motor out. It ain't gonna happen. The LA 40 seems to be reasonably happy for stunt use when the peak rpm is around 11,500-11,800. If it can't turn the prop that speed when the needle valve is adjusted for peak rpm you need to open the throttle, so to speak, by increasing the venturi area and/or exhaust area, or go to a smaller prop. Richen the mixture until the motor is running 10,200 or so and it should settle into a 4 cycle in the air.

Head Gaskets- these, or opening up the combustion chamber in the head, adjust the ignition timing. The stock head is timed for the 12-14,000 rpm range. It may work just fine with certain planes and propellors when running 10,500-11,000 or so. If not, adding head gaskets retards the timing and will let the motor run more smoothly on a larger prop.

Fuel- the LA is built to run well on typical RC fuel with 18% or so synthetic oil. Adding oil, usually by adding some castor to the fuel, will change how it runs when in a 4 cycle and how smoothly it transitions from a 4 to a 2. More oil does something to the combustion and usually smooths out the 4 cycle running and helps keep the motor from picking up speed throughout a flight. No need to go to Stunt 35 fuel with 29% castor. Up to 25% oil, by adding castor to a gallon of RC fuel, will help.

>If the LA 40 runs away it is overheating from a combination
>of any number of things- rpm, prop load, venturi area, muffler
>exhaust area, airplane size, and possibly fuel.
>RPM- the peak torque is right around 10,000 rpm. If you prop
>it to run lower than that at a rich setting it will always be
>in a position to warm up and jump to an rpm over 10,000. As
>Brett B. has pointed out several times, if the engine is
>running below peak torque and rich it can also run above peak
>torque and way faster. Setting it up to run normally faster
>than the peak torque rpm gives the motor only one running
>setting, so it can't runaway. It may still overheat and go
>lean, but it won't suddenly jump 2000 rpm and go from 5.5 laps
>to 4.5 laps.
>
>Prop Load- this is a 40, not a 50 or 60. It has limited
>torque and will not be happy turning too big a prop. A
>smallish prop, like an 11/4+- the APC 10.5/4.5, or a Master
>Airscrew 3-blade 10/7 depitched to 3-4 in. is about the max
>for comfortable, consistent running.
>
>Venturi area/Exhaust area- these control the amount of air
>going through the engine and the peak power. They interact
>strongly with the prop size. Think of it as an RC carburetor.
> When you close the carb, the rpm drops. Nobody in their
>right mind would think of trying to get the wide-open peak rpm
>at half throttle by leaning the motor out. It ain't gonna
>happen. The LA 40 seems to be reasonably happy for stunt use
>when the peak rpm is around 11,500-11,800. If it can't turn
>the prop that speed when the needle valve is adjusted for peak
>rpm you need to open the throttle, so to speak, by increasing
>the venturi area and/or exhaust area, or go to a smaller prop.
> Richen the mixture until the motor is running 10,200 or so
>and it should settle into a 4 cycle in the air.
>
>Head Gaskets- these, or opening up the combustion chamber in
>the head, adjust the ignition timing. The stock head is timed
>for the 12-14,000 rpm range. It may work just fine with
>certain planes and propellors when running 10,500-11,000 or
>so. If not, adding head gaskets retards the timing and will
>let the motor run more smoothly on a larger prop.
>
>Fuel- the LA is built to run well on typical RC fuel with 18%
>or so synthetic oil. Adding oil, usually by adding some
>castor to the fuel, will change how it runs when in a 4 cycle
>and how smoothly it transitions from a 4 to a 2. More oil
>does something to the combustion and usually smooths out the 4
>cycle running and helps keep the motor from picking up speed
>throughout a flight. No need to go to Stunt 35 fuel with 29%
>castor. Up to 25% oil, by adding castor to a gallon of RC
>fuel, will help.

Scuze me?!! The LA .40 is one of the best engines I've ever used!!! Dirt cheap and runs out of the box!!

Hi Phil

Thanks for the detailed reply. That all makes really good sense. In the winter when I first built it, the 40 ran great. But then in the summer this problem began.

I have put an 11-4 APC, tongue muffler, and added 1 head gasket and opened up the air vents around the engine, now I just need to get some more castor for my fuel, then I'm ready to go for a test fly.

Warren Leadbeatter
Port Stephens - Australia
AUS-14782

I talked a bit with Don McClave about his .40LA setup, and the one thing that he mentioned that really stuck is that they don't like a lot of exhaust backpressure. A tongue muffler for a Fox .35 fits (also fits Magnum and ASP .25/.36)...but maybe it makes too much backpressure for the .40LA. This doesn't mean the muffler is bad. But you do need to tweek the setup to make it work for YOU, in this case, opening up a few more holes. Your model, at XX ounces, your fuel, your flying site, temp, humidity, altitude, line length, and whatever props you like. Some folks won't use certain props, because they don't like the looks. If they work good, use them. They pretty much look the same when the engine is running! Steve

Steve Helmick
Renton, Washington
USA

>Hi Phil
>
>Thanks for the detailed reply. That all makes really good
>sense. In the winter when I first built it, the 40 ran great.
>But then in the summer this problem began.
>
>I have put an 11-4 APC, tongue muffler, and added 1 head
>gasket and opened up the air vents around the engine, now I
>just need to get some more castor for my fuel, then I'm ready
>to go for a test fly.
>
>Warren Leadbeatter
>Port Stephens - Australia
>AUS-14782

HI Warren,

Not about the OS 40LA, but about my buddies "down under". It's still hard, after all these years, to remember that y'alls "seasons" are reversed from ours. Winter here, summer in your part of the world! Crazy ain't it!! LOL!!

Big Bear <><
Character: It's what you do when no one else is watching.

>Not about the OS 40LA, but about my buddies "down
>under". It's still hard, after all these years, to
>remember that y'alls "seasons" are reversed from
>ours. Winter here, summer in your part of the world! Crazy
>ain't it!! LOL!!

Nearly as crazy as this "white Christmas" you "north of the equator" folks keep talking about!

Christmas day here was over 32C / 90F, and we spent several hours in the pool. That was a cool Christmas compared to 2005, where temperatures in Brisbane soared to nearly 40C / 104F.

The positive side of our climate is that there is no concept of a 'building season'. You can fly all year round. I guess people in Florida, California, Arizona, etc. have that as well.

cheers,
Colin

I've been playing with the LA 40 in these planes for several years. Basically good results, but last year I had a problem similar to yours. In the winter and spring it ran fine on 10% fuel and the 10/4 3 blade. Then in the summer when it hit 95deg/95% RH I started having problems. Fixed 'em by chopping some off the prop, using a larger venturi, and drilling out the muffler outlet as large as I could. That's tricky to do and I chewed the outlet tube up a bit, but it worked.

An 11 inche prop seems to be a bit much. You may want to try 15-20% nitro.

I put the tounge muffler away and went to the stock muffler and had much better runs.

I have had problems with my 40 also. Come to find out it was a needle valve problem. I did notice in the spring I would have to cleanout my Needle valve once in a while because you get flying insects, mostly knats. that will actually go through the whole fuel systen and be stoped by the filter screen. As far a 2-4 beak it does not need to be retimed but added gasket will soften the break. I have always used an 11-5. Zinger prop on my 40 engines and also works very well on the LA 46. Another thing that can happen is your fuel tank is not working right and this is not to be overlooked.

Don't know if this will add to the discussion but I will mention that I have had absolutely no problems with this setup:

-- Vector 40 airplane, 48 oz.
-- LA.40 engine, absolutely stock. No changes to anything.
-- Randy Smith tongue muffler
-- APC 11x4 prop
-- Running rpm right around 9,600, though it will happily go faster; that seems to be a good speed for this particular airplane.
-- Fuel, either 10/10/10 or 10/20, runs fine on either
(10/10/10 is 10% nitro, 10% synthetic, 10% castor; 10/20 is 10 nitro, 20 castor)
This plane/engine has more than 2 years and I would estimate about 400 flights. Only thing I would improve is the pilot, alas .

John Thompson

P.S.: Full disclosure: Some who have seen this plane will recall some odd runs in the first year, which were the result of a plumbing/tank issue, nothing to do with the engine.

P.S.S.: I will say, in response to the thread originator's exasperated remark, that a Brodak .40 is a very nice engine. I have one in the Ares (see the avatar) that chugs along like a John Deere. Sweet sound, beautiful runs (the plane has only about 10 flights, but I love the engine so far).

http://flyinglines.org
Flying Lines — News of Northwest Control-Line Model Aviation

Thats pretty much the same setup that I have now.

I think it must be the heat because it's the middle of summer here now and when I first flew it, it was the end of winter and I was flying only in the mornings then. The temps were between 10 & 20 deg C or 50-68F.

Now it's summer the temps I have been flying in are in the 30's (>86F)
I flew it the other morning and it was cool and it was stable again.

I haven't flown it since adding another head gasket yet. Will let you know how I get on.

Warren Leadbeatter
Port Stephens - Australia
AUS-14782