Stixoz

G'Day all,

I'm a total newb and have all but finished building my Boomerang 40 with an OS 46 AX (Hitec Optic 6 radio gear), i had planned on getting this plane to a club for my first flights but it's just not happening, closest club is over 2 hours away and not really to interested in helping (very small "boys club" style club) the other club which i can get assistance from is over 4 hours away and not really feasible.

I do have a few people in my area who fly RC aircraft who i may be able to get help off but don't worry i'm not going to try and fly it by myself straight off the bat.

My question is can i safely run this engine by myself? I'm not a complete idiot but the more i learn about this hobby i realise how much i don't know. The manual for this engine does seem to contradict itself a bit and it mentions "two cycle" and "4 cycle" which i'm not familiar with. Are there any good online article that might be available or general advice for my next step in my RC aircraft career?

Thanks in advance

Stix

bkdavy

My Feedback: (1)

The manual isn't so bad once you've actually followed the directions. What they refer to in the manual as "4 cycling" is a misnomer that has become common. What they are talking about is an engine that is running so rich, its only firing every other cycle. You must have the glow igniter connected to achieve this. It is essentially a mode where you are providing far more lubrication than normal at a much lower operating temperature than normal. Essentially force fitting the piston and cylinder.

There are two schools of thought on this, and I'm sure you'll hear from both. One school says follow the manual exactly. Its what the manufacturer recommends. The other school says by doing that you're unnecessarily wearing out the thin nickel layer between the piston and the cylinder, and by providing all the extra lubrication, you're preventing the piston and cylinder from getting their proper running fit.

Once the engine has been started, as you richen the high speed needle, you'll hear the engine slow down. You will get to a point where it drastically drops in RPM. Thats the "4-cycle" break. When you lean out the needle, you'll hear RPMS rise to a very high pitch. Then you'll hear a slight drop as you pass the peak. DO NOT RUN IT in that lean condition for more than a few seconds or you will cause unnecessary wear.

OS recommends you cycle the engine between these two points in the directions.

Yes you can safely run the engine by yourself, but make sure you have the plane firmly braced, either by a stake and bungee cord around the tail, or having the wings against stops planted on the ground. Unless you have a starting table, do this on the ground.

BTW, I'm of the second school. For my engines, I get them started, find the high speed peak, richen it to about 500 RPM below peak, and then for one tank of fuel I cycle the throttle like I'm flying. After that, the break in occurs in the air.

Brad

CGRetired

My Feedback: (1)

Of course you can run it yourself. Running the engine is not the problem. It's what hearing that engine running will do to you as you sit there wanting to put it in the air.

First of all, the OS 46 AX is a two stroke or a two cycle engine. A four stroke has.. well, four strokes: Intake, Compression, Power, and Exhaust. Each happen in half strokes of the engine. A full four stroke cycle takes two revolutions of the crank shaft.

A two stroke does everything in one revolution of the crankshaft. You can google two cycle or two stroke vs. four cycle or four stroke engines and get a complete description of what they are and how they work.

As far as starting your new engine is concerned, you will be surprized at how quickly it starts and how well it runs right out of the box. First, carefully read the instructions regarding starting the engine. What I usually do for the first start of a new engine is this:

First of all, secure the aircraft so that it WILL NOT roll after you start the engine. You can do that by tying a light line (not string) from the rear to something you have driven into the ground so that it will not move.. a foot long wooden tent stake would be fine. Wrap the rope or line around the horizontal stab and attach that to the stake. Pull the plane until the line is taught (but not till you pull off the horizontal stab).
1. Carefully rotate the high speed needle valve (that's the one on the left side of the carb that you had to install yourself) all the way in or rotate it clockwise until it stops. Don't force it.
2. Turn it out 2 1/2 turns.
3. DO NOT hook up your glow driver yet.. make sure you have attached both the fuel supply and the muffler pressure tubes to the fuel tank.
4. Turn on your TX and RX. Push the throttle to full open using your radio. Put your finger over the carb intake (the large hole at the top) to stop air from coming in, and rotate the prop by hand 3 to 5 revolutions, or until you see fuel flowing in the tubing leading to the carb. Close the throttle to full closed.
5. Attach your glow driver.
6. Open the throttle only a small amount, only enough to see that the throttle intake is open a very small amount.
7. Using an electric starter, or a chicken stick (not your fingers!!!!) flip the prop.. looking at it from the front, you will flip it to YOUR left.

After a few flips it will start.

Follow the instructions in the manual as to how much mixture to use.. it should be blubbering rich for the first couple of tank fulls.. don't be afraid to run it up to full throttle after it warms up for about a minute after starting.. run it up to full slowly but let it go to full and run it there for about a minute, then run it back to idle for about 20 seconds, then back to full for a minute.

After a few cycles of this full to idle to full... run it to full throttle then slowly close the needle valve until it peaks out in RPM. Let it run there for about 10 seconds then run it back to blubbering rich operation. You will definitely see the difference as you do this, but don't run it full throttle for long until you are finished with a couple of tank fulls of fuel.

After this, you should be fine, but when flying it, run it on the rich side of lean.. you should see a smoke trail when flying the plane.

Best of luck with finding a field. There are several Ausies on here that are very nice people and will work with you in finding a place to fly, even if it isn't in your direct area.

CGr

downunder

A 2 stroke engine will 4 stroke if it's rich enough but in this case it simply means that it skips one firing stroke before firing on the next and so on. Basically it just means the normal 2 stroke cycle only happens every other rev. The engine makes two totally different sounds when running in either the 2 or 4 stroking and it's quite easy to set the mixture so that it hunts between these two modes once you get familiar with the sounds. So the manual is quite correct when it mentions 2 and 4 stroking but it assumes the modeller understands what's meant. With a 10x6 prop on your 46 it'll begin to 4 stroke at around 12,000 revs or so when it's richened. The safest way though is to have the needle rich enough to be well into a 4 stroke the first time you go to full throttle because you don't want to run it lean. This is the blubbering rich that CGRetired referred to.

Jetdesign

My Feedback: (8)

I didn't find the difference in sound to be as noticeable as I expected when breaking in my first (46AX) engine. Now it's as clear as night and day.

When it's in four stroke, it will have a certain pitch. As you turn the needle slowly to the right, you'll get to a point where the pitch seems to jump between two frequencies (i.e. four and two stroke). When you get to this point, turn back to the left 1/8 turn or so, and you're in 'four stroke' operation. Conversely, two stroke is the higher of the two pitches, and it is in two stroke operation just when it stops jumping from low to high, and just stays in the higher pitch.

Just want to reinforce the point of having the plane secured, which is especially important if you are alone. I used a screw-in type dog run and a dog leash looped over the tail of my plane. With my nice planes, I now use two garden stakes with foam pipe insulation around them and brace the wings.

[link=http://www.hooked-on-rc-airplanes.com/nitro-engine-tuning-tips.html]Here's a link on basic tuning.[/link] There are better ones out there I'm sure, but this is a start.

Stixoz

Thanks a heap guys, i'm going to give it a go today, i will let you know how i go.

bigtim

My Feedback: (13)

what hasn't been mentioned here is the reason for the 2 and 4 stroke cycling, the 4 stroke cycling is so you don't over heat the new engine, causing exessive wear on your piston liner,and other new moving parts, its a gradual process of seating the parts.
when going into the lean run,or 2 cycle operation, your heating the metal and allowing the parts to seat and find its comfort zone when running, this should be done gradually, the reason for the alternating rapid needle valve settings when first running the engine in.

the 4 strokeing allows more oil and fuel into the combustion chamber allowing the engine to run cooler durring the 4stroke cycle,fireing at every other cycle, while still seating the parts like others have pointed out .

OS recomends a rich run for several tanks before leaning your 46AX, I started noticing a slight hesitation with mine after about 8-10 tanks requiring a small amount of leaning of the low end to smooth the transition from idle to full throttle otherwise I never touch the needles at all.

simply put, read the OS manual, if there is a area that doesn't make sense read it again untill you do understand it, there pretty simple to follow,there are many who recomend there own way of breaking in there engines thats good for them but if there is a problem with your engine you can comfortably say you followed the manual to the letter,when you send it in for repair or warentee work.
I have broken in several 2 and 4 stroke OS engines by the manual, there running perfectly every one.

Stixoz

She started first go no worrys but now it wasn't smoking? I had it running richer than the manual suggested? Now it won't start and i keep spinng the prop nut off?

bigtim

My Feedback: (13)

flooding the engine can cause hydro lock- the cylinder floods with fuel and won't turn over,DO NOY TRY TO FORCE THE ENGINE TO TURN,this can cause dammage to the piston and connecting rod.
close the needle, pull the glow plug out and with a rag or paper towel over the glow plug hole, spin the engine over with your elec.starter,make sure to cover the hole because fuel will come spraying out of the hole all over the place including you.
once the exess fuel is cleared, open the needle 1 1/2 turns and it should start just fine and still keep running you will probably need to run it at 1/2 throttle to keep it running when its still new.
open the throttle to full and procede with the break in procedure prescribed in the manual.
your engine won't idle or run smoothly untill its broken in,and will need a little extra throttle to keep running at lower RPM's since its new and the more runs/tanks it has through it the better it will work for you.

w8ye

My Feedback: (16)

A friend had a OS 50SX that he claimed no longer had the power it used to.

After inspection he had forced the piston through compression with it hydro locked and it had dished the piston head. Essentially it was a very low compression 50SX