Toxik

Like the title says, the prop on my OS 40 LA keeps coming off right after startup. It's a brand new motor and this was the first day I've started it. Is there something I'm doing wrong?

Thanks

Gray Beard

My Feedback: (-1)

Tighten it up real tight!!! Is the engine back firing or doing anything wrong or is the prop just getting loose?? They do take some tightening, my youngest student can't get his on tight either. Come to think about it, I have never seen him pull pop top either.

ErikElvis

My Feedback: (2)

I made the mistake a few times of thinking "real tight" was tight enough. Just grab that prop (as long as its not a sharp apc) and pull the wrenh and the prop together as tight as you can get it. You using a spinner?

Toxik

Yes I'm using a spinner. Could that be the reason I'm not getting it tight enough? The engine seems to be running well (other than it is starving for fuel and stalls as well but that is a different problem). By grabbing the prop (it is plastic) and tightening it so hard, will I not damage something on the motor? Sorry for the ignorant questions, but I'm new to flying.

RealPilotAce

Use a rag or something to grab the prop with, take a wrench to the bolt, and tighten it super tight. Then use the leverage of the wrench and the prop blade to get it even tighter. Your not going to over tighten it. And, when you think it's tight enough, tighten it some more, then it's tight!

Allfat

My Feedback: (1)

No, nothing will be damaged on the motor, just tighten the prop nut down as much as you can. You will not strip the threads or anything, they are made of hardened steel, and pretty much impossible to strip out by hand, so don't worry about it and just tighten it down.

Campgems

Follow the instructions on tightening the prop, then go about four or five clicks to the rich side. The prop is spitting off because the engine is suddenly stopping. This is usually from a over lean top end. Being as it is a new motor, it isn't broken in yet and will sieze up if it is to lean. Keep it well on the rich side for at least 30 minutes running Follow the instructions for break in very carefully. The first two ro three tanks are the most critical. Once you get it broken in, don't peak out the high speed needle. You want to find the peak and then back off four or five hundred rpm to the rich side. Maybe a bit more until you have several tanks of fuel through it.

Don

Villa

Most people use the cross wrench used for the glow plug to also tighten the prop nut. I did that for years also. After having the nut occasionally come loose, I now use a 10 inch adjustable wrench. That is too much wrench, so you need to learn how to use it. I have NEVER had a problem since I made the change. I also stopped using the plastic spinners and instead use the large nuts that a started rubber cone can grasp. No more problems.

JohnBuckner

My Feedback: (1)

No that is the problem. Reread Campgems post. Are you attempting to run this engine by yourself with no knowledgable help? Get some hands on help from someone that has some experiance in running glow engines.

John

Toxik

Guys, thanks for the help.
John.
Yes I am new doing this by myself. I'm new to flying but not to new to nitro engines. I have an rc monster truck with nitro engine. I don't know anyone local that has a plane unless I go to the LHS. After re-reading the manual last night I noticed that the angle of the plane could have an effect on how it runs if it is tuned improperly. Last night when I was trying to run the motor, the front of the plane was quite a bit higher than the back of the plane. So today I will start by changing the angle of the plane to see if there is any difference in how it runs. Unfortunately the design of the plane makes it so I can't take out the fuel tank unless I start cutting part of the inside of the fuselage.

MikeL

My Feedback: (3)

Go to the LHS and ask if they can put you in contact with an instructor. If you're going to participate in this hobby, why not do it right? You'll make a new friend, enjoy the hobby more, and have much more success.

JohnBuckner

My Feedback: (1)

Which brings to mind what airplane are you going to use in this attempt to fly with? Your RC truck is going to provide no help there. Go to the LHS seek out help, its there or this airplanes flight time is numbered in seconds perhaps minutes.

2slow2matter

My Feedback: (1)

Your monster truck nitro engine doesn't swing 10 inch knives which can cut your fingers off.
You should get some help, as it is obvious that you don't know what you are doing.

JollyPopper

My Feedback: (6)

Do yourself a favor and invest in a couple of box end wrenches to eliminate rounding those nuts off. Because it is necessary to tighten these things so tight, an adjustable wrench could slip and round off the points on the prop nut. There are only a couple of sizes, maybe three or so, in the size you will be needing for awhile10mm, 5/16, 12mm maybe. Stores sell pretty decent wrenches fairly reasonably now.

carrellh

I tend to agree that you need to get the prop tight.

Read the manual carefully beginning with page 16 for initial needle setting and the next several pages have info about break-in and tuning.

I suspect you are running the engine too lean.
Your RC car engine turned many more rpm than your plane engine will, and the sound is different. For the plane, having a tachometer would make tuning easier. RPM will increase as you lean the engine, then it will decrease again when it is too lean and beginning to overheat. You can hear this but a tachometer makes it easy.

Page 37 of the manual gives specifications at 16,000 rpm. Chances are your engine will turn more like 10,000 to 12,000.

Hossfly

It seems never to be mentioned here except for a few that bring up the point every once in a while when this question comes up.

If you have a spinner with metal backplate or hard smooth plastic, you need a sandpaper washer between the spinner backplate and the thrust washer that part of the engine that the spinner backplate or prop with no spinner backs up to.

Simply fold over a small piece of wet/dry sandpaper of 180-320 grit. Cut a small half moon out about the size of the prop shaft. Then cut around that hole another half moon slightly larger than the thrust washer. Unfold and you have a washer. Place it on the prop shaft with the grit against the backplate. The prop will tighten up easily. The prop will be tight until you loosen it. No big heavy tugs, just a firm tighten-up will do. EXCEPTION: Using wood props will require a retighten every day of flying. Wood compresses thus lossening up the prop. After a few months it will not be significant, but some wood-prop fliers always do and definitely should if model sits for over a couple weeks.

Good luck!

opjose

No this does not make a "big difference" as to how the engine runs at all!

The tank height to carburator height merely affects the siphoning effect of fuel running into or out of the carb.

If the carb is lower than the mid level of the tank you MAY experience some siphoning INTO the carb. With the throttle set to idle, this should be no more than a SLOW "drip".

Conversely if the tank is too low the fuel will siphon back into the tank SLOWLY at idle setting, making the engine more difficult to prime initially.

Once the engine is started, the tank/carb difference will have almost NO effect on any typical ARF... On a typical ARF the most you can affect the tank/carb difference is usually LESS than .5" or so, which is done by inverting the engine.

You have not done that, so there is no problem with this.

Examine the order you have things on the engine...

Assuming an engine w/o the prop/spinner installed...

On some O.S. engines there is a small metal thin "washer" that goes onto the prop shaft. This looks like a very fine washer and is VERY important if your engine uses one. This goes on first.

Next there is usually the prop driver. This is supplied with the engine, and is a cylindrical piece with "teeth" on it's surface to grip the spinner back plate.

Next you put on the spinner backplate, usually with a spacer ring to keep the spinner centered.

After the spinner backplate, comes the prop itself.

After the spinner backplate there is a stronger thicker metal prop retention washer.

After the prop retention washer, the prop nut itself goes on. This must be put on so tight, that you'll swear you are going to break the prop itself!

On larger models you may have a jam nut and/or a spinner retaining nut. The latter may have a thread at the end for the spinner bolt.

After this is the spinner itself, followed by the screws or bolt used to retain the spinner.


Is your assembly put together as per the above?

I've seen novices omit prop nuts, or the prop retention washers...

Campgems

Horrace, I guess you have been flying a lot longer than I have, but I've got to disagree with the sandpaper washer. If you tighten the prop tight, using a proper wrench vs the glow plug wrench, there is no need for the sandpaper. The aluminum back plates all have some nurling on them, fore and aft. You can get as better bite on them that the sandpaper. Plastic back plates are a whole nother problem. All I have seen are soft enough that they will deform badly with a tight composite prop. I won't use them anylonger. They are a lot like the wood props, you need to tighten them up every day.

While on the subject of spinners and props, I'm finding that the low pitch props that I like, 13x4 and the like, don't have enough thickness to get the prop nut tight without a spinner back plate. The threads bottom out before the prop gets captured. So, I have to use an aluminimum back plate. I am fond of the Great Planes aluminum back with nylon cones. They are inexpensive and work very well.

Don

jmv

There is tons of good information in this article (and many other good articles) here on the AMA website.

http://www.masportaviator.com/ah.asp?CatID=8&ID=47

GSNut

My Feedback: (8)

Do Not use sandpaper disks... they wear/sand out the prop drive hub and so on !!

Tight, Tight on the Prop and try richening up the mixture just a bit untill your engine is broken in some.
Seek an instructor if at all possible.

Then see below...

1. How ever with using APC Props I have found them so hard that nothing short of a couple of thin leather washers (one on each side of the prop) would allow them to stay put. Thin like in glove leather works best. Only use them once then discard and cut new ones if you must.

1a. Double nut as the 4 stroke folks do !

2. When using any spinner trim them to fit allowing no spinner edge to touch the prop except the rear spinner back plate itself. Plastic spinners can get old and brittle causing them to explode !! as can old composite props, if nicked or split dispose of them by sawing them in half with a hack saw at home. I have seen trash divers pull them out of the trash at the flying site..... !!

3. Do a (walk around ) safety inspection each time you prepare to fly not just when you get to the field ! Real Pilots Do This Everytime ! Set a routine and stick to it !


Fly Safe **

Cheers

GSNUT

JohnBuckner

My Feedback: (1)

Alex7403

my props fell off when there was too much fuel in the cylinder, it caused a hydraulic lock so the prop fell off.

in this case you unscrew the glow plug and swing the prop few turns.

other things, do you have prop washer?

do you have plastic spacer between the spinner back plate and the shaft, some spinners need that?

as mentioned, instructor is the best resource.

good luck
Alex

Campgems

PROPS DON"T FALL OFF. They will spin off if the engine suddenly stops. This is due to a lean condition that causes a back fire. If the prop is on tight enough to stand up to the torque of the starter, then it will stay on the engine until the engine suddenly stops. If you properly tighten the prop, it will stand up to a lot more strain of a sudden engine stop, but a back fire will almost always spin the prob loose.

This is kind of like running your car off the road and hitting a tree. It will dent in the bumper. The fix isn't to make the bumper stronger, but quit running off the road and hitting the tree. Fix the problem, not the result.

Don

CHEWIT

Hi I'm new to model flight also If the prop becomes loose Why don't the manufacturers add a lock nut or reversev the thread on the shaft[If you don't ask][/You won't find out]

Top_Gunn

My Feedback: (6)

I've wondered for years why they don't use a left-hand thread on the shaft. Is it just because they figure everybody assumes right-hand threads all the time? Anybody know? I tighten the prop nut on my 4-stroke engines after every flight. A left-hand thread would make that unnecessary, wouldn't it?