I am trying to get a higley + sons propnut to stay tight on the front of a hangar9 F4U that I just put together. Regardless of how hard I crank on it, the nut still manages to fly off. Loctite seems like a good idea but I'm wondering if I'll ever get the thing off if I break the prop.... Any thoughts or recommendations?

thanks

Chicken

No, you should not put locktite on the prop nut. I know you said you have it as tight as you can get it, but it's still not tight enough. Use a box end wrench to tighten the prop nut with. Don't worry about damaging it as the nut and shaft are both steel. Also use a glove on the hand you are holding the prop with so you don't cut yourself.

Ken

Have you considered "Double - nuts"

No it's not a dirty idea

You put on a single nut (a thin one if possible) and then the normal Propnut - the two nuts bind against each other and form a rock solid bond - they will not come off! (if done properly)

Richen up the mixture if you are using a 4-stroke glow engine. Loctite comes in three strength grades. Blue, Red, and Green. You want to use the Blue Loctite.

No - you DON"T want to use Loctite PERIOD, on a propshaft.

What engine do you have?

If the nut keeps coming loose, there is something else wrong. Find the problem and fix it, don't cover it up and create MORE problems.

ALSO REFERED TO AS A JAM NUT

KNOW LOCTITE! I agree you might have a problem else where. I have had the same problem on a Cub with higley propnut, even with really cranking it down. I put a star washer behind it and it stayed on.

EASY BOYS this is supposed to be fun

HE is right but he didn't "splain" himself Lucy. SOMETHING has to give so let it be the nut. beats the heck out of rebuilding motors. and if it is popping or backfiring fix that ASAP. Also are you useing the washer that is suposed to be in front of the prop? It is possible that you are bottoming out the propshaft in the hub. By the Way I like those hubs too.

I have the prop washer on behind the higley prop hub[nut]. Behind it is the prop and then the base, behind it is another smaller washer then the engine itself. This is on a brand new OS.61 FX. I hand started it for a while thinking it was the electric starter over torquing things. The engine actually started backwards once! It seems like these should be reverse threaded or the engines + props should turn in the other direction.

So some folks indicated that I should fix other problems. Unfortunately, the only problem I thought I had was that the higley was falling off :-)... What else should I be troubleshooting first? Or, is this just a typical "tighten it more you idiot" case? I did some research and found that Higley actually sells an additional thin nut...I'm going to be kinda depressed if I'm going to have to go drive to east jesus for something that the Higley folks should just be sticking in the bag.

thanks for the responses

Remove the washer behind the prop. There prop should be directly touching the backplate of the engine. If I had to venture a guess as to why it's coming off it would be because of this washer. The back of the prop and the backplate of the engine have a rough texture in order to keep the prop from slipping. What's happening is the washer that you have between the prop and and the backplate is allowing the prop to slip, in turn this lets the prop nut loosen and come off. Remove this small washer and I'll be willing to bet your problem will be solved.

Ken

I use APC props. I put on a glove and hold the prop (regardless of size) along with a very big wrench. These things should not be "snug" but crank the "[X(]" out of it.

Ken ,I think the washer he is talking about, is the one between the engine crankcase and prop drive spacer. It`s supoose to be there.
His post says , it`s between the propdrive and the crankcase. ? I think I read his post right. lol

Never seen any OS engine, much less their 60s, backfire more than once. Something does not make sense about the backfiring. Two cycles very seldom backfire. As for them running backwards........ Their timing is VERY solidly set. No way to vary it unless you've disassembled it and reassembled it with the sleeve in backward.

Solve the backfiring. You have something very wrong with the engine or the way you're handling it.

Ok, Let's hold on a moment - You're all answering questions before you know all of the facts.

Let's see what we know so far:

It's an OS 61FX which is a 2-stroke.

The prop, washer and nut seem to be placed correctly.

What we don't know is:

When does it come off? Does it come off immediately as you're starting the engine, or does the engine start, run for a few seconds/minutes, and THEN come off?

This is not unusual at all. It happens when the engine has been primed too much.

No, the thread is in the correct rotation. As the prop spins CCW (looking from front) it helps to keep the nut tight (Because the nut tightens CW). It's when an engine backfires that the engine tries to rotate CW that the nut will come loose because the prop and nut are spinning CCW so once the engine switches to running CW that momentum causes the prop and nut to spin off.

it probably doesn't help having the starter rubbing on the prop hub to loosen it.

As MinnFlyer stated, two strokes will run backwards, but usually only at very low throttle openings. Overprimed two strokes also like to kick back hard while starting if the engine is cold. All the extra liquid fuel in the cylinder serves to raise the compression ratio which causes the fuel-air mixture to ignite way to early. A hot two stroke that is overprimed simply won't fire.
To make sense of this, first you have to know that the fuel and air doesn't know or care whether it is in the cylinder of a two or four stroke engine. A lean mixture fires earlier than a rich mixture does, that's why four strokes kick off the prop when the needle is too lean. We actually use the fuel air mixture to fine tune the ignition timing of a glow engine.
So why does a cold flooded engine kick back? Because in a cold engine, the actual air/fuel vapor mixture is actually a bit lean, liquid fuel does nothing but take up space in the cylinder. When the engine is hot, the fuel vaporizes making the air/fuel vapor mix too rich to ignite with the engine's compression ratio.

If the idle is too rich, the engine will slowly load up while it is idling until it quits. A restart is the same as starting an over-primed engine and can cause it to loosen the prop.

Once the high speed needle and the low speed needle is properly adjusted, the engine should idle for an entire minute and transition cleanly to full power when the throttle is opened. An engine so adjusted is also so easy to start that you can throw your electric starter away.

Chicken, what material is your propnut made out of? Higley makes both brass and aluminum. If your nut is aluminum, I'd be very careful about over-tightening it. The threads will strip. Same for the Higley aluminum lock nut. I've ruined a few of these by over-tightening. Could it be the threads of your prop nut are already stripped?

Use white plumber's teflon tape and wrap the threads after the prop is in place, then tighten the nut. Wrap enough tape that it is difficult to turn the prop nut by hand when you put it on. Then tighten the bejeebers out of it.

Hi Folks - it's a brass propnut.. Now - for the other questions. This happened while I was attempting to break the engine in. I was running it at full throttle and transitioning it in and out of "4 cycle" mode as indicated in the instructions. So it was really rich down to a little leaner - then back out again. It was during this time that the thing flew off. It came off once before when I had started the process but was starting the engine with my electric starter.

We need to do a poll as to when the nut is coming off

Bad Propnut,

Try a different propnut and then pick out the solutions you like best and go with them. I have had 2 Tru Turn spinners slip and ruin 2 large APC props on my Saito 1.50 4-stroke. Now I am using a Magnum spinner and hope I have better success with it. If anyone has noticed there are prop spinners and nuts with a nurled back and some that don't. I think the star washer idea with a new nut would be the way I would go.

JMHO,

Gibbs

Isn't that how it's supposed to happen? It's how it happens all the time, isn't it?

Sounds to me like it is a little to rich in the rich part of the break in causing some early detonation. Should resolve itself as the engine gets less tight and less hot.

I use higley heavy hubs (brass) all the time directly on the prop, currently on a 91 4S with no problems. Does your nut have the correct threads? Are you sure you're not running out of threads?