I am new to RC. I am running an OS .40 LA on my trainer. Being a newbie, it sometimes takes me a few attempts before getting the engine to start, especially in this cold weather (chicken stick). Sometimes, I would crank on it so much that the prop nut would come loose inside the spinner. Obviously this is a huge pain in the butt. Although it probably was not the best solution, I decided to fix the problem by using thread lock to secure the nut to the crankshaft. I have flown the plane several times with no problem but I recently ground off the outside 1/2" of propeller on a bad crosswind take-off. Now I need to change props but sure enough, I can't get the friggin' nut off. The thread lock advertises that components can be taken apart with normal hand tools. The problem is that i have nothing to grip the crankshaft with in order to resist the tremendous torque necessary to remove the nut. If I grab the prop for leverage, it and the spinner just remain stationary while the nut and attached crankshaft spin.

Needless to say, this is quite a pickle. I have come up with a couple of slightly destructive solutions to this problem but I need some help. Does anyone have any experience with this type of problem or have some possible solution. My engine manual is out of my reach for the next three weeks or so. There may be a simple fix in those pages. Please respond with any advice.

Thank you!

I've never been in this pickle, but if it were me I'd try gently heating the nut/shaft with a propane torch. It might work. Also see if there's some type of solvent the locktight mfg suggests. May be you could immerse just the shaft and nut in the solvent overnight then try to break it free. And finally my most destructive method if you can do it, wrap the drive washer(this is the washer behind the propeller) in electrical tape, then hold the washer with plyers or vice grips. Be very carefull, not too much force and be sure you don't get them on the crankcase as you dont want to distort it, then try to break the nut free. When you do get it off either double nut the prop or use a nylock nut then you wont have to use locktight. Good luck

Nate:

There is a tool that screws in place of the glow plug, with an extension that blocks the piston. It's commonly used by the car guys when tightening their flywheels on the crank. Using that will let you get the prop nut off easily.

But heating the nut with a torch should work too, just don't heat the crank end.

Bill.

Remove the glow plug, and fill the cylinder with some string. I will work like a piston stop and keep the crank from turning, without damaging the piston or cylinder. Just make sure you leave the end hanging out of the glow plug hole, so you can remove it. Cord about the size of string trimmer starting rope works best, but anything close will do.

The above suggestions probably will work, however if they do not, remove the glow plug and, after positioning the prop where you want it, fill the cylinder with fuel and re install the glow plug.

You now have a hydraulic lock with the load spread equally over the piston. Remove the nut and then drain the cylinder.

Don't use any more thread locking compound on your prop shaft. NEVER EVER use red Locktite unless your don't ever want to disassemble the parts again !!! That's a fact !

If you have an extra nut of the correct size, and a Dremel with a cut-off wheel, cut through the nut at one of the points. Thread it on the drive shaft and using ViseGrips clamp it on the flats, 90 deg. from the cut. Heat the Loctited nut with a soldering iron until it lets go.

William, Terry, Onewasp,

This could easily cause the crankshaft to break.
It happened to me with a hydraulic lock and a mere starting attempt (20 years ago).

A prop wrench puts much more force on it, so it is apt to break.

Crank break??????

Yes, Terry.

In an HB .40 engine. The crankshaft has a crescent shaped counter-weight and it broke between the crank-pin and the gas passage. The con-rod was bent also,

I also saw numerous OS FX engines that had broken the crankshaft at the shaft valve opening (below the carburettor), because of the same reasons.

Some people are too ignorant to check whether their engine can turn over. They don't bother to prime it properly, and simply "wack" it with the starter.

A hydraulic lock is a solid, incompressible resistance. And when coupled with a reasonably strong starter (Sullivan?), the result is a catastrophic crankshaft breakage, and/or twisted rod, and/or perforated piston, and/or broken wrist-pin.

Some modelers are their own engine's worst enemy.

When you heat the nut with the propane torch....the Lock-Tite
(which turns to a plastic when it dries) will melt, and the nut can be
removed as easily....is if the Lock-Tite wasn't even there.

Dar Zeelon , With a hydrauliced motor and electric starter, yes, but not with a loctite'd nut.

I'd take the back plate off and wedge a peice of wood between the crankcase and the crank's counter balance to prevent the crankshaft from turning. ... and some heat.

Hi!
Just heat the nut with a heatgun...it will eventually melt the plastic spinner but that you shouldn't use in the first place so just get rid of the remains......
Many newcomers use cheap plastic spinners .....I know that.....the airplane looks better that way...... but using a aluminum rounded nut is much better.Then you start the engine by reversing the rubber insert on the electric starter and the prop could be tightened firmly without having problems losening the prop later.
OS have aluminum propnuts for all their engines and these suits most other engines too. Naturally a aluminum spinner could be used but this is much more expensive.

Regards!
Jan Karlsson

Just my two cents worth (again). I'm not for any of the solutions that involve locking the piston, (string in the cylinder, the tool the car guys use, or hydraulicly locking the cylinder with fuel) all put you in danger of bending the connecting rod.

Darren

I would have thought locking the piston in some way and trying to undo the prop nut is about the best way to bend the con rod.

I bet the nut will come off if you heat it, place it sideways so one flat is on a very heavy piece of metal and tapping it on the opposite flat.

-David C.

Remove the glow plug. Turn the crank to lower the piston to just above the intake and or exhaust port. Stuff some string into the cylinder through the glow plug hole, leaving the end of the string hanging out of the hole. Don't let the string go through the ports as the travel of the piston will shear the string and leave debris in the crankcase. Turn the crank in the direction to loosen the nut until the piston compresses the string. Maybe put some alcohol on the thread lock material. Apply steady non-jerking torque on the nut. It should remove slowly. I've used this trick many times in the past. Don't force the nut. Just pressure it steadily. The string will form evenly across the piston top and form into the combustion chamber. Once the nut is off, turn the crank the opposite way to allow the string to be pulled out through the glow plug hole.

i use the rope trick all the time on gas conversions for installing or removing prop hubs and it works fine but i would hesitate to recommend it for a glow engine that uses a cantilever crank with a big hole cut in the middle of it. in your case though it may be the only solution along with some heat on the nut. i don't think the engine has enough room on the prop driver to hold it with pliers.

once you get it fixed do like jaka says and ditch the plastic spinner, it most likely caused you problem. it prevents the prop driver from gripping the prop and keeping it from spinning. a prop should never come loose from just hand- propping the engine. the nut is just there to clamp everything together


dave

Many locktite compounds are released by cold, rather than heat. Put dry ice on it for several minutes until it is well frozen then try to remove the nut.

I wish Skynate would tell us what he did. His initial post was in October!
Luis

Here is the correct answer....for the tool impaired hobbyist....

....one touch with this 3/8 "butterfly" air impact wrench, and that
nut is off....in about .03275 seconds....

....and our little friend can hug his snowman, and watch....

Merry Christmas everyone....[sm=thumbup.gif]

Dave.

that worked!!! just take your bic lighter used for your weed, light up the screw, and stick part of a rag in the exhaust pipe, screw came right off, then what not to do is hold the engine up with the hand that has all the open wounds and cuts, and poor the fuel down there to flush out the possible rag debris