TDubya

is their a trick to removing prop nut off of shaft on OS 120AX

RCKen

My Feedback: (9)

Your best bet is to use a box end wrench. Put a glove on to hold the prop with and then use the box end wrench to remove the prop nut.

Ken

TDubya

The shaft is moving with the nut. The prop is slipping and the shaft is turning

RCKen

My Feedback: (9)

Ok, get a vise grip and a rag. Wrap the rag around the prop adapter right behind the spinner backplate, and then grip it with the vise grip wrench. You want to use the rag so you don't mar the metal of the prop adapter. Once you have a good hold on it with the vise grip use the box end wrench to remove the prop nut

Hope this helps

Ken

TDubya

I have not put a spinner on yet and have the cowling on. Should I try using a rag to the shaft or could I crush the threads? Thanks for all the help

RCKen

My Feedback: (9)

You want to avoid grabing the threads if you can. See if you can get behind the prop and grip the adapter that way. If not you can grab the threads, but make sure you have a rag or something to protect the threads.

Ken

Campgems

First, is there a lock nut on the main nut? Can you get it loose. Wrenches on both the prop nut and the lock nut.

If there is room for two more nuts on the threads, screw one almost to the nut holding the prop, screw the second up tight to the first one. Lock them together, really tight. Make sure you have at least four turns on the last nut, or you may strip the threads. Once you have the two new nuts jamed together, the hold the nut holding the prop and with a second wrench on the last nut, try to screw the shaft in, IE turn the nut to the right. You should have less than 1/2 turn between the prop nut and the new combination. As soon as the prop nut loosens, unlock the new nuts and remove them. You should be home free then.

A second method that might work, if you have a wood prop, is to invert the prop into a pan of water, just enough to cover the prop and leave it over night. The wood should swell enough to lock the prop to the thrust washer.

In any case, keep the vice grips and pliers away from the engine. You stand a chance of cracking the crank case at the front bearing, damaging the front bearing, damaging the thrust washer, and maybe the crank. If the two previous don't work, sacrifice the prop, Cut it out, being very careful not to cut into the crank or washers. Cut and chip. Be careful not to bend the shaft.

One last thing comes to mind, and this would be the last thing to try, well try it before trying to cut the prop out. Very carefully put some thin Ca glue at the prop to thrust washer seam. Don't get it behind the washer, or it will screw up bearings and seal the thrust washer to the crank shaft. Give the CA a couple hours to set, then try to take the nut off again. If you are lucky, all you will have to do is to seperate the prop from the thrust washer. Stick the prop and washer in the freezer and leave them for a couple hours. There should be enough difference between the thermal expansion between the prop and the washer to break them loose.

Don

Campgems

One more idea came to mind here. Get a nut that fits the crank shaft. Slice it with a hack saw, cutting into the threads. Once you have the nut cut, screw it onto a screw to clean the flashing from the cut up, then screw it onto the crank shaft, almost to the prop nut. Now, and this is the only place to use them, really clamp down on the split nut with your vice grips. You want the jaws placed so the cut is at 12:00 and the jaws at 9:00 and 3:00. You should be able to effectly lock the threads. Now try to unscrew the prop nut. When it breaks loose, remove the vice grips and the split nut. Your threads should be in good shape.

One question, did you use thread lock on the nut? If so, this is why thread lock on a prop nut is not a good idea.

Don

mscic-RCU

My Feedback: (6)

Have you tried grabbing one blade of the prop and pulling on it to jam the prop at an angle to the crankshaft and against the backplate. this works sometimes too.

Dr1Driver

Try inserting a hardwood srick into the exhaust port to jam the piston. Then loosen the nut with a box-end wrench as originally recommended.

IMO, PLEASE don't grab anything with vice grips, rag or no rag.

Dr.1

RCKen

My Feedback: (9)

Dr1,
I had heard about doing that before and I totally forgot. Thanks for the refresher.

Ken

downunder

I'd be very reluctant to do that, especially with a ringed engine where it could squash the top of the piston and jam the ring in the groove (or worse if it has a Dykes ring). At the best I'd invert the engine and fill with oil part way to get a hydraulic lock but even then I wouldn't use too much force. My way would be to take off the backplate and use a piece of wood to jam the crankshaft (either the crank pin or balancing cut out) against the crankcase side. Once the nut is off then find out why it was so tight.

dszabo2

My Feedback: (1)

There is a piston locking pin you can get at any LHS that sells nitro cars. It designed to lock the crank shaft. You simply remove the glow plug and screw in the pin and it will keep the piston from going beyond TDC. I have used it many times on Nitro cars and it work great.

Dave

downunder

I think you'll also find the LHS sells new piston/liner sets after you punch a hole in the piston or cave in the crown

What some heli guys use is a tool that fits inside the crankcase (after you take off the back plate!) and has a groove cut in it to locate around the rod/crankpin. A bit more techo than the bit of wood I use sometimes but will do the job.

tramsay

I have the same problem...Dubro alum spinner nut on a Saito .82. I have a torch. Would it be ok to try and heat the alum up to see if it will turn?

shakes268

Here is what I did in a situation like this...

I took off the glow plug, fed in a shoe string. It's soft. Filled up the cylinder with it. Turned the prop nut, piston can't move due to the string and off came the nut. Now, you have to be very careful not to really force it or you will bend something that you don't want to bend.

tramsay

what if you can't get it off with out really forcing it?...I ask because I have already really tried to get this thing off, and I am afraid it is not going to be coming off with out some real force. I assume the alum is softer than the threads...is that right?

the_madgenius

tramsay, what you have to do is sacrifice the alum nut. What is happening is that the thread in the alum is breaking loose, ie the thread is stripping, and any effort on your part to undo it is only causing the stripped thread to roll up on the shaft and thereby causing it to jam harder. You will have to cut the nut loose, by using a hacksaw to cut diagonally across the nut, being extremely careful not to cut into the shaft thread. Then prise a screw driver into the slot to spread the nut enough to allow it to be undone. Then by using some means to hold the shaft , by going in through the back plate, you should be able to get the now wasted nut loose. Remember you need to be able to allow the nut to expand to stop the roll of alum jamming the shaft thread.
As for tdubya's problem, beg , borrow, or purchase 2 nuts of the same size as your shaft, screw one nut onto the shaft up to a full thread from you prop nut , the screw the second nut up to the nut you just fitted,and tightenthese two nuts. Placing a spanner on the outer nut, try undoing the prop nut. If the 2 nuts are too wide, the file them down in size by removing a third of their depth, and refit as described above. Just remember to only hold the outer nut with the spanner while trying to undo the prop nut.
Bill , a retired engineer and model pilot

tramsay

Dam! Sounds like I cranked down to hard on it huh?....

Thannks for the info! I will try what you suggest madgenius.

Would it be ok to cut most of the way thru, so I am almost at the shaft threads, then heat up with the torch to try and pry and loosen? I would think the heat would help the alum to be more soft and get out of the Shaft threads...but I also don't want that heat to travel and damage the motor.

mscic-RCU

My Feedback: (6)

Last resort might be to go to an autosupply store and get a nut splitter. you could then just replace the nut.

striderjg

Instead of a hack saw to cut the nut I recommend a dremal and cut off wheel if u have it.
-John

piper_chuck

My Feedback: (12)

Out of curiosity, have you been able to get this loose yet? If not, here's one more thing you could try before you start cutting things. With a gloved hand, hold the prop very tightly. Position the wrench on the nut in a position that will allow you to smack the end of the wrench with a hammer. The impact from the hammer might loosen the nut before the prop has a chance to spin.

the_madgenius

striderjg, I had considered your method but rejected it on the grounds that it is harder to accurately gauge how deep your cut is until you see sparks flying, then it is too late as you have started cutting the shaft thread. By using the hacksaw method , if you inadvertantly go a fraction too deep, the hard steel of the thread will soon let you know you are deep enough , so stop immediately. In preferrence i would use a junior hacksaw, as the teeth are finer to start with and as the motor is still atached to the aircraft, it will be easier to control.
tramsay, i would refrain from using heat at all , as it is difficult to control the amount of heat you will require, so consequently you could run the risk of damage to the front bearing.
I hope this has been of assistance to you and you have success in fixing your problem. I also apologise for the spelling mistakes in my previous posts.
Bill

tramsay

No problem MadGenius...I do it all the time!

So i was able to get the nut off but now I have alum in the shaft threads! I still need to get my prop nut off and don't want to start this process all over again. Any suggestions on how to remove the alum from the shaft threads?
~Tip

Campgems

John, all that abrasive dust fro the cut off wheel can't be good for an engine.

Don