How to unscrew a nut from a generator

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I was hoping with the academics and engineers present on this forum, somebody could enlighten me. I have a generator with a nut on the end of the rotating shaft. However, if I try to unscrew it, the entire shaft rotates with it, and I can't hold the shaft still because it seems the nut's torque is too great. Is there a way to get it off?
 

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  • #2
berkeman
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I was hoping with the academics and engineers present on this forum, somebody could enlighten me. I have a generator with a nut on the end of the rotating shaft. However, if I try to unscrew it, the entire shaft rotates with it, and I can't hold the shaft still because it seems the nut's torque is too great. Is there a way to get it off?
Can you post some pictures?
 
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  • #3
jim mcnamara
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Are you sure of the handedness of the threads? i.e., you spun the shaft with a fingernail the thread groove. I have sometimes wasted a few minutes trying to unscrew a nut - the wrong way.
 
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  • #4
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Can you post some pictures?
Are you sure of the handedness of the threads? i.e., you spun the shaft with a fingernail the thread groove. I have sometimes wasted a few minutes trying to unscrew a nut - the wrong way.
http://imgur.com/t0CCxVG
http://imgur.com/t0CCxVG
This is a stock generator direct from a seller. We have not yet modified/touched it.
 
  • #5
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This is a stock generator direct from a seller. We have not yet modified/touched it.
What Jim refers to is its not uncommon for the threads securing the nut to be threaded in the opposite direction of shaft rotation.
 
  • #6
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What Jim refers to is its not uncommon for the threads securing the nut to be threaded in the opposite direction of shaft rotation.
The shaft will turn both ways.
 
  • #7
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The shaft will turn both ways.
This would be normal however you need to define the direction it turns while its generating power.
 
  • #8
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This would be normal however you need to define the direction it turns while its generating power.
It is in the counter clockwise direction.
 
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  • #9
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It is in the counter clockwise direction.
At this point I usually search for online service manuals, there is undoubtedly a method for locking the shaft regardless of which way the threads turn.
 
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  • #10
billy_joule
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Presumably the sprocket is splined or keyed to the shaft, have you clamped the sprocket to hold the shaft? Scrap wood will prevent tooth damage.
 
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  • #11
Baluncore
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Get a short length of roller chain that fits, then drop it over the sprocket. Google images 'chain pipe vice'.
Hold the sprocket by the chain in a vice, or with a Stilson pipe wrench, the chain will protect the sprocket teeth.
Then undo the nut by turning it forwards and backwards with ever increasing torque.
At some point the nut will turn easily and come off the threaded shaft. You will then know if it is LH or RH threaded.
If it is a tight fit you may then need to use a puller to remove the sprocket from the keyed shaft.
 
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  • #12
jim hardy
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I like the chain idea - how practical !
Or get a 1/2 inch drive socket that fits the nut
ask the guys at your local tire shop(or a handyman neighbor) if they''ll spin it off with their "impact wrench"


First though, it would be prudent to call whoever sold you the generator and ask whether it's left or right handed threads.
 
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  • #13
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You may need to use some impact. Like a box end wrench on the nut and a hammer. And note that if the nut and shaft are threaded to "tighten" in normal use then the nut would come loose turning it the same direction as normal rotation. I'd go with right hand as a first guess unless you can see some threads.
 
  • #14
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Get a short length of roller chain that fits, then drop it over the sprocket. Google images 'chain pipe vice'.
Hold the sprocket by the chain in a vice, or with a Stilson pipe wrench, the chain will protect the sprocket teeth.
Then undo the nut by turning it forwards and backwards with ever increasing torque.
At some point the nut will turn easily and come off the threaded shaft. You will then know if it is LH or RH threaded.
If it is a tight fit you may then need to use a puller to remove the sprocket from the keyed shaft.
So to ensure I'm doing this right, I'm basically trying to hold the shaft still with the chain via a pipe wrench?

You may need to use some impact. Like a box end wrench on the nut and a hammer. And note that if the nut and shaft are threaded to "tighten" in normal use then the nut would come loose turning it the same direction as normal rotation. I'd go with right hand as a first guess unless you can see some threads.
Thanks! I will definitely try this.
 
  • #15
Baluncore
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So to ensure I'm doing this right, I'm basically trying to hold the shaft still with the chain via a pipe wrench?
Yes.

Your picture shows a nut with a rounded outer surface. That looks like a “nylock” nut which will almost certainly be a right hand thread.

I am a bush engineer when I do not have all the tools I need. To do this job I would simply rest the sprocket on a block of wood with the motor just off the floor or bench. Put a ring spanner on the nut, then hit the end of the ring spanner with another block of wood. The inertia of the rotor will prevent rotation during the short initial impact. The block of wood that the sprocket rests on will prevent damage to the motor bearings.
 
  • #16
jim hardy
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Put a ring spanner on the nut, then hit the end of the ring spanner
"Ring spanner" is a proper British term, for Americans it's "box end wrench".

Don't expect it to budge on first blow.
 
  • #17
CWatters
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Doing it up again might be harder.
 
  • #18
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Doing it up again might be harder.
My thought, too. Are you sure you need to remove the nut ? Are you changing the sprocket? Or has removing the nut become a challenge in itself?

If it must come off, a chain around the sprocket and use of an impact wrench would probably be the safest approach.
 
  • #19
jim hardy
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Check tool sales . I found an el-cheapo electric impact wrench ½"drive for $40 at one of the import discount store sales. It's just right for little jobs like this and you dont have to have an air compressor. Paid for itself on first use.
 
  • #20
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There is a special pipe wrench called a (chain wrench)

http://www.bing.com/images/search?q...54ddcdb848c8e9b6b76dd1c2721daa31o0&ajaxhist=0

You have to cut a small block of wood to put on the jaw but it will hold it so you can remove the nut. baluncore and Billy_joule were on the right track. I have had to deal with these before and they are a pain in the butt!

Note: if the sprocket has a keyway keeper (shear pin) you WILL probably dent it and need to replaced it unless you have an impact gun.
 
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  • #21
Baluncore
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You should not have to buy an impact wrench for a job like that. I have several impact wrenches, but I would not use one on that nut. You will have no idea how tight it was previously if you remove it with an impact wrench. You need to put it back on with a similar torque. You need to do it with feeling, that is not a job for an impact wrench set up for regular work.

If you are in the USA then get a box end wrench and a couple of blocks of wood. Anywhere else on Earth, just substitute a ring spanner for the box end wrench. I would have had the nut off in less than 30 seconds.

Have you removed it yet ?
If not, what is stopping you doing it now ?
 
  • #22
Baluncore
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There is a special pipe wrench called a (chain wrench)
Those chain wrenches use a special stronger structure chain, unlike roller chain, that does not have the rollers to hold the sprocket teeth. It is not applicable to holding a sprocket without damaging the sprocket tips or spreading the chain.
 
  • #23
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Those chain wrenches use a special stronger structure chain, unlike roller chain, that does not have the rollers to hold the sprocket teeth. It is not applicable to holding a sprocket without damaging the sprocket tips or spreading the chain.
I have done it more than once it will work, Never damaged a chain or sprocket, that's why you add the block of wood to the jaw. I worked on a crew in a factory that used chain drive electric motors for 3 years. And it works like a charm. The only thing we ever damaged was the shear pins and those were made to "give" before the chain or sprocket teeth in case the motor gets in a bind. We never completely sheared a pin, some times wed dent them most times we never had a problem.
 
  • #24
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I was hoping with the academics and engineers present on this forum, somebody could enlighten me. I have a generator with a nut on the end of the rotating shaft. However, if I try to unscrew it, the entire shaft rotates with it, and I can't hold the shaft still because it seems the nut's torque is too great. Is there a way to get it off?
I have to see the assembly, but why are you not able to hold the sheave still? Can you post an image? You may find good advice at www.practicalmachinist.com. GL.
 
  • #25
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Thank you all. I'm still confused as to what I'm supposed to do with the wood?
 

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