Torquing a nut

[Graham_Wright]

My Panda Fischer generator suffered a damaged start ring thread. I bought it with a known fault (simply rectified) for £800.
Panda Fischer could supply a replacement ring, i.e just the ring, for £800!
I found a nearly new flywheel on eBay for £100.
To remove the old flywheel took some mighty blows to loosen the nut.
The replacement torque is 200 nm.
How do I react that?
There is nothing to brace the standard "lump of wood" against.
Will a lower, i.e. maximum achievable, torque with added loctite be safe?

Suggestions very welcome.

 

[rogerthebodger]

I normal remove the starter motor and jam a piece of angle iron in the starter hole that jam the teeth of the starter ring to stop the engine crank shaft turning

 

[Graham_Wright]

I normal remove the starter motor and jam a piece of angle iron in the starter hole that jam the teeth of the starter ring to stop the engine crank shaft turning

The flywheel is only accessible by removing the generator coil housing. The starter motor goes with it.
The rotor is attached with four bolts into the flywheel face but, with that torque, I would be fearful of bending them.

 

[rogerthebodger]

Which panda fisher do you have

I have a generator using a ferryman engine which is the same as one used by panda fisher

Any pics

 

[Skylark]

That’s quite a high torque. Can you post a picture to help understand what you’re up against?

 

[Ammonite]

Deleted

 

[B27]

Impact driver?

 

[penberth3]

Impact driver?

That would tighten it, probably overtighten it. You couldn't measure the torque.

 

[Graham_Wright]

I have reassembled the engine and tightened the nut using a socket, Tee bar and mallet. Unfortunately it wasn't enough.
The nut undid and wrecked the key slot in the crankshaft. I've now regenerated the key recess in the shaft and it's ready for flywheel replacement. The flywheel has two large, otherwise unused, axial holes near the periphery and I will try to contrive something to engage with them. I agree the torque figure is high and I'm fearful of strpping the nut thread. I'll use Loctite.
Photos to follow.

 

[Poignard]

I have reassembled the engine and tightened the nut using a socket, Tee bar and mallet. Unfortunately it wasn't enough.
The nut undid and wrecked the key slot in the crankshaft. I've now regenerated the key recess in the shaft and it's ready for flywheel replacement. The flywheel has two large, otherwise unused, axial holes near the periphery and I will try to contrive something to engage with them. I agree the torque figure is high and I'm fearful of strpping the nut thread. I'll use Loctite.
Photos to follow.

Could you put a Dyneema or wire rope through one of the holes in the flywheel and attach it to a strong point?


Or put a round steel bar through so that it bears against some part of the cylinder block?

 

[rotrax]

Harley Davidson motorcycles have the primary chain front sprocket fixed to the crankshaft with 150 pounds feet of torque. 150 lbs-feet is close to 200 NM's.

Harley suggest removing the spark plug of the front cylinder just before TDC with the valves shut - i.e. coming up to the compression stroke - and feeding a short length of 1/4 inch cord into the combustion chamber. Turning the engine forward locks the engine by compressing the soft cord, allowing the nut to be tightened to the correct torque. Turning it backwards allows the cord to be removed.

I dont know if taking the injector out will allow this method to be used, but it might be worth investigating.

 

[B27]

A lot of assemblies where the shaft nut is done up to a high torque, you're not just doing the nut up to avoid the nut coming undone, you're tensioning the shaft so the other component is held on to it by an axial force. That's what locks the components together and avoids all the torque going through woodruff keys or whatever.
Loctiting the nut will never be a substitute for this.
It's also crucial to use the correct washers and so on, the washers may be some kind of spring to maintain tension through thermal variations and or some kind of locking mechanism. Belleville or Nordlock washers (etc) are sometimes used in these kinds of circumstances and may benefit from being replaced. A new nut may be prudent too.

Also check that the nut is actually tightening the flywheel or whatever onto the shaft, not just bottoming the nut against the end of the thread or whatever, which can easily happen if a washer is missing or sometimes using mix and match parts from engines of different years for example.

The factory manual probably shows a special tool for locking the flywheel, that can often be improvised or the method adapted.

A lot of Li-Ion impact drivers are rated pretty close to 200Nm, I doubt you'll break anything by being a few % out.
200Nm sounds a lot but it's only 20kg x 1m, it's not my weight on a 1ft spanner.

 

[Ammonite]

Harley Davidson motorcycles have the primary chain front sprocket fixed to the crankshaft with 150 pounds feet of torque. 150 lbs-feet is close to 200 NM's.

Harley suggest removing the spark plug of the front cylinder just before TDC with the valves shut - i.e. coming up to the compression stroke - and feeding a short length of 1/4 inch cord into the combustion chamber. Turning the engine forward locks the engine by compressing the soft cord, allowing the nut to be tightened to the correct torque. Turning it backwards allows the cord to be removed.

I dont know if taking the injector out will allow this method to be used, but it might be worth investigating.

I suggested this earlier but deleted the post as the rope method is not generally recommended where the torque required is much more than 50 lbs ft but I imagine the Harley internals are built like a brick outhouse.

 

[rotrax]

I suggested this earlier but deleted the post as the rope method is not generally recommended where the torque required is much more than 50 lbs ft but I imagine the Harley internals are built like a brick outhouse.

They certainly are!

 

[rotrax]

A lot of assemblies where the shaft nut is done up to a high torque, you're not just doing the nut up to avoid the nut coming undone, you're tensioning the shaft so the other component is held on to it by an axial force. That's what locks the components together and avoids all the torque going through woodruff keys or whatever.
Loctiting the nut will never be a substitute for this.
It's also crucial to use the correct washers and so on, the washers may be some kind of spring to maintain tension through thermal variations and or some kind of locking mechanism. Belleville or Nordlock washers (etc) are sometimes used in these kinds of circumstances and may benefit from being replaced. A new nut may be prudent too.

Also check that the nut is actually tightening the flywheel or whatever onto the shaft, not just bottoming the nut against the end of the thread or whatever, which can easily happen if a washer is missing or sometimes using mix and match parts from engines of different years for example.

The factory manual probably shows a special tool for locking the flywheel, that can often be improvised or the method adapted.

A lot of Li-Ion impact drivers are rated pretty close to 200Nm, I doubt you'll break anything by being a few % out.
200Nm sounds a lot but it's only 20kg x 1m, it's not my weight on a 1ft spanner.

Very few crankshaft assembies are pre-loaded - which is what you suggest. A little end float is normally required.
If you weigh 147lbs, that weight at 1 foot from the centre of the nut is 200 NM's. 200NM's is 147 Foot Pounds. It is quite substantial torque setting. For example I recall the torque setting for the Mini steering ball pins. "70lbs feet, after torque is set they should have zero to 3 thou end float, even articulation."

 

[Poignard]

I imagine the Harley internals are built like a brick outhouse.

With a performance to match?

 

[rogerthebodger]

The flywheel has two large, otherwise unused, axial holes near the periphery and I will try to contrive something to engage with them. I agree the torque figure is high and I'm fearful of stripping the nut thread. I'll use Loctite.
Photos to follow.

Easy to make a big pin spanner like a large version pf a angle grinder nut spanner to fit in the two large holes to hole the flywheel still

A hole in the spanner to fit the socket into to fit the nut to tighten

 

[Gustywinds]

For example I recall the torque setting for the Mini steering ball pins.

Funnily enough one of the ones I remember is the Mini flywheel nut which factory recommendation was 115lbs/ft but a lot of the experts recommended taking to 150 on tuned engines. There was a specific tool for looking the ring gear for that, I have one in my garage somewhere along with a bunch of other Mini tools (cone compressor and the like) even though I sold my Mini-based car more than 20 years ago!

 

[B27]

Very few crankshaft assembies are pre-loaded - which is what you suggest. A little end float is normally required.
If you weigh 147lbs, that weight at 1 foot from the centre of the nut is 200 NM's. 200NM's is 147 Foot Pounds. It is quite substantial torque setting. For example I recall the torque setting for the Mini steering ball pins. "70lbs feet, after torque is set they should have zero to 3 thou end float, even articulation."

No, I'm talking about bolting a clutch or a flywheel or whatever to a shaft, not preloading any bearings.

 

[Poignard]

Deleted.