holding the shaft stationary while torqueing the prop nut – how?

[BabaYaga]

A couple of years ago I took off my feathering prop for the first time since installation in 2006. When reinstalling it, I borrowed a torque wrench in order to be able to tighten up the prop nut sufficiently. The value aimed for was 220 Newton-metres. But I found no really good way of counter acting this force, that is, preventing the shaft from turning. With a fixed prop I suppose I could have used one of the blades, putting a timber between this and the ground. Not advisable with a feathering prop, I would think.
What is the preferred way of holding the shaft stationary in a situation like this?

 

[rogerthebodger]

I use a wooden pole under one of the prop blades to the ground to stop it turning when tightening prop nut

 

[BabaYaga]

I use a wooden pole under one of the prop blades to the ground to stop it turning when tightening prop nut

Yes, but would you do so with a feathering prop?

 

[rogerthebodger]

Yes, but would you do so with a feathering prop?

I would try it by setting the feathering prop blades open.

If you are concerned about damaging the prop you could use 2 wooden poles on to the ground and one to the boat hull

I have also do it by using a flat bar through the engine coupling to the hoat hull

 

[PCUK]

If you put the wood block at the root of the folding blade it won't damage the prop'.

 

[BabaYaga]

I have also do it by using a flat bar through the engine coupling to the hoat hull

That was my first attempt. Although I used a substantial screwdriver, c 30cm in length and 10mm shaft. It broke.

 

[rogerthebodger]

That was my first attempt. Although I used a substantial screwdriver, c 30cm in length and 10mm shaft. It broke.

A screw driver would be too hard and brittle

I used a flat piece of mild steel between the coupling bearing in the coupling bolts

I have used a big monkey wrench or stealsens but it can damage the shaft

 

[Pye_End]

Block of wood between prop and hull.

 

[BabaYaga]

If you put the wood block at the root of the folding blade it won't damage the prop'.

Maybe so, but how can you be sure? BTW it is a feathering blade, not folding. This shows what's inside the hub, or rather gear box:

 

[BabaYaga]

I used a flat piece of mild steel between the coupling bearing in the coupling bolts

Yes, probably the best approach. Perhaps a steel bar with matching holes for two of the bolts on the halv coupling flange.

 

[B27]

On my folding prop, there was an M8 tapped hole in the body.
I basically used that to anchor a strap wrench around the body.

If that had not worked, we were looking at clamping the shaft with a vice and an old anode.

A rattle gun might be an option?

Do the manufacturers offer an opinion on the problem?

 

[rogerthebodger]

Yes you could do it that way . I would try to get a flat bar between the white part and th upper silver part.

i have also used spanners on 2 of the coupling nuts to prevent the prop shaft turning

 

[PCUK]

Maybe so, but how can you be sure? BTW it is a feathering blade, not folding. This shows what's inside the hub, or rather gear box:
View attachment 169870

Ahh, right!

 

[penberth3]

Yes, probably the best approach. Perhaps a steel bar with matching holes for two of the bolts on the halv coupling flange.

View attachment 169871

And don't forget to remove it when you've finished!!!

 

[BabaYaga]

On my folding prop, there was an M8 tapped hole in the body.
I basically used that to anchor a strap wrench around the body.

If that had not worked, we were looking at clamping the shaft with a vice and an old anode.

A rattle gun might be an option?

Do the manufacturers offer an opinion on the problem?

I would expect the body of a folding prop to be more solid and therefore able to sustain a greater force, compared to the 'hub' of a feathering prop, which is more of a housing for the gears. That is why I was reluctant to put too much force on it, especially by using the blades as a 'lever'. However, see below.

Simply clamping the shaft would not have been possible as I see it. 220 newton metres is quite a force, some 20 kilograms applied at the end of a lever of 1 metre length.

Rattle gun – possibly. Don't know how precisely they can be set, though.

Have not found any advice from the manufacturer.

How I went about it in the end: In fact I did put some force on the housing, which was possible due to the fact that it is somewhat triangular in shape. I did however not reach the 220 newton metres aimed for by this method, probably because the timber was too soft, allowing the hub to rotate when the force got too great. I reckon that I did manage to apply somewhere between 150 and 200 newton metres on the nut though.

 

[Refueler]

Personally I do not like using prop blades as holding points ....

I prefer an old seamans approach to it .... natural fibre rope ... and a piece of stout wood or rag wrapped bar.

You can wind the rope round the shaft in a binding manner - taking care to make sure of direction of binding !! - and then use the wood bar to lock the end against hull or across shaft tunnel ... turn the prop nut tightening the binding ....... once it reaches full bind - you will be surprised how much hold that rope will exert ...

Please do not use synthetics such as polyprop / nylon .. as the heat generated can weld the synthetic rope to the shaft .. or at least damage the rope.

 

[rogerthebodger]

I did however not reach the 220 newton metres aimed for by this method, probably because the timber was too soft, allowing the hub to rotate when the force got to great. I reckon that I did manage to apply somewhere between 150 and 200 newton metres on the nut though.

Yes that would be a possibility and as he wood even hard wood is softer that the boss of the prop a piece of mild steel plate on the top and /or bottom of the post.

Do yo have a split pin hole if so you may need to tighten the nut to align the split pin hole with the nut

 

[BabaYaga]

Personally I do not like using prop blades as holding points ....

I prefer an old seamans approach to it .... natural fibre rope ... and a piece of stout wood or rag wrapped bar.

You can wind the rope round the shaft in a binding manner - taking care to make sure of direction of binding !! - and then use the wood bar to lock the end against hull or across shaft tunnel ... turn the prop nut tightening the binding ....... once it reaches full bind - you will be surprised how much hold that rope will exert ...

Please do not use synthetics such as polyprop / nylon .. as the heat generated can weld the synthetic rope to the shaft .. or at least damage the rope.

One would need a fair length of shaft to try this, I imagine. I have 11mm between the stern tube and the prop hub...

 

[BabaYaga]

Do yo have a split pin hole if so you may need to tighten the nut to align the split pin hole with the nut

No hole, the nut is secured by a tab washer, there is also some loctite on the nut/shaft thread.

 

[Refueler]

One would need a fair length of shaft to try this, I imagine. I have 11mm between the stern tube and the prop hub...

What do you have inside the boat ? On my 25 - I have a reasonable length of shaft between coupling and stern seal ...