Greasing Pro-Shaft/Propellor Contact Surfaces

[pmyatt]

Have, after much hammering on prop extractor by yard workshop, had the prop removed from shaft, after 2 years being fitted. In future, should the shaft/prop contact surfaces be greased to facilitate removal? Am being given conflicting advice - Yes, good idea - No, anode on end of prop will be inhibited from working properly and grease will form a "hydraulic lock" on the shaft making removal harder next time. Any advice, anyone?

 

[vyv_cox]

It has to be borne in mind when fitting a propeller to a shaft that it is a tapered fitting. If the nut is torqued up to the sort of values used in a normal fastening, for example a cylinder head, then the propeller will be driven extremely hard onto the shaft. Subsequent removal will become difficult. When the prop is replaced use a little restraint - little more torque than nipping it up is needed, the split pin prevents it from backing off.

I don't usually put grease on the shaft, although I do on the threads. I can't see that it will adversely affect anything. Hydraulic locking has been blamed for many engineering cockups but probably doesn't exist.

 

[davidej]

hydraulic locking can't occur as there is no blind hole involved in this operation.

 

[pampas]

Bear in mind that you cannot compress a liquid, therefor as the grease/ oil leaches out then the prop is no longer tight ( In theory).

In a past life I have seen a large coupling come loose after some idiot greased a Forced draught fan coupling in the mistaken belief that it would make easier to come off in the future.

 

[pmyatt]

It has to be borne in mind when fitting a propeller to a shaft that it is a tapered fitting. If the nut is torqued up to the sort of values used in a normal fastening, for example a cylinder head, then the propeller will be driven extremely hard onto the shaft. Subsequent removal will become difficult. When the prop is replaced use a little restraint - little more torque than nipping it up is needed, the split pin prevents it from backing off.

I don't usually put grease on the shaft, although I do on the threads. I can't see that it will adversely affect anything. Hydraulic locking has been blamed for many engineering cockups but probably doesn't exist.

Now remember seeing the yard engineer using a long extension tube on the socket handle to tighten nut otherwise the split pin hole was not accessible - thought it was a good idea at the time!!!

 

[JimC]

It has to be borne in mind when fitting a propeller to a shaft that it is a tapered fitting. If the nut is torqued up to the sort of values used in a normal fastening, for example a cylinder head, then the propeller will be driven extremely hard onto the shaft. Subsequent removal will become difficult. When the prop is replaced use a little restraint - little more torque than nipping it up is needed, the split pin prevents it from backing off.

An exception has to be made for some makes of folding propeller e.g. Flexofold. They don't have a split pin to stop the nut unscrewing because the nut screws down into a tunnel in the hub and is inaccessible when tightened. Instead the nut is held by a grub screw which screws through a tapped hole in the hub and locates against one of its flats. Flexofold state in their fitting instructions that the nut needs to be 'very tight', I forget the torque figure. If the nut should slacken with this type of prop, and the key fail or not be fitted, then there is nothing to stop nut and prop spinning off the end of the shaft as a unit.

 

[bikedaft]

would rather have it difficult to get off rather than fall off spontaneously (don't ask!). at least you are only ever trying to get it off when boat out water

remember heat as well to help get it off

as an aside - greasing threads - are torque values not given for non greased threads, as greasing them can lead to over torqueing?