How to... Remove a prop that doesn't want to shift???

[ClassicPlastic]

How to... Remove a prop that doesn\'t want to shift???

Time to re-do the cutlass bearings, so I liberally WD-40'd the prop assemblies a few times, spun the lock-nuts off, and set about trying to get the props off... They're run-of-the-mill four blade jobs, with a long stright key-way, and the locking thread runs up to the rear face of the propeller. The shaft goes up to a UJ, then a short shaft to a UJ on the gearbox, so I don't want to whack anything too hard for fear of damaging the joints, gearbox, or alignment. I've tried tapping the prop, knocking it off-wards with a hammer and a drift, and I'll have a go tomorrow at differential heating, but...

Has anyone got any better ideas???

Or would you say I simply need to whack it harder???

 

[Ships_Cat]

Re: How to... Remove a prop that doesn\'t want to shift???

I wouldn't wack it. Beg, steal or make up a prop puller (like a gear puller) as that is what is usually used.

John

 

[Mirelle]

Yes.

Often an ordinary flywheel puller will do the job.

 

[William_H]

Re: Yes.

A puller if you wish to make one. One design is to get a flat plate of steel at least 6mm thick preferably more. You need a large bolt like 12mm or 1/2 inch that is about 3 inches long with a lot of thread length. This is either tapped into the middle of the plate or you get a nut welded on one side. Now you need large U bolts 2 or 4 or you can use bolots and nuts and steel plates so that the plate is clamped to the prop with the U bolts going around the blades and the bolt in the centre presses on the shaft now when you tighten the middle bolt it will tend to pull the prop off the shaft. usually it will move with a little pressure. If not, leave the puller under tension and tap the prop or even try heat. There will be loud crack as it lets go. I suggest you make or buy something like this as prop pulling will be something you don't do only once. I suspect you won't be able to buy or hire one that clamps onto the blades properly so you may end up making one. commercial ones tend to be made for bearings etc. It is important to get the attachment to the blades correct to avoid damage.
good luck olewill

 

[30boat]

Re: How to... Remove a prop that doesn\'t want to shift???

Yep ,a puller is the only way.A neat trick is to apply a reasonable amount of pressure by screwing the puller tight and then hit it(the puller bolt head) with a heavyish club hammer.Usually the prop jumps right out so you should put something on the ground to absorb the impact or else it might distort the thing.

 

[jerryat]

Re: How to... Remove a prop that doesn\'t want to shift???

Exactly. Would only add that the lump hammer used should really be very heavy - at least seven, and preferably fourteen pounds. With the puller tightened as hard as you can using a socket set, a HARD single strike to the end of the bolt will virtually ensure success. I have never had to strike more than once. There is little or no chance of damaging the transmission train.

30boat is also correct re protecting the prop(s) as there is usually instant release. My little prop is ok cos I can catch it/hold it, but I'd either have a friend handy or put something soft under the boat.

Cheers Jerry

 

[Vara]

Re: How to... Remove a prop that doesn\'t want to shift???

What an excellent post,especially the bigger the better comment re hammers

 

[rich]

Re: How to... Remove a prop that doesn\'t want to shift???

If it's a bronze prop on a taper, suport the prop and give it a good wack on the boss between the blades. not on the end, /forums/images/graemlins/shocked.gif

 

[spannerman]

Re: How to... Remove a prop that doesn\'t want to shift???

I would add that when we come to refit them,we warm the boss before then tighten the nut and as it cools it will grip the shaft tighter.

 

[uforea]

Re: How to... Remove a prop that doesn\'t want to shift???

I agree with other posters regarding a puller etc. To avoid damage to prop. or self,don't remove the shaft nut completely, just a couple of turns should be enough. This ensures that the prop. doesn't fall on the ground and it also helps to prevent the end of the shaft spreading under the load applied by the puller.
Ted.

 

[ClassicPlastic]

Re: How to... Remove a prop that doesn\'t want to shift???

Many thanks for the comments...

I should have said at the start that I don't have a puller of the correct dimensions handy, nor easy access to one. However, following a little further fiddling today, I have concluded that it's time to fabricate one. Should be straightforward.

All the best,

CP

 

[graham]

ReUse 2 equal hammers

By tapping two hammers simultaneously on the outer circumference of the hub between the blades and as near opposite each other as possible The shock wave will pop a bronze prop off the taper. The equal forces stop any sideways force which could do damage.

I have used this method after people have failed with pullers and heat done carefully no damage will result.

Dont try to hammer the prop in the direction you wish it to go ,firstly it wont work and secondly you may damage your gearbox.

 

[Mirelle]

Just to put it into perspective...

Imagine the happy scene when a large containership's propeller refuses to come off the shaft, in drydock!

These things happen more often than one might suppose!

 

[rich]

Re: ReUse 2 equal hammers

Graham, You put it in words better than i can /forums/images/graemlins/smile.gif

 

[alienzdive]

Re: ReUse 2 equal hammers

Working as a diver a few years ago there was a 120 foot super yacht (power boat) with a damaged prop. Keep in mind that we regularly pulled props off underwater and there was at first nothing unusual about this particular job. It needed a quick repair prior to the owner coming out and all the hard stands for boats that size were full at the time and the earliest possible booking was 4 weeks away. So we usually tie a rope around the prop to the wharf, this way when it is knocked off it falls to the edge of the pier and can be lifted out. this prop was possibly 1.4 metres across and needed a few hands to haul it out.

We had dificulty undoing the nut and first off had to cut a 180mm spanner shape out of a sheet of steel. After several taps with a spanner, we had to weld a 14ft pole to the handle for extra leverage and weight.

Then we put a 1 ton jack behind the prop. That did not work, actually it broke under the load. So we hired a 4 tonne hydraulic jack, not telling the hire shop it was going to be used in the salt. After getting it under full load and a few taps with a large sledge hammer onto a plate we were holding behind the prop and, nothing...

So we got a hydraulic kango, electric ones do not work to well under water. A little positive bouyancy as it was the sort they use on the road works. Put the plate back in place behind the prop to protect it loaded back to 4 tonne and after an hour on the kango, nothing.

We took the hire tools back and went back to a shed in a secret location and grabbed a roll of cordite. with several raps around the shaft, and butted up against the prop to for directional blasting. Got the crews off all the boats in close proximity, got out of the water our selves, pressed a button and presto, the prop swung in down under the pier for hauling out.

It was at this stage that the engineer who put the prop on flew in from half way around the world to give advice. He came down not realising it was off and explained the prop shaft was imperial and the prop was metric, it was so hard to get on that it would never come off. He also said that the nut was on so tight that we would not get that off either.

 

[AvanLoon]

Re: Just to put it into perspective...

There is a big difference between our size of props and the real big one's. The tricks to get a big prop off, is preaparation during building. Since there are a kind of grooves (just as for oiling a bearing) hydraulic pressure can be put between the shaft en the prop itself. By the really high pressure the foot of the prop increases a little bit in diameter, and shift easily of the shaft.
There is no problem to do the same in smaller props, but who produces this construction?

 

[Thistle]

Re: How to... Remove a prop that doesn\'t want to shift???

Try somewhere like Halfords.

 

[graham]

Re: ReUse 2 equal hammers

Sorry Rich,I was in such a rush to show off my vast knowledge I hadnt noticed you had beaten me to it!

Amazing how well it works ,Isnt it?

 

[ghost]

Re: ReUse 2 equal hammers

two oak wedges, with a slot cut out to straddle the shaft, a lump hammer
oppose the wedges and hit em

 

[tcm]

slide hammer, hydraulics

i'd make a slide hammer, rather than a puller. Greater impact, a better machine that stays on the job without the puller's tendency to open and (made properly) no damage to the prop. You need engineering facilities to make one, but it's not high tech.



To make the prop some off more easily next time, you can drill a small hole straight though the prop to the tapered shaft, and drill and tap it to accept a a hydraulic pump, so that loosening the shaft nut and a few pumps of the hydraulic forces the fluid in an and free the thing.