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Failed to remove the shaft coupling

Lucas Gan

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5 Oct 2018
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414
@John100156 All screws surely removed. As you can see the photo in #36, one of the screw hold on top show on the picture. All removed.

Yes, now I will leave it to the boatyard to remove whatever they can.
 

penfold

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25 Aug 2003
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5,190
Location
On the Clyde
A disc of thick steel like cvta used, except the middle bored out so it slides over the threaded section of your hydraulic puller and 6 bolts long enough to fasten onto the coupling while sandwiching the puller's spider. That along with a large blow torch, not a dinky little creme brulee torch with a canister, will shift it.
 

Falling Star

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4 Mar 2011
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522
Location
Essex
I had the same problem when trying to remove the coupling on my Broom. After trying just about everything, I hired a 25 ton pump and cylinder set from Dutest in Basildon, Essex. I made up a plate and used high tensile studding to leave a gap to get the jack in. It worked!

Screenshot 2021-07-22 at 01.11.36.png
You may be able to hire something similar from a company more local to yourself.
Cover the set-up with an old duvet or similar when applying the pressure. It does make a good bang when it lets go.
 

Lucas Gan

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5 Oct 2018
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414
The job now backs to my hands as the boatyard said they can't do it in the coming week. I am going to order a grinder, a 10-ton hydraulic cylinder, a bigger gas torch and bolts. Just need to find a piece of the metal plate at least 15mm thick.

I am afraid the 10-ton hydraulic cylinder is not strong enough, but after measure, the coupling sizes between the two bolts maximum size is 80mm. It won't be able to fit a bigger cylinder in. The 10-ton cylinder size is 83mm X 63mm x 56mm (L*W*H).
 
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Croftie

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19 May 2015
Messages
519
As all the above, get that puller (or whatever) with as much pressure as you can. Use both torches on either side and get that coupling HOT. Then leave over night, don't expect immediate results
 

vas

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21 Jun 2011
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6,647
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Volos-Athens
Measured 130C+ on heating with a blowtorch with a half litre canister
took me a good 10-15mins heating (under stress)
tightened them a bit more and left it under stress, next morning it was released
 

Croftie

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19 May 2015
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519
Also worth turning the shaft 90 degrees after heating for 5-10 mins and starting the heat cycle again and again and.....
 

Falling Star

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4 Mar 2011
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522
Location
Essex
Sorry for the rubbish sketch.

I suggest you use 4 lengths of M20 HT threaded rod (Screwfix). You also need some 20mm thick mild steel plate (ebay).

Drill the plate so that the holes will clear the base of the 25 ton cylinder. You will need to angle the holes inwards slightly so that all 4 lengths of studding taper together at the coupling. If you can't get the studding through the coupling holes then you need to make up a back plate to get behind the coupling flange.Sketch 1.jpeg
 

vas

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only issue in your sketch is that on a 45mm shaft, I doubt the holes in the coupling are larger than 10mm!
 

burgundyben

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28 Nov 2002
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Niton Radio
I dont understand...

Lucas insists its not a taper.

The pic in the first post shows 2 screws have been removed, looks like axially in the same place, so grub screws not through bolts.

I doubt very much its an interference fit.

So what is taking the thrust? It cant be a transition fit and grub screws.

(I still think its a shallow taper, that's why its a bastard to get off)

A lot of heat is the answer.

I might be wrong!
 

Lucas Gan

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5 Oct 2018
Messages
414
@Falling Star thanks.

@vas Yes, you are right, the hole only about 11 mm, the original bolts are 10mm. There are 6 holes.

@burgundyben There are only two screws, all removed. The end of the shaft exactly 45mm so I confirmed it's parallel.

I have ordered a 20mm thick 150mm X 150mm steel plate. 10 bolts of M10 (10mm X 120mm).
 

Hurricane

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11 Nov 2005
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8,298
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Sant Carles de la Ràpita
Just a thought.
In one of your pics, there seems to be a keyway (it must be a keyed shaft or the flange would turn on the shaft)
Have you tried to knock the key out.
Maybe the key itself is tapered so maybe it could be knocked out from the propeller side of the flange.
Please keep us posted with your progress.
 

vas

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21 Jun 2011
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Volos-Athens
before you spent more money on press kit that you'll never use, maybe you should see if there's another coupling you could buy for 100quid and cut the bastard off!
I still bellieve proper heat will do the job, so looking forward to the success story soon!
 

Croftie

Active member
Joined
19 May 2015
Messages
519
I noticed that key before. But can't remove it in anyway.
Always take care trying to move a key, too much hammering/tapping/drifting can end up with damage/swelling to the key making matters worse.
For info re removing couplings there is a thread going on in the PBO forum at the moment mainly about R&D type but interesting
Removing shaft from R&D coupling
 

Falling Star

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4 Mar 2011
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522
Location
Essex
only issue in your sketch is that on a 45mm shaft, I doubt the holes in the coupling are larger than 10mm!
Yes. That's right.
I did say - "If you can't get the studding through the coupling holes then you need to make up a back plate to get behind the coupling flange."
 
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Lucas Gan

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5 Oct 2018
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414
@vas Yes, that's why I have bought a grinder to get ready to cut. Should deliver today.

This old bastard coupling is hopeless. Tight, no hydraulic puller can fit, even the smallest hydraulic cylinder also can't fit in because the 6 bolts space is limited. So the last chance will be heating a lot under a DIY 20mm thick plate puller in the next coming days. If this failed, then I should practice my grinder skills.
 
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Croftie

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19 May 2015
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519
If you are going to replace the flange with say a R&D split, measure the shaft very carefully, 45mm is virtually 1.75" but it is NOT the same, is your shaft metric 45mm or imperial 1.75?
 
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