Separating a shaft from the gearbox clamp

Malish

Malish

Well-Known Member
Joined
9 Nov 2004
Messages
3,942
Location
Rochester, UK, boat in SYH
Visit site
Hi
I need to withdraw a 1" shaft from the gearbox clamp in order to replace the shaft seal. The shaft is clamped using four bolts, two either side, there is no evidence of a pin or similar. I've undone the bolts but my best efforts with a wooden drift and 4lb club hammer on the prop have yet to budge the shaft more than 1mm (and that is being optimistic!) Any tips from the forum? I have hunch that heat on the clamp is the way to go but there is not much elbow room
 
You say you have undone the bolts but have you removed them?

In some types of coupling the bolts engage in grooves in the shaft and, unless removed, they will prevent the coupling being pulled off.
 
Have only done this once, but as you find, it was a b****r. I think we eventually used a soft metal drift, wood just takes up the shock. We also had one man inside levering the clamp open with a very large screwdriver. You could try Plusgas round the clamp?

You say you have checked there is no pin or grubscrew.
.
 
Try reversing the bolts in the clamp, inserting a piece of sheet steel in the slot, and then tightening the bolts against it to prize the clamp open.
 
Another trick is to undo the coupling and pull it back a little. Place a nut the size of the propshaft between the shaft and the gearbox and then do up the coupling so as to squeeze the shaft out.

While the coupling is undone you have better make sure there is not a key that holds the shaft from slipping out - it may be that you need to knock the coupling up the shaft to free it.
 
Moonfire said:
Thanks for the suggestion but the bolts are well away from the shaft
Click to expand...

Have you cleaned up the coupling to make sure there is not a pin through the coupling and shaft. I know you said there wasn't, but cleaning up the coupling with emery, may show the end of a pin. There was a long bolt through the coupling on our shaft, that came out easily.

Keep us in the loop as to what you find and how you get the coupling off.
 
Moonfire said:
Hi
I've undone the bolts but my best efforts with a wooden drift and 4lb club hammer on the prop have yet to budge the shaft more than 1mm (and that is being optimistic!) Any tips from the forum?
Click to expand...

Tip 1. Never hammer anything on a boat! The impact force that you are applying with your four pound hammer is being resisted by the ball bearing on the output shaft of the gearbox. If there is one thing that ball bearings do not like most, it's impact. You could finish up having to replace the bearing.

Tip 2. As others have said, drive the shaft out of the coupling hub by tightening either the gearbox flange or a made-up substitute against it, through a solid object such as a a large nut. There's a photo, courtesy another forumite, at http://coxengineering.co.uk/Aquadrive.aspx, where a long bolt is being used to give sufficient thrust to drive the hub right off.
 
MoodySabre said:
Another trick is to undo the coupling and pull it back a little. Place a nut the size of the propshaft between the shaft and the gearbox and then do up the coupling so as to squeeze the shaft out.

While the coupling is undone you have better make sure there is not a key that holds the shaft from slipping out - it may be that you need to knock the coupling up the shaft to free it.
Click to expand...

The above advice is the way to go. Use the clamp as a press. Put in a spacer and using the bolts on the flange, tighten evenly and push the shaft backwards in the clamp. You may need longer bolts, but it will work without causing damage or stress to any components. Good Luck,Rotrax.
 
When I had to get my 30mm shaft out, I used the method described by Vyv Cox, but I discovered afterwards that the clamp had two forcing screws in it that opened it up in the same way described by PVB. A combination of both methods is the way to go.

Getting the shaft back in was actually harder than getting it out, and it was only the discovery of the forcing screws that enabled me to do it.
 
pvb said:
Try reversing the bolts in the clamp, inserting a piece of sheet steel in the slot, and then tightening the bolts against it to prize the clamp open.
Click to expand...

I tried the above. All that the reversed bolt did was to put a dent in the steel, trapping it in the slot. I now cannot use the boat until it is sorted out. I did think of heat but there is very little room to work and I doubt if my back and joints would stand the cramped position for long enough to wield a blowlamp.
My solution is to hand the job over to the local boatyard.
 
If your clamp is the same as a Yanmar there are splits along the sides of it.
Go to a builders merchants and buy a brickies line kit. In it there are two flat ended pins and some twine. All you want are the pins. Hacksaw off the points by about 1/2 an inch. You can then insert one into each of the slits and gently tap them in. They will widen the slit there by opening the clamp and allowing you to withdrawn the shaft. It works a treat.
 
Yes, the clamp has splits along the side. I might have a go with a couple of old chisels if the boatyard does not soon get around to the job. But then I might end up with the chisels stuck fast too.
 
Thanks to all, I'll be pursuing the bolts through the flange route this weekend. One last little related question - do they go back in easier than they come out because I don't see a route for pulling them back in?
 
Miker said:
Yes, the clamp has splits along the side. I might have a go with a couple of old chisels if the boatyard does not soon get around to the job. But then I might end up with the chisels stuck fast too.
Click to expand...

I tried chisels they don't fit easily into the slit parallel to the shaft and as you tap them in the handle pushes against the shaft forcing them out of the slit. The tool I mentioned is flat and tapered eventually becoming round. Like a six-inch nail with a flattened end and much easier to insert into the slit. I think I bought mine at wikes for about £4.00. The bolt method would only work for me once the slits had been opened.
 
You must log in or register to reply here.

Share this page

Top