Drive Plate Problems

[matty40s]

Having an unusual free day, I have had a good day in the engine bay, refurbished alternator back in (with a momentous fight), engine serviced and other jobs. Kathy and I are both off on holiday next week for a long cruise so everything needed to be checked (That round Tuit list was brushed off.)

I thought I would try to find the source of an unusual scraping noise which is still there - (I thought it was the alternator fault which has been there several months)

I finally stuck my head far enough down below the brass flywheel housing to see something rattling round where it shouldnt be.

Off with the housing to reveal the back of the drive plate spinning freely on the gear box splines - has been doing it for a while looking at the groove.

 

two springs left in the remains of the plate and 3 others in the engine bilge (one missing) . there were also two rivets which I presume held the back plate to the rest of the plate.

 

I have managed to source a new drive plate from ASAP for £58 next day delivery.

 

 

My problem is getting the drive plate out - I havnt seen this set up before and was wondering if anyone can advise

 

The flywheel is to the left in the top picture and the drive plate sits inside the metal flange centre of picture which itself sits on the shaft. There was an allen-keyed grub screw on one side(now removed) but on the other, there is a hole which does not go all the was down to the shaft., looking along the metal flange from the flywheel end, there is an indent, and the shaft also has a channel.....in line with the hole.

no movement of the flange along the shaft is possible...........

 

 

 

[RLWP]

no movement of the flange along the shaft is possible...........

 

 

 

 

 

Well, not now anyway. It would have been able to slide once upon a time

 

Richard

[Tony Dunkley]

Having an unusual free day, I have had a good day in the engine bay, refurbished alternator back in (with a momentous fight), engine serviced and other jobs. Kathy and I are both off on holiday next week for a long cruise so everything needed to be checked (That round Tuit list was brushed off.)

I thought I would try to find the source of an unusual scraping noise which is still there - (I thought it was the alternator fault which has been there several months)

I finally stuck my head far enough down below the brass flywheel housing to see something rattling round where it shouldnt be.

Off with the housing to reveal the back of the drive plate spinning freely on the gear box splines - has been doing it for a while looking at the groove.

 

 

two springs left in the remains of the plate and 3 others in the engine bilge (one missing) . there were also two rivets which I presume held the back plate to the rest of the plate.

 

 

I have managed to source a new drive plate from ASAP for £58 next day delivery.

 

 

My problem is getting the drive plate out - I havnt seen this set up before and was wondering if anyone can advise

 

The flywheel is to the left in the top picture and the drive plate sits inside the metal flange centre of picture which itself sits on the shaft. There was an allen-keyed grub screw on one side(now removed) but on the other, there is a hole which does not go all the was down to the shaft., looking along the metal flange from the flywheel end, there is an indent, and the shaft also has a channel.....in line with the hole.

no movement of the flange along the shaft is possible...........

 

 

 

You'll have to either move the gearbox back a few inches [sterngear, thrust bearings etc permitting] , or lift the gearbox out of the way.

The 'channel' in the shaft is a keyway for a feather [straight] key, and the grub screw is to prevent movement of the key in the event of it becoming loose.

[RLWP]

and the grub screw is to prevent movement of the key in the event of it becoming loose.

 

Or to lock the flange in place by pressing the key into the keyway

 

Richard

[Tony Dunkley]

 

Well, not now anyway. It would have been able to slide once upon a time

 

Richard

 

Not necessarily, . . . the half coupling may be, and really should be, a shrunk-on interference fit.

[RLWP]

 

Not necessarily, . . . the half coupling may be, and really should be, a shrunk-on interference fit.

 

And as we both know, what should be and what actually was done on a boat often bear no relationship

 

I'm with Tony, go for the gearbox. I suspect you could spend ages trying to shift the flange where half an hour with spanners will have the VelvetDrive out of the way

 

Richard

[matty40s]

Thanks for your help gentlemen.

Does this mean that the key once fitted is there permanently, or is it removable - everything else has been well engineered on the boat .

The grub screw only went a short distance into the other side of the shaft, not through to the back of the key channel .

I do have access to pullers/sledgehammers etc and the like tommorow.

Not sure I have the time to remove the gearbox as well as I am away with the daughter this weekend doing silly things like zipwiring and cliff bungee jumping at the Eden Project !!!! errrkkk.

[Tony Dunkley]

.I do have access to pullers/sledgehammers etc and the like tommorow.

Not sure I have the time to remove the gearbox . . . . . . . . .

 

I wouldn't go near it with a puller, or anything else with the intention of disturbing the half coupling fit on the shaft. If it's tight on the shaft and doesn't want to move, then it's best left that way.

If you did manage to move it along the shaft towards the engine flywheel, it's not likely to get you anywhere because, if the half coupling has been fitted as it should be, there probably won't be enough room between the end of the shaft and the gearbox splines to withdraw and re-fit the drive plate anyway.

Edited August 30, 2016 by Tony Dunkley

[RLWP]

 

I wouldn't go near it with a puller, or anything else with the intention of disturbing the half coupling fit on the shaft. If it's tight on the shaft and doesn't want to move, then it's best left that way.

 

Or worse - it moves along the shaft, sticks and you can't get the damn thing back!

 

Go for the gearbox

 

Richard

 

MORE: Let's face it, the simplest way of moving the flange back (if it will move) is to use a large hammer and drift onto the end. But you can't do that because the gearbox is in the way

 

So, maybe you could pull it off - but you can't get a puller in because the gearbox is in the way

 

Go for the gearbox

Edited August 30, 2016 by RLWP

[matty40s]

 

Or worse - it moves along the shaft, sticks and you can't get the damn thing back!

 

Go for the gearbox

 

Ricard

Pernod for me thankyou

will start at first light!!

 

I wouldn't go near it with a puller, or anything else with the intention of disturbing the half coupling fit on the shaft. If it's tight on the shaft and doesn't want to move, then it's best left that way.

If you did manage to move it along the shaft towards the engine flywheel, it's not likely to get you anywhere because, if the half coupling has been fitted as it should be, there probably won't be enough room between the end of the shaft and the gearbox splines to withdraw and re-fit the drive plate anyway.

ok, thanks to you both for your input, I will cease bashing the hole (key?) and try the gearbox out tomorrow - drive plate not expected until Friday, when I should be goggleeyed zipwiring at 60 mph!!!!

[matty40s]

Following the good advice above I loosened the gear box bolts and dropped the propellor shaft off at the back end

 

 

with a bit of effort and a few grunts, then moved the gearbox back enough to remove the drive plate - or what was left of it.

 

 

 

Thankyou Richard and Tony.

 

Now all I have to do is wait for the replacement to arrive and remember how to do it all backwards.

[Jess--]

I think this just helps to reinforce that you should investigate unusual noises as soon as they appear.

 

A friends boat had an unusual rattle that appeared only when in gear and moving at about 3mph (so not a convenient time to lift deck boards) until about a week ago when the engine pitch suddenly changed and smoke / steam came through the boards.

 

the unusual rattle was the engine mounts letting go, and the smoke / steam was the stern gland being cooked as the engine went out of line (BMC), apparently bmc's are quite impressive when they are not being held down at all.

 

it was bodged to get them back home to the north oxford canal from the thames in london (I didn't ask how) but now with new engine mounts they have horrific vibration (in time with the prop) and a stern gland that smokes so we suspect they have bent the prop shaft.

 

it comes out of the water next week to go over everything

[Tony Dunkley]

I think this just helps to reinforce that you should investigate unusual noises as soon as they appear.

 

A friends boat had an unusual rattle that appeared only when in gear and moving at about 3mph (so not a convenient time to lift deck boards) until about a week ago when the engine pitch suddenly changed and smoke / steam came through the boards.

 

the unusual rattle was the engine mounts letting go, and the smoke / steam was the stern gland being cooked as the engine went out of line (BMC), apparently bmc's are quite impressive when they are not being held down at all.

 

it was bodged to get them back home to the north oxford canal from the thames in london (I didn't ask how) but now with new engine mounts they have horrific vibration (in time with the prop) and a stern gland that smokes so we suspect they have bent the prop shaft.

 

it comes out of the water next week to go over everything

 

Unless the boat is being docked for any other reason it would be well worth disconnecting the tailshaft at the half coupling and checking for run-out on that and the gearbox half coupling before doing so.

Some makes of gearbox can suffer bent output shafts or distorted output half couplings, and some types of flexible/resilient couplings can be permanently distorted following major engine mounting failures.

Edited August 31, 2016 by Tony Dunkley

[Tony Dunkley]

 

 

 

 

 

Those two photo's may be exhibiting a possible cause for the knackered driveplate.

 

Unless the gearbox is in perfect angular and axial alignment with the tailshaft, and/or the plummer block doesn't permit even the slightest [fore and aft] axial movement in the tailshaft, the end thrust on that intermediate shaft [with the Hooke joints on each end] when in gear will be exerting a mis-aligning force on the free-standing gearbox.

 

If the gearbox mounting is sufficiently rigid to prevent even the slightest sideways displacement of the box, then there's no problem, but in practice, even the most substantial and strong looking pieces of steel fabrication will flex to a surprising degree when put under load.

It would also be well worthwhile to check the half coupling that carries the driveplate for run-out.

[matty40s]

The drive plate is approximately 17 years old and has had 9 years abuse from me, it has lasted well!! The steel mount is heavy engineering style, and does not budge at all, the gearbox fits like a hand in a medical glove.

The central shaft also has been carefully balanced with a small plate welded on one side.

Edited August 31, 2016 by matty40s

[Tony Dunkley]

.... ..... ..... The steel mount is heavy engineering style, and does not budge at all, the gearbox fits like a hand in a medical glove.

The central shaft also has been carefully balanced with a small plate welded on one side.

 

A fabricated steel structure which doesn't flex or move to some degree under applied load has yet to be made, and being statically or dynamically balanced won't prevent run-out on a rotating shaft and coupling assembly, or guarantee that the engine flywheel is in perfect axial and angular alignment with the gearbox input shaft.