So far so good

Well here we are 100 yards from where we started after an hour's cruise. No don't worry, we have had to get out of Calcutt marina and ascend three locks in that time. The new drive plate has made quite a difference. No big clunk when we engage gear and the engine seems very smooth and quiet. As to the alternator, they bench tested the old one and it was giving over 16v on the bench even after having a new regulator fitted. So that's good news, meaning there is nothing else wrong with the electrics.

Calcutt give good value I reckon. 270 quid for a new drive plate and alternator including fitting labour and vat.

We're staying put tonight and then moving to Braunston tomorrow. Me by boat and Kath by car and bus. The car has to get back to Crick.
Sent from my HTC

Drive plate failure–and why it makes me want to weep

Gubbins alert. Gubbins alert. If you have no interest in bits of engines breaking, look away now.
On Sunday Rick came over and we played with poking a screwdriver into Herbie’s flywheel casing. The reason ? To have a dig at the drive plate.  Now some of you might know all about drive plates, but for those who don’t.  I’ll try and explain.  Lets start at the beginning.

Now that our engine is now running smoothly thanks to our new camshaft, it enables us to hear a nasty clattering sound in the background.  Not all the time.  I suspect it comes and goes depending how hard the engine is having to push.  The clattering seems worse when the engine is lightly loaded.

Reading around on the forums, it’s a fair bet that the clattering is the drive plate.  I know little about drive plates save this much:

The drive plate acts as a cushion absorbing sudden changes in torque transmitted between the engine and the gearbox.  So when you engage gear, the running engine suddenly faced with the load of the gearbox and propeller feels less of a shock.  If you have a diesel car, there’s a fair chance it has a type of drive plate known as a dual mass flywheel.  The one on our old Focus got very clattery and I had to have a new flywheel and clutch costing me over £600.

In a boat engine it all goes together like this (yes, another Sketchup diagram)



The big rectangular block is the engine. The thick mauve disc is the flywheel and the drive plate is the thing bolted on to the flywheel. The smaller disc at the front of the drive plate is somehow flexibly attached to the back plate allowing a certain amount of torsional play between the two. At the centre of the front plate is a splined hole into which the input shaft of the gearbox fits, and the gearbox drives the propeller shaft and the propeller drives the boat. So when the boat goes into gear, or there is a sudden change in torque for whatever reason, the plate absorbs the torsional shock. With me so far?

Like I said I don’t know what connects the two halves of the drive plate and how the flexing is managed. There seem to be some nylon parts in there. Anyway we were able to poke at it with a screwdriver and it seemed to us that the front plate was pretty loose and had little torsional resistance. Reading up on the forums, this sounds like a failed drive plate which usually sounds like “a bag of spanners rattling”. Aaah yes, that’s the noise we get.

How do you get at it with a screwdriver when the flywheel is encased ? – I hear you ask.  Ah well Herbie’s engine, unusually,  has two gert big  holes in it’s flywheel casing.  They are there to allow the passage of drive belts for a long gone 240v  generator that used to be on the engine before we got the boat.

Anyway here is one of the holes so you can see.



Don’t panic that the exhaust pipe has fallen off and the gearbox oil cooler is disconnected.  I took the photo when they were getting the engine out for the camshaft job.

The arrow points at the drive plate that is bolted onto the flywheel. 

If the plate has failed, then why? Well apparently they often do in time. I suspoect our previous engine rough running and dodgy engine mounts had something to do with it. On our old car the plate failed after 95,000 miles and eight years. Herbie’s engine has done the equivalent of 150,000 miles and is eleven years old, so I can’t grumble really. It’s a routine job for a good mechanic to replace the plate, but I’m gutted that we didn’t spot it when we had the engine out because it would have been dead easy to do at the time and would have saved a lot of labour cost. 

 Look, they had it at their mercy! A ten minute job. Grrrrr!  It makes you want to weep.  Why didn’t they notice it when they put the gearbox back on?



The plates themselves are about £80.  The engine doesn’t have to come out, just the gearbox has to be pulled off.  We’ll have to have it done sooner rather than later because it can fail completely and engine will fail to drive the gearbox.  What’s more, if the plate falls to bits at speed, it might damage something else.

Does anyone know what’s inside these plates and how they work?

The root of the problem?

If you didn’t read  yesterdays post – read that first – it’s an ongoing story!
Measurements of the valve rise and fall showed that the cam shaft was indeed worn especially on one cylinder, which would certainly cause the engine to run out of balance.  So we bit the proverbial bullet and authorised fitting a new camshaft.  We moved the boat down to near the workshop and Jim set about disconnecting all the pipes and cables that attach to the engine.  Then before we knew it the crane was lifting out the engine.
Jim holds her steady:

A quick steam clean, then working like men possessed Jim and Ian set about dismantling an alarmingly large proportion of the engine, or so it seemed to me at any rate. 

I hope they remember where all the bits go.  As Ian has stripped and rebuilt literally hundreds of these engines he ought to.
It wasn’t long before Ian arrived at the boat triumphantly bearing the camshaft showing a very badly worn cam for No3 cylinder inlet.

As you can see, one of the cams is really worn down and pitted.  Compare with the ones further along the shaft.
At the end of the working day, the new camshaft was in and the engine was partly reassembled.
Then, after a stressful day, we got a visit from Rick and Marilyn who ferried us out to the pub in Flecknoe where we had a rather fine pie and chips and a very nice ale called Goats Milk.  Also we came second in their pub quiz- only let down by our incomplete knowledge of pop song lyrics.  I even failed to spot a line from Baby Love by the Supremes.  I’ll never live it down.
Now Herbie’s empty engine bay lies clean and hoovered out waiting for what we hope is a smooth running motor.

All a tremble at Calcutt

As I write, fitter Jim is wielding spanners in Herbie’s engine bay while virtual pound coins drop from my wallet into a bucket at a rate of one every 80 seconds.  Jim is doing his best to cure our engine shake, but up until now we don’t have a solution.  Let me begin at the beginning.
We reported at the wharf at 9 on Tuesday morning and after quite a while of engine running and listening and feeling around, Jim spotted that  the front engine brackets had a mounting tab broken off.  Here’s one:-

It’s twin on the other side was much the same and he securing bolts had shaken loose.  These days Calcutt have designed a modification to prevent this from happening.  This plate
 
fits across the end of the engine like this :

giving something stronger for the brackets to grip.
So that’s what we did.  The broken bracket were welded up,and  the new plate fitted. The engine was re-aligned to the prop shaft and we started her up.  Hmmm.  Our original vibration at about 1200 rpm had gone.  In fact there was a noticeable improvement higher up the revs too.
But, there was now a strong vibration at tickover or thereabouts.  We decided to ignore this for the time being and see how it affected us in cruising mode.  It could be that we could avoid these revs in practice.
Next day we ascended the Napton locks and it was becoming more and more apparent that the vibration was still a substantial problem.  What was more, the engine shaking was working various fuel pipes and unions loose and we were leaking diesel in a number of places.
So having ascended the Napton flight, we turned straight round at the top and came all the way down again. Grrrrr!
Returning to Calcutt this morning, we are back in Jim’s hands,and after consulting a colleague he is changing the four engine mounts as one of them did feel a bit soft.  It was felt we had to do this to eliminate it from the list of possibilities. Very soon now we will see if it has worked.  If it hasn’t, well, we had to replace the broken brackets anyway, and  I suppose  the new mounts won’t hurt.  Eleven years is not a bad life for such things.  So any money spent thus far has not been entirely wasted, but the prospect of the original problem of vibration not being solved is a real worry.
One thing that is good about Herbie’s design is that the front of the engine is accessible from inside the cabin, via a removable hatch under the steps.

This tends to make us remarkably popular with mechanics / fitters.

STOP PRESS
It didn’t work. :-(
Now we move on to the theory that it might be camshaft wear setting the engine running off balance.  This could get very expensive. An initial look at the rise and fall of the valves reveals that one of them might not be rising and falling enough but measurements have to be taken and checked.
Apart from all the potential expense and worry, our cruising plans are now all awry.
Watch this space.  I may post again later today as things develop.