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bob uk
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Posted on Saturday, 15 July, 2006 - 03:56:   Edit PostDelete PostView Post/Check IP

This is not about a Rolls-Royce but deserves a posting because it was unusal.

My daughter Peugeot 405 deisel estate kept getting a flat battery.

I checked alternator, starter and battery all OK.

I was watching the engine run and noticed that when the engine was revved the alternator seemed not to rev with the engine.

The crankshaft pulley has a torsional vibration damper which also drives the alternator the water pump is driven by the timing belt.

The rubber had become unbonded allowing the rim to slip causing no charge from the alternator.

So as a temporary fix I drilled a shallow hole in the face where the rubber joint is and plug it with a cut off bolt aqnd tacked the bolt so that it could not fall out.

Now it charges OK and I will not have to go to MacDonalds car park again and jump start it.

The damper is fitted so that the crankshaft does not wind it self up and break.

So I have limited my daughter to 40 Mph until she can get another pulley. They are quite expensive.

Fortunately or unfortunately Rolls-Royce uses a friction damper on the 6 cylinder engines otherwise again the crankshaft could break. These are really expensive and I have seen quite a few of these needing otherhaul.

If anyone has a 6 cylinder car do keep an eye on the crankshaft pulley and damper because they can give trouble.

Why Rolls-Royce used this type of damper I have no idea because they work no better than the rubber bonded type.

The V8 does not need a damper because the cranshaft is much shorter and much stronger.

On of the advantages of V engines is a short crankshaft whereas a straight six or even worse a straight eight have over long crankshaft and more twist. This is one of the reason it is not a good idea to Red line Jag XK engines because the crankwinds up and makes the engine rough as it makes nonsense of the valve and ignition timing. The front cylinders will be correct but the rears will be out -- it only takes 1 or 2 degrees of twist to muck it up. Jag cranks have been known to break.

V12s can also suffer this fate if over revved. --2 sixes nailed together.

I have given some V8s such as the Rover/Buick lump serious rev abuse and I once had a SD1 engine running at 6500 rpm for over an hour one night on a motorway when the Borg Warner 65 auto box would not change into top.

In the early days of Rolls-Royce engines ( such as the Ghost) it was not unknown for the engine to have crankshaft trouble.

RR policy of modifying older models to the lastest spec meant that when the crankshaft problems were finally fully sorted ( about 1915 at a guess) the existing cars were retro fitted.

So no need to worry if you are lucky enough to have a Ghost

(Message approved by david_gore)