continuing dynamo pulley probs

[ginga]

Thanks to those that responded to my previous post on this but unfortunately its still happening.

No 9 dynamo pulley on its way out, I've replaced the key a couple of times now and it appears the keys are dying quickly due to the fact that the keyway is worn even though dynamo is only 2000 miles old. Could the fact that the garage when fitting the new dynamo used an old worn key and this has helped wear the keyway so now whatever i do the pulleys are disintegrating due to the play between pulley and shaft?....if that makes sense.

Is it possible to get the dynamo rebuilt witha new output shaft? or should i just get new dynamo or even better upgrade to alternator?

cheers
Ginga

 

[moler]

...Could the fact that the garage when fitting the new dynamo used an old worn key and this has helped wear the keyway so now whatever i do the pulleys are disintegrating due to the play between pulley and shaft?....if that makes sense.

Yes

Is it possible to get the dynamo rebuilt witha new output shaft? or should i just get new dynamo or even better upgrade to alternator?

cheers

You might be able to find an engineering firm that could cut you a new keyway in the opposite side of the shaft, although I'd do the ungrade

 

[alikat]

Possibly a poor key, or cheap shiny Chinese pulley that fit poorly to start with. Probably best to go with a new alternator - you might ask the garage if they would like to contribute as it should have lasted longer than that. You might want to wave the Sale of Goods Act at them if you had mentioned the first pulley failure to them (and have proof) as they should have some liability as they supplied and fitted it.

 

[Trikky2]

If the key keeps failing it means the pulley is still not properly tight on the shaft (see my post on your earlier thread).


The pulley is clamped in place by the nut compressing the shims and pulley against the end stop on the dynamo shaft.

Woodruff keys, in all applications, are never used/intended to transmit all the forces, they are merely and aid / locator.

In other words, even without the woodruff key in place the pulley should still be tight and not be able to spin round on the shaft.

 

[moler]

If the key keeps failing it means the pulley is still not properly tight on the shaft (see my post on your earlier thread).


The pulley is clamped in place by the nut compressing the shims and pulley against the end stop on the dynamo shaft.

Woodruff keys, in all applications, are never used/intended to transmit all the forces, they are merely and aid / locator.

In other words, even without the woodruff key in place the pulley should still be tight and not be able to spin round on the shaft.

I'm very sorry but I disagree, the shaft on an alternator or dynamo is straight and not tapered, so offers no mechanical interaction to keep it tight. Without a taper it would require a tremendous torque setting on the nut, especially as you have 20 surfaces interacting together, to keep it tight enough not to slin.

 

[Trikky2]

.

 

[Trikky2]

I'm very sorry but I disagree,

:lol: :lol: In that case maybe you would like to prove your point by removing the shims between the nut and the pulley on your engine and driving around without them for a while? :lol: :lol:

 

[moler]

I'm very sorry but I disagree,

:lol: :lol: In that case maybe you would like to prove your point by removing the shims between the nut and the pulley on your engine and driving around without them for a while? :lol: :lol:

I never said it doesn't need tightening up, of course it does, but without the woodruff key you wouldn't be able to get it tight enough to not spin.

 

[Oslo_mark69]

what dynamo is it I bought one from vw Heritage



NOW i HAVE THIS :mrgreen: :mrgreen: :mrgreen: :mrgreen: :mrgreen:

 

[Trikky2]

I don't know why I bother :roll:

Aw - just funnin - [hug smiley] Think we were talking at angry dolphins - didn't mean you could run without the key, just that it should feel tight even without - it if you get my drift - it needs help.

 

[Trikky2]

Problem is poor ginga is on his 9th pulley so chances are its all a bit academic now since the pulley will likely have chattered on the shaft and key so much that the shaft is likely damaged. Probably safest to replace with new or second hand IMO.

 

[Trikky2]

what dynamo is it I bought one from vw Heritage



NOW i HAVE THIS :mrgreen: :mrgreen: :mrgreen: :mrgreen: :mrgreen:

Serpentines certainly make belt adjustment a doddle I dont know why VW never went that route (other than maybe cost savings :lol: )

In the past I have come across a couple of serpentines that suffered from bearing failure, possibly because of the high rate of rotation but I would guess that by now they have either improved the bearing or increased the size of the pulley in the kit so it turns slower.

 

[alikat]

Another problem with the serpentine system is that , unlike the VW set-up, it doesn't allow the belt to slip, and if you turn your RPM up too much even a welded fan won't stop it imploding - really messy!

The best pulleys have 2 locating tabs as well as a flat on the outer half locating hole. Cheap ones have neither and the hub is poorly spot welded on. and it parts company just like the one in the pic! Genuine VW ones only have the flat on the centre hole, but are way better than Asian aftermarket quality.