Alternator drive follow-on;- fear

[Graham_Wright]

Following my post on the power required to drive my 130A alternator and the erudite and very helpful educational posts in reply, I now have a BIG concern.

Wondering if it was possible to double up the grooves on the crankshaft pulley, I gave the nut/screw securing it a jerk with a socket spanner. (The access is restricted - very). No joy.

Tried counter-clockwise and it turned. Still innocent, I kept turning and a screw emerged - together with the pulley.

This pulley is additional to the original automotive water pump/alternator drive pulley which remained and was added to drive the Jabsco raw water pump.

The marinisation was carried out by T Norris.

There was no evidence that the additional pulley was locked to the crankshaft at all.

It will be clear that this is not only bad engineering but positively dangerous.

Should the Jabsco seize or encounter something indigestible, it will act as a band brake on the belt and possibly unscrew the crankshaft drive pulley at 2000rpm.

The consequences are scary to contemplate.

Apart from the observation on the poor marinisation (it was carried out long time ago (don't ask why!) and there is no point contacting Norris), can anybody suggest a solution? I have been unable to establish how the "fan belt" pulley is locked to the crankshaft but, if were possible to remove that (and the section drawings I have imply it is), I could produce a triple groove pulley to replace the pair and they would then be safely secured.

Anyone know how this original pulley is secured?

I guess it might help to add that the engine is a BMC 1.5 litre diesel.

Will I ever get afloat?

 

[rogerthebodger]

normally the front pulley is driven by a woodruff key and the front pulley bolt is locked to the crank shaft with a tab washer.

The pulley on my leyland has the same arrangement and I added an extra 2 groove pulley by through bolting on to the front of the existing pulley.

 

[Graham_Wright]

normally the front pulley is driven by a woodruff key and the front pulley bolt is locked to the crank shaft with a tab washer.

The pulley on my leyland has the same arrangement and I added an extra 2 groove pulley by through bolting on to the front of the existing pulley.

That's reassuring.

My A C Belting guru says the same thing. Access is grim but I could lift the front of the engine a little. If I can remove the "fan belt" pulley, I can produce a triple groove replacement.

 

[Avocet]

Lots of pulleys just rely on friction these days and seem fine. I've even seen car engines with cam pulleys held in this way.

 

[DownWest]

Lots of pulleys just rely on friction these days and seem fine. I've even seen car engines with cam pulleys held in this way.

Same here, just make sure the procedures are carried out. If not....whoops.

On my Ford, friction plus a roll pin to locate. But the bolt to hold the cam belt pulleys to the crank are high torque, one use only, stretch type.
Easiest is to add a pulley by threading the existing one (if enough meat) for three or four bolts outside the centre boss.

 

[rogerthebodger]

Easiest is to add a pulley by threading the existing one (if enough meat) for three or four bolts outside the centre boss.

That's how I did mine but you will need to machine a lip on the existing pulley to locate the new pulley concentric with the old one otherwise bearings will be damaged by the increased and eccentric loading.

 

[Graham_Wright]

Lots of pulleys just rely on friction these days and seem fine. I've even seen car engines with cam pulleys held in this way.

Unfortunately, Mr Norris had added a grub screw locking the pulley to the bolt. Without that grub screw, if the pulley slackened, maybe it would just slip. With the grub screw it would spin the whole lot off with dire consequences.

However, things are looking up! See next post.

 

[Graham_Wright]

Progress!

Last night, I managed to remove the crankshaft pulley by levering both sides after the application of hot air gun heat.

The construction is interesting.

There seems to be a central core with a ground bore carrying the keyway. Around this, there is a rubber sleeve over which there is a single-grooved pulley proper. This pulley actually has room for one more "A" groove. The reason for the sleeve is not clear. If the crankshaft mating core is a standard part allowing different pulleys to be utilised, why not just a metal-metal press fit?

Anyone suggest?

Frustratingly, now I have removed it, I can see two diametrically opposed 5/16" UNF threaded holes. It would have been a doddle to extract using these. Next time!

Now I have to decide whether to separate the inner and outer parts and turn up a four groove replacement for the outer or to bolt on an additional pulley. It would be ideal to re-manufacture the whole lot so that if/when it all goes wrong, I have a backup.

I could go for different diameters allowing me to increase the ratio to drive the alternator at higher revs following the mechanical power/speed advice. I need to check the upper recommended revs limit for the alternator first. I could also make one groove a small diameter to calm down the Jabsco (making like a fire pump at the moment).

Looking at the weather forecast, the village real ale festival, the barbecue and beacon lighting, the kids party and the street party all look threatened.

Could be a weekend in the factory!

 

[rogerthebodger]

I have seen rubber bush mounted pulley's before and in think they were an attempt to be a vibration damper , for what vibration I don't know.

I would not even consider turning up my own Vee belt pulley when you can get then from Fenner so cheep and easy to fit to shaft or in your case the boss mounted on the crankshaft as the inner part of the original pulley runs on the lip seal in the front engine cover.

Depending on the condition of the original pulley boss I would remove the grooved pulley and replace it with a multi groove pulley from Fenner with a taper lock bush sized to fit on the boss removed from the original pulley.

No keyway is needed in the new pulley as the tightened taper lock bush will carry the torque. The only down side is that you would not be able to have different sizes for different grooves unless you went to my arrangement of bolt on pulleys but you will need to machine location recesses to ensure the pulleys are concentric.

You could then enjoy the weekend as very little workshop time is needed

 

[Graham_Wright]

I have seen rubber bush mounted pulley's before and in think they were an attempt to be a vibration damper , for what vibration I don't know.

I would not even consider turning up my own Vee belt pulley when you can get then from Fenner so cheep and easy to fit to shaft or in your case the boss mounted on the crankshaft as the inner part of the original pulley runs on the lip seal in the front engine cover.

Depending on the condition of the original pulley boss I would remove the grooved pulley and replace it with a multi groove pulley from Fenner with a taper lock bush sized to fit on the boss removed from the original pulley.

No keyway is needed in the new pulley as the tightened taper lock bush will carry the torque. The only down side is that you would not be able to have different sizes for different grooves unless you went to my arrangement of bolt on pulleys but you will need to machine location recesses to ensure the pulleys are concentric.

You could then enjoy the weekend as very little workshop time is needed

A great burdensome failing of mine is to assume I have to make everything myself. Having a high end engineering factory at my disposal, I just choose a machine and get stuck in. The fact that I could pop down the road and buy what I need for a fraction of my time spent getting things right, seems to escape my attention.

I think the crankshaft boss may be a little big for a taperlock fitting but it's a thought.

Thanks for the help.

 

[Graham_Wright]

I have seen rubber bush mounted pulley's before and in think they were an attempt to be a vibration damper , for what vibration I don't know.

My A C Belting Man (Keith - I can't believe how helpful and knowledgeable he is) advises that the original reason for the rubber bush was to stop static due to interference to radios. A secondary reason was to add a little bit of resilience to the driven belts.

He advises shrinking on any additions I make and then grub-screwing axially (like taper lock) between the two halves.

 

[rogerthebodger]

My A C Belting Man (Keith - I can't believe how helpful and knowledgeable he is) advises that the original reason for the rubber bush was to stop static due to interference to radios. A secondary reason was to add a little bit of resilience to the driven belts.

He advises shrinking on any additions I make and then grub-screwing axially (like taper lock) between the two halves.

I think an insulator between the pulley rim/belt would allow static to build up where if the pulley was electrically connected the static would drain to ground but what do I know. The resilience bit I can understand.

The shrinking on will work but then the pulley cannot be removed from the boss unlike with the use of taper locks.

 

[Graham_Wright]

O.K, - job finished.

Final solution was to machine a spigot on the existing pulley to accept a counterbored new 2 groove pulley. This will drive the alternator with both grooves. This two groove pulley in turn has a turned spigot onto which is a fitted a counterbored smaller diameter pulley for the Jabsco.

Where the pulleys mate, they are locked together with two dowels.
Through the centre of the lot is a turned shaft that matches the internal diameters of the pulleys (bored as originally they were tapered for taperlocks).

The crankshaft end of this is threaded male (5/8" X 16 tpi - weird - Unified 12 thread Series) and the other M16 female. This accepts a bolt on cap that pulls the whole lot together. The cap is doweled to the small pulley and the dowels also locate a locking tab washer.

Now - how do I know if it's worth balancing the assembly and, if it is, how do I do it.

This is outside my skill range.

 

[rogerthebodger]

My modified front pulley was done very similar to the way you did yours as as every thing is concentric I just checked that there was no run out with a clock gauge with the pulleys mounted on a dummy shaft running on bearing vee blocks.

This can also give an indication of static balance by spinning the assenbly several times and marking the stopping point for each spin.

The more random the stopping the better static balance the assembly is.

I am balancing my new fabricated stainless steel prop that way doing the same.

Dynamic balancing is done on a machine like a tyre balancing machine, in fact if you make an adaptor a tyre balancer could be used with the removal is some material opposite the position the balancer says the weight should be fitted