Technical Dynamo pulley

[Yellblob]

Hi all,
Putting my engine back together now the car has been resprayed. I hope you can see from the pictures that the two pulleys are about 10mm out of alignment. The new dynamo seems in the correct place with the hole and screw aligned on bracket, also the tinware. What have I got wrong?! Any suggestions?
Thanks in advance.
David

 

[fiat500]

What have I got wrong?! Any suggestions?
Thanks in advance.
David

Try putting the two pulley halves in the opposite order; I think the most deeply-dished one with its back to the engine.

 

[Yellblob]

Alas that is how the halves are on now. The dynamo seems to be in the right place judging by arrowed screw or is that what I have wrong? The 3 screwed hub is fully onto the woodruff key too. I'm stuck on this. :bang:

 

[jackwhoo]

Compare the position of the locating screw on new dynamo with old dynamo

 

[Yellblob]

Ah, I had to send the old one as an exchange (Ricambio). I thought it was a like for like but maybe not....

 

[jackwhoo]

Would it work for you if you can remove the screw and fit dynamo by eye.
Any part numbers on the dynamo? Cross check it's correct for your motor?
Ask company that sold you the exchange for advice?

 

[Yellblob]

Yes, I was starting to think the same thing on both points. Hard to believe there would be different dynamos though.

 

[fiat500]

The dynamo is located by being bolted to the cowling and the aluminium cradle just supports and steadies it. The screw you mention was a plastic stud on my dynamo. You won't be able to change its position to any meaningful extent. There can't be many, if any dynamos that could be an alternative fit so it's hard to see how you could be wrongly supplied. Do you have the inboard end of the dynamo properly located in the housing?

 

[Vitesse]

The pulleys don’t look right to me. On the side on picture of the pulleys, it looks like on the inside where the two sides meet together tapers into a point, the part the belt would run through. There should be a flat where the two pulleys meet of about 8mm and that is provided by the front pulley which has much deeper dish in it. Or it could just be it’s not clear in the picture. Plus they look like they maybe sitting slightly skewed on the shaft?

 

[Yellblob]

Yes, there is a skew on the rotation like a wobbly wheel -it's something to do with the 3 screwed hub-but thats another matter.
Ill take off the hub and pulley to see if it could be further inboard than it is.
Thanks again.

 

[Toshi 975]

Are you able to measure this part of the boss?

 

[Franko500]

Going by the dimensions where the alloy casing ends and the front face of the 3 stud hub, it looks to be the right size dynamo. So I can only think you have the pulleys on back to front. They are universal and fit both the alternator & dynamo but are fitted in reverse. Here are the photos of mine.

 

[Franko500]

Heres a photo of when it originally came off the engine

 

[Yellblob]

Thanks Franko,

I took it apart, repositioned the screw in the hole in the bracket as I thought it must sit in that position and loosened all the mounting screws. I found I'd put a spacer on between hub and first pulley half, I also suspect the hub somehow had not gone fully to the hilt. It seems OK now but apart from the spacer I'm not totally sure what I did wrong. Oh well I'm pleased to be able to finish the assembly. First time I've ever stripped an engine down, it seems to be turning OK, here's hoping it runs well!!

 

[Vitesse]

Thanks Franko,

I took it apart, repositioned the screw in the hole in the bracket as I thought it must sit in that position and loosened all the mounting screws. I found I'd put a spacer on between hub and first pulley half, I also suspect the hub somehow had not gone fully to the hilt. It seems OK now but apart from the spacer I'm not totally sure what I did wrong. Oh well I'm pleased to be able to finish the assembly. First time I've ever stripped an engine down, it seems to be turning OK, here's hoping it runs well!!

Looks like you have the belt on inside out now.

 

[babbo_umbro]

I suppose you realise that belt tension is set by the spacers between the two halves of the pulley at the dynamo - you take spacers out, so that the pulley clinches up more closely, to increase the tension/take up the slack, and distribute the spacers on either side of the pulley to get/keep the belt aligned.

 

[fiat500]

distribute the spacers on either side of the pulley to get/keep the belt aligned.

I'm sure that it might give an opportunity to accommodate slight misalignment in that way. But in general, there's no need to put spacers between the dynamo flange and the inner pulley half. The belt stays in alignment as spacers are changed; it just rises and lowers in the pulley. Spacers are stored on the outside of the outer pulley half.

 

[sludgeguts]

Ah, I had to send the old one as an exchange (Ricambio). I thought it was a like for like but maybe not....

As an interesting aside, exchange units aren't always the right. I've had a couple of occasions over the years whereby the exchange unit, at first glance, appears identical but when placed side by side are actually different sizes. I even had one motor factor assure me that their exchange unit was correct and that the alternator I removed must've been incorrectly fitted.
I spent a fortune visiting as many local spares shops as I could & since the alternator wasn't working, I had it on the seat next to me to compare in the shop.
instead of the £50 replacement unit, I ended up paying almost £150 for a genuine part.

Strange thing was, the exchange unit was wrong for my vehicle, it was also wrong for the previous version as well as the latest - so everyone's books was listing the wrong exchange - yet nobody could tell me what the part actually came off.

The second occasion involved an exhaust system. The book had the middle section 4" shorter than it actually was! Fortunately, I had a mate who was handy with a welder & we managed to cadge a short length of steel pipe big enough to slip over & weld on.

 

[babbo_umbro]

I'm sure that it might give an opportunity to accommodate slight misalignment in that way. But in general, there's no need to put spacers between the dynamo flange and the inner pulley half. The belt stays in alignment as spacers are changed; it just rises and lowers in the pulley. Spacers are stored on the outside of the outer pulley half.

If spacers are removed and placed only on the outside (ie rear of the car) the centre of the pulley moves towards the body of the dynamo - it's only a small amount but why not retain the precise alignment?

 

[fiat500]

If spacers are removed and placed only on the outside (ie rear of the car) the centre of the pulley moves towards the body of the dynamo - it's only a small amount but why not retain the precise alignment?

Good point, but if we worried to that extent then we'd probably have to set up each new belt with external spacers to ensure centrality as you can't assume that all belts and pulleys just happen to start with exactly the right basic fit for each other; it all gets a bit involved.
But this maybe partly explains the frequent mention of rubber dust that often gets worn off the belt.