Which alternator for a Yanmar / Barrus Shire 1950?

[Froggy]

7 minutes ago, Tony Brooks said:

Let's get the teeth out off the way first. They are only there to allow the belt to bend around a tighter radius and thus aid gripping on the smaller pulleys we tend to use, so that is very unlikely to be here or there.

 

What is vital, especially in your situation, is ensuring the new belts match the pulleys because with that belt size there are at least tow different cross-sectional profiles and if you get the wrong one it will not  grip across the full side faces of the belt, will wear faster and squeal more. The bottom belt has had it. If you don't know the belt profile/part number I think  I would buy a couple from Barrus but even then I had a case where they supplied the wrong profile.

 

 

 

Ok, thanks. Profiles looked more or less identical although photos don't really show this, but old belt has been binned so can't double-check. New belt ran about 6 hours before alternator failure. Hopefully just coincidence, there were no obvious indications of belt slippage.

[Tony Brooks]

3 minutes ago, Froggy said:

 

Ok, thanks. Profiles looked more or less identical although photos don't really show this, but old belt has been binned so can't double-check. New belt ran about 6 hours before alternator failure. Hopefully just coincidence, there were no obvious indications of belt slippage.

I can see no way a belt, even the wrong one, could cause an alternator to fail.

[Froggy]

8 minutes ago, Tracy D'arth said:

I think that it is just a manufacturing difference providing the width  of the back of the belt is the same,

I would use a Gates belt, they are generally considered to be the best available.

 

The failed belt looks to me to have failed due to overheating due to slippage ( squealing )  rather than normal wear.

 You are correct, belt had been slipping for a while on startup, it usually resolved after 5-10 minutes, i tended to have to readjust belt roughly once a month but hadn't got around to it that time. What can you see in the photos to indicate slippage, is it the way the backing has parted company in the second photo?

1 minute ago, Tony Brooks said:

I can see no way a belt, even the wrong one, could cause an alternator to fail.

 

Ok, well that's reassuring, i just wanted to cover all bases since the repair is costing about £160.

[Froggy]

I'm guessing though that a blown diode might possibly indicate too large a load could have been imposed on the alternator at the time of failure by running too many high-demand appliances?

[Tony Brooks]

9 minutes ago, Froggy said:

 You are correct, belt had been slipping for a while on startup, it usually resolved after 5-10 minutes, i tended to have to readjust belt roughly once a month but hadn't got around to it that time. What can you see in the photos to indicate slippage, is it the way the backing has parted company in the second photo?

 

 

I would suggest the damage on all the belts suggests long term overloading and overheating, probably caused by slip.  Just because it has stopped squealing does not mean it has stopped slipping.

 

Although I checked several times a year, my belt on hey Bukh with a 70 amp alternator never needed adjusting after the initial stretch. I think it was going strong after nearly 10 years. I am afraid that you have to live with monthly readjustment and short  belt life.

2 minutes ago, Froggy said:

I'm guessing though that a blown diode might possibly indicate too large a load could have been imposed on the alternator at the time of failure by running too many high-demand appliances?

 

It might, but I think lack of cooling air would be more likely from what you have said. If you expect it to produce full output at idle, that would contribute to diode overheating (insufficient air flow).

[Froggy]

9 minutes ago, Tony Brooks said:

 

I would suggest the damage on all the belts suggests long term overloading and overheating, probably caused by slip.  Just because it has stopped squealing does not mean it has stopped slipping.

 

Although I checked several times a year, my belt on hey Bukh with a 70 amp alternator never needed adjusting after the initial stretch. I think it was going strong after nearly 10 years. I am afraid that you have to live with monthly readjustment and short  belt life.

 

It might, but I think lack of cooling air would be more likely from what you have said. If you expect it to produce full output at idle, that would contribute to diode overheating (insufficient air flow).

 

Ok, thanks, i was forgetting how badly blocked those vent grills at the rear were, we were quite shocked when we took the alternator off, it wasn't evident from the top and front when checking oil and water levels.