Alternator belt slipping/screeching

[pig]

UPDATE

having put up with the rapid belt wear, and slipping on first startup in the morning, for what I see to be four years (doesn’t time fly!), I decided to bite the bullet and replace the 65mm tinplate pulley with a machined steel 80mm pulley.

Removing the pulley in situ was easy with an impact driver. The new pulley needed the shaft hole making bigger to fit- easily done with a step drill.

The belt was refitted, and so far so good- no slipping/screeching on startup. It does seem to be a much snugger fit to the pulley.
The rev counter has an adjuster on the back so I reset it at idle speed, to what it was previously.

Theres no sign of reduced charging, so all in all a success.

Thanks for the help.

[Tracy D'arth]

2 hours ago, pig said:

UPDATE

having put up with the rapid belt wear, and slipping on first startup in the morning, for what I see to be four years (doesn’t time fly!), I decided to bite the bullet and replace the 65mm tinplate pulley with a machined steel 80mm pulley.

Removing the pulley in situ was easy with an impact driver. The new pulley needed the shaft hole making bigger to fit- easily done with a step drill.

The belt was refitted, and so far so good- no slipping/screeching on startup. It does seem to be a much snugger fit to the pulley.
The rev counter has an adjuster on the back so I reset it at idle speed, to what it was previously.

Theres no sign of reduced charging, so all in all a success.

Thanks for the help.

Thanks, its nice to know.

[Jen-in-Wellies]

3 hours ago, pig said:

UPDATE

having put up with the rapid belt wear, and slipping on first startup in the morning, for what I see to be four years (doesn’t time fly!), I decided to bite the bullet and replace the 65mm tinplate pulley with a machined steel 80mm pulley.

Removing the pulley in situ was easy with an impact driver. The new pulley needed the shaft hole making bigger to fit- easily done with a step drill.

The belt was refitted, and so far so good- no slipping/screeching on startup. It does seem to be a much snugger fit to the pulley.
The rev counter has an adjuster on the back so I reset it at idle speed, to what it was previously.

Theres no sign of reduced charging, so all in all a success.

Thanks for the help.

Good to hear of the solution. Out of interest, was the very root of the old pressed steel pulley groove shiny? If so, then it could mean that the sides of the V belt weren't in contact with the pulley, which would have considerably reduced the grip.

[pig]

52 minutes ago, Jen-in-Wellies said:

Good to hear of the solution. Out of interest, was the very root of the old pressed steel pulley groove shiny? If so, then it could mean that the sides of the V belt weren't in contact with the pulley, which would have considerably reduced the grip.

I haven’t had a good look at it, and it’s now at home, so I’ll inspect it in a week or so when we get back. Certainly the belt seems to fit more exactly to the new pulley.

[MtB]

4 hours ago, pig said:

replace the 65mm tinplate pulley with a machined steel 80mm pulley

 

Bear in mind the rev counter will read slow now. (Assuming it gets its pulse from the alternator.)

 

 

 

Edited May 9 by MtB

[dmr]

A bigger pulley can make a big difference, more wrap and more surface contact area, but the alternator will run slower so less amps and it might well run hotter (less amps but even less airflow).   The best but very expensive solution is a fancy alternator controller that can limit the current.

[pig]

14 hours ago, MtB said:

 

Bear in mind the rev counter will read slow now. (Assuming it gets its pulse from the alternator.)

 

 

 

Indeed. I set the engine to idling, and turned the adjuster on the back of the rev counter to match previous revs.

[MtB]

55 minutes ago, pig said:

Indeed. I set the engine to idling, and turned the adjuster on the back of the rev counter to match previous revs.

 

That only calibrates the tacho at one speed. For all the other engine speeds it will read the true speed x 65/80 out. So at speeds above it will read 18.75% slow and speeds below your calibration speed 18.75% high, by my arithmetic. 

 

Happy to be corrected if there is some process by which the tacho can detect the new, changed pulley ratio.

 

 

None of this particularly matters, provided you are aware of the slightly inaccurate tacho reading now. 

 

 

[pig]

16 minutes ago, MtB said:

 

 

 

None of this particularly matters, provided you are aware of the slightly inaccurate tacho reading now. 

 

 

Not too concerned with its accuracy: for my purposes it should read:

 

idling

bimbling

chugging

thrashing

 

 

[MtB]

18 minutes ago, pig said:

Not too concerned with its accuracy: for my purposes it should read:

 

idling

bimbling

chugging

thrashing

 

 

 

Just be aware then, that when  "Thrashing", what would have been (say) 2000 on the rev counter now reads 1650 for that same 2000 engine speed.

 

[dmr]

54 minutes ago, MtB said:

 

That only calibrates the tacho at one speed. For all the other engine speeds it will read the true speed x 65/80 out. So at speeds above it will read 18.75% slow and speeds below your calibration speed 18.75% high, by my arithmetic. 

 

Happy to be corrected if there is some process by which the tacho can detect the new, changed pulley ratio.

 

 

None of this particularly matters, provided you are aware of the slightly inaccurate tacho reading now. 

 

 

Nah, just calibrate it at one spot speed and it should be good accross the speed range.

Calibrating at a higher speed should be more accurate.

I suspect you can get some sort of speed measuring app for your phone?

[Jen-in-Wellies]

56 minutes ago, dmr said:

I suspect you can get some sort of speed measuring app for your phone?

Yes, I've done this. Look for an audio spectrum analyser app. This gives a graph of volume against frequency, working off the phone, or tablet microphone. It will will show several sharp peaks that can be related to engine speed. You have to be careful, a 4 cylinder 4 stroke engine will give one bang from the diesel every revolution, so multiply frequency (Hz) by 60 to get rpm. However, at idle you will likely see the first harmonic, double the frequency, so multiply by 30. An 800rpm idle is around 13Hz, which is probably below what a cheap phone microphone can pick up, so the next harmonic up will be the lowest spike. At higher speeds, the fundamental frequency spike will appear, plus harmonics. You need to have a rough idea what the engine speed actually is to pick a sensible spike and deduce what to divide the frequency by to get the right engine speed. If you do, it works well.

 

56 minutes ago, dmr said:

Nah, just calibrate it at one spot speed and it should be good accross the speed range.

Agreed. If the calibration originally had no offset (zero engine speed = zero on the dial) and the needle tracks the speed in a linear fashion, then recalibrating at one speed is fine.

[Tracy D'arth]

I doubt that many tachos on boats are accurate at all.

The old cable drives maybe, but driving them off a belt driven alternator that may well have been changed from the original several times in the life of a boat I doubt if it will be anything near right.

[beerbeerbeerbeerbeer]

How important is a Tacho?

I don’t need one to tell me I’m revving the nuts of the engine and I can equally hear when the engine is idling comfortably.

It can tell me that the alternator is charging, and I guess it might be a reference for diagnosing problems.

 

 

 

[Tonka]

5 minutes ago, beerbeerbeerbeerbeer said:

How important is a Tacho?

I don’t need one to tell me I’m revving the nuts of the engine and I can equally hear when the engine is idling comfortably.

It can tell me that the alternator is charging, and I guess it might be a reference for diagnosing problems.

 

 

 

Tells you when to change the oil if it has the hour counter in it

[Alan de Enfield]

7 minutes ago, beerbeerbeerbeerbeer said:

How important is a Tacho?

 

Quite important, as well as showing the revs, they also (usually) have an hour meter so you can tell when you next oil change is due.

[beerbeerbeerbeerbeer]

No hour counter on mine,

I have to jot down the hours on a piece of paper,

 

[dmr]

1 hour ago, Jen-in-Wellies said:

Yes, I've done this. Look for an audio spectrum analyser app. This gives a graph of volume against frequency, working off the phone, or tablet microphone. It will will show several sharp peaks that can be related to engine speed. You have to be careful, a 4 cylinder 4 stroke engine will give one bang from the diesel every revolution, so multiply frequency (Hz) by 60 to get rpm. However, at idle you will likely see the first harmonic, double the frequency, so multiply by 30. An 800rpm idle is around 13Hz, which is probably below what a cheap phone microphone can pick up, so the next harmonic up will be the lowest spike. At higher speeds, the fundamental frequency spike will appear, plus harmonics. You need to have a rough idea what the engine speed actually is to pick a sensible spike and deduce what to divide the frequency by to get the right engine speed. If you do, it works well.

 

Agreed. If the calibration originally had no offset (zero engine speed = zero on the dial) and the needle tracks the speed in a linear fashion, then recalibrating at one speed is fine.

 

Yes, just like been back at work 😀 I did wonder if there was an acoustic tacho app that just did speed but it would need to be very clever. Sometimes the fundamental gets quite low and a harmonic or even sub harmonic can be the largest spike, but as you say, its all a lot easier if you know the approx speed. Working off a higher harmonic can give very accurate results

32 minutes ago, beerbeerbeerbeerbeer said:

No hour counter on mine,

I have to jot down the hours on a piece of paper,

 

You've done a lot of boating, how many hours do you think you have put on that engine?

Edited May 10 by dmr

[Martin Nicholas]

Optical tachometers are not much money.

[beerbeerbeerbeerbeer]

49 minutes ago, dmr said:

 

Yes, just like been back at work 😀 I did wonder if there was an acoustic tacho app that just did speed but it would need to be very clever. Sometimes the fundamental gets quite low and a harmonic or even sub harmonic can be the largest spike, but as you say, its all a lot easier if you know the approx speed. Working off a higher harmonic can give very accurate results

You've done a lot of boating, how many hours do you think you have put on that engine?

Without going back through my notes it’s hard to tell,

there was a time when I only ever ran the engine to move,

It’s still running clean and sounds right so I don’t worry too much

[Jen-in-Wellies]

18 minutes ago, beerbeerbeerbeerbeer said:

Without going back through my notes it’s hard to tell,

there was a time when I only ever ran the engine to move,

It’s still running clean and sounds right so I don’t worry too much

You can get a stand alone hours meter, wired across the ignition 12V for not a lot of pennies, if you decide you need one.

<pedant>Yes I know diesel engines don't have an electrical ignition!</pedant>

Assuming your boat's engine has an electrical system associated with it and not hand start and mechanical instruments.

[beerbeerbeerbeerbeer]

9 minutes ago, Jen-in-Wellies said:

You can get a stand alone hours meter, wired across the ignition 12V for not a lot of pennies, if you decide you need one.

<pedant>Yes I know diesel engines don't have an electrical ignition!</pedant>

Assuming your boat's engine has an electrical system associated with it and not hand start and mechanical instruments.

It’s something I’ve considered but there’s always been something else that needs doing,

perhaps it’s time I made the effort,

It’s just never got very high up on my to do list

[Tacet]

3 hours ago, Jen-in-Wellies said:

Yes, I've done this. Look for an audio spectrum analyser app. This gives a graph of volume against frequency, working off the phone, or tablet microphone. It will will show several sharp peaks that can be related to engine speed. You have to be careful, a 4 cylinder 4 stroke engine will give one bang from the diesel every revolution, so multiply frequency (Hz) by 60 to get rpm. 

Two bangs per revolution for a four stroke, assuming it's not misfiring.

[Alan de Enfield]

2 hours ago, beerbeerbeerbeerbeer said:

No hour counter on mine,

I have to jot down the hours on a piece of paper,

 

 

Where do you get the 'hours' number from ?

[beerbeerbeerbeerbeer]

4 minutes ago, Alan de Enfield said:

 

Where do you get the 'hours' number from ?

not sure what you mean?

Are you gonna tell me engine hours speed up and down?