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Old 03-02-2018, 09:08   #1
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Torque converter on Alternator

I'm not sure if this has been discussed here but it may be of interest to some of our members. It is a different type of alternator pulley that greatly reduces belt wear, vibration and noise. Here are several links to Youtube videos.





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Old 03-02-2018, 09:29   #2
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Re: Torque converter on Alternator

Interesting for sure. Although one wonders if there is a boat app really, most boats dont have 8 pulleys!
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Old 03-02-2018, 10:37   #3
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Re: Torque converter on Alternator

I don't see that "OAD" being a torque converter of any kind. It is just another one-way clutch.

All the excessive belt tensioner movement, and the excessive belt movement, can be caused by the clever vendor simply not having adjusted the belt tension correctly. Could be a bad tensioner (a big problem now with serpentine belts) or it could be a wrong belt.

Clutches aren't used on alternators normally because they add mass and drag and expense. When the electric system is not putting any load on an alternator, it creates very little drag on an engine. Newer car "power management systems" actually SHUT the alternator when the battery reaches full charge, and leave it shut until some specific point is reached (i.e. 95% charge or a large load) so that the alternator freewheels and the engine gets better mpg when power is not needed.

A solution in need of a problem, as opposed to a robust "just buy fuel" solution. Clutches, computers, all less reliable than "just buy fuel". Especially when the tensioner seizes up and takes all the rest with it.
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Old 03-02-2018, 10:57   #4
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Re: Torque converter on Alternator

Its a sprag clutch, and sprag clutches wear and fail.
My guess is that they found an engine and ran it at an RPM that corresponded with the natural harmonics of the spring loaded tensioner.
Id bet if they replaced the spring loaded tensioner with a simple one that you locked down with a bolt then the excessive belt movement would also go away, but not have a sprag clutch to wear.
Best common example of a sprag clutch is a bicycle freewheel, they rarely ever fail as they are so lightly loaded and are cycled infrequently.
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Old 04-02-2018, 15:00   #5
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Re: Torque converter on Alternator

These Alternator Drive pulleys have been developed because the small Diesel engines have a "vibration " period which has an adverse effect on alternators.
They allow the Alternator to " Freewheel" much like a push bike as described.
They are expensive to replace and an added complication, which probably should have a service life.
They are a sod of a thing to remove if you dont have the specific tool.
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Old 04-02-2018, 16:28   #6
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Re: Torque converter on Alternator

IIRC the old Perkins diesels were the diehard engines in London's black taxi's. Fleet use like that, surely, is going to strain alternators more than the light use on boats. Alternators with just belts have managed to rack up a lot of hours in a lot of commercial applications, I can't see that boat diesels are so much more demanding?
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Old 04-02-2018, 19:46   #7
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Re: Torque converter on Alternator

Quote:
Originally Posted by hellosailor View Post
IIRC the old Perkins diesels were the diehard engines in London's black taxi's. Fleet use like that, surely, is going to strain alternators more than the light use on boats. Alternators with just belts have managed to rack up a lot of hours in a lot of commercial applications, I can't see that boat diesels are so much more demanding?
But the above would not have run a serpentine belt, I think that is the issue.
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Old 04-02-2018, 21:56   #8
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Re: Torque converter on Alternator

These are common, and necessary, on many VW diesel car engines.
As mentioned, a sprag clutch to prevent overrun, likely due to some natural period/harmonic issue with the engine/belt drive/alternator combination.
Unless one was having a problem with belt life, I see no reason to consider it. If one has a problem, it may offer an easy, and reasonable cost, solution.
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Old 05-02-2018, 07:59   #9
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Re: Torque converter on Alternator

This is fairly common on modern diesel engines where in the interests of fuel economy they have gone for fewer cylinders and higher bmep, (torque). This means that the speed irregularity when each cylinder fires, when operating at low engine speed but high load, is much higher than normal. This is no problem for the engine but it is a problem for the belts because they have to transmit this high oscillating movement to the auxiliaries which means high loads in the belts. A one way clutch on the alternator reduces this load significantly.

This can hardly be a problem for boat engines however because the propellor curve power absorption characteristics do not allow high torque at low speed. The only cases may be a fast power boat trying to get onto the plane at low engine rpm, or a sailing cruiser with a truly truly enormous alternator.
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Old 05-02-2018, 15:13   #10
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Re: Torque converter on Alternator

Serpentine belts: I don't think that's an issue, automatic tensioners when working properly make them about the same as conventional (not serpentine) belts. It is just damned hard to tension belts that wind all over the place, making the automatics theoretically better on all systems. (And worse when they fail.)

Perna, rough cylinder firing even in one-banger diesels has always been an issue. Car engines use active harmonic dampening shafts, counterbalances, mass on the flywheel...there's a very big effort into smoothing out engines and I don't see that alternator belts would be suffering more than drivers' butts. So to speak.

OTOH, I have literally seen a simple v-belt hunch up like an inchworm and walk off the alternator pulley when the house batteries were switched in. A new belt and better tension helped but deeing that inchworm was a real eye-opener about the whole concept of "belt saver" regulators.
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