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Old 19-10-2019, 13:35   #16
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Re: Serpentine vs dual V belt?

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Originally Posted by SV Demeter View Post
Sounds like a lot of support for the serpentine belt. Do not the larger alternators as in 200amp and up prefer dual v over serpentine?

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I'm running a 320 amp Leece-Neville fire truck alternator on my port side engine driven by triple belts. I use Gates Green Stripe belts with no special effort to match them. The entire set up has been trouble free for 9 years and several thousand hours of operation. I was fortunate to already have a triple groove sheave on the front of the engine, a DD6-71 Johnson and Towers conversion. I did have to get a custom mount built by a local machine shop.
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Old 19-10-2019, 13:55   #17
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Re: Serpentine vs dual V belt?

In addition to the vessel we also have a transit bus converted to a motor home. The bus runs a 300A 24 V alternator and a 24 battery system driven by a commercial Serpentine belt. BUT the largest engine powered device is the compressor for the 90,000 BTU AC unit it is powered by a dual v-belt system with an idler puller. The V-belts are essentially a Serpentine backed dual v-belt. Based on thie installation I would guess the for all out power V-belts can transfer more power. A newer bus has a 500A 24V alternator it runs the same belt as the 300A alternator.
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Old 19-10-2019, 14:39   #18
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Re: Serpentine vs dual V belt?

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Originally Posted by a64pilot View Post
A toothed drive belt would be better than a serpentine, again in my opinion and for that kind of money I’d expect one.
There is a bazillion different sized camshaft drive belts, why not drive an alternator and water pump with one?
I built a genset using a 2 cylinder Kubota driving two 110A alternators. I used toothed pulleys and an appropriate toothed timing belt to drive. No belts, not even the “super strong” Kevlar belts, lasted more than 20 starts/stops before they started losing teeth. The sudden stop of the engine versus the inertia of the alternators was more than the belts could handle. Turning a camshaft, it seems, is a lot less stressful than the stored energy in a spinning alternator rotor. I abandoned that, changed to a single B section V belt, no more issues.

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Originally Posted by a64pilot View Post
Belt diagram on my old truck that had a high amp alternator, you can see how much belt wrap there is, the idler pulleys is why.
Attachment 201798
Absolutely. Your picture of the engine with a serpentine belt shows the essence of the concept. The belt goes around the pulleys often using more than 70% of the circumference as a contact area. This is what makes them really effective and why they are called “serpentine”. It’s not about the multiple grooves as is generally believed. Serpentine belts that go around three pulleys largely lose the value of the concept as their surface contact is rarely more than 40%.

The V belt effectiveness is the manner in which the belt pulls into the V and creates friction. If the belt bottoms in the V, no amount of tension will stop it slipping. Yet when looking at a serpentine belts, it seems that all the little V’s bottom in the grooves and the belts is stopped from slipping purely by virtue of the surface area related to the belt width. That’s my opinion, YMMV.

I have two alternators running in front of my engine (not mounted directly on the engine). One is 150A the other is 120A. Both are driven using B section V belts, neither have ever slipped, no black belt dust and both belts are now probably 4 years old. I wouldn’t swap them for serpentine belts even if someone else was paying for them.
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Old 19-10-2019, 16:58   #19
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Re: Serpentine vs dual V belt?

"I built a genset using a 2 cylinder Kubota driving two 110A alternators. I used toothed pulleys and an appropriate toothed timing belt to drive. No belts, not even the “super strong” Kevlar belts, lasted more than 20 starts/stops before they started losing teeth. The sudden stop of the engine versus the inertia of the alternators was more than the belts could handle. Turning a camshaft, it seems, is a lot less stressful than the stored energy in a spinning alternator rotor. I abandoned that, changed to a single B section V belt, no more issues."



Interesting. I wonder if you would have had those issues with a 4 or 6 cylinder engine. Did you have a spring tensioner or a solid type belt tensioner? Did you contact Gates about the tooth stripping issue?
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Old 19-10-2019, 17:08   #20
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Re: Serpentine vs dual V belt?

Ted, My experience tells me your gut is wrong, go for the Serpentine conversion, as I did. I have a 120 amp alternator, it burned V belts in weeks. I Change to a Serpentine kit designed of Volvo 55 hp engine. (I have a perkins 22c engine which is the same that volvo use to reband it) from Canadian suppler. It was an easy fit and the power output was amazing. I discovered I now had full use of the alternators output unlike before. You may find you do not need the 150 ah alternator. also two V belts to ajust them maybe an issue as sometimes two belts are not exactly the same size.



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Originally Posted by SV Demeter View Post
Wasnt sure if this would be better posted in engines or not but here goes. Im looking to improve the setup on our 4JH-DTE which currently has a balmar alternator and single v belt. I believe the alternator is about 100amp but Im planning at some point to upgrade to a higher output say 150amp alternator. I was thinking to convert the belt system now as I need to replace the belt at a minimum so thought why not make the change now.

My gut tells me I would prefer dual V over serpentine but I wondering? Are there any opinions (dangerous question I know) on sepentine vs dual v belt setups and if going dual V can anyone suggest a reputable vendor for the conversion kit? I see the serpentine kits all over the place.
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Old 19-10-2019, 17:20   #21
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Re: Serpentine vs dual V belt?

Ted, My experience tells me your gut is wrong, go for the Serpentine conversion, as I did. I have a 120 amp alternator, it burned V belts in weeks. I Change to a kit designed of Volvo 55 hp engine from Canadian suppler. it was an easy fit and the power output was amazing. I discovered I now had full use of the alternators output unlike before. You may find you do not need the 150 ah alternator. also two V belts to ajust them maybe an issue as sometimes two belts are not exactly the same size.see photos.



Quote:
Originally Posted by SV Demeter View Post
Wasnt sure if this would be better posted in engines or not but here goes. Im looking to improve the setup on our 4JH-DTE which currently has a balmar alternator and single v belt. I believe the alternator is about 100amp but Im planning at some point to upgrade to a higher output say 150amp alternator. I was thinking to convert the belt system now as I need to replace the belt at a minimum so thought why not make the change now.

My gut tells me I would prefer dual V over serpentine but I wondering? Are there any opinions (dangerous question I know) on sepentine vs dual v belt setups and if going dual V can anyone suggest a reputable vendor for the conversion kit? I see the serpentine kits all over the place.
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Old 19-10-2019, 18:42   #22
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Serpentine vs dual V belt?

Iím at a loss to explain the stripped teeth on the alternator belt unless it was too loose, no way should an alternator be harder to turn on start up than a pair of camshafts.

However bottom line, there is nothing magic about serpentine the way we use them, which is incorrect for serpentine, itís major advantage is itís so much more flexible that it can be made to wrap nearly all the way around a smaller pulley like an alternator.
Anyway to increase the surface area until the loading is low enough to not slip without excess pressure will work, dual belts have worked for decades before serpentine belts were a thing.
However I got a serpentine kit myself due to availability, if a dual V kit had existed for much less money I would have gone that way

However our kits use the same geometry as a V belt and donít therefore fully utilize the serpentine belt, couple that with no spring tensioner idler and you lose another advantage of serpentine.
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Old 19-10-2019, 21:19   #23
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Re: Serpentine vs dual V belt?

I have the same engine: 4JH-DTE (88 horse?). When I acquired the boat, it had two large alternators, one hung off each side of the engine, each driven by a v-belt ó and a log book with 30 years of problems. I burned the belts the second outing, then once had to run 20 hours at 1200 breathing black smoke because belt dust had clogged the turbo.

A little research turned up that the max horsepower a 1/2 inch V-belt wants to handle was much less than a large alternator wants to consume making amps.

I replaced with an Electromaxx serpentine and single but larger alternator. Hundreds of hours later, the belt does not get hot, slip, cause any dust. Engine room is cleaner, I am more serene, and I would not go back to v-belts for any reason.
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Old 20-10-2019, 01:41   #24
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Re: Serpentine vs dual V belt?

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Originally Posted by NYSail View Post
I have a 4JH4E yanmar. Last season put on a Balmar 150 amp alt with serpentine belt. Would never do duel v belts...... serpentine is great. And looks cool too! Balmar makes engine specific kits.......
You might be interested in buying the genuine Yanmar idler and the longest belt that fits your engine room & adjuster:
https://www.yanmarshop.com/catalogue...r12v-120avaleo
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Old 20-10-2019, 13:57   #25
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Re: Serpentine vs dual V belt?

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Iím at a loss to explain the stripped teeth on the alternator belt unless it was too loose, no way should an alternator be harder to turn on start up than a pair of camshafts.
Interestingly it wasnít about start-up that damaged the belts, it was about stopping. Small diesels stop quite suddenly and the inertial energy stored in a spinning rotor of a larger alternator proved too much for the belts. As Darylat said perhaps on a 4 or 6 cylinder that doesnít stop as suddenly, one would have more success. But to be sure, the energy needed to start, run and stop even a pair of camshafts doesnít come close to the energy needed to quell the latent energy in a spinning alt, remember that an alternator spins up quite fast, the rotor is ideally geared to do 3 times (or more) the rpm of the engine.

For the record, the belt was always tight with an idler (not sprung) to improve the Ďwrapí around the driving pulley. I abandoned this project some years ago but may still have some pics of the setup. If I have, will post for interest.
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Old 22-10-2019, 03:56   #26
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Re: Serpentine vs dual V belt?

I converted my single belt drive to a dual belt drive about 10 years ago. The first set of belts was short lived because I didnít realize how carefully the belts must be matched. However, that was easily remedied by hitchhiking 30 miles to the nearest rural garage to pick up a spare belt or two. Try doing that with a serpentine belt!
I also managed to burn out the bearing on my water pump before the conversion because of the need for high tension in the belt. Two belts solved that problem.
I eventually found two identical belts, installed them, and they have worked flawlessly - without replacement- ever since. That was about 10 years and thousands of engine hours ago.
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Old 22-10-2019, 13:38   #27
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Re: Serpentine vs dual V belt?

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Interestingly it wasnít about start-up that damaged the belts, it was about stopping. Small diesels stop quite suddenly and the inertial energy stored in a spinning rotor of a larger alternator proved too much for the belts. As Darylat said perhaps on a 4 or 6 cylinder that doesnít stop as suddenly, one would have more success. But to be sure, the energy needed to start, run and stop even a pair of camshafts doesnít come close to the energy needed to quell the latent energy in a spinning alt, remember that an alternator spins up quite fast, the rotor is ideally geared to do 3 times (or more) the rpm of the engine.



For the record, the belt was always tight with an idler (not sprung) to improve the Ďwrapí around the driving pulley. I abandoned this project some years ago but may still have some pics of the setup. If I have, will post for interest.


While I canít say your wrong cause you did it, but Iím shocked there is enough inertia in an alternator to do that.
The tiny belt on my autopilot is tooth belt drive and if it gets in a bind the belt jumps on the pulleys and doesnít strip.
However does your motor have a compression release? If so use it to stop the motor and that will end the sudden stoppage.
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Old 22-10-2019, 14:14   #28
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Re: Serpentine vs dual V belt?

I used tooth belts and pulleys on racing engines that ran 6-10,000 rpm with sudden rpm changes. I never had a failure. There are a lot more custom size tooth pulleys and drives available from racing sources than serpentine from any source if you have a non common engine or application.
But if you have a non standard use, dual pulleys are cheaper than tooth or serpentine.
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Old 22-10-2019, 17:27   #29
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Re: Serpentine vs dual V belt?

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While I canít say your wrong cause you did it, but Iím shocked there is enough inertia in an alternator to do that.
Remember (as I have said before), alternators spin at 3 times crank speed. Camshafts spin at half crank speed. Thereís a significant difference. And inertia is exacerbated by the weight and diameter (peripheral velocity) of a rotor compared to a camshaft.

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Originally Posted by a64pilot View Post
The tiny belt on my autopilot is tooth belt drive and if it gets in a bind the belt jumps on the pulleys and doesnít strip.
However does your motor have a compression release? If so use it to stop the motor and that will end the sudden stoppage.
If the belt is correctly tensioned, it should never jump a tooth. Imagine how many cars would be standing on the side of the road if this were possible?

There are many applications which suggest my experience was erroneous. Some 1200cc Harley Davidsons run on toothed belts instead of chains. Large-volume superchargers run on toothed belts. Hi-performance go-carts have toothed drive belts. I know that, thatís what led me to use one. But my experience is what it is, I stripped four or five belts before giving up. The belts I used were far lighter than the examples I cite (timing belts), necessitated by cost and space.

Anyhow, not only did I solve the problem with V belts, Iíve abandoned that whole project for other reasons so thanks for the input but Iím bowing out.
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Old 23-10-2019, 13:48   #30
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Re: Serpentine vs dual V belt?

One picture and 3 lines to make your choice:
https://setsail.com/poly-v-belts-for-big-alternators/
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