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Old 11-02-2010, 22:06   #31
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So a relation exists between belt speed and belt power. This explains to some extent why an alternator may cut-in at 1500 motor RPM. Lowering the speed of the motor may be detrimental to the belt if the alternator at that time is loaded to the full capacity of the belt.

See belt designer at Fenner Drive Designer
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Old 27-02-2010, 03:48   #32
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CAD mad..

here are some more pics of the mount for the dual alternator. Ive put the accessory alternator on this side of the engine leaving the bracket at the top right free for a water maker pump.
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Old 27-02-2010, 07:14   #33
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WKD928,
Lot of stuff hanging off that crank. Is that a large frame alternator?
Pretty soon the main crank bearings will be in danger!

The thing is, for much over 100A, one V-belt is not enough and the problem with double belt setups is they never run the same. One will be vibrating while the other does the work.

About 30 years ago we used to get matched sets from the local motor shop. Now they say that they are sooo good at making belts that you don't have to match them anymore. Yeah Right.

Anyway, if you want a big honkin alternator, use a poly-V belt, less wear, less tension and your crank may survive the abuse.

On the lighter side, the biggest problem with young new engineers is that they think that if they can draw it in CAD that it CAN be built.

Have fun
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Old 27-02-2010, 07:34   #34
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Highlander,
well thats ok then as im not an engineer it should work fine! the extra alternator is modelled on the amptech L200. I am sure your correct about the poly v belts being a better choice but its too late for me now, i got carried away with the pretty pictures and sent away the file to have a pulley cut

As for making the bracket, i will wait and see when i get back to the boat - its in the USA and im in the UK. There is value in the modelling software to explore a solution without actually having to construct it. For myself at a distance to look at how it fits as best as i can determine without going down to the boat and measuring is useful. The only alternative mounting scenario that ive come up with would be to build a platform out in front of the engine cantilevered from the engine mounts.

I have no definite idea what kind of stress would be put on the engine bearings although the fact that there is an existing PTO pulley is somewhat reassuring.
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Old 27-02-2010, 09:11   #35
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WKD928,

Just remember that the further out in front the pully is located, the greater the stresses on the crank.
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Old 04-03-2010, 14:42   #36
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2nd Alternator Mount Kit w/ Serpentine Pulley Conversion. V-Belts v. Cogged v. Synchr

A Serpentine Belt & Pulley kit for Yanmar engines to support second alternators, etc.:
AltMount Products AltMount Products AltMount.com

A note on the pros & cons of V-Belts vs. Cogged or Synchronous Belt Drives from U.S. Dept. of Energy:
http://www.nrel.gov/docs/fy00osti/27833.pdf

Info on Serpentine Belt wear & longevity:
http://www.gmfleet.com/pdf/serpentinebeltssavings.pdf
http://www.carquest.com/common/downl...ilure-2009.pdf
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Old 04-03-2010, 16:06   #37
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Couple of notes:
Serp belts are for "on engine" mounts only. If the alt. is off the engine multiple v belts are the way to go.

It pays to check with the mfr. for acceptable crank side loading- Most of the time you'll need a layshaft and external bearings. it's not only the side load but the fact a big alt. can induce torsional stress in the crank- Serp belt installs may require an overrunning clutch on the alt.

There's more to it than just hanging stuff on the front of the engine.
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Old 04-03-2010, 20:12   #38
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"Serp belts are for "on engine" mounts only. If the alt. is off the engine multiple v belts are the way to go."
Since the belt neither knows nor cares what the alternator is bolted onto, how does being on or off the engine make any difference in the appropriate belt type?

All those references to serpentine belts are a bit misleading. They have got nothing to do with serpentine belts, they are discussing a change in the compound used to make premium quality RIBBED belts, which in turn are normally used in serpentine belts. Among other uses.

Very interesting to know that ribbed belts can be made from two very different compounds, and how they differ in wear characteristics. Another good reason to buy from a name brand rather than whatever is on the store shelves this week.
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Old 05-03-2010, 07:51   #39
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Quote:
Originally Posted by hellosailor View Post
"Serp belts are for "on engine" mounts only. If the alt. is off the engine multiple v belts are the way to go."
Since the belt neither knows nor cares what the alternator is bolted onto, how does being on or off the engine make any difference in the appropriate belt type?

All those references to serpentine belts are a bit misleading. They have got nothing to do with serpentine belts, they are discussing a change in the compound used to make premium quality RIBBED belts, which in turn are normally used in serpentine belts. Among other uses.

Very interesting to know that ribbed belts can be made from two very different compounds, and how they differ in wear characteristics. Another good reason to buy from a name brand rather than whatever is on the store shelves this week.
You're incorrect, the strains applied to an off engine accessory are different.

Since there is differential motion between an off engine alt. and the engine, you can't keep tension constant. V belts are less senstitive to changes in tension than serp belts due (among other things) to the larger vertical dimension of the belt. The compound doesn't make any difference in this regard, it's the design of the belt that makes the requirement.

If you didn't have flexible engine mounts and everything were rigidly mounted, then it wouldn't make a difference. But you dont, so it does.
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Old 05-03-2010, 08:08   #40
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S&S, What you describe, mounting off the engine.

Is just plain a bad idea, with any belt.

One added benefit of the flat belts is that if needed, a tensioner may be used which eliminates all problems of proper tension adjustment as well as vibration transmission.

Flat belts still are the better product for load carrying, life span, reliability and putting less stress on the engine.

It's just a matter of time.
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Old 05-03-2010, 09:04   #41
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S&S, What you describe, mounting off the engine.

Is just plain a bad idea, with any belt.

One added benefit of the flat belts is that if needed, a tensioner may be used which eliminates all problems of proper tension adjustment as well as vibration transmission.

Flat belts still are the better product for load carrying, life span, reliability and putting less stress on the engine.

It's just a matter of time.
All true, they just don't handle varying tension as well. Even with a tensioner, the loaded side ot the belt loop will "feel' the engine movement- the tensioner is on the slack side..
I agree that "off engine" mounting is not ideal, but sometimes stuff just won't fit any other way- so you have to make do.
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Old 05-03-2010, 12:19   #42
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Ah, the engine mounts that no one changes every five years or so, as per the maker's recommendations. Given that a serpentine, ergh, ribbed<G> belt is almost always running with an automatic tensioner, and that tensioner should be able to accomodate a wider range of motion that simply forcing against a v-belt...

I can't help thinking that a ribbed belt would be the best solution, regardless of the relative motion and changing tension. Again assuming the normal installation with a tensioner.

And, that an off-engine belting of any kind would simply be bad design, unless steps were taken to eliminate relative motion. i.e. by a tensioner or fixed engine mounts.
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Old 05-03-2010, 12:25   #43
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Originally Posted by hellosailor View Post
Ah, the engine mounts that no one changes every five years or so, as per the maker's recommendations. Given that a serpentine, ergh, ribbed<G> belt is almost always running with an automatic tensioner, and that tensioner should be able to accomodate a wider range of motion that simply forcing against a v-belt...

I can't help thinking that a ribbed belt would be the best solution, regardless of the relative motion and changing tension. Again assuming the normal installation with a tensioner.

And, that an off-engine belting of any kind would simply be bad design, unless steps were taken to eliminate relative motion. i.e. by a tensioner or fixed engine mounts.
As said above, while a tensioner helps, it's on the slack side of the belt so it won't take care of everything. Cogged belts would probably be even worse. In any event the engine mfr's. engineers canned serp belts for off engine mounting for the reasons described.
It's all compromises- a great on engine mount won't work if the assembly won't fit. Next best being v-belts and a tensioner. Off engine is not "bad" design, it's just not optimal- if your only parameter is belt life.
I don't think anyone would like to seriously consider rigid mounting. (certainly not me)
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Old 11-06-2010, 23:18   #44
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perkins 2 alternators

talk to us we are doing similar
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Old 14-06-2010, 15:30   #45
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I will take some photos of my 4-154. I have exactly the set up wkd928 is suggesting. Separate v-belt 100amp balmar. Mounted just were his drawings suggest. So far has not been a problem and appears to work well.
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