Dual alternator belts on 3qm30

[Mathurin]

We are finally done with modifying the alternator setup on Mathurin II . To make a long story short, we've had problem after problem during our 9 months trip because of a bad alternator installation. The prior owner installed a 120amps Balmar alternator in the original configuration on our 3qm30. Well that wasn's such a good idea. A 120amps alternator need at least one 1/2'' belt to run properly, preferably two (but not necessary).

The problem is that the stock crankshaft pulley on the 3qm30 is designed for one 3/8'' wide belt. So when we left Montreal, we slowly realized that the belts where slipping, so to avoid slipping we had to put more tension on the belts, thus more tension on the water pump... To resume the situation, we went through 14 belts and 3 water pump bearings in 9 months (950 engine hours). That's 290$ !!!!

That is already impressive, but to top it off, 3 days prior to our arrival at our home port, the alternator got loose and the 3 bolts holding it in place broke, we had to do the last 3 days with a belt mockup to run the water pump (god you love to have a Power-Twist V-belt on board these days) and the generator on deck. Had we known all of that before leaving, we would have put a 55amps alternator back in it's righteous place.


Now that we are back (with 3 broken bolts in the engine) we decided to address the problem once and for all. This meant custom dual sheave pulley on the front pto, custom off engine alternator bracket, new dual sheave pulley for the alternator and custom water pump bracket (the water pump needs to have some sort of adjustment now that it's running with it's own belt).

I designed the new pulley to fit on the pto using the specs found in the original service manual (Thanks again Jose). The drawing is included in this post. That pulley was machined by a local machinist for almost nothing (95$ including material). I found a brand new dual sheave pulley for the alternator for 30$ (Ford F1HU10A352AB) in a local alternator refurbishing shop, which is a lot cheaper than the 120$ retail price Balmar displays on it's website. The bracket where done using scrap metal.

The picture were taken before the water pump bracket was installed. You can see the red Power-Twist V-belt still in place. You can also see why it's a bad idea to paint when it's 100F outside, the alternator bracket will need to be repainted.

 

[Mathurin]

Btw the alternator bracket in mounted on the forward port side engine mount and it's also secured to where the old alternator tensioner used to be fastened via a smaller bracket to reduce vibration.

Oh and we had an unpleasant surprise yesterday when we removed the water pump... apparently not all impellers are created equal, this one is only 250 hours old...

 

[Ed Schenck]

Exactly the reason that I went with the 80 amp Balmar. The new 3YM30 came with an 80 amp but I already had invested in external regulation with the old 2QM20. But the installation is poor and there is a lot of belt dust. It is probably the issue that MaineSail wrote about, poor alignment between the pulleys. But I don't think a single belt should be a problem for 80 amps.

 

[Don12364]

A Cautionary Tale

Seems as if you are well on top of the problem now; but for others perhaps considering 'upgrading' to a similar alternator, the recommendation is that the alternator output to be 25% of the battery ampere hour rating. So unless one has a 480 Ah house bank the 120 amp alternator is over the top.

Even then ask whether your batteries would be able to accept all the current on offer.

Also, as the horsepower drawn from the engine is roughly 1 HP per 25 amps of output and, apart from the increased bearing loads on the engine's front main bearing etc, make sure you don't ever need the last 5 horsepower from the Yanmar 30.
Or is there a way of turning the alternator off when you get into a tight spot?

See extracts below from Balmar data brochure and their recommendations:-
http://www.pyacht.com/balmar-alternator-guide.pdf

Alternator Rating / Battery Capacity Formula
Rule of thumb is that the alternator output equal 25% of the battery capacity, so for a 400 amp hour bank, our 100 amp alternator would be a wise choice. You can figure 1 hp draw per 25 amps (12 volt) at maximum output.

Be sure to read the information about batteries and resistance, on the following page. There are many factors that play into the correct sizing of the alternator to the battery bank.

BATTERIES & RESISTANCE
Often it is not the output of the alternator, or even its regulation
that causes the disappointing recharge scenario. This
can many times be attributed to the rate of charge the batteries
can accept. Typically, batteries absorb current at a
rate of about 20-30% of their capacity. Your battery manufacturer
can answer questions that you may have in this
regard.

FWIW: Many years ago my R & D team and I found out the hard way when we designed an alternator for a new model small Alfa Romeo car to be built in the south of Italy.
It worked beautifully - but took so much power from the engine (5 Bhp) that Alfa refused to buy it!

 

[Mathurin]

Battery bank = 460 amp hours, and the alternator is officially a 100 amps but will charge to 120 amps, so it's roughly 25% of the amp hour...

14.1Volt * 120amps = 1692 Watts
1 hp = 745 Watts
1692 Watts = 2.25 hp

So even with all the lost in the belt (which are normalle low) and diffrent loading conditions, the alternator will never require more than 3hp to run. Furthermore, if you need all the power your engine can give, you can wire a half power switch on the external regulator (in between the alternator temperature gangs on the regulator)....

 

[sail_4_me]

I have a 3QM30F

I'm in process of replacing my old Balmar 90 series alternator. Balmar maintains that this model is supposed to put out 90-100 amp and its supposed to be externally regulated, but I have no regulator. It puts out something like 20 amps under power. ( As I learn these things I am repairing them, I'm 3rd owner.... )

I've ordered a 60 series alternator (100 amp) and the ARS-5 regulator package. I already have a 1/2" belt on this engine, after my first shredded-belt experience. I also have a different engine configuration from yours, I'm hoping I don't see the bearing problems you've encountered.

The regulator supports a belt-management function to reduce output while reducing wear on the belt. The alternator itself has a built in simple regulator to get you home if the external one fails. The regulator also has alternator and battery temp sensors, and will reduce load to manage.

I have 400 amp hours in the house bank, and an echo charger for the engine battery.

The picture is my old alternator config.

 

[Mathurin]

Our alternator is also an older Balmar 90-100D (dual output) but it is externally regulated via Balmar MC-512 regulator. It still works fine, actually the internals are very beefy. Our old setup was just like yours Sail_4_me, the problem is the the 3QM30 is very weak (bolt size and thread depth) and it's design to run on a 3/8'' belt. Your 3GM looks like it can handle a 1/2 belt just fine.

 

[Maine Sail]

Our alternator is also an older Balmar 90-100D (dual output) but it is externally regulated via Balmar MC-512 regulator. It still works fine, actually the internals are very beefy. Our old setup was just like yours Sail_4_me, the problem is the the 3QM30 is very weak (bolt size and thread depth) and it's design to run on a 3/8'' belt. Your 3GM looks like it can handle a 1/2 belt just fine.

FWIW Electromaax is building serpentine pulley kits for most of the Yanmar's. You can aslo usually get away with less belt tension using a serpentine.

My issues with dual pulleys and v-belts is that it often takes going through 15-20 belts to get a matched pair, if you can find a match. They used to sell them as matched pairs but I have not been able to find them lately. I have a few customers with dual v-belts and one belt is always tight and one always flopping around. It still works better than a single v-belt but it is just tough to get a well matched pair.

How did you find your belts to match up? On many Balmar regs there is also small engine mode and it gives you choices for field % output.

 

[Maine Sail]

I'm in process of replacing my old Balmar 90 series alternator. Balmar maintains that this model is supposed to put out 90-100 amp and its supposed to be externally regulated, but I have no regulator. It puts out something like 20 amps under power. ( As I learn these things I am repairing them, I'm 3rd owner.... )

I've ordered a 60 series alternator (100 amp) and the ARS-5 regulator package. I already have a 1/2" belt on this engine, after my first shredded-belt experience. I also have a different engine configuration from yours, I'm hoping I don't see the bearing problems you've encountered.

The regulator supports a belt-management function to reduce output while reducing wear on the belt. The alternator itself has a built in simple regulator to get you home if the external one fails. The regulator also has alternator and battery temp sensors, and will reduce load to manage.

I have 400 amp hours in the house bank, and an echo charger for the engine battery.

The picture is my old alternator config.

No external reg on an older Balmar? Seems like an odd installation. Before you toss your old alt there may not actually be any problem with the old one. There are many things that can cause low current output.

Poor ground wiring: This is a VERY common DIY error. Balmar's are isolated ground not case grounded and I come across this more often than you'd think.

Poor positive wiring: What's the gauge?

Diode isolators: Are you sensing the battery voltage? A lot less current flows at 13.6 volts than does at 14.3-14.6v. Voltage is pressure and low voltage at the battery terminal often equals less current flow...

Batteries not deeply discharged: Even a 400 Ah bank will only ever take about 100 amps when flat out dead. If the batts are above 80% SOC your going to see considerably less accepted current.

Bank size: I've seen folks think they were charging the house bank and it was the start bank thus less accepted amps.

How the system is wired: You need proper wiring paths to allow the rated current to flow.

Temp sensors: Temp sensors can cause headaches when it comes to "expected" output vs. reality.

You may be spending good money to find out you have the same output issues. I would have the old one tested and repaired if necessary then add an ARS-5 if you still feel it to be necessary.

 

[Mathurin]

Maine Sail, I ordered a matching pair from the start, but it was difficult, the guy at the local store lacked knowledge, he told me that all belt where the same length... Though about telling him about manufaturing tolerances but he seemed so uninterested I gave up and decided he didn't deserve the sale. Went with an industrial reseller and had no problem ordering a matched set there (I had more trouble with the fine tuning the alternator position).

 

[Don12364]

As I am sure you noted my remarks were more to make others aware of what they might be getting into rather than to criticise your installation. However, whilst I can agree with your maths, equally one cannot disregard the data from Balmar.
BTW you need to add for the losses of the diode bridge rectifier which has a voltage drop of 1.5 volts and this makes your 14.1v up to 15.6v and output wattage to 1872.
Add for the heating effect in both wiring and iron plus the additional effect of RMS to mean current. This is a very peaky waveform when working into a bridge rectifier and a low internal impedance battery and gives rise to considerable increases in internally generated heat.
Add for windage losses with the fan etc.
And more for belt transmission losses.

Have just received an answer to my earlier e-mail to Balmar asking if they have a Bhp input curve for your machine as measured on a brake whilst actually charging a large battery bank. They advised your machine and regulator were no longer in production but were helpful regarding an output curve http://www.betamarinewest.com/balmar/6-series-sheet-web.pdf; but again reiterated the need for 1 Bhp per 25 amps of output. No doubt this is a conservative max power recommendation. They were coy over an actual horsepower power input curve.
However one needs to remember the machine is wound to provide useful 16v output at low engine rpm - say 1000 engine or 2000 rpm alternator. Accordingly it would be trying to generate 42v at your engine's max revs of 2,600. Reducing the field current controls the output voltage and current but the windage, belt transmission and iron losses increase by the square.

The power reducing switch seems a good thing but might be a refinement too far!

 

[Bill Roosa]

Just a couple of thoughts.
Your 5 HP draw is only when the batteries are compleatly dead so you are probably not going to incounter a situation where you need both that 5 HP to drive the boat and charge the batteries.
I'm pretty sure the engineers at Balmar have some small understanding of their product and you can use the 25 amps/BHP figure.
NAPA sells matched pares of belts. I would recommend that during the design process you consider determining some possible belt sizes and ask if they are avalable in pares before bending metal.

 

[Mathurin]

FYI Napa only sells automitive section belts (11A..., 13A..., XL..., K) and FHP belts (3L and 4L) but doesn't sell industrial desing belts (At least in Canada). I went with a AX33 v-belts which is an industrial belt and easier to have a matched set (when it comes to design process I higly recommand to have a proper Machine Elements reference book or at least the Machinery's Handbook).

 

[Bill Roosa]

OK Mathurin2
I was not aware of the variety of belts at NAPA. My understanding is that there are only two Vee angles and then the various widths and of course length. I've always just ought them so they fit. Are the belt types you listed differences in power handling capabilities or what?

 

[Mathurin]

In the v-belt sector, there are a lot of different models, the main reason being that before credible organism started defining some stardard, every compagny was using it's own standard. That said, some design apply better to certain situation, so a lot different model are still availible today. All belts are not created equal, they differ a lot in therm of construction, so they do not have the same power rating and do not handle shock loads the same way. A good overview of ''Heavy duty belts'' can be found here : http://www.gates.com/catalogs/index.cfm?requesting=ptcatalog&location_id=524#ddm (go in the ''Drive Design Manuals'' section and open the .pdf entitled ''Heavy Duty V-Belt Drive Design Manual'').

 

[Mathurin]

Oh and automitive belts, such as the ones sold at Napa are never to be found in any Machine Elements books, specifications are only available to car manufacturers.