Dual Alternator Tensioning with Turnbuckle ?

[s/v Jedi]

Guys, this thread is falling apart. These formula's are correct I think but you must know how to use them. Engine's don't have power factors and if your 12V 100A alternator is going to use 8 hp I can tell you that you need new bearings somewhere.

Also, a couple of pounds for a little bracket isn't going to break your engine mounts or let your engine tipple over. That weight is nothing in comparison to the alternators you put on.

Also, when your batteries are in float at 16.2V you just fried your batteries but even it the float would be 13.2V, there is no power transfer to speak of because the batteries are full and current will be nothing. Volts do not equal power.

cheers,
Nick.

[Seahunter]

The true PF is stamped onto the alternator after it's calculated from the test spin to 14000RPM. True PF is the difference between real power and reactive power. For those who don't think it's realitive to diesel engines; tell it to Cummins and Detroit. Remember we're dealing with DC here, AGM batteries float at 16.2 volts; gel at 15.5 and acid at 14.8 depending on manufacturer and regulator settings. Based on my calcs, this system (with a PF between .8-.85) will result in a magnetic field failure, maybe before the seals/bearing give out. But WTH one has to try.

[chala]

Originally Posted by s/v Jedi

Also, a couple of pounds for a little bracket isn't going to break your engine mounts or let your engine tipple over. That weight is nothing in comparison to the alternators you put on.
cheers,
Nick.

Little bracket?

Originally Posted by akio.kanemoto

Greetings Gentlefolk,
(the alternators are mounted on a big hunk of steel that is bolted to the engine mounts - on the engine - not the bed - so the engine and alternators move together)

By experience a smaller little bracket with one only alternator can break a 12mm Grade 8.8 foot holding bolt, also if the engine is flexible mounted all mounts need retuneing if the CG of the engine is changed. It is all for the installer to consider. Simple rule: when you install extras you can expect extra problem.
By the way Volvo used to sell an add on AC generator mounted on the top of the engine, I suppose to change as little as possible the CG.

[akio.kanemoto]

Originally Posted by chala

Little bracket?


By experience a smaller little bracket with one only alternator can break a 12mm Grade 8.8 foot holding bolt, also if the engine is flexible mounted all mounts need retuneing if the CG of the engine is changed. It is all for the installer to consider. Simple rule: when you install extras you can expect extra problem.
By the way Volvo used to sell an add on AC generator mounted on the top of the engine, I suppose to change as little as possible the CG.

All mounting feet have been upsized (Yanmar #100) and will definitely be re-levelled.

Also, for the bolts, there are 12 (6 per side) Grade 10.9, 12mm bolts mounting this to the engine. I would expect the engine block to fail before the bolts do.

This part, I did think through thoroughly.

[s/v Jedi]

Originally Posted by Seahunter

The true PF is stamped onto the alternator after it's calculated from the test spin to 14000RPM. True PF is the difference between real power and reactive power. For those who don't think it's realitive to diesel engines; tell it to Cummins and Detroit. Remember we're dealing with DC here, AGM batteries float at 16.2 volts; gel at 15.5 and acid at 14.8 depending on manufacturer and regulator settings. Based on my calcs, this system (with a PF between .8-.85) will result in a magnetic field failure, maybe before the seals/bearing give out. But WTH one has to try.

PF: alternators yes of course, they are AC before that is rectified to DC. But I can assure you that "reactive" and PF are electrical thingies and have nothing to do with diesel engines.

Also, you got your battery terms all mixed up. Float is the last phase, the voltages you are talking about are the highest as found during the absorption phase, not the float phase.

Pls. explain your magnetic field failure and the calculations you used to come to your conclusion.

cheers,
Nick.

[s/v Jedi]

Originally Posted by chala

Little bracket?

;-) I wasn't referring to the alternator brackets but to the one that supports the power take-off like someone posted a diagram for.

I will find some photo's of our brackets, they must be the mother of all brackets with those two extra 210A alternators.... plus I also have a 15,000 GPH crash pump with magnetic clutch on one of them ;-)

ciao!
Nick.

[GordMay]

See the Delco Remy White Paper “Improving Alternator Efficiency Measurably Reduces Fuel Costs”, for an excellent explanation of the "losses" & efficiencies of typical alternators (±50% - 75% efficient).

➥ http://www.delcoremy.com/pdfs/High_E...hite_Paper.pdf

[chala]

Originally Posted by GordMay

See the Delco Remy White Paper “Improving Alternator Efficiency Measurably Reduces Fuel Costs”, for an excellent explanation of the "losses" & efficiencies of typical alternators (±50% - 75% efficient).➥ http://www.delcoremy.com/pdfs/High_E...hite_Paper.pdf

It should be remembered that boat engine are stationary and are not subject to the same flow of cooling air than an engine installed in a vehicle. Slowing down an automotive alternator to improve its efficiency may not be a valid option.

[s/v Jedi]

I don't understand that Chala... the alternators have a fan and the diesel engine is breathing so much that you have fresh air all the time. There will be a difference of course but I don't think it'll be much. Let's get those IR thermometer-guns out! ;-)

I do agree that automotive alternators only have 1 good thing for use on a boat: price. Large frame is the way to go.

cheers,
Nick.

[HHNTR111]

Did we ever resolve using turnbuckles vs. tensioning brackets? Otherwise, very interesting thread.

[James S]

Yes...turnbucles are excellent for tensioning.

[HHNTR111]

Thanks, now on the list!

[chala]

The original question was

Originally Posted by akio.kanemoto

Greetings Gentlefolk,
can I use a large turnbuckle or threaded rod between the upper alternator mounting holes to tension both alternators at the same time?

"a large turnbuckle or threaded rod". "a" as one.
And the answer is?