Alternator Pulley Question

[jok]

Hi All,

I have an electrical question, sort of.

I purchased a Niehoff 24 Volt, 270 amp, Alternator that I would like to use to charge my house batteries while underway. I have 2 - SW 4024 inverters with 4 - Lifeline Batteries. Also 17.5 kW diesel Generator. My goal is to run at least two roof airs without running the generator.
http://www.ebay.com/itm/321082245462?item=321082245462&viewitem=&sspagename=ADME:B:EOIBSA:US:3160&vxp=mtr

The bus has its own 24 volt, 75 amp, belt drive alternator. I will be running both alternators.

The question is; What diameter pulley should I use on the Niehoff alternator. 1990 Prevost  XL with 8V92. I will be able to run two belts off the existing crank pulley. See any problems? What diameter pulley? Where is a good place to get the pulley?

Thanks,
jok

[Tony LEE]

I would think that if you are going to be running either alternator at anything close to rated output, the limiting factor will be how to transmit enough power via vee belts. The one on my MC8 has three belts each running half way around each pulley

[chessie4905]

I would think one of that inverter would be plenty to power two roof airs

[wg4t50]

The simple answer to the RPM question, contact Niehoff, they can tell you the max rpm for the rotor, we  got involved with those questions when we installed the 24 V 285 A I think, in place of the OEM Delco in our special GM vehicles.  Just to run radio equipment.
Did 6 in Egypt about 1993.  Belts were the big issue, Belts made in Egype are like taffy, never keep tight, just stretch and stretch. Finally got hold of belts from Mitsubishi (?), they worked, completed the contract and got home.
Dave M

[luvrbus]

1st is to find the needed rpm for the alternator then size the pulley like if your 8v92 has a 7in pulley the way I do it is for example finding a fan speed is 7in pulley * 5in pulley = 1.4 x 2100 rpm = 2940 final speed same with a alternator. Just a guess I would think the alternator is going to need to spin in the 7000 rpm range only a guess

I don't think you have enough battery bank and alternator to run 2 going down the road all day on a hot day here in AZ the amp draw goes up on a AC
 
Dave already posted the rpm issue as I was doing my 1 finger typing

good luck

[Len Silva]

My guess is that after you find the right pulley size for best alternator RPM, you are going to need at least three belts for that kind of load.

[luvrbus]

1 good serpentine belt will run the alternator lots of choices in configuration on those I would not try to use a v belt JMO

[wg4t50]

Looks like most Niehoff larger alternators are rated up to 8000 RPM, but check out your actual model, it could be more/less.
Dave M

[Zeroclearance]

I have two of the larger 450 amp units..   One is a spare...   They are driven off the aux drive pulley with a serpentine 11 rim belt with a auto tensioner.   I can measure the pulley for you if you'd like..   

As a recommendation, I would install the Balmar smart regulator.   This will save your battery bank and belts.   It will allow a soft start to ramp up the  charge cycle.

[jok]

Thank you everyone for all the info.

Zeroclearance, I would appreciate if you could measure the diameter of your pulley.

jok