T&T: Cummins 5.9 High Output Alternator Large frame & belt bagel

[Phil de l'Etoile]

Jim,

In a telephone conversation that I had with Brian yesterday, I
explained to him why I believe that all of the Cummins 4 cyl, and now
apparently some of the earlier 6 xyl models, had been setup wth much
less alternator pulley belt contact area than models produced later on
and today. Now with much bigger alternators than were used in the late
'80's when both mine & Brian's engines were built, the belt routing
was changed to provide much more contact area. The 4's like mine, had
a short production run, which I expect explains why no modifications
were likely done. It wasn't until Brian brought it up that I realized
that apparently some of the early 6's were also designed like the 4's.

When I replaced my 50 amp alternator last year on my 4BT3.9T with a
150 amp model, I had the same problem that you and Brian talk about.

Because Cummins does everything by engine ser #, and because they also
apparently don't want much to do with modifications of their engines,
I was unable to get much help in fixing the problem.  Their "solution"
was to not add such a big alternator.

It was only after I discovered that the blocks of both the 4 cyl the 6
cyl are essentially the same (just longer), and then provided them
with the serial # of a friend's newer 6 cyl engine, that I was able to
identify and order the 6 cyl parts (belt tensioner, bracket, and
pulley or idler) which fit on my  4BT3.9T.  This resulted in me being
able to reroute the belt & solve the slippage problem.

Brian was able to figure out how to reroute his belt using original
equipment, and now I realize that is in fact possible.  In my case, I
had first identified the bigger belt tensioner through a dealer rather
than the distributor.  When this proved to be still inadequate, I then
went to the distributor with the newer 6 cyl engine # and got the
replacement parts.  As I recall, the cost of parts was not a big deal,
but that may be because I was already deeply invested in the
alternator and I was now in the process of trying to dig myself out of
a hole.

I've seen pictures of Brian's current setup with his original parts
and it looks almost the same as mine.  The only difference is that I
have slightly more pulley contact area and a bigger, stronger, belt
tensioner. Otherwise his setup is about the same & looks fine to me.
My belt tensioner is also positioned somewhat differently and may
provide more pressure, but I'm no sure of this.  But again, the
routing is the same & the belt contact area is nearly the same.

I don't know how big Brian's battery bank is (mine is 900 amp/hrs),
but the biggest potential for belt slippage occurs whenever the
batteries have been drawn way down, so if you don't use the house bank
a lot, you may actually go awhile without any problems.

If you want to see a before/after picture of my setup, let me know. I
can also provide you with part numbers and even a newer engine # if
you like.  I would think that because the 6's were eventually modified
(while I don't believe that the 4's ever were)
you should actually be able to get all this from Cummins.

In any case, just let me know if I can help.

Phil


On 12/3/08, Jim Healy <gilwellbear at gmail.com> wrote:
> Hi Brian,
>
> I have the exact problem you describe on my 4BT-3.9 Cummins.  I upgraded to
> a Balmar HO alternator (not the large frame; exact replacement for the OEM
> Delcotron), and the short contact around the Cummins alternator 6 vee pulley
> causes it to squeal until the belt gets warm, then settles down.  Obviously,
> I would like to correct that if possible.  The belt routing on the 4B and 6B
> must be the same.
>
> In looking at it, I wondered if the belt routing could be changed, but saw
> that the water pump would rotate "the other way."  So, I want to confirm
> what you said.  Is Rob saying that the routing with the 90 degree contact
> surface is incorrect?  Your comment: "Incidentally, after correcting this
> routing problem, I can now get 200Amps out of the alternator without the
> noise," seems to say that the 180 degree contact routing is correct, but I
> couldn't get that from Rob's note (at least, without the pictures).
> Changing the belt to get 180 degree contact would take all of 3 minutes and
> really be better for the alternator and belt!!!
>
> Thanks much!!
>
> Peg and Jim Healy aboard Sanctuary,
> currently lying St. Lucie River, Stuart, FL
> _______________________________________________
> http://lists.samurai.com/mailman/listinfo/trawlers-and-trawlering
>
> To unsubscribe or modify your subscription options (get password, change
> email address, etc) go to:
> http://lists.samurai.com/mailman/options/trawlers-and-trawlering
>
> Trawlers & Trawlering and T&T are trademarks of Water World
> Productions. Unauthorized use is prohibited.