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Author Topic: Replacement 24V Alternator for MC5...8V71  (Read 6271 times)
DrivingMissLazy
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« Reply #30 on: September 09, 2007, 11:22:20 AM »

No, Richard, there's no outboard exciter on this alternator.  Too, something I not only didn't mention nor did I test, is that there is another relay in the circuit, a load relay I believe, but that shouldn't come into the picture...yet.  The alternator relay closes with the closing of the master switch so I then have power to the + terminal for the regulator.

I guess it boils down to whether or not there are brushes in this old alternator and I suspect there are not as the cross section of the MC5A Repair Manual shows none.

I will read the field resistance today (guests coming for supper) and that should throw more light on the mystery.

Bob

Boy, I would really like to see one of those animals. In the 50 years and thousands of different type alternators and generators going back to 40's era design, I have never heard about anything like this.
Richard
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« Reply #31 on: September 09, 2007, 12:09:54 PM »

Richard,

I went to a vocational high school to become an "industrial electrician".  That was in 59 and in the era that this technology would have been current.  I studied all sorts of generators, both AC and DC, and I never heard of it either.  Slip rings for AC and commutator for DC....PERIOD.  In the ensuing 30 years in the field of electronics (broadly) it never surfaced.  It would be nice to be able to UNBOLT the stator and field windings and those diodes must be real pieces of serious work to stand up to engine room temps for 30 years.  A remote three stage regulator would be somthing to wish for.  Lasted 39 years.  If I didn't have one of these puppies, I would be looking for one.    It might need bearings and diodes and that shouldn't break anybodys bank.  If you handed the field to ANY motor rewinding shop it would not cost that much to have it done.  If you will go for $800 for a new stator or $1,900 for a rebuild....I now of a local generator/starter rebuilder that will let me co-locate and I will go into bus.  274 amps!  Who knew?Huh

I'm half serious here and I will give a warranty.  Mostly I am making a point.  You have company, Richard.

John
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The price of apathy towards public affairs is to be ruled by evil men." Plato
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NCbob
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« Reply #32 on: September 09, 2007, 01:37:12 PM »

Fortunately, for me, there's an expert nearby. Thanks to a previous poster I learned about Gene Rochester who is nearby in Walhalla, SC.  Some of you may remember Gene...he's a former BusNut and Eagle expert who owns a very large alternator/starter rebuild shop either in Greenville or Spartenburg, SC. Gene still maintain a small shop in Walhalla for his hobbies...building scale model Mack trucks.

I spoke with him again the other day and it didn't take long for me to realize that this guy is sharp.  He told me that he's more concerned with 'ripple voltage' getting out of the alternator than any other factor...that it eats batteries like Pacman on a binge!  Over my head, for sure....but I fell I'm in safe hands.

Rebuild costs? This is a bus...and it's our home and our link to travel to be with our family and BusNut friends. In for a dime....in for a dollar. What am I going to do?  Plant flowers in it for lack of an operating component?  Not so's you'd notice.

All I lack at this point is a willing pair of strong arms to pull that rascal out (and I know a fellow who matches that description) and I'll take it to Gene, after I do some preliminary checks, and we'll get the job done.

I'll keep you posted, if you'll allow that, so that the archives will reflect the experiences and advice offered here. Isn't that what this Board is all about?

Thanks again for your input and thoughts....and the beat rolls on.......

Bob
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JackConrad
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« Reply #33 on: September 09, 2007, 01:56:20 PM »

Bob,
   Please do me a favor and tell Gene I said HI.  I knew he had a shop in Spartansburg, but did not realize he lived in Walhalla. I sure would have stopped by to visit if I had known.  Ask him if he still has his "Bumper Dumper"? That might be a nice addition to your bus.  Did you know he still holds the speed record for class 8 Semi Trucks at Atlanta Motor Speedway. He set the record back when they had the Great American Truck Races.  Jack
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JohnEd
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« Reply #34 on: September 09, 2007, 02:40:58 PM »

Bob,

Glad you got hooked up with a tried and true expert.  And a bus nut to boot!  You are homefree as far as I am concerned.

Your comment about "ripple" is pregnant with meaning for me as that anomaly has surfaced many times in my career.  Knowing nothing about that design of generator, it would make sense that it has fallen out of the mainstream if it has ripple as a characteristic.  Then again, all alternators have ripple as they are unfiltered.  When an alternator looses a diode it developes very high ripple.  I really hope you will be able to expound on the "eats batteries like pacman" comment.  Really, I do.

Thanks,

John
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
Tony LEE
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« Reply #35 on: September 09, 2007, 11:57:25 PM »

Richard, the 50DN really doesn't have any brushes. Not a single one.  There are no slip rings or commutator either although I guess the design of the stator acts as a sort of magnetic commutator.
If you want an exploded view let me know and I will email it to you - although my copy is not too sharp and it may be difficult to get an idea of how it is constructed..
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