The 50D Alternator strikes again

[chessie4905]

One of the different drive ratios may have been for the 6v-71 or some other application. I have two alternator gears that have 3 less teeth on them.

[daddysgirl]

I still have the OTR AC, so we retained the 8D's with the 50D on the engine side.
For the house, I have a 90A converter charger that has AC, DC and three charging levels to keep the batteries charged.

For whatever reason, we never connected the house bank to the engine bank, but I could run a transfer switch easily enough if I needed to.

[fortyniner]

I wonder if the higher amperage alternators fail more often. I think mine is 270amps but Ive seen them as small as 240 amps and as large as 500.   That said I have had three 4106 and the according to records the alternators on two of them were repaired due to low output. No actual gear failures and one bus had over 900k on the clock.

[richard5933]

I wonder if the higher amperage alternators fail more often. I think mine is 270amps but Ive seen them as small as 240 amps and as large as 500.   That said I have had three 4106 and the according to records the alternators on two of them were repaired due to low output. No actual gear failures and one bus had over 900k on the clock.

I spoke with a tech at https://www.elreg.com/ about the 50DN alternators recently. Part of the discussion was about the newer high-output versions of the 50DN which are being used in some newer coaches due to the amount of load being placed on them. He told me that while a 270-amp version can last 100,000 miles or more without service/rebuild, the high-output versions will require service much sooner. My guess is that the higher output results in higher temps, and higher temps are not good.
When your alternator was repaired, do your records show exactly what was done? If the bearings were not replaced over 900K miles, that would be something I'd be doing pretty soon.

[fortyniner]

I believe it said "rebuilt alternator" and cost over $600 (1990). I pulled it and the gear looks nearly new. 
.
Subsequently I replaced it with one from a 4905 for 24v conversion. That one has no records but gear looks very good condition at least.

Still I think Ill snag a new one just for peace of mind before running around this summer.

[richard5933]

It's not the gear in the alternator that's the main culprit from what I understand. It's the bearings failing and causing the alternator to seize up, thus causing destruction of the gears in the engine which drive the alternator. Or destruction further down the line in the engine if the gears hold out for a moment or two before failing. Someone with more direct experience can hopefully spell out exactly how these things fail, but the bearings are a main piece of the equation and that's why they added the second oil port in them at some point.

[lostagain]

The new Prevost H3-45 coaches have 2 24V at 150A or 250A alternators. MCI J4500 have 2 24V at 250A. All belt driven. They power all the usual stuff, plus the electric fans on the radiators these last few years.

[buswarrior]

Look carefully in a Prevost, some have 3 alternators hung all over the Volvo powerplant.

There were add-on small "get home" alternators being retrofit by some fleets, on the electronic coaches with only the single big one.

It would keep the drivetrain functional, in the case of a traditional alternator failure.

That voltage in the batteries slips to that magic point... better have a warm coat, hat and boots...

Happy coaching!
Buswarrior

[richard5933]

Sometimes it is difficult to mount one belt driven alternator on a GM V-drive. Can't imagine trying to mount 2 or 3.

[fortyniner]

 Hmmm. for the high output alternators adding a little power steering cooler in the oil supply line might help. Kind of hard to cool with 180 degree oil.  Is hot oil one of the issue with the bearing or just lack of reliable lubrication (old style alternator). 

[chessie4905]

Delco found issues with life of old design over time and upgraded it, including extra oil line. Conjecture here now, but fast idle with heavy charging mode and lower oil pressure and less oil cooling was probably causing more bearing wear. More robust bearing design plus oil line added to that new design setup took care of the issue. If you check their site, the new 450 amp  belt driven version uses that same additional oil line.
They do list service intervals for that alternator in their manuals.
Bearing starts wearing out like a front wheel bearing, gets sloppy. Allows excess slop at gear and cup drive to the point some teeth break and catastrophic  failure. The basic design of the overdriven gear unit is fine. Been used in millions of automatic transmissions for decades with great reliability. Only important item is to be sure the alignment procedure is correct. The instructions are in the shop manual.

[luvrbus]

I had one 50d the casnio owned in a MCI 12 their mechanic installed from a rebuilder the rebuilder didn't punch lock the nut on the drive gear on the 50D and the mechanic didn't either,  the nut came off and fell into the gear train I all got to use was the block .alignment is very touchy and take times to get it right if not it's going to break something   

[chessie4905]

sort of like of tune up on the engine and not following factory directions.

[Jcparmley]

Reading this thread has me worried.   Anyone know if a 1996 mci 102dl3 with a 12.7 series 60 has a belt or gear driven 50d?  I would go out to my storage lot where it's parked but it's buried under 13 feet of snow and it's -20 degrees wind chill today?

[6805eagleguy]

Most likely same as mine it's a 99