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Electrical Discussion of preventative/corrective maintenance and other technical issues regarding your coach's electrical system.

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Old 03-12-2009
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Bumpersbird Bumpersbird is offline
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Default 50DN Alternator Story


Here you will find a complete history of the alternator most often used in heavy applications for motor coaches. We hope that you find it helpful in providing information on why your coach needs the properly remanufactured alternator and not one of those lower costs ones that so may suppliers are offering.

We have "highlighted" specific points such as the special bearings mentioned as critical. Their costs are substantially higher because they were manufactured especially for this up-grade. Make sure to purchase only those alternators that meet this DELCO specification.

The 50DN alternator has been the main electrical power supply for coaches since its indtroduction in 1958. The requirements have increased from the original 12 volt, 215 amp to today's 24 volt, 270 amp output. Also, the mounting configurations have proliferated to include several flange mountings and a belt-driven version.

Remanufacturing units must be done for a specific application because the possible combination of parts can create assemblies that would not function properly on any OE vehicle and cause premature failure of the generator. Servicing older units adds serveral other mountings and performances.

There have been several design modifications in various components in the 50-DN alternator directed toward meeting the longer life desires of our customers. SEVERAL of the changes can be incorporated in previously built units by the fleet mechanics.

The rotor suppressor ring was changed from a brazed bronze ring to a TIG welded STAINLESS STEEL ring. The strength of the assembly was greatly increased.

The stator conductor configuration was changed to increase the space between conductors on both ends to reduce changes of shorting and the glass sleeving was removed to obtain better cooling to increase stator life. Also the wire insulation and impregnation were upgraded. Tests indicate the stator life has been increased five fold.

The bearings and means to lubricate and cool them have been changed significantly. An external oil line, tee and elbow were added as part of the alternator assembly to deliver oil at the lowest practical temperature to the bearings. The tee features a special small orifice in its upper leg to control the amount of oil to the bearings. If a commercial tee is used, so much oil will go to the bearings and too little oil will go to the alternator resulting in higher alternator component temperature causing short generator life.

The double-row ball bearing was replaced by a SPECIAL roller bearing made to NON-STANDARD dimensions. The radial clearance is less than a standard bearing to reduce the chance of ROTOR RUB! Also, it was desirable to have the new roller bearing fit into the same drive end housing bore as the double-row ball bearing, so fleets could upgrade the alternators without the need to purchase a new housing. However, the double-row ball bearing outer race is a slip fit in the drive housing end bore and the roller bearing outer race MUST BE a press fit in the housing. Therefore, the roller bearing outer diameter was made OVERSIZED. A standard roller bearing WILL NOT FIT PROPERLY IN THE DRIVE END HOUSING BORE AND MAY "WALK" TOWARD THE GEAR CREATING A SERIOUS PROBLEM AND OR PREMATURE ENGINE FAILURE.

The single row ball bearing is special in that it has a SMALLER then normal radial clearance, has heat treatment for high temperature operation, has a shield on one side and the ball cage is made from reinforced nylon. The low radial clearance is needed to prevent edge loading and the end of the rollers in the roller bearing.. The shield needs to be placed next to the rotor to keep the hotter oil in the generator away from the bearing and it also acts as a dam to create a pool of oil in the bearing cavity.

Knowing who is remanufacturing your unit or providing you with an exchange and knowing whether they know all the criteria as mentioned above, may mean the difference of failure and optimum performance.


Kurt Horvath
95 PT 42
10AC
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