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Replacement of Hydraulic Fan Motor for '92 U-280

November 05, 2012, 09:32:04 pm

REPLACEMENT OF HYDRAULIC FAN MOTOR ON 1992 U-280, FOR CUMMINS 300 HP C 8.3 MECHANICAL ENGINE

To set the stage, this radiator is cooled by a single fan, mounted on a 3' long, double box tube frame.

The previous (original?) fan motor was mounted on a bracket, the base of which was bolted to the above frame and opposite end was inserted into the fan blade housing, where the motor's shaft inserted into a fan blade "adaptor" that was bolted to the blade housing.

MOT didn't have any replacement fan motors (Haldex-Barnes #1820009); they thought FOT had them so I went to the Parts Dept there. FOT's Mike Grimes was the only one who had a clue as to the "history" of the fan motors for the C8.3 mechanical Cummins.  The motor was a proprietary motor designed and built just for FT.  The manufacturing company would only sell them in batches of 25, the last (batch) of which was bought in the late '90's.  When FOT ran out of that batch sometime around 2007 or 2008, they contacted the original manufacturer, who would only make/sell them in batches of 25.  FOT's CEO declined to buy that many, as they were only selling 2-3 each year.
 
So, FT contacted a Longview firm, gave them the specs for the motor, and asked them to "find a motor that meets those specs".  The motor they found is made in Italy.  It's entirely different in its shape and size from the previous motor.  Shaft has a different taper.  Motor alone costs $660 before Motorcade discount. 

Since the motor shaft is a different diameter, one must purchase a different fan blade "adaptor" (3 inch diameter disc) , which receives  the shaft and is bolted into the blade housing.  It costs around $300! 

The original bracket that the motor was mounted to wouldn't accommodate the new motor.  So, FOT had a new bracket (10"X10"X ¼") machined locally, along with the blade adaptor.  This flat plate bracket cost more than $150.
The adaptor did fit into the fan blade housing; the bolts secured it well.  The new motor shaft even fit into the adaptor.  Beyond that, nothing worked as promised.  The new bracket was too large, wouldn't come close to fitting into the fan blade housing.  Moreover, it wasn't built to mount to the double box tube frame. 

I shared all of this with Mike Grimes, who then said that this new system was really designed for a two fan/motor setup, not for a single fan arrangement.  Thus, if you do have the double fan system, be prepared for double the cost (Mike says you can't replace just one fan motor at a time). To resolve this dilemma, I took the blades/housing, new motor, the new bracket, and the double box-tube frame to a local (Nacogdoches) commercial welder.  They cut the corners off the new bracket so it would fit into the fan housing and modified it to project 2 ½" from the tube frame;  this modified bracket was then welded to the tube frame.  I have used Thomas Welding before.  They were great to work with.

Surprisingly, everything fit.  However, one of the new hydraulic fittings (smallest of the three) screwed into the motor, but was way too small a diameter to mate with the existing hydraulic hose.  FOT doesn't carry the correct fitting for the Grandvillas' small hose.  By this time, I really wasn't too surprised.

We have a good hydraulic shop (A&D Hydraulics) just up the road from FOT (down the road from MOT); The owner, David Horn determined that we were dealing with metric threads on the hydraulic motor side of the fitting and SAE threads on the hose end.  Fortunately, he had the correct fitting and we finally finished the replacement with NO leaks.

As luck would have it, according to Mike Grimes, I am the first with a '92 U-280 to need one of the new fan motors.  So I guess I was the "guinea pig".  That's why I decided to share my experience with all of you.  There's bound to be a few 280 owners out there that will face a similar situation down the road.

I forgot to take any pics until the fan motor was installed, but I have included that photo.

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #1 – November 05, 2012, 10:08:13 pm

Don, knowing you I'm betting you researched all of the alternatives to this system. I have wondered why an electric fan or fans would not work. What's your opinion?

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #2 – November 05, 2012, 10:22:00 pm

Kent,

Although I didn't pursue the electric fan possibility aggressively, I did ask if an electric fan could be used.  I was told by a FOT mechanic that for those big radiator fans an electric motor "wouldn't hold up".  I didn't question his comments any further.

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #3 – November 05, 2012, 11:20:38 pm

I think I remember that the hydraulic fans take 10-15 HP at speed, so running on electric would mean not only impressive fan motors, but also a MUCH larger alternator... 15 hp = ~ 11 KW, so that would be a ~900 amp alternator

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #4 – November 05, 2012, 11:49:45 pm

Dave,

If your calculatioins are correct, I am glad to learn that there wasn't a quicker, simpler alternative to my approach, i.e., making the hydraulic fan motor work.

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #5 – November 06, 2012, 10:21:03 am

I saw a city bus in Austin a few weeks ago that had 10 electric fans on the radiator.
Some flexibility there. You could run half of them all the time and add others with temperature switches as needed.

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #6 – November 06, 2012, 12:59:38 pm

John,

Wonder if that city bus was a hybrid.  That is about the only way I can think of powering electric fans that could move enough air to satisfy the cooling requirements.  There is no free lunch-- 10-15 HP is a LOT to produce electrically.  A cake walk hydraulically.

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #7 – November 06, 2012, 01:47:05 pm

Don, If you saved the old hydraulic motor I would suggest that you go by a hydraulic repair shop and see if they can rebuild it.  May not do you any good at this point but could educate others.  I had a hydraulic shop tell me that if the rotor and outerr case were intact that any of them could be rebuilt.
Gary B

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #8 – November 06, 2012, 08:03:58 pm

Gary,

I took the fan motor to A&D Hydraulics here in Nac, along with a new Seals kit I bought from FOT. When the motor was opened, 6 of the bearings had disintegrated and scored the interior of the housing. The owner said the "motor (housing) was damaged beyond repair", that the seals wouldn't hold and I should take them back for a refund ($135).

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Re: Replacement of Hydraulic Fan Motor for '92 U-280

Reply #9 – November 07, 2012, 08:03:57 am

Don, OK that squares with what I was told.
Gary B

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