Kenefick Park and the UP 4023 and 6900

rrman posted:

Just returned from Omaha to visit the UP museum and were going to North Platte to visit Baily Yard tower, but that part was abandoned due to bad timing, will do North Platte next year.

Anyway got to see the 4023 and 6900 up close and personal.  You just don't realize how BIG they are until you walk the length around them!  Of course you "real railroaders" know this, while us armchair RRers just read about those engines.

Curious why the Centennials were removed from service. 

Simply put,,,,,,they were worn out! The UP had completely overhauled all of their 6900 Class DDA40X units,after about a million miles, and then ran them for another million miles. By then, there were many more modern and higher horsepower single units, so all the classes of DD units were finally used up, and sold off.

Wikipedia stated it was because better engines were coming on line.  Were there mechanical issues such as frame cracking due to length and twisting?

No, not at all. See answer above.

The 6939 is still in service for excursion use.

Found a Youtube of moving the Centennial in pieces to where the 4023 was.

https://www.youtube.com/watch?v=he0ugl06-P0

I have seen 6936 in service.  IT IS LOUD!

Like HW said, the 6900's were worn out after a long service life.

Why weren't they rebuilt again? Various reasons:

They were a non-standard model with many unique parts. The engines were 645-E3A tweaked for higher horsepower than a 645-E3 as used in hundreds of SD40-2's. Injectors, camshafts, turbocharger etc were different parts from SD40-2's. They were predecessors for development of the GP40X and 50-series locomotives. They were the first production locos to have plug-in modular electronics, which became standard on the dash-2 series.

They were all geared for higher speeds and generally used on hotshot trains, often MU'ed with "8000" series SD40-2's which also had the high-speed 59-18 gear ratios. The 6900's were not used on run-through trains to other railroads AFAIK. They served a somewhat specialized niche.

The unique 8-wheel trucks tended to wear flanges on the #1-4-5-8 axles of each unit because of the longer truck wheelbase. Not an optimum arrangement for modern diesel power.

About 1980 the FRA came up with a new rule requiring that locomotives used for any road switching must have bottom steps with 9" horizontal clearance, so a crew person could stand without needing to use both hands to hang on. Locomotives which didn't meet that rule could only be used in the trailing positions of an MU consist. There was no practical way to modify the 6900's to comply.

In 1980 the FRA had new noise abatement rules for locomotives. EMD installed exhaust mufflers and developed quieter radiator fans for new locomotives beginning in 1980. That's why older high-HP locos may seem louder under load.

North Platte 1980

Thank you Hot Water and Ace for the interesting details.

I did not look closely at the Centennial trucks to note if the center two axle wheels of each truck were blind or flanged.  I assume flanged based on Ace comment about wheels 1-4-5-8 scraping rails.  Wonder if those problems would have gone away if they had had the EMD self steering radial trucks (if I understand how they worked).