Arnold U25C Decorated Samples

[CBQ Fan]

U25B's were used in the northwest pool which freed up 8 SD-9's for coal duty in Illinois.  U25C units seem to have done the same. 

As far as all the cables I recall reading that there were two sets to run certain SD units with GE units.  I will have to some digging in my resources for additional information.

The Burlington bought the C as an evolution over the B unit and then moved on to the U28B, U28C, U30B, U23C.

[Bob Bufkin]

I'll hold out for PRR or PC units.  I do know the Q U boats made it into NJ in pool service with the PRR and then PC so I might get one just for that reason.

[Sokramiketes]

The Road # and Number Board font on the NP sample is way off when compared to the prototype.  We at the NPRHA Modeling Committee provided Hornby USA with correct fonts, so this is disappointing, to say the least.  It's hard to tell from the photo's angle but the Road Name looks somewhat closer.

Well that's disappointing.

[Sokramiketes]

Everything including fit and finish look pretty good, but the couplers look a little large.

Compared to a scale coupler, definitely large.  But they are smaller than an MTL N scale knuckle, so not sure why they would look large in that comparison.  Do you think it's a proportion issue where your mind is used to seeing an N scale MTL coupler, and now with a smaller coupler head but needing the same gather distance to interchange, the coupler visually looks wider?

[jpwisc]

I'm glad to see they have the level of detail they do, and the couplers look great.

I think the black green separation on the BN unit is a little fuzzy. The white striping is nice and crisp, hopefully the black line gets fixed before production. The airhorns look a little chunky on the ends that should be open. Those can always be replaced with Atlas or Kato horns once they get on my bench.

I do like the firecracker antenna and the fact the windshield wipers are installed already.

[Nato]

     "Hey! Hey! Hey! Looking Good." Remember these are just pilot model samples, the final paint, lettering and truck color are subject to change. It is too bad about the NP number boards after information was provided by the NP Historical Society. Nate Goodman (Nato).

[Leggy]

The BN sample looks like the most pre production of all the samples, look at the roughness around the windows vs the Conrail one.

[nkalanaga]

Javier:  Part of the reason for six-wheel trucks was weight on light rails, but another was slow-speed operation.  At low speeds the limit is current draw by the motors, and resultant heating, rather than horsepower.  Extra axles spreads the total current, which is limited by the main alternator, and thus horsepower, over more wheels, allowing full power at slower speeds.

At high speeds, the limit is horsepower, as effective tractive effort drops with increasing speed.  At some point, the extra weight of the larger locomotive isn't needed for traction, and a lighter 4-axle unit can pull the same train, at lower initial cost and with less maintenance.

[Ngineer]

@ Brian (CBQ Fan), @ N Kalanaga

Thank you for the information! Didn't know that.

Does that mean that the U25B and U25C were never used (mu-ed) together?

And where was the North-West pool? Montana, Wyoming and South Dakota?

Javier

[CBQ Fan]

@ Brian (CBQ Fan), @ N Kalanaga

Thank you for the information! Didn't know that.

Does that mean that the U25B and U25C were never used (mu-ed) together?

And where was the North-West pool? Montana, Wyoming and South Dakota?

Javier

I see no reason why they would not have been mu'd together.  I can't recall seeing a photo with the combination, but I honestly have had no reason to search for one.  I would assume the nw pool would be Omaha, Billings, Denver triangle but I can't say for certain.

[nkalanaga]

No, 4 and 6 axle power will MU just fine, as long as the gear ratios (top speeds) are similar.   The GN used to run their passenger trains with a mix of SDP40/45s and F3/7 B units, which did look a little strange, but worked fine.

If you're using them for slow, heavy trains it's important to watch the motor amperage, and the same consideration applies to any train using dynamic brakes. 

From the "Burlington Northern Inc. Pacific Division" "Special Instructions No.1, Friday May 10, 1968":
"When six-motored diesel units are coupled in multiple with four-motored diesel units, each six-motored diesel unit must be counted as two units to arrive at the maximum allowable dynamic brake amperage permissible as shown under Table 1."  The specific example that they give is two NP 2500 series and two NP 200, 300, or 7000 series units.  That would be two U25Cs and two GP9s or F9s.

For what it's worth, the allowable amperage is lower for a six-motor unit than for a four-motor, and is lowered as the number of units increases regardless of the type.  These are per-motor amperages, and the limits are to, quote, "avoid derailing cars in the head portion of freight trains while descending grades of 2.2% or greater", so the limits may not apply on lesser grades.  Apparently too much braking on the front end can result in cars being squeezed out of the train, the opposite of "stringlining". 

And, yes, these are BN Special Instructions from 1968.  My father worked for the NP, and both timetables and SI were printed and distributed before the courts blocked the first BN merger attempt.  The Thirteenth Subdivision section even has half a page printed in red, for the "Electrified Zone" between Argo and Maple Valley, where the MILW had shared track with the GN, on what was officially the Pacific Coast Railway.