What is the maximum number of locomotives?

Hi All,

BNSF, Santa Fe, in the Cajon Pass area is still maintaining helper engine capability. There might just be additional engines on the tail of that train.

Mkd7 wrote:So I gather that there is a limit to prevent what, rail and traction motor damage?

Saving fuel is the biggest reason.

Mkd7 wrote:So I gather that there is a limit to prevent what, rail and traction motor damage?

Saving fuel and preventing excessive draft forces.

Buffing forces are much more of a concern, than Drafting forces are. Hence, the reason for less DB axles allowed, than motoring axles.....

GOLDEN-ARM wrote:Buffing forces are much more of a concern, than Drafting forces are. Hence, the reason for less DB axles allowed, than motoring axles.....

Yeah, true , but too much draft will find the limitations of the draft gear.

GOLDEN-ARM Posted: Thu Aug 31, 2006 2:17 pm Post subject:

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Buffing forces are much more of a concern, than Drafting forces are. Hence, the reason for less DB axles allowed, than motoring axles.....

BlackDog Posted: Thu Aug 31, 2006 2:55 pm Post subject:

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GOLDEN-ARM wrote:
Buffing forces are much more of a concern, than Drafting forces are. Hence, the reason for less DB axles allowed, than motoring axles.....


Yeah, true , but too much draft will find the limitations of the draft gear.


New term and fuzzy terms; for some reason I want to associate draft gear with the coupler & coupler pocket, and I don’t have a clue about "Buffing Forces".

I do know that an EMD choo- choo is most efficient (ton/miles) while running in N8 fully loaded and light loading of the traction motors will eat the commutator quicker over time by burning off the patina. (The commutator is not an issue with AC traction motors.)

I was informed by a Train Engineer during a test train operation in Indiana that the limiting factor in train length is the weakest link being the Knuckle. Each Locomotive has a specified design pulling limit and these two factors dictate train length. (T or F ???)

When I understand draft gear and Buffing, it may all tie together. Please respond....

ExEMDLOCOTester wrote:

New term and fuzzy terms; for some reason I want to associate draft gear with the coupler & coupler pocket, and I don’t have a clue about "Buffing Forces".


I was informed by a Train Engineer during a test train operation in Indiana that the limiting factor in train length is the weakest link being the Knuckle. Each Locomotive has a specified design pulling limit and these two factors dictate train length. (T or F ???)

When I understand draft gear and Buffing, it may all tie together. Please respond....

Buff forces are the weight of the cars pushing against the motors and the cars ahead of them in the train. Severe buff forces are nasty run-ins and a change from light dynamic use to a heavy one. Too much dynamic brake ability on some trains with a mixed bag of empties and loads, you could derail one or more of the empties towards the headend of the train. Same thing in helper runs, an empty flat next to the helper unit, run the chance of lifting her up and off the track. Same goes for empty flats with too much tonnage behind it.

Someone on here knows the knuckle and draw bar limits, i dont. The weakest link is the knuckles, if your gonna rip a train in half, dont want it to be the car itself. "Ya we went in two dispatcher... bout 100 tons of grain on the ground out here" The pulling weight on the knuckles is the draft force. The RR limiting train length/tonnage has to do with the territory. (siding lengths, grade, fuel consumption, the yard track it was built in, locomotive availability...) If ya get a big heavy trains that powered up well, an engineer needs to keep that in mind when pulling a hill, starting and stopping, power braking... Taking off too fast and getting a wheel slip once ya do have it up and running will often be the reason for busting her in half on a big train.

Thanks UPRR for the simple to follow explanation! I noticed these forces in my preteen days while running my HO set. I learned quickly to put the lighter cars in the rear because they stayed on the track through the curves and quick stops or starts. I never imagined the forces had names...

When riding the EMD test car in the "Pride Coal Train" on the Southern from Pride AL to Atlanta GA, I was amazed that the mid train helper RC unit did not derail while the train was being loaded. In addition to the Radio gear are the Mid train RC units ballasted???

IS "Draft Gear" the hardware consisting of the Coupler, Knuckle, Pin & Pocket???

Hi All,

Interesting point. You need to go to the NMRA standards for weight of freight cars. As I remember it, a freight car should weigh at least four ounces, HO gauge. If the car is lighter, you will definitely have to put it at the end of your train. Easy enough to add weights to the car to bring it up to an acceptable weight. Good luck.

ExEMDLOCOTester wrote: In addition to the Radio gear are the Mid train RC units ballasted???

IS "Draft Gear" the hardware consisting of the Coupler, Knuckle, Pin & Pocket???

DPU's (Distributed Power Units) are no different then a motor without the radio controlled equipment.

Draft gear is the whole drawbar assembly-- knuckle, drawbar, draft key. Guess you could include the cusioning device and the end seal.

Sorry UP, I should have been more descriptive. The RC units looked like a short caboose with Antennas, coupled between, & MU'ed to both mid train helping locomotive units. They (Southern) ran with three SD 50's or 60's up front and two SD 50's or 60's mid train.

Thanks for clearing up my Draft Gear / Draw bar confusion...

pennsy wrote:Hi All,

Interesting point. You need to go to the NMRA standards for weight of freight cars. As I remember it, a freight car should weigh at least four ounces, HO gauge. If the car is lighter, you will definitely have to put it at the end of your train. Easy enough to add weights to the car to bring it up to an acceptable weight. Good luck.

Thanks Pennsy... That info will be handy when I get my Grand kids an HO set ....

UPRR engineer wrote: The weakest link is the knuckles,

Not always...

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