Powered FB units

[WGL]

 After reading about making consists of 2 or more locomotives, I wonder what a powered F7B unit would add to my F7A.  Is it more realistic to run FA with FB?  Would a powered B unit add more speed & more pulling power?  Does it use about as much electricity as the locomotive?  Would I have to re-program it to run at the same address as the F7A?  I have an Intermountain EMD F7A Great Northern locomotive.  I realize that for appearances only, an unpowered B unit is a cheaper alternative.

[GlennW]

WGL, In a normal DC setup, you can get better performance from a 2nd powered unit. Try to get a 2nd unit similar to the first, or buy your power in pairs.

1) The 2nd unit will "nudge" the first, giving a slightly lower starting speed.
2) You may gain about 10% pulling power in using 2 units. For example, if the FA pulls about 30 cars, 2 units will pull more than 60 cars. (Actual amount depends on your layout).

[WGL]

GlennW,
Thanks.  I don't know how a 10% increase in power equals pulling twice as many cars, but I can understand if both units have equal power, they can pull twice as many cars.
  I want to know what B unit would work with my DCC FA.  I don't see how a DC B unit would work with a DCC A locomotive.  I see some B units with DCC & sound, but it makes no sense to me to pay for sound in a B unitl  I find few details of specifications on manufacturers' or sellers websites.

[Guilford Guy]

Why not DCC in a B? If you are going to be running them coupled together you can just operate the sound functions in the B. If they A and B's are of the same manufacturer, you can usually pop off the shells and swap frames.

[Jim Banner]

I don't know how a 10% increase in power equals pulling twice as many cars, but I can understand if both units have equal power, they can pull twice as many cars.

WGL, I suspect Glenn meant to say you may gain 110% in pulling power.  A 100% increase would be double the pulling power.  But sometimes you may find two locomotives pulling together can pull more than the sum of what each locomotive could pull when working alone.

By all means if you are using DCC in the A unit then also use DCC in the B unit.  Did someone suggest that you use a dc B unit with your DCC A unit?

To answer some of your other questions:

You can add either a powered B unit on another powered A unit to your present A unit and get about twice the pulling power.  Both are realistic as both were done by real railroads.  If they ran a second A unit, they normally ran it backwards.

A powered B unit or another powered A unit would use as much electricity as your present A unit.  Makes sense - to get twice the power, you need twice the electricity.

You can reprogram the B unit or second A unit to the same address as your present A unit to make the two units run as one locomotive.  This is called BASIC consisting.  If you choose to run a second A unit, you can reverse its normal forward direction to make it run backwards when you command control is set for forward.

You did not mention which DCC system you use.  With some systems, you can tell the command station which locomotives to run together as a consist.  It then sends the speed and direction information to both addresses when you make speed and direction changes with your throttle.  Digitrax calls this UNIVERSAL consisting.

If your locomotives have decoders that support it, and your command system allows you to program the decoders to do it, you can also use ADVANCED consisting.  This allows units programmed to one address to operate as if their address was a different address.  This is my favourite method of consisting because of the ease of setting it up and taking it apart.

[WGL]

Jim Banner,
  I am using the E-Z Command Control & expect that I could re-program a B unit to the same address my F7A uses.  Since DCC without sound is much cheaper than DCC with sound, I think it makes sense just to have DCC & sound in the A unit & DCC without sound in the B.  However, I don't see this option for the Intermountain F7A DCC with sound I have or for any other F7A-F7B combination.  This means paying as much for the B unit as I did for the A locomotive.  I'm surprised at how much I've already spent getting started during the last two months. 
Thanks for explaining the amount of power a powered B unit would add.  My F7A pulls 8 passenger cars at a top speed of 69 scale mph.  That's a longer train than the 12 freight cars my Spectrum EMD SD-45 pulls at a top speed of 85 mph.

[GlennW]

GlennW,
Thanks.  I don't know how a 10% increase in power equals pulling twice as many cars, but I can understand if both units have equal power, they can pull twice as many cars.
  I want to know what B unit would work with my DCC FA.  I don't see how a DC B unit would work with a DCC A locomotive.  I see some B units with DCC & sound, but it makes no sense to me to pay for sound in a B unitl  I find few details of specifications on manufacturers' or sellers websites.

Sorry for the confusion. Yes, adding a second unit does get a 100% increase in pulling power. However, you get about 10% more than that. Real units have the same result. In N/Z scales I do this all the time with regular DC units. You should get a similar result with a pair of DCC units.

In your case, I'd go with a DCC FA type unit of the same brand. You can decide if you want to have a ABA, ABB, type set. In DC land, I look for units that will be similar in operation. Buying my locos in pairs usually solves that problem.

In DCC, you have the option of using another mfr's units. It may just take a little more work for everything to work together. THis solves the problem of A) one unit starting before another or B) The speed range of the units is closely matched. C) TE will be increased because you have more weight & axles on the rail to move the train.

[WGL]

 I have on my wish list the Intermountain FB unit that is made for my Intermountain FA.  I just don't understand the need for sound in a B unit, which jacks up the price from just DCC without sound.

[Guilford Guy]

Intermountain trying to make more money...
BTW. EMD units are referred to as F(#)A's/F(#)B's. So there were FTA's, F2A's, F3A's, F7A's, F9A's, and strange locomotives like FL9's, FP7's, and FP9's. FA's and FB's were ALCo Products designated as FA-1, FB-1, and FA-2, FB-2.

[Frisco]

Intermountain makes a DCC ready B-unit and it would be easy to add a DCC decoder to it(I would  recomend Digitrax) this would be an easy conversion or if you don't want to your LHS might.

[WGL]

Frisco,
Thanks for the suggestion.  My "local" hobby shop is a 60-mile roundtrip.  The owner is more interested in RC planes & cars.  Most items I want his train person would have to order specially.  Consequently, if I am not satisfied with the product, he can't just return it to his shelf & doesn't want to bother with me.
  The nearest model train club is just as far away, & they did not respond to my e-mail asking about hobbyists in my home town.  With a population of 15,000, there must be other hobbyists, but I haven't figured out how to find any yet.

[Yampa Bob]

For a short freight or passenger setup, the usual head up would be at least an A-B. If another A were added up front, it would be running backwards.  Then the 3 loco consist could run either direction, at either the head or at the rear.

One of my DVDs shows a Rio Grande freight train with F7s,  ABABA up front, ABA in the middle, a caboose at the end with another ABA.  Pretty awesome sight. 

[RAM]

When the FT units came out, they were designed as AB set.  They were to be used as either an AB or a ABBA.  The Santa Fe said we want  to be able move the units as needed so couplers were added.  It was not until 15 or 20 year later that the A units modified so that A unit could be MUed nose to nose.

[WGL]

 You confirmed my guess that F7A-F7B are typical & not F7A alone.

[RAM]

F7s A-unit did run solo on lite trains.  You got to remember that the f unit did not have that much power.  I think a 4 unit FTs were rated at 5,000HP.  A 4 unit F9 was about 7.500 HP.