Did the EMD F-7 “B” units have any power. As a hostler I was shown how to lite the boiler in the unit by depressing a pedal and turning a switch to “on” and was told that the boiler in the unit provided the steam heat for the passenger cars. But in never asked if there was a prime mover in the unit although I later saw another hostler moving one by itself while he had the side port-hole window opened. My questions are: did the B Units have power ? What were their purpose? How is their function performed by todays locomotives? Could the A units be run without them. What if one went out while on the road. Is that why the transcontiental trains Chief, etc. had more than one in their consist? What eventually happened to them? Thanks.
The differance between an A unit and a B unit is the B unit has no cab. Otherwise they are the same. It’s a way for the railroad to save money. The purchase price is cheaper and they don’t have to maintain the cab equiptment. But they are not as flexabe as A units as they can’t lead (obviously) Railroads still buy B units from time to time but it is not that common
Yes, they had power. An F7B is mechanically and electrically identical to an F7A except for having a control cab. F7Bs were built with hostling controls which provided very limited control capabilities (and in most cases were later removed or disconnected).
The function of an F7B is to add tractive power to a train without incurring the expense of purchasing and maintaining a control cab.
B units fell into disfavor as the disadvantages of their inflexibility became apparent, and as unit horsepower increased, reducing the number of units required to give a train a sufficient horsepower-per-ton ratio.
Any unit in any power consist with multiple-unit connections can be isolated or fail without affecting the others. An A unit can control up to 7 more A- and B-units (8 is the recommended limit, but it was often exceeded) whether the A unit is live or dead.
Yes, having more than one unit on a train gives it the ability to keep moving if one unit fails. On the other hand, the more units you have on a train, the more likely any one of them is to fail, and maintenance costs rise in proportion.
S. Hadid
Except when they finished out their service life as RCE repeater/receiver cars with a big block of concrete where the prime mover used to be.
Except when they finished out their service life as RCE repeater/receiver cars (ATSF) or slugs (CNW -BU units plus a few others) with a big block of concrete where the prime mover used to be.
One might add to all this that one of the motivations – very early on – for the ‘B’ unit concept (and almost all road diesels in the carbody age had B units available, even if they didn’t sell well) was the uncertainty as to whether MU’d sets of diesels would require only one head-end crew, or if each unit would require its own crew; B units, having no controls, automatically meant no crew, either.
In the event, the unions involved agreed to the idea that a MU’d set of diesels only required one crew.