How do Dynamic Brakes work??

[Anonymous]

How do Dynamic Brakes work and how do they differ from regular brakes????
Thanks!

[Anonymous]

As you may know, locomotives are diesel-elect. So..the diesel spins an alternator, the juice passes thru a rectifier, now it's dc power. On ACs an invertor is used. This power is wired to the traction motors on the trucks for power. For d.b., the electricsl circuits are re-arranged, turning the motors themselves into generators. Since it takes power to turn a generator, the speed of the train, now shoving the engine, is retarded. On a typical loco. consist (d.c.), we start with 2-300 amps, and increase the amperage with the top handle on the controller, to retard the train. Also, since we're generating elect. here, the juice is wired to grids..those blisters on the top sides of the older locomotive, sort of concealed behind grills on the newer ones. The grids absorb the energy and dissipate it.
Terry...l-o-n-g time BN engr.

[Anonymous]

Terry
Just out of curiosity... Which Locomotives have the better dynamic brakes?

[Anonymous]

Donald..one of those questions where 10 eng'rs give 10 diferent answers...but here's how a lot of us rate them: GE44CW (DC)..powerful, but tend to slip heavily. I work on our trackage rights over the Moffat (D&RG/UP)line and when they slip in the curves (reduce their loading or capacity) you can get in trouble quickly. SD70MAC-very good, SD75-very good, SD-40-2:to us dinousaurs still the best. One problem is lack of extended range, the ability to maintain amperage at 10 mph and lower.Some of the ex-BNs are retrofitted with this feature, as all Santa Fe's are. The EFFECTIVE RANGE of DBs is 18+ mph, as the wheels are turning fast enough to generate amperage/power. Typically,the heavier engines and 6 axle trucks provide the best db adhesion and effect. All BN and Santa FE Geeps 38's, 39's, etc. are equipped with DBs, but aren't too effective due to their weight and power, better than nothing..BTW..with the cost of fuel skyrocketing the use of DBs instead of air brakes when possible, is now the rule. Hope this helps.....Terry

[Anonymous]

Terry
Thanks for the reply. Yes it does help. I like to know how the customer feels about the product.
Don Luttrell, EMD

[Anonymous]

Wow!!...In golf that's called sandbagging a guy. Here I went thru this big ol'routine..BTW, where were you guys when The Krebster bought all those GEs???!!
In 1969, as a cub engineer and fireman on the UP, I remember standing on the platform at Laramie,WY, hand the eng'r (the best I ever worked for, the orders addressed to the UP 3625. He looked at me and said, Terry that SD 45 is the finest engine ever built. The Crank problems would come later. This coming from a man who ran every steam and deisel the UP had to that time. In my book, nothing's really changed. There's feedback!!

[PaulWWoodring]

For Don Luttrell;
GE AC6000's really have powerful DB, sometimes too much for a light train. Downside is a tremendous low speed vibration problem on starting and stopping. One thing that was not mentioned by the others is that 23 mph is the optimum speed for maximum braking power in dynamic. Why does CSX keep going back to GE for their newest power, is it strickly for fuel consumption? Also, is anybody going to make a medium hp 4 axle unit again for shortline/branchline use. The 38's and 40's aren't getting any younger! (A CSX engineer)

[Anonymous]

Don, as far as GE and EMD are concerned, they are basically dedicated to 6-axle, high horsepower road locomotives. There are so many older motors around, they are leaving 4-axle business to loco rebuilders and lessors. I dont recall specifically, but I thought EMD offered some sort of new 4-axle motors a couple of years ago. I would have to do a little research and reading to refresh my memory.