Who will be the first

[wabash1]

The question is, If you was blind folded and was seated at the control stand and your hand was placed on either the throttle or the dynamic how would you know the differance by holding onto just that handle?

Engineers run trains everyday and never give this a thought. so lets see who the first is to answer this one right. The answer will not be the dynamic is on top because you will only have your hand on that handle only it could be either. So lets see who is paying attention.

[eastcoast]

I'll give it a shot.
The throttle is shaped like a " T " handle while the dynamic is not.
All I can refer to is MS TRAINSIM, so hoping I am close?????

[CShaveRR]

I believe that both levers are elliptical in shape...but white the throttle ellipse is horizontally oriented, the d/b is vertically oriented. They would definitely feel different.

CSXT has an SD40-2 that might be an exception...

[Anonymous]

Eastcoast, the automatic is shaped like a T (on desk type engineer consoles). Wabash, one handed on the desk type stand..........they are the same handle. I forgot that you hail from the NS and y'all use the AAR style control stand, so enlighten me.
Ken

[Anonymous]

Wabash, is there distinctly different feel or "vibe" from the different controls? As it relates to their function. What I mean is, does the throttle hum or vibrate while the dynamic does not?

Getting curious about the answer.

Jeff

[edblysard]

Throttle handle is round, and its range of motion, or "sweep" is smaller than the Dynamic brake, which has a oval shaped handle, and a longer range of travel or sweep.
Most throttles are in the upper half of the control stand, on a standard control, with the brake lower down.
So, how close?
Ed
And where did you leave the mirror again?

[Jackflash]

One moves front to back the other back to front, one has notches the other
travels smooth without notches, in addition to what has already been said
concerning the orientation of the handles. jackflash

[Mookie]

QUOTE: Originally posted by edblysard

Throttle handle is round, and its range of motion, or "sweep" is smaller than the Dynamic brake, which has a oval shaped handle, and a longer range of travel or sweep.
Most throttles are in the upper half of the control stand, on a standard control, with the brake lower down.
So, how close?
Ed
And where did you leave the mirror again?

I am beginning to think the mirror is with the keys used to start the engine!

Mookie

[zardoz]

On the first series (6801-6815) of SD40-2s that the CNW received back in '73, the throttle AND dynamic brake used the same handle; what changed function was a small "changeover" lever that was placed just above the throttle.

This handle could only be moved if the throttle was in 'idle', and the reverser was in forward or reverse. The changeover lever had only two operations: push forward to engage throttle, pull back to engage the dynamics.

[jrw249]

All good points, but the question states just holding the handle , not moving it.

[wabash1]

Ok i was called to work sorry to leave you all hanging. even though you all have good insight and all things are generally right the key here was just having your hand on one handle. and Cshaverr is right on. the AAR control stand with seperate dynamic and thorttle the shape of the throttle handle is horizontal while the dynamic is vertical.

there is no vibration differance to either handle that i know of or ever felt. Iron ken we have the desk top type of stands and when i did this that was the fartherst thing in my mind. I dont like desk top myself. but what you was describing was the automatic brake not dynamic.

Jack fla***his is the other answer i exspected alot but as i stated i was looking for feel not motion. I have often wondered why they do work that way . zardoz yes this is the other style of control stand Non-aar that i never gave thought to when i come up with this. I have learned something from this also when thinking of a question remeber to think of the other things that are true but not what i was looking for. thanks for everyones contributions.

Now For ED I left the mirror in the bathroom for you. i didnt want you nowhere near the window. when you aint paying attention that is when accidents happen.at least on a loco bathroom you wont get hurt to bad.

[Anonymous]

No, Wabash. I didn't make myself clear. I was clarifying for annother poster that the T handle he was describing was the Auto. What I was driving at was that on the desk type stand the throttle and dynamic are the same lever. I was tired when I posted that one and tend to express myself crappy when I am tired.
Ken

[edblysard]

Wow!
Still looking out for the rock pounders!
What a guy!
Stay frosty,
Ed[:D]

[yellowducky]

Now my question is, does everyone know what or how dynamic brakes work? When I hired on the B&O back when, an engineer asked me, to see if I knew which way is up I guess. He was surprised I knew, my being just hired. Maybe someone wants to tell about how they work? (Was this covered on that other thread where Mookie and was it Nora kept asking questions? I'm only to page 12 and haven't read any past that. Must say I learned a bit from that thread.) FDM[:)]

[Modelcar]

....In simple terms....Current being generated by traction motors [when called into action] is fed to resistance grids causing load on traction motors and causing them to act as brakes....Excess heat generated and fed into the resistance grid is dissipated to atmosphere via strong cooling fans. Am I close...

[yellowducky]

Sounds good, but I,m no expert. Thought someone might wonder, but not dare to ask the basic question. Just trying to be help. FDM

[jchnhtfd]

QUOTE: Originally posted by Modelcar

....In simple terms....Current being generated by traction motors [when called into action] is fed to resistance grids causing load on traction motors and causing them to act as brakes....Excess heat generated and fed into the resistance grid is dissipated to atmosphere via strong cooling fans. Am I close...

Close enough for guv'mint work, anyway. [:)] Any electric motor will act as a generator if it's being spun by something else and there is a little current to the field windings (it's a little messier with AC, but same principal). You can control the current generated by controlling the field current -- that's what the dynamic brake control handle really does. On diesels, there's nothing useful to do with the current generated, so it goes to those resistance grids. On some (but by no means all) electric motors -- think Milwaukee and Great Northern in the Rocky Mountains -- the current was fed back into the catenary to help other guys going up the mountain. That's regenerative braking, but it's the same principle.

And if you shut down the prime mover on a diesel, you lose the field current to the traction motors, and you lose the dynamics. [:(] I seem to recall this resulted in a rather spectacular runaway some years back out in California, but I don't recall the details...

[edblysard]

Correct me if I am wrong, but isnt the term Back EMF(Elector Magnetic Field)?
Could the same results be obtained by switching the leads on a DC motor?
I have seen the resistance grids, they really do look like the material your electric stove top uses, just bigger in all aspects.
Stay Frosty,
Ed

[jchnhtfd]

QUOTE: Originally posted by edblysard

Correct me if I am wrong, but isnt the term Back EMF(Elector Magnetic Field)?
Could the same results be obtained by switching the leads on a DC motor?
I have seen the resistance grids, they really do look like the material your electric stove top uses, just bigger in all aspects.
Stay Frosty,
Ed

No, you're not wrong... really. All electric motors when in operation create a back EMF which opposes the voltage and current being supplied to the motor by, in a diesel engine, the prime mover's generator. When the combination of the power demanded from the motor (for instance, to start our hypothetical train!) and the power represented by the back EMF equals the power which the prime mover is allowed to supply (by the engineer), the system is in equilibrium -- if less (i.e. the train is moving slower) the thing will speed up; if more (i.e. starting up a grade) the thing will slow down. Dynamic/regenerative braking is a little different; the prime mover supplies a field current to the motor (known as the excitation current -- in regen, the motor is self-exciting) and the armature (we're talking DC here -- I told you AC was messier) leads are connected to the resistance grid, instead of to the prime mover. (slightly simplified here... for the backshop guys with the circuit diagrams and manuals, I apologise!)

Reversing the leads to the armature only of the motor will reverse the direction the motor will try to turn in. Which is how you back up. If the motor is being forced to turn in one direction by the train, though, and you reverse the leads (shift the reverser), any one of several things can happen; very few of them good. The best you can hope for is that the armature circuit breakers will open before the motor windings fry.

[CSSHEGEWISCH]

Electric locomotives equipped with rectifiers had to have dynamic braking. Motor-generator sets (GN) or straight AC or straight DC electrics had regenerative braking.

[Anonymous]

I guess that Wabash1's initial question should have stated what genre of locomotives he was talking about. Many of the modern ones use a combined power handle, which is throttle from neutral toward you and dynamic brake from neureal away from you. At least that is how the GE 9-44CW and later are set up; I assume other makes are the same for the sake of conformity.

Rich Witt

Rich Witt

[yellowducky]

I can wire my house circuits, model train layouts (AC and DC), etc., but:
How is direction of rotation changed on an AC motor? Actually the more I think about motors, the less I think I know. Anybody have a primer on electric motors? If I understood how they work better, I could most likely answer my own question. Come to think of it, we had a couple of games and books on electricity.

Maybe I should just ask a simple question here.
Concerning dynamic brakes: At what ground speed do they become ineffective? Does this speed vary significantly between AC and DC traction motors? FDM

[Modelcar]

....Sounds like an article on dynamic brakes in TRAINS would be a good idea...or am I half remembering it's already been done...How about it Mark...?

[Modelcar]

....Anyone remember if in fact TRAINS did do an article on dynamic brake action and how it is done, etc....

[Jackflash]

Changing the direction of a AC traction motor is done by changing the
phase rotation of the three phase power, feeding the motor with
an ABC order will result in counter clockwise direction, feeding the
motors with an BCA or ACB order will result in a clockwise direction.
jackflash