Inside an operating F3 diesel...

[JCitron]

http://youtu.be/Lt4J9SZBRvU

Here's a tour of an operating F3 diesel. The engineer explains the air brakes, throttle, and a bit about the diesel engine parts inside.

John

 

[jacksonbarno]

I drove an F7 once. In Portola Ca, there is a museum there that has a drive a locomotive program, and you can rent one of nine locomotives there to drive for about an hour. It's an amazing experience.

 

[JCitron]

That sounds cool. What did you think of the engineer dumping the air like that when he pushed down on the brake handle? That's something that should be modeling in the diesel cabs we have...

John

 

[jacksonbarno]

Yeah, I agree. I thought that feature was only inf first gen cabs though, because that feature isn't in later EMD and GE diesels. Maybe if somebody made a shiny new F unit cab or a GP cab, it could be put in in some way.

 

[BN1970]

That sounds cool. What did you think of the engineer dumping the air like that when he pushed down on the brake handle? That's something that should be modeling in the diesel cabs we have...

John

Actually, John, (now I'm revealing my age, LOL), when you do a reduction (say 10lbs) with the automatic brake valve the engine brakes will apply even though your independent brake handle is in release. Doing what he did ( we call that 'bailing off' the independent) releases the remaining pressure in the engine brakes to zero. When I ran F3's and F7's (these braking systems were also found in GP's and SD's) was to hold down the independent brake handle in the release position while making your reduction with the automatic brake handle. This kept the engine brakes 'bailed off' so they would not apply during the reduction.

Well, time to get back to my rocking chair for a nap!

 

[JCitron]

Actually, John, (now I'm revealing my age, LOL), when you do a reduction (say 10lbs) with the automatic brake valve the engine brakes will apply even though your independent brake handle is in release. Doing what he did ( we call that 'bailing off' the independent) releases the remaining pressure in the engine brakes to zero. When I ran F3's and F7's (these braking systems were also found in GP's and SD's) was to hold down the independent brake handle in the release position while making your reduction with the automatic brake handle. This kept the engine brakes 'bailed off' so they would not apply during the reduction.

Well, time to get back to my rocking chair for a nap!

Never mind the rocking chair this is totally excellent information that's worth sharing!

That makes sense, I think. Let's see if I've got this figured out. He's basically setting a valve at a set level to hold the air there rather than completely drain the reservoir all at once. By doing this he can then apply a small amount of brake pressure rather than a full application which can cause the freight cars to jostle into each other.

John

 

[norfolksouthern37]

Yeah, I agree. I thought that feature was only inf first gen cabs though, because that feature isn't in later EMD and GE diesels. Maybe if somebody made a shiny new F unit cab or a GP cab, it could be put in in some way.

No this is still in locomotives today and has been in every braking system I know of. It's called bailing off as described above.

Some examples of modern US locomotive bail off controls: the depress similar to above(horizontal), or they have a button on the handle (desktop), or you push the handle to the side (desktop), or pull up on a ring under the handle (desktop).

Never mind the rocking chair this is totally excellent information that's worth sharing!

That makes sense, I think. Let's see if I've got this figured out. He's basically setting a valve at a set level to hold the air there rather than completely drain the reservoir all at once. By doing this he can then apply a small amount of brake pressure rather than a full application which can cause the freight cars to jostle into each other.

John

He bails off to cause a release of any automatic brake application existing on the locomotive. Bailing off causes the cars to slow the train from the rear. This helps maintain an acceptable level of slack/buff in the couplings.

 

[JCitron]

Thank you for the explanation, Justin. That makes sense to me now.

A question though...

Wouldn't applying air from behind cause coupler breakage since the cars slowing down behind the rest of the train moving forward cause a strain on the couplers?

John

 

[norfolksouthern37]

Well I realize the comment is very general and doesn't apply to every situation. I edited my post so it wasn't too confusing. You need different levels of each brake of different situations of stopping (uphill, downhill) and even different considerations if your locomotive has dynamic brakes. The key here is to maintain control of the train with the locomotive(s) and not allow the cars to push or pull too much. This is the reason for the independent brake to begin with. having the ability to bail off from a train brake application is just an extension of that. if you didn't have the independent control of the locomotive brakes, the locomotives would behave as any of the rest of the train and this is usually not desirable if you wish to remain in control starting or stopping.

BTW, the bail-off is only recently modeled in Trainz. I don't know of cabs that support it directly, but there is a keypress now.