mixing dynamic/non-dynamic brake equipped locos

[nkalanaga]

Questions for members who've run, or worked with, prototype locomotives:

I have three EMD diesels, to be run together, a GP-9 and a GP-18, each with dynamic brakes, and a GP-7, without DB.  Can this consist be set up so that the dynamics are usable, even though one unit doesn't have them?

If it can, how would it be done?  Would the GP-7 have to be the trailing unit, or would it work  with it in the middle, as long as the MU cables were connected?  Obviously it couldn't be the lead unit - no DB controls.

I looked in three prototype references and couldn't find anything useful.  Plenty on running with a DB-equipped unit which has had the DB disabled, for whatever reason, but nothing on mixing DB and non-DB units.

Thank you!

References: 
GP-38 operator's manual
BN "Air Brake and Train Handling" manual
BN Portland Region Special Instructions from 1970

[sd45elect2000]

The non dynamic brake equipped engine cannot be the lead engine if you want to use dynamic brakes. The two dynamic engine need to be adjacent to each other.

The non dynamic would be the trailing unit.

[nkalanaga]

Thank you!  That's what I suspected, but didn't know if the control signals could be passed through the non-DB unit. 

Fortunately I run the set on a "turn", and the turn-around point has a wye, so that's not an issue.

If I had another undecorated GP-9 with DBs, I'd solve the problem with some paint!

[Hawghead]

It's been a long time since I had a consist that had an engine that didn't have any dynamic brakes at all, but I'm pretty sure it doesn't matter where the non-db engine is in the consist other than it can't be the leader.

Scott

[narrowminded]

I find this interesting but it also makes me ask what happens that makes it matter? 

[sd45elect2000]

It's been a long time since I had a consist that had an engine that didn't have any dynamic brakes at all, but I'm pretty sure it doesn't matter where the non-db engine is in the consist other than it can't be the leader.

Scott

On newer engines it usually doesn't matter but on old GP-7 engines the three MU wires (17,21,24 ) wires are often not installed. In addition, older engines are sometimes set up for field loop so a non dynamic engine doesn't have the field loop wires.

On engines newer than a GP 30 it shouldn't matter where in the consist non dynamic engines end up.

[Missaberoad]

I find this interesting but it also makes me ask what happens that makes it matter?

The unit without dynamic brakes will be missing the dynamic brake handle (or selector lever on older units)

We have this issue with our ex Soo 4400s...

[nkalanaga]

Right - it can't lead, if one wants the brakes to work, as there's no controls for them. 

Mine are all BN units, the GP-7 is ex-CB&Q, the other two have Potential, not Field Loop, according to my BN Locomotive book.  If all that is needed is three wires between the MU sockets, a shop should be able to install those.   Maybe I won't have to turn them every run after all!

[Hawghead]

sd45elect2000,

I'm sure you know more about what makes the dynamics work more than I.  I'm sure the only engines I've ever had in one of my consists that didn't have dynamic brakes would have been an SD-40 or GP-38.

The way I understand it, is back in the day not having a leader with dynamic braking wasn't really an issue as the engineer would just stretch brake the train.  Talking to the old heads when I was firing, they really didn't trust the dynamics anyway.  They weren't very effective and it was not unheard of them catching on fire, so engineers would more often than not just stretch brake their trains even if the were equipped with dynamic brakes.

Scott

[nkalanaga]

I know the NP, at least in the early diesel years, didn't trust them.  But, then, the NP didn't trust diesels, considering them "overgrown (highway) trucks", and "too complicated".

The GN and MILW, on the other hand, loved them.  They'd had long experience with regenerative braking on their electrics, and thought of diesels as "wireless electrics".   

[sd45elect2000]

I know the NP, at least in the early diesel years, didn't trust them.  But, then, the NP didn't trust diesels, considering them "overgrown (highway) trucks", and "too complicated".

The GN and MILW, on the other hand, loved them.  They'd had long experience with regenerative braking on their electrics and thought of diesels as "wireless electrics".

The Rock Island years ago had a couple of high-profile derailments attributed to dynamic brakes. From the stories it was clear that there was insufficient training in their use. Many railroads had and still have restrictions placed on certain territories because of track issues. using dynamic brakes requires well anchored track with at least 18 inches of ballast shoulder. Stretch braking is useful but it uses much more fuel than dynamic braking. Dynamic braking is safer than cycle braking. With a non-dynamic leader, the choice is clear as to the method used. My personal choice would be to change up the consist and use dynamic brakes.

[pedro]

There’s a whole new generation(s) of engineers who would struggle to get a train over the road without dynamics. Stretch braking on BNSF is generally frowned upon, and cannot exceed throttle 4 without a call from the authorities. Coasting, throttle manipulation, dynamics are the order of the day for us. In temps <0 they don’t want us using the air at all unless absolutely necessary, and yes that’s in writing! All this results in inexperienced engineers that are afraid to touch the air. When I have students I cut the dynos out and make them.

I haven’t seen anything non-dynamic on BNSF since the last of the SD7 switch engines were retired. Maybe there’s still some n/d odds and ends lurking around in yards, but certainly not any in road service. (On BNSF)

Derailments caused by excessive dynamic braking are still a thing, maybe more so now. We are limited to the number of dynos we can have cut in on the head end, generally 28 “equivalent dynamic axles” unless it’s a solid loaded unit train, then you can have up to 32. The modern 6-axle power is all rated at 8 or more “dynamic axles” each. If I have 4 units on the head end of an intermodal train I’ll have to cut one of the dynos out to stay below the 28 axle limit.

[sd45elect2000]

There’s a whole new generation(s) of engineers who would struggle to get a train over the road without dynamics. Stretch braking on BNSF is generally frowned upon, and cannot exceed throttle 4 without a call from the authorities. Coasting, throttle manipulation, dynamics are the order of the day for us. In temps <0 they don’t want us using the air at all unless absolutely necessary, and yes that’s in writing! All this results in inexperienced engineers that are afraid to touch the air. When I have students I cut the dynos out and make them.

I haven’t seen anything non-dynamic on BNSF since the last of the SD7 switch engines were retired. Maybe there’s still some n/d odds and ends lurking around in yards, but certainly not any in road service. (On BNSF)

Derailments caused by excessive dynamic braking are still a thing, maybe more so now. We are limited to the number of dynos we can have cut in on the head end, generally 28 “equivalent dynamic axles” unless it’s a solid loaded unit train, then you can have up to 32. The modern 6-axle power is all rated at 8 or more “dynamic axles” each. If I have 4 units on the head end of an intermodal train I’ll have to cut one of the dynos out to stay below the 28 axle limit.

I can’t imagine coming into restricted speed without hot brake shoes when it’s below zero, the rules change a bit as temps fall. Conditioning the brake shoes needs to be a priority when it’s cold and snowing . I use any opportunity to use the automatic to that end . Although I prefer dynamics I also want the comfort of having warm shoes on the train. I have no issue dragging a 10 lb set downhill in restricted speed.

[John]

This is starting to become a great lesson on train braking -- thanks to all the pro's for chiming in .. would you please explain "stretch braking" for this foamer?

[sd45elect2000]

This is starting to become a great lesson on train braking -- thanks to all the pro's for chiming in .. would you please explain "stretch braking" for this foamer?

Stretch braking is essentially pulling the train with the brakes set with the slack stretched. it's a good way to have good control over train speed as all you need to do to stop is shut off the power with train stretched. Bunched is the other slack condition bunched is when braking force is applied to the head end of the train causing the trains slack to bunch to the head end.