DD51 push-pull

[hans-diesel]

Hi all,

 

I see many photos and videos on the internet with trains with 2 DD51's, one in front of the train and one on the tail. I see this both on some passenger trains and also on some (container) freight trains.

 

With the passenger trains I have the idea that the extra power is not needed. And that two DD51's makes going back at the terminus faster. Thus the DD51 at the tail will not be powered up. Is this correct?

 

With a freight train I find it strange to take some extra weight (the second DD51) with you. And I expect that fast going back is not such an issue. So, I expect that the DD51 at the back is also powered up and pushing the train. Is this correct? And if the train is powered by 2 DD51's, how is the second DD51 controlled? A second engineer? Or?

 

Thanks in advance, Hans

Edited November 5, 2015 by hans-diesel

[cteno4]

Some answers in these posts with great videos.

 

http://www.jnsforum.com/community/topic/3468-sekihoku-line-documentary-dd51-pushpull/

 

http://www.jnsforum.com/community/topic/2222-high-speed-freight/

 

Jeff

Edited November 6, 2015 by cteno4

[bikkuri bahn]

here is that NHK broadcast of the DD51 push-pull onion trains, as the original uploads are now gone:

Edited November 6, 2015 by bikkuri bahn

[SuRoNeFu 25-501]

here is that NHK broadcast of the DD51 push-pull onion trains, as the original uploads are now gone:

However, the usage of DD51 on the "onion train" (as called by many of people in Hokkaido, as well as the railfans) has been discontinued from 2013, due to the locomotive that suffered aging problem (that's it, they have been largely replaced by DF200 from the start of 2000s)...

[katoftw]

Most DD51s have been replaced.

[kvp]

http://livedoor.blogimg.jp/koukendaisuki/imgs/d/4/d43a76f5-s.jpg

http://www.youtube.com/watch?v=t8ldInZ3JPQ

Does anyone have more info?

[SuRoNeFu 25-501]

http://livedoor.blogimg.jp/koukendaisuki/imgs/d/4/d43a76f5-s.jpg

http://www.youtube.com/watch?v=t8ldInZ3JPQ

Does anyone have more info?

It seems that they did the same with DF200s.

 

One of the reason why JR Freight uses push-pull on Sekihoku Line's freight trains is because at Shin-Asahikawa and Engaru the locomotive is required to perform run-around operation (which means that the locomotive must move from one end to the other end, if the locomotive is present in only the front end of the train). This work requires lots of time for completing the process. But with push-pull system, it only needs to change the direction without performing run-around process, which saves enough time...

Edited November 7, 2015 by SuRoNeFu 25-501

[kvp]

Thanks!

[hans-diesel]

Many thanks for the very clear answers. I had seen the video before, but without the explanation in the other topic, it didn't inform me that much. So, now it is very clear that with freight trains both locomotives provide traction. When there was no direction changing needed, would they have put both locomotives at the front of the train?

 

And, how about the passenger trains with a locomotives at the front and at the back?

Edited November 6, 2015 by hans-diesel

[kvp]

When there was no direction changing needed, would they have put both locomotives at the front of the train?

I think they did excactly that with some sleeper trains. With no cars between them they could be run with MU control (if the locomotives are equipped for it) without equipping the cars with MU through cables and there is no need for the radio communication seen on the linked video. Below is the cassiopeia with two DD51-s:

Edited November 6, 2015 by kvp

[SuRoNeFu 25-501]

how about the passenger trains with a locomotives at the front and at the back?

It is likely that almost no diesel-hauled passenger trains are using this method (even from JNR days), since most of loco-hauled passenger trains has been already replaced by DMU or even EMU, because loco-hauled passenger trains are considered as very slow. This comes from the fact that train timetable in Japan becomes tighter and tighter from time to time, so distributed power system that used by DMU and EMU are more suitable for tighter timetable than the centralized power system (as found on loco-hauled passenger trains)...

[katoftw]

I noticed after watching a few youtube videos of this line that it has very sharp turns and a lot of S-bends.  Could using 2 locos front and rear also be for reducing load effect on couplers and bogies due to the tight radi curves on heavier freight services?

Edited November 7, 2015 by katoftw

[Sacto1985]

I believe this type of operation for freight trains is still common in Hokkaido, where most of the mainline operations are not electrified. 

[SuRoNeFu 25-501]

I noticed after watching a few youtube videos of this line that it has very sharp turns and a lot of S-bends.  Could using 2 locos front and rear also be for reducing load effect on couplers and bogies due to the tight radi curves on heavier freight services?

Possibly. Sekihoku Line is notorious for its sharp curves, as well as sharp gradients (of course it is not as crazy as Usui Pass), so it is something reasonable for using push-pull system on heavy freight trains that running over the line (along with the elimination of needs for run-around at Shin-Asahikawa and Engaru).

[yakumo381]

Tried running freight on my Niihama layout with a Kato DD51 and front and rear. Not a good result as even though running them in tandem is fine, running them some distance apart made them run at slightly different speeds resulting in a pile up...

[Claude_Dreyfus]

Tried running freight on my Niihama layout with a Kato DD51 and front and rear. Not a good result as even though running them in tandem is fine, running them some distance apart made them run at slightly different speeds resulting in a pile up...

 

I have tried top and tailing DD51s on Kanjiyama (no run-round loop) - with much the same result...particularly when using the very light Tomix Hoki800 hoppers.

[katoftw]

You'd really have to find a dead engine and gut it out and make it a trailer if you wanted to go a similar prototypical push-pull consist.

Edited November 8, 2015 by katoftw

[kvp]

Or just use DCC and apply different throttle settings to even out the forces or use heavier cars, or try it with locomotives without traction tires, so they could slip in case of a power difference.

[katoftw]

Yes kvp, they are all very obvious possible options.  And also not suitable for varying reasons.  And most likely tried which is why the discussion turned the way it did.

[kvp]

 

 And most likely tried which is why the discussion turned the way it did.

One thing i constantly get reminded of is to never assume anything and what i mentioned is actually what you can see in the video.

 

For the DD51-s, it's possible to replace the traction tired wheels with ones that doesn't have any and you can put weight under the ballast cars or even into them under insertable loads. It could work as long as none of the locomotives stalls.

Edited November 9, 2015 by kvp

[Claude_Dreyfus]

You'd really have to find a dead engine and gut it out and make it a trailer if you wanted to go a similar prototypical push-pull consist.

Indeed...perhaps the best option here. Some manufacturers do provide dummy locomotives, but this is not the most cost-effective approach as dummy locos can still be pricy. Better to strip out a dead example for this...I am keeping a half eye out for one.