Wind Resistance

[RME]

Paul of Covington

Anyway, a few days ago I saw on the Rochelle cam a case where the arrowedge contributed negatively to streamlining. Behind the locomotives was a single container with an arrowedge, but it was followed by about ten more single-stacks, then a bunch of doubles-stacks. If anything, the arrowedge should have been on the last single before the doubles, but then the cost of the extra time to move it would probably make it not worthwhile.

Perhaps the train was to get additional loads in those 'empty slots' before traveling a long distance, or at higher speed, or in windier areas.

Drag on the train is, of course, higher with an Arrowedge that does not have a container immediately behind it -- same basic reasoning as for a bobtail with one of those roof deflectors.  (But the additional drag is likely as minuscule compared to overall train resistance as the 'streamlining' advantage was in the first place.)

It might be interesting to see whether special spreaders or attention are needed to move an Arrowedge vs. a standard top-lock container.  I think a smart designer would rig the thing with collapsible 'legs' in front that would be raised to engage a standard crane spreader frame.  If not ... Euclid!  Here's another chance to get a major patent improvement!

[Paul of Covington]

RME

Yes, there have been schemes to fill the gap between units with something that is more 'aerodynamic', including one using special 20' units on articulated mounts between 'coupler' ends of multiple-well units.

   Hey, I had been thinking about that.

   Anyway, a few days ago I saw on the Rochelle cam a case where the arrowedge contributed negatively to streamlining.   Behind the locomotives was a single container with an arrowedge, but it was followed by about ten more single-stacks, then a bunch of doubles-stacks.   If anything, the arrowedge should have been on the last single before the doubles, but then the cost of the extra time to move it would probably make it not worthwhile.   By the way, I'm skeptical about the value of the thing, too.   (Not that I'm qualified to judge, though.)

[RME]

In my considered opinion, Arrowedge is a scam.  The quartering drag between stacks is enormously greater than the reduction (not elimination) of the frontal resistance of the first container; there's a reason long forebodies on locomotives weren't and aren't successful requirements for freight speeds.  (If you were talking Super C speed and better, there begins to be an advantage for nonrevenue specially-handled streamlining ... but I suspect you could get far better results out of something like Airtabs on the trailing container edges.

I don't want to say Arrowedge is a sweetheart deal but I think there is some special, dare I say McKeen-like relationship there.

You have very astutely pointed out that empties for 'better continuity' might make sense, as any gap in the stack introduces most of the frontal resistance an Arrowedge device supposedly overcomes. I have not seen a calculation of the added train resistance due to container tare weight (which is surprisingly little) vs. the measured air resistance.

Yes, there have been schemes to fill the gap between units with something that is more 'aerodynamic', including one using special 20' units on articulated mounts between 'coupler' ends of multiple-well units.

[Dakguy201]

This morning I saw a UP container train westbound at Rochelle.  It was on the  track 1, so it could not have been destined for Global III.  It had one of the Arrowedge devices on the first car.

I wasn't counting, but the train had to be at least 150 cars.  The vast majority were double stacks.  However, at six or so places in the train, there was just one car that was single stack.  

I am wondering that since the railroad finds the efficiency of the Arrowedge sufficient to surrender a revenue producing place on the train, would it also make sense to ship an empty container on any car that would otherwise be a single stack?