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...and while I'm at it: You've another 47 seconds to finish up and get back here before I gotta throw her in reverse...

Acting Navvy on the Marube @63kph and ~4km distance from a forthcoming train

Welcome to a future. Mankind has brought doom upon themselves, their cities have been flattened by war and weather, and most of the northern hemisphere is radioactive badlands.

After having helped their planet to cool down a tad, humans start emerging from their underground retreats to once again make the surface theirs.

Patching and recommissioning pre-war trains engines they reconnect and spread along the old rail infrastructure. Settling the, now temperate, equatorial regions and scouring the desolate northern ones for technology.

Due to the vast expanse & unregulated nature of these rail-networks, and the size, state & character of these post-war communities, there is no single organisation or group that could realistically control more than a small section of the network - huge parts of it are thus wild.

As a result of that, most trains don't go above speeds at which they can safely break, if there is something wrong with the tracks or an oncoming train. Spoorcaneers (rail-pirates) actively make use of these circumstances by keeping their trains short and quick in order to catch-up with booty or even overtake it.

Pirate trains are usually made up of a single engine and a multi-purpose boxcar. Some compositions feature another boxcar or a flatcar offering additional space for e.g. gun emplacements or expected special cargo. There are seldom trains with two ore more engines, as a second engine is of much more use driving a second, independent, train instead.

When boarding, the more adventurous pirates pull their trains up in parallel to their bounty - akin to the buccaneers of old. This provides more area to transfer valuables between cars and even allows to transfer bigger things.

========SPOORCANEERS->>=====================================<<-ONCOMING-TRAIN=============
======VERY-RICH-BOUNTY-TRAIN->>===========================================================

Just in case. The above diagram is obviously not to scale..

Due to the nature of their business though, pirates need to be able to turn on their heels at any moment. Be that to escape the possible artillery of a train they preyed upon unsuccessfully, or to clear the tracks before an oncoming train smashes theirs to bits.

An example of the latter would be two trains moving towards each other, both at ~60kph. The pirate train can spot the oncoming train at ~4km distance (curvature, horizon). As soon as they can see the oncoming train they will have to think about reversing, yet they still need some time, give some ~30-45s, to clear their crew off the bounty train.

Q: How could a system be designed to allow reversing a train at high speed over such a short distance?

A good solution:

  • is sustainable, track infrastructure and trains suffer as little damage as possible
  • can turn quickly:
    • the less time between speed -> stop -> speed, the better
    • the less distance it takes between a full break back to starting speed, the better
  • does work for higher speeds, being able to do this at higher speeds means being able to prey on faster trains
  • makes use of as little engines as possible, engines are valuable and two independent trains are worth much more than one slightly faster train

This question is NOT about:

  • finding solutions to alternative situations; an example is given in the body, please do not start changing things to fit your idea
  • finding a workaround; switching tracks is a great idea, but it's not a solution to the issue at hand
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    $\begingroup$ You got train pirates? You need a Sail Train! ![Sail train](i.stack.imgur.com/PAdGz.jpg) reflectionsonfilmandtelevision.blogspot.com/2010/11/… This fine sail train is from Spacehunter: Adventures in the Forbidden Zone. It is as good a post-apocalyptic sail train as you will find on the web, I think. But I have issues with those sails, which look like some fixed Viking apparatus. No, you want clipper ship type sails on your trains to take advantage of the winds blowing over the desolate plains. Your track $\endgroup$ – Willk Mar 27 '18 at 19:12
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    $\begingroup$ Put on hold by user request to allow time to provide clarification. $\endgroup$ – James Mar 28 '18 at 18:44
  • $\begingroup$ I need some clarification. What is your miniumum acceptable distance between the spoorcaneer (SC) and the oncoming train (OT) at the moment the SC matches its velocity? What is the exact time needed to evacuate the target? Are the tracks made from today's alloyed steel? Or is it something more futuristic? (need stats). I'm going to assume the wheels are made from the same material unless you say otherwise. What are my tech/resource limitations? Can I use rockets? Electro magnets? How much harm may I bring against the SC crew and SC itself? And what's the SC mass? $\endgroup$ – JBH Jun 19 '18 at 5:56
  • $\begingroup$ (*continued*) Can I assume the OT's velocity will remain constant, or is it likely to try and brake? If it'll try to brake, I need either (conveniently) it's braking characteristics or at least its mass and velocity. Ah, I'll need its velocity in any case. (You know that if the velocity is equiv. to the SC's 63kph that a 4km sighting means the SC has 2 minutes less the evac time (max 45 sec leaving only 1.25 minutes) to slow, reverse, and accelerate. That's 1,050 m/s in 37.5 seconds or 28 m/s^2 or 2.85G (avg, best case). That's a hair uncomfortable....) $\endgroup$ – JBH Jun 19 '18 at 6:06
  • $\begingroup$ (*continued*) And just because I'm having some fun with this... here's a link with some passenger vehicle braking deceleration numbers that could represent "comfortable deceleration." The max is about 1G. Suggesting that at 3G you're peeling your eyeball off the windscreen. :-) Yeah! Baby! It's the pirate's life for me! (of course, my numbers could be completely wrong. If so, I apologize.) $\endgroup$ – JBH Jun 19 '18 at 6:16
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So, to get a couple comments out of the way first, I'm not really sure why you would want to rob the train from another train (except for the rule of cool), especially since they are traveling so slow. I can totally see there being a Mad Max style thing where a racing vehicle drives up next to the train, someone jumps out of the vehicle onto the train, and either takes the engine, or decouples some cars so they can be looted. Alternately they could also just come up behind them with a train on the same track, have someone jump forward to the target train, and take it over, so they don't have to worry about oncoming trains.

But those are both just comments, and don't answer the question.

So part of the problem is that freight trains are not meant to be stopped and started or reversed quickly. It's just not their purpose.

They need to be able to have as little rolling resistance as possible, and with all that weight you potentially have miles of distance before you come to a complete stop.

But the pirate train needs to be able to get up to speed quickly, stop quickly, reverse quickly, and doesn't have to be big or heavy. So instead of a freight train, it could be a passenger train, which by definition need to be able to do all of those things.

They can even go from 80 kph to 0 in less than 20 seconds.

You strip out the seats, put some tie downs inside, gun emplacements on top, and it has everything you need.

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An Anchor

Or a modified arresting gear, to be precise. These systems are used regularly to stop 50,000 lbs/23,000 kg aircraft going 150 mph/240kph in less than 300 ft/100 m.

A scaled up version suitable for a locomotive and a boxcar could function like this:

  • opposing train is spotted

  • "anchors" are dropped into the ground by some device, possibly hydraulic in nature

  • arresting wire spools from the engine as it brings the locomotive to a halt (some slack should be necessary to prevent snapping the wire of giving the Spoorcaneers whiplash)

  • after locomotive and car are brought to a halt, the arresting gear can now be used a slingshot to launch the locomotive and car in the other direction

  • arresting wire and anchors are collected by the Spoorcaneers return passage, ready to be used for the next close call

Lighter and smaller locomotives would also be more beneficial in this setup since there is less weight and inertia working against the arresting system.

Faster speeds would be possible with more wire, stronger arresting system, etc.

Damage to track and train in virtually null, since breaking occurs independent of both.

Could lead to some unfortunate accidents where the wire breaks, or close calls where an infamous Spoorcaneer survived with only one wire. Might also be the origin of the saying "It came down to the wire", though some pre-war records disagree.

Or a Bunch of Wheels

If you're looking for a more grounded option, I would suggest you just add more wheels to the engine and car. The crucial part that makes railroads such effective at mass transportation is how little rolling resistance there is. An entire, 50+ car train may have no more contact with that ground than the surface area of a coffee table. If you're going to slow it down, you need to increase your contact with the ground. Adding a bunch of wheels does that.

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  • $\begingroup$ I am quite amazed by the idea of using arresting gears. While I was thinking about anchors at some point I discarded the idea because they'd likely tear up the ground and so forth, but by using wire to give the whole system slack you can even reuse the kinetic energy. Very cool!! $\endgroup$ – dot_Sp0T Mar 28 '18 at 11:30
  • $\begingroup$ I’ve got an image of steam cannons firing harpoons into the ground on either side of the track now. That is very cool. $\endgroup$ – Joe Bloggs Jun 19 '18 at 8:16
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How about rockets? Something akin to the JATO rockets the military uses on some aircraft (Wikipedia page). Have a couple of sets of those installed on the train, pointing in different directions, and you could (more) quickly stop/accelerate in either direction.

As an added bonus, if the oncoming train is a police train (or the like), you can just wait a little longer to fire off the rockets. Not only do you get stoped and reversed before crashing, but the rockets can blind/disorient/fry the oncoming train at the same time!

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  • $\begingroup$ A nice idea that minimises damage to train and tracks, plus features rockets. $\endgroup$ – Joe Bloggs Jun 19 '18 at 8:17

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