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Transportation Science

Scientists Discover How To Stop Luggage From Toppling On the Race Through the Airport (theguardian.com) 183

An anonymous reader quotes a report from The Guardian: Scientists have worked out why suitcases tend to to rock violently from one wheel to the other until they overturn on the race through the airport. This most pressing of modern mysteries was taken on by physicists in Paris, who devised a scale model of a two-wheeled suitcase rolling on a treadmill and backed up their observations with a pile of equations and references to holonomic restraints, finite perturbations and the morphing of bifurcation diagrams. Fortunately for non-physicists, the findings can be reduced to simpler terms. For the suitcase to rock it had to hit a bump or be struck in some other manner; the faster the suitcase was being pulled, the more minor the bump needed to set it off. So far, so obvious. But Sylvain Courrech du Pont wanted to know more. Why did a rocking suitcase swerve and make such violent movements that it might eventually topple over? After more treadmill tests and more equations, the answer popped up: because a suitcase's handle pulls from the middle and the wheels are at its sides, the suitcase swerves inwards whenever it tilts up on one wheel. If the rocking overcomes the dampening effect that happens when each wheel touches the ground again, the suitcase will keep on rocking or eventually flip over. In conclusion, the researchers discovered that "when a suitcase starts to rock out of control, the correct response is not to slow down but to pull it faster." The scientists have published their findings in the journal Proceedings of the Royal Society.
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Scientists Discover How To Stop Luggage From Toppling On the Race Through the Airport

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  • by chuckugly ( 2030942 ) on Thursday June 22, 2017 @11:42PM (#54672959)
    Or just get one that has 4 wheels and don't look like a dork
    • Re: (Score:3, Informative)

      by ad454 ( 325846 )

      actually I prefer two-wheeled suitcases, but they are nearly impossible to buy new.

      stores nowadays just sell four-wheeled.

      unfortunately four-wheeled suitcases suck over rough ground, especially over cobble stone sidewalks common in Europe, with their tiny plastic wheels that easily break.

      • by AmiMoJo ( 196126 )

        Why not just buy a 4 wheeled case and tilt it like a 2 wheeled one? Or are you saying that all 4 wheeled cases have small, weak wheels? That doesn't seem to be the case (no pun intended) when I buy luggage, and I don't get particularly expensive stuff.

        Or are you thinking 10cm+ diameter wheels?

        • Why not just buy a 4 wheeled case and tilt it like a 2 wheeled one? Or are you saying that all 4 wheeled cases have small, weak wheels? That doesn't seem to be the case (no pun intended) when I buy luggage, and I don't get particularly expensive stuff.

          Or are you thinking 10cm+ diameter wheels?

          I believe the OP of the whole thread is already off topic because it has nothing to do with TFA. TFA is talking about a study of how a luggage can be flipped over while being dragged (with 2-wheel). The reason is that the handle is in placed in the middle of the luggage. So using a 4-wheel as 2-wheel doesn't make any difference from what TFA stated if the handle is placed in the middle of the luggage (which is true to all luggages I've seen). In other words, TFA implies the design of handle placement is a f

      • I got a suitcase with two rollerblade wheels on each side, but they're just there to do double duty. Best roller suitcase I've seen yet, and it was like forty bucks at Ross in Vegas. I bought crap while I was there and needed more luggage space, turned out to be a happy accident.

      • actually I prefer two-wheeled suitcases, but they are nearly impossible to buy new.

        stores nowadays just sell four-wheeled.

        unfortunately four-wheeled suitcases suck over rough ground, especially over cobble stone sidewalks common in Europe, with their tiny plastic wheels that easily break.

        Agree. Those tiny swivel wheels on the four-wheelers aren't big enough to negotiate a lot of rough terrain, and for a carry-on size I have no need for more than two wheels. You can still find them, just bought two for my kids last month.

        Anyhow, glad to see the French are tackling societies' most vexing problems.

      • No way to lock 'em on a hill. But they win on smooth level ground.
    • Or just get one that has 4 wheels and don't look like a dork

      Most of the four-wheeled ones are designed also to be tipped forward and roll on two wheels. But, actually, I think they solve this problem even when on two wheels.

      To work in four-wheel mode, the wheels have to be on swiveling casters. When you tip them into two wheeled mode, the casters go into a restricted movement position, but they can still move a little. When you hit a bump, then, and one side bounces up, the caster on the other side can turn, allowing it to maintain a straight line rather than tipp

  • This is new? (Score:5, Interesting)

    by Solandri ( 704621 ) on Thursday June 22, 2017 @11:50PM (#54672983)
    People who tow trailers have known about this for decades [youtube.com].
    • Beat me to it.
    • No, when your trailer starts to rock, you are supposed to slow down, not slam on the gas.

    • After a few years you'll get boringly familiar with journalists misreporting familiar things in lurid terms. Media hacks usually know next to nothing about science - and a good headline is much more desirable than strict accuracy even when they do. Put in perspective: this was an undergraduate research project, such as just about every student who takes a degree will undertake at one point or another. Such things are about getting the students to practice and demonstrate their abilities to investigate a pr
    • Re:This is new? (Score:4, Interesting)

      by swillden ( 191260 ) <shawn-ds@willden.org> on Friday June 23, 2017 @09:12AM (#54674761) Homepage Journal

      People who tow trailers have known about this for decades [youtube.com].

      As demonstrated in that video, trailer sway isn't caused by rocking back and forth between the wheels causing swerving but by weight distribution away from the axle creating large yaw inertia. With suitcases, while packing the weight far from the wheels does make the rocking worse, it will still happen even with the weight packed close to them (low yaw inertia). So, we're mostly talking about different effects. As evidenced by the fact that if your trailer starts rocking you should ease off the throttle, not go faster.[1]

      Even if this were the same effect, there's a huge difference between merely knowing about a phenomenon and having some rules of thumb about how to handle it, derived from experience, and having a mathematical model and a computer simulation of the phenomenon. Having those opens up many more options for finding solutions.

      [1] In my experience, the very best thing to do is to use the brake controller to activate the trailer brakes and slow that way, assuming a trailer that has electric brakes. I've only experienced sway on one trailer that doesn't have brakes; my flatbed (no brakes) when I have the tractor loaded too far back and not enough weight on the tongue. Easing off the throttle calms it down. None of the other trailers I've had (boat, utility, ATV) have ever swayed.

      • A quick tap on the gas to pull it straight before letting off the gas to slow yourself (without braking, of course) is actually more effective. What you don't want to do, of course, is floor it and then maintain that speed, as the next event that triggers the swerve will be worse if you're going faster.
  • Move the handle (Score:5, Informative)

    by viperidaenz ( 2515578 ) on Thursday June 22, 2017 @11:53PM (#54672989)

    The handle is also on the same side as the wheels, so when you're pulling it along the weight is above the pivot point between the wheel still on the ground and your hand.
    If the handle was on the opposite side from the wheels the weight wouldn't be as high (it would be more in line with your hand and the wheel), so the suitcase would be more stable.

  • Just like trailers (Score:3, Insightful)

    by Sir Holo ( 531007 ) on Friday June 23, 2017 @12:02AM (#54673041)

    The same physical principal applies to two-wheeled trailers pulled by cars with a hitch.

    Have you ever seen someone driving down an interstate, two-wheeled U-Haul or similar trailer in tow behind their Honda Civic? I sure have. I back off, and watch while the driver tries various maneuvers. The trailer will start to swing side-to-side. Then it will start skipping from side-to-side. Then I get bored and pass... two lanes over. Never once has one of them simply decelerated and pulled over to the shoulder.

    • As I just posted below - before seeing your comment - those idiots need to hit the accelerator when the trailer starts swerving! Any other maneuver is bound to lead to a bad day.
      • by Sir Holo ( 531007 ) on Friday June 23, 2017 @12:33AM (#54673201)

        As I just posted below - before seeing your comment - those idiots need to hit the accelerator when the trailer starts swerving! Any other maneuver is bound to lead to a bad day.

        Speeding up does work.

        A second technique that works is to put the car in neutral, effectively decoupling the travel-direction forces transmitted through the hitch. With no more tugging it along, the trailer will settle down (this stops any more energy from being put into the trailer's motion, letting roll-resistance quench out the speed and oscillations). I have done this. Just decouple and coast.

        You are correct that hitting the brakes is the absolute worst thing that the driver can do.

        • by sconeu ( 64226 ) on Friday June 23, 2017 @12:43AM (#54673229) Homepage Journal

          I was about 10.... We were on the way home from a camping trip, and my mom was driving.

          Some asshole cut her off, and she instinctively hit the brake. My dad was yelling at her to hit the gas... to no avail. We jacknifed and flipped. That's stuck with me ever since. If your trailer is out of control, speed up.

          • by drinkypoo ( 153816 ) <martin.espinoza@gmail.com> on Friday June 23, 2017 @06:44AM (#54674129) Homepage Journal

            Some asshole cut her off, and she instinctively hit the brake. My dad was yelling at her to hit the gas... to no avail. We jacknifed and flipped.

            Your parents were the assholes. They either had too much trailer for not having trailer brakes, or the trailer brakes were misadjusted, or the tow vehicle was in some other way inadequate.

            • by sconeu ( 64226 )

              This was 1973.

              Car was a late 1960's Ford Country Squire station wagon. The trailer did have brakes.

              • by sconeu ( 64226 )

                Here are the specs. I'm assuming my parents had the 302.

                http://www.automobile-catalog.com/make/ford_usa/full-size_ford_8gen/full-size_ford_8gen_ltd_country_squire/1969.html [automobile-catalog.com]

                • The specs of the car are irrelevant without the specs of the trailer and load.

                  • by sconeu ( 64226 )

                    23 footer. Don't even remember the make or model, though "Santa Fe" rings a bell.

                    • Was it a ham can, or an airstream, or what? We've got a '62 Streamline 'Duchess' and that's supposed to be a 3500 pound trailer with a 500 pound tongue weight. That's just narrowly within the capabilities of a big station wagon of those days. That trailer came with electric brakes, though. The only thing I've towed it with was my 1992 F250 7.3 Super Cab XLT, which is currently down due to engine failure from cavitation, in spite of running a cooling filter with SCAs in it. But I digress. That truck weighs a

                    • by sconeu ( 64226 )

                      It wasn't an airstream. It was a 1970 Santa Fe 23. White corrugated aluminum.

                      It was 45 years ago or so, but we did have a Reese hitch with sway control. This was 1973, nobody had an SUV/CUV. Except for people who worked farms or construction.

                    • This was 1973, nobody had an SUV/CUV. Except for people who worked farms or construction.

                      Nobody but nobody had a CUV, they weren't invented until 1979, with the AMC Eagle.

          • Most modern trailers come with electronic brake controllers. When you hit the brakes, the trailer brakes also engage thus assuring that the car is always pulling the trailer, instead of the trailer pushing the car. The only trailers using the old surge brakes are boat trailers - the hydraulic actuator can withstand getting wet, unlike electronic controllers. Surge brakes only engage when the trailer begins pushing the car. So the trailer's braking cannot exceed the car's braking (the surge brake disenga
            • Surge brakes only engage when the trailer begins pushing the car. So the trailer's braking cannot exceed the car's braking (the surge brake disengage the moment that happens), which is what's needed to dampen out the swaying.

              Actually, just a damper in the brake system can keep that tendency down. But what is actually used to stop swaying in cases where that is a problem is a sway control hitch. It basically just adds a torsion bar spring to the hitch such that it pushes the trailer back towards center, and that seems to work okay.

              Sway is a non-issue in most cases with an adequate tow vehicle. For really heavy loads for which there otherwise would be no adequate tow vehicle, we solve the problem completely by simply moving the h

        • You are correct that hitting the brakes is the absolute worst thing that the driver can do.

          Assuming you have them, the best thing to do is to hit the trailer's brakes. If you're towing a largish trailer you should have electrically-controlled brakes and a brake controller where the driver can easily reach it. Just brake gently from the trailer and it will straighten out immediately.

        • by Rakarra ( 112805 )

          As I just posted below - before seeing your comment - those idiots need to hit the accelerator when the trailer starts swerving! Any other maneuver is bound to lead to a bad day.

          Speeding up does work.

          A Hollywood screenwriter just got an idea for Speed 3 and is trying to sign Sandra Bullock and book a wing of an airport.

        • >A second technique that works is to put the car in neutral

          What's wrong with the clutch pedal? Oh I forgot. It's probably Americans driving.

    • TLDR; YMMV!

      I live in a country that has 2 lane highways. One lane to the city, the other going away from the city.. YOU INSENSITIVE CLOD!

      Passing 2 lanes over might be in the next province of my rural province in the mighty Socialist Republic of Vietnam.

      And, furthermore, GET OFF MY LAWN1 :)

    • by edx93 ( 4858619 )

      Never once has one of them simply decelerated and pulled over to the shoulder.

      My dad has...it almost killed us all.

  • by swell ( 195815 ) <jabberwock@po[ ]c.com ['eti' in gap]> on Friday June 23, 2017 @12:14AM (#54673097)

    Simple enough to design shock absorbers for the wheels. A proper shock absorber reduces harmonic effects. On vehicles these devices are remarkably affordable and effective. For luggage they could be very cost effective. A simple friction device with a compressed gas cartridge would do the trick. Feel free to design & patent- I don't need the millions it will bring.

    • Simple enough to design shock absorbers for the wheels. A proper shock absorber reduces harmonic effects. On vehicles these devices are remarkably affordable and effective.

      Shock absorbers are not effective at killing trailer sway. That's why we still have sway control hitches. An easier answer would be to use a tow strap which is a loop which attaches to the outer corners of the bag rather than the center of the bag.

      • I think what's really going on here is a wheelbase that is too narrow for the height of the centre of mass.

        What's needed is pop-out wheels to extend the wheelbase, possibly also with a small computer and an electric motor so the suitcase can follow you (perhaps a pager-type object on your belt) and scream if somebody tries to steal it from you.

        Or go one step further and design it to carry a human and provide a Bluetooth joystick control so not only don't you have to carry or pull the thing, it can carry or

        • The weight constraints here are fairly problematic. It's certainly possible to get your luggage to follow you around, even given that you've got to be able to get the luggage and its contents down under 50lb or even less, depending on the airline. But being able to ride around on it as well is probably asking too much.

          • How about pedals for manual assist?

            • It's not wholly inconceivable. But I think at that point you're better off just basing it on a razor scooter.

              • Not bad, actually; Have the scooter slide out from underneath and treat the bag like a side car, or leave the scooter underneath and the handle shaft leans forward so you can comfortably tow the bag behind you.

                If you're clever enough and add a wheel lock, you could even use a modified handle as a portable chair.

                Then the question becomes... do you leave it with tiny wheels expecting it to only be used on very smooth surfaces, or do you waste some space and weight on bigger wheels, maybe make it detachable f

  • by 93 Escort Wagon ( 326346 ) on Friday June 23, 2017 @12:37AM (#54673209)

    I would think that would get you shot, nowadays.

    • That problem will be addressed in a follow-up paper, with more complicated equations. In layman's terms, it comes down to: the level of fascism of the location you're at; the trigger happiness of the police; the color of your skin; and finally the day of the week.
      It's already a well known fact that more people are shot by the coppers on Fridays - it spices up an otherwise boring weekend.

    • I would think that would get you shot, nowadays.

      Well to be honest I do get an overwhelming compulsion to kill any tool I see dragging a Drag Bag

      • I would think that would get you shot, nowadays.

        Well to be honest I do get an overwhelming compulsion to kill any tool I see dragging a Drag Bag

        Airports must be very difficult for you, since every other passenger (at least) has one.

    • I would think that would get you shot, nowadays.

      Nearly all running in airports is by people trying to make tight connections, and happens inside the "sterile" area, not anywhere near security. No one is going to care if you're running unless it looks like you're trying to run through the security checkpoint. Not that you could get shot even there; TSA agents aren't armed.

  • Anyone who has ever driven a trailer should have been told about fishtailing. (If you have driven a trailer and haven't been told you should google it immediately.)

    It's the same thing.

    The only thing preventing this scientific breakthrough was the apparent inability to intersect the community of truckers and physicists despite their relative interdependencies.

    • Re: (Score:3, Insightful)

      by Anonymous Coward

      he only thing preventing this scientific breakthrough was the apparent inability to intersect the community of truckers and physicists despite their relative interdependencies.

      There is a huge difference between knowing about something and understanding it. Equations of motion for nontrivial situations can get messy fast, and often beyond a few simple general methods, a lot of cookbook, situation-specific methods are used. Expanding upon those cookbook methods is still useful, and sometimes has applications in other situations.

  • Coilovers (Score:4, Funny)

    by mobby_6kl ( 668092 ) on Friday June 23, 2017 @02:55AM (#54673591)

    So what this is telling me is that I need to install coilovers on my suitcase. This way I could adjust the dampening and spring rates to ensure the best response on uneven terrain. I could then even lower it if I wanted, but it's pretty slammed as it is.

    • So what this is telling me is that I need to install coilovers on my suitcase. This way I could adjust the dampening and spring rates to ensure the best response on uneven terrain. I could then even lower it if I wanted, but it's pretty slammed as it is.

      Nice ride you got there. I'm gonna go with front and rear anti-sway bars for better handling, along with low-profile wheels.

      And I'm gonna skip the coilovers and go straight with bluetooth bagged suspension(bags for bags). Use my phone app to slam it when rolling through baggage check.

      Oh, and don't forget the axle-back wheel agitators, for that aggressive sound when cruising at low RPMs.

      Boom.

    • by sl3xd ( 111641 )

      So what this is telling me is that I need to install coilovers on my suitcase.

      Just how badly do you want some homeless guy/gal to steal your suitcase from baggage claim? A suitcase like that signals they are a somebody.

  • ... when a suitcase starts to rock out of control, the correct response is not to slow down but to pull it faster.

    [27] Response may be different s/suitcase/penis/, but this has not been tested on a treadmill.

  • Hey guys, how do you nominate someone for the Nobel prize?
  • This article just rocked me to the core. It blew my mind. Since my brain is only attached to the rest of my nervous system by a single connection and was unable to generate a significant accelleration ... it toppled over (despite traveling cautiously and at slow speed)

  • when a suitcase starts to rock out of control, the correct response is not to slow down but to pull it faster."

    Then it hits something again, you speed up again, repeating until you're moving like O.J. Simpson in the airport.

  • ...Now figure out why we put a man on the Moon before we put wheels on luggage.

  • "when a suitcase starts to rock out of control, the correct response is not to slow down but to pull it faster."

    My buddies who race cars always maintain that braking never solved anything, you save yourself with the gas pedal.

    • This is, indeed, true in almost every situation. Even on the road; you brake and the guy behind you hits you instead of you hitting whatever was in front of you; at the end of the day you still got in an accident. The difference is, if you brake, the asshole who actually caused the accident gets to keep driving like nothing happened.

      In that scenario, you could either floor it and swerve around or, if that's not a possibility, let go of the wheel, relax your body, and prepare for impact (tensing up and gra
      • by b0bby ( 201198 )

        Even on the road; you brake and the guy behind you hits you instead of you hitting whatever was in front of you; at the end of the day you still got in an accident. The difference is, if you brake, the asshole who actually caused the accident gets to keep driving like nothing happened.

        In my book, if you can't stop in time and hit something, you caused the accident. I agree on keeping an eye on the person behind you to see if they are going to hit you, but there's no excuse for me to hit the person in front of me.

        • If they pull out in front of you by less than your stopping distance, well, there's one example of them causing the accident. Likewise if they cut you off without signaling and brake suddenly.

          In the flow of traffic, though, I do agree; there is no excuse for you to hit the guy already on the road and in your lane in front of you. If you do, you were driving too close or too fast.
  • Sort of like those "For Your Consideration..." ads the movie studios run in trade magazines before the Academy Award voting. Granted the Ig Noble awards are much more prestigious, but this seems like an attempt at building early name recognition.

    Besides, my luggage has short skis instead of wheels. Much better over a variety of challenging terrain.

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