Lateral stability

[Seeker]

An interesting article has been posted at TIQ, and then ensuing discussion, as it relates to the lateral stability of the Segway.

I'm not an engineer, and dabble in Science, but as I understand it, they are saying that the Segway is stable in the backwards/forwards direction, but not the side to side direction. The implication is that this presents safety issues ( eg hitting a pothole and flying sideways).


What do you guys think, is there a way to reduce the lateral instability of the Segway, while still maintaining its side by side wheel configuration ?

Seeker

[Blinky]

I'm glad you brought this up, Weskifm would be a good person to answer this one, from experience of course.

[GlideMaster]

I'll try and answer this later from the book.:)

quote:Originally posted by Blinky

I'm glad you brought this up, Weskifm would be a good person to answer this one, from experience of course.

[GlideMaster]

Ok I've got a moment. "The Segway HT balances you front to back. You must continue to actively maintain your lateral (right/left) balance, especially during sharp turns at speed. Keeping your knees slightly bent and leaning into turns is the best way to maintain safe lateral balance. Take the time to gain experience using these turning techniques."[^]

quote]Originally posted by Blinky

I'm glad you brought this up, Weskifm would be a good person to answer this one, from experience of course.
[/quote]

[Blinky]

Weskifm writes..
quote:Ok I've got a moment. "The Segway HT balances you front to back. You must continue to actively maintain your lateral (right/left) balance, especially during sharp turns at speed. Keeping your knees slightly bent and leaning into turns is the best way to maintain safe lateral balance. Take the time to gain experience using these turning techniques."
Well this makes sense. I guess you can't just stand on the Segway-HT and expect it to take care of the rest of the ride.

But back to Seekers question, by bending our knees while riding(making turns). Does that provide enough stability for the Segway-HT?
I would think so, and besides I don't think it would ever get fast enough to get to the point where the user would not be able to handle the machines stability.(my opinion ;))

Of course we should keep in mind that people will most likely tests it limits. Time will sure tell.

[ftropea]

Thinking about the lateral stability...

It looks like a Segway HT is as laterally stable as a person standing with their feet spread apart slightly. Knocking a person over (to their left or right) while in that position would require more than a "bump" plus it seems much more stable position than a person on a bike.

In fact, you may be more laterally stable on a Segway HT than standing by yourself. My reasoning for this... while on a Segway HT, and assuming you're holding onto the handle bar, you have 60+ pounds beneath your feet - lowering your center of gravity. It should be harder to knock a person over while on a Segway HT because you would have to apply enough force to resist their leverage against the Segway.

Am I missing something here?

Regards,

Frank A. Tropea

[JohnM]

quote:Originally posted by ftropea
Am I missing something here?


Yes you have. The rider's center of gravity is seperate from the Segway unless his feet are locked down. (Not an impossiblity if using ski bindings.) We've all seen the video of the rider being tossed off. (Ask rollin if you haven't.)Don't pretend it can't happen, even a slow speeds.

The only time the lateral stability of a Segway would exceed that of a bike would be a low speed. That what makes the Segway superior at slow pedestrian speeds of 3-4 mph on the sidewalk. Trust me: The only times I've spilled a bike due to lateral instability were at speeds where I should have dismounted and walked. At any speed higher the bike wins. Flip on the Outdoor Life network on Thursday nights and watch the mountain bike races. Then ask yourself if a Segway could handle those moves.

[ftropea]

Now we're getting to an interesting point John...

You've stated that a Segway is *superior* to a bike at speed around 3-4mph. What begins to happen at speeds between 5-8mph? Are Segways and Bikes tied? And then at speeds between 9-12mph.. do you give the advantage to the bike? Why? (What is the basis? I think you've hit on something interesting here...)

It's not that I don't "trust you" but perhaps you could find some factual basis for some of your statements.


Regards,

Frank A. Tropea

[JohnM]

quote:Originally posted by ftropea

Now we're getting to an interesting point John...

You've stated that a Segway is *superior* to a bike at speed around 3-4mph. What begins to happen at speeds between 5-8mph? Are Segways and Bikes tied? And then at speeds between 9-12mph.. do you give the advantage to the bike? Why? (What is the basis? I think you've hit on something interesting here...)

It's not that I don't "trust you" but perhaps you could find some factual basis for some of your statements.



No 'facts', just real world experience at walking and cycling in major urban environments. Mostly Boston, but I've cycled in NYC, Chicago and Denver. And of course, ManchVegas NH. Where have you Segwayed recently? ;)

Follow someone on a sidewalk at a walking speed (2-4mph), maintain a distance in which you can react to their moves and you won't hit them. Segways are very steady at walking speed, bikes wobble, so Segways will work better on the sidewalk at walking speed. At speeds greater than the walking speed of a pedestrian, ie, speeds at which a traveler is no longer moving with the flow of walking traffic, but overtaking it and weaving in and out, the chance of collsion goes up. On a busy sidewalk people are moving in both directions, constantly altering their courses, without signal or warning, to avoid each other. Its appears to be chaos, but its a free form dance that works as long as everyone minds the tempo. If you double your tempo, someone's toes are going to get stepped on. The lack of rules is balanced by uniform speed.

At speeds above walking speed, I believe the Segway rider and bicyclist are greatly increasing their possibility of sidewalk mishap. Who wants to cruise safely at 3mph if you can to 12.5mph or higher? Do you believe that the crowded sidewalk will part like the Red Sea so you can use all the speed at your disposal? If you ever want to hit your top speed in a busy city, the street is the place to be.

A cyclist should always ride in the street. (NYC demands it.) The street has rules, lanes, signals. Two way traffic is split into seperate lanes. Fast traffic stays left, slower to the right. Etc, etc. Even with vehicles moving at differnt speeds there is order as long as everyone plays by the same rules. The lack uniform speed is balanced by codified rules. A bike rider that doesn't play by the rules is looking for trouble and will usually find it. But if he does follow the rules, a vehicular cyclist is as safe as anyone else on the road. The laws are written that way based upon 120 years of experience. My 30 years of city riding is all the 'factual basis' I need.

Will the same street rules hold true for the Segway? My gut says yes. Most of the state Segway laws allow for some road use. 12.5 mph is fast enough to hold your own in the street, but just not safe on a sidewalk with any pedestrian traffic. Thats why the lawmakers are offering a choice in many states. If you want to tie with the bikes at 5-12mph you have to join them in the street. Otherwise you'll have to settle for your sidewalk superiority at 3mph.

[ftropea]

I agree with many of the things you've said JohnM and I respect your experience as an avid cyclist. I'd only point out that I can't imagine people sustaining 12mph speeds down any city sidewalks I know of. I'm imagining a more glide and go sort of ride... picking your spots... your free sidewalk lanes, if you will.

You make an excellent point about "sidewalk tempo" and comparing it to a sort of dance. That's exactly what it seems like at times. I'd argue that the Segway is the perfect invention to "dance" with pedestrian traffic.. able to stop and go.. drift back.. turn left and right on a dime... simply empowering a pedestrian - enhancing their capabilities... making them better "dancer" in a way :)

And since a bike isn't as maneuverable as a Segway, that's exactly why I think bikes should be restricted from sidewalks while Segways deserve the benefit of the doubt. Whether Segways could effectively and safely be used in streets.. that's all sugar on top.

By the way, I have never ridden a Segway. Have you?

I have ridden a bike. However, I'm not nearly as experienced as you seem to be. I anticipate that I'll become a very experienced Segway rider once they become available to consumers. I wonder if Segwayers will show bike riders a trick or two? :) But now we're getting off topic...

Segways are already laterally stable. There! Back on topic :D

Regards,

Frank A. Tropea

[Casey]

here is a picture of a Segway being ridden longitudinally on a hillside. If it was not stable it would not be able to accomplish that.

The same is true of riding with one wheel on and one off a curb, or in this case a rock.

http://66.241.210.178/forum/photo_album_view.asp?cname=Main+Album&mid=5&cid=2

http://66.241.210.178/forum/photo_album_view.asp?cname=Main+Album&mid=5&cid=2&page=2

quote:Several of us got to try it on a small hill with gravel, ruts, and dirt. It worked pretty well, even for people who had just started using it a few minutes before.

[JohnM]

But why "glide and go" on the sidewalk if you can do a flat out 12.5mph for blocks at a time?

The manueverability of the Segway is certainly unargueable at slow speeds. At 6 mph you may be able to dance with pedestrians. But who wants to? At 12.5mph all you have to do is dodge potholes and the occasional jaywalker.

I'd love to try a Segway. And maybe they can show bikes a trick or two. But when its time to move out and go somewhere, either run with the big dogs or stay on the porch. Bikes aren't for everyone, but the street is where it's happening it you want to get around town. For Segways, too.

[Blinky]

JohnM writes..
quote:But why "glide and go" on the sidewalk if you can do a flat out 12.5mph for blocks at a time?
Shouldn't the Segway-HT be able to handle slow and fast speeds. After all, it is going to be mostly used on sidewalks.