Diff between gen 1 and 2

[wweens]

I'm looking to buy a used one, and I did see an HT for sale for around $2500. He said it had the upgraded Li Ion batteries that had 95% life in them. I didn't ask him the miles on it. What improvements did they make to gen 2 machines? If I want to use an HT to travel trails through a state park will the HT negotiate a relatively smooth trail or should I try to get an offroad model?
Thanks for any info you can provide. It's hard to know the differences in models. It would be nice to have a website that would show all the models, old and new and their plus points and minuses.

[Bob.Kerns]

The single biggest difference between Gen1 and Gen2 is the steering. The leansteer steering makes the Gen2 very intuitive to use. Even better, it makes it more stable -- that is, if you get off-balance to the side, say from hitting a bump on that trail, and you keep the leansteer column in front of you, it will very quickly get itself back under you.

Some people prefer the Gen1 because the steering column is rigid, and it helps them balance on the platform. If you need that, it can be pretty important.

The Li-Ion batteries can't be taken on passenger planes, and Gen2 can't use the older NiMH batteries, so that's another reason some prefer the Gen1.

There are a lot of more subtle differences as well, that you can find discussed on many threads here. Some even prefer the older software over the new, because it is a bit more aggressive.

Yes, you can take a non-offroad model off the beaten path. I do so frequently. You do have to be a bit more conscious of the limits -- you have a bit less ground clearance, you're more likely to sink into soft surfaces, or lose traction from loose stuff.

But if you'e not on a steep hill, a bit of loose gravel, or even deep sand, won't stop you, if you take it slow. But a rock big enough to hit your battery bottom in the middle and high-center you, will cause you to lose control, or a steep hill with loose sand or gravel. In fact, other than having a bicyclist fall on me, those represent the only two falls I've had in about 1600 miles. (And I was deliberately pushing the envelope at the time, just to learn what to watch out for).

In fact, after I fell on the dusty hill, I tried to get up -- and slid down the hill on my hands on knees. (Now THAT did some damage! The fall itself didn't hurt me at all.) So the Segway actually did better on that terrain than I did.

Still, I avoid steep slopes with loose stuff. Steep slopes and pavement is not an issue at all. (Ice and snow would be another story).

For most people, the drawbacks of the X models, with their wider size (wider than a lot of doors) and less-than-friendly appearance indoors and on sidewalks, and in many places, their less-friendly legal status, far outweigh the advantages off-road.

But they definitely have their place.

[CovRob]

... It's hard to know the differences in models. It would be nice to have a website that would show all the models, old and new and their plus points and minuses.
If you look at pages 18-22 of this "Unofficial Segway Code" (http://www.legalisesegways.co.uk/segwaycode.html) pdf compiled by Gareth you'll see a pretty comprehensive summary of the various models and features. Hope it helps.

[SegNerd]

I'm inexperienced, so correct me if any of the following are wrong. In addition to the things already mentioned:

-Gen1s use three different keys for low, medium, and high speed. Gen2s have a single key (or multiple copies of a single key) and let you choose the speed via the interface.

-Gen1s don't have a speedometer, clock, or odometer available to the rider... I believe Gen2s do have these (although you can accomplish these three things with a GPS).

-Gen2s have more detailed error reporting on the built-in screen, so if something goes wrong, you have an increased chance of identifying, and possibly fixing, the problem yourself.

-Most Gen1 models shipped with NiMH batteries, although some Li-On upgrades were available. Gen2 models come with Li-On.

[jryan]

I'm inexperienced, so correct me if any of the following are wrong. In addition to the things already mentioned:

-Gen1s use three different keys for low, medium, and high speed. Gen2s have a single key (or multiple copies of a single key) and let you choose the speed via the interface.




The infokey as found on the gen2's cannot change the speed. The only speed changing you so on the gen2 key is by putting it in turtle mode (limiting the speed to, I believe, 6mph or taking it off turtle mode with a speed limit of 12.5). On a gen2 you use the leaning of your body back and forth to change the speed between 0mph and 12.5 mph. The keys on the gen1's just set your maximum speed as well! You cannot adjust your speed on a gen2 using the key. It is all done by your body, however speed adjustment is something most get used to fairly quickly!

Jeremy Ryan

[segsurfer]

See this thread:http://forums.segwaychat.com/showthread.php?t=18453
-segsurfer

[SegNerd]

Well, I didn't actually say you could change the speed on a Gen2 with the InfoKey... in fact, my point was that you can't. I just said that you use other aspects of the user interface to adjust the speed on a Gen2, which was an admittedly vague description because I don't own, and haven't used, a second-gen.

The infokey as found on the gen2's cannot change the speed. The only speed changing you so on the gen2 key is by putting it in turtle mode (limiting the speed to, I believe, 6mph or taking it off turtle mode with a speed limit of 12.5). On a gen2 you use the leaning of your body back and forth to change the speed between 0mph and 12.5 mph. The keys on the gen1's just set your maximum speed as well! You cannot adjust your speed on a gen2 using the key. It is all done by your body, however speed adjustment is something most get used to fairly quickly!

Jeremy Ryan

[Gihgehls]

The infokey as found on the gen2's cannot change the speed. The only speed changing you so on the gen2 key is by putting it in turtle mode (limiting the speed to, I believe, 6mph or taking it off turtle mode with a speed limit of 12.5). On a gen2 you use the leaning of your body back and forth to change the speed between 0mph and 12.5 mph. The keys on the gen1's just set your maximum speed as well! You cannot adjust your speed on a gen2 using the key. It is all done by your body, however speed adjustment is something most get used to fairly quickly!

Jeremy Ryan

You're just misunderstanding what he wrote. Turtle mode was what he was talking about.

[jryan]

You're just misunderstanding what he wrote. Turtle mode was what he was talking about.

Yes, so easy to say after he responds with a clarification, don't you think! Your timing was a bit off Gihgehls!

Jeremy Ryan

[KSagal]

None of the keys mentioned ever change speeds.

Speed is changed on all machines, in all modes, by simply how far you lean... If you lean more, you go faster, if you lean less, (closer to standing straight up) you go slower or stop...

In any machine, with any key, you can change your speed by your amount of lean from 0 to 5 mph...

In Gen 1, with the black key, or in gen 2 in turtle mode, you can change your speed from 0 to about 6mph

In Gen 1, with the yellow key, you can change your speed from 0 to about 9 or 10 mph.

In Gen 1, with the red key, or in Gen 2 (not in turtle mode) you can change your speed from 0 to about 12.5 mph...

The keys do not change the speed, they simply set the maximum speed that the machine will allow.

[SegNerd]

Yes, technically I should've said that the keys on a Gen1 affect your maximum speed and not just your speed.

This thread was supposed to be about differences between the two generations - my point is just that Gen1s have three levels of max speed and you choose between them with the keys, whereas Gen2s have two max speed levels and the key is not involved in choosing between them.

[wwhopper]

Gen one machines (fixed control shaft - twist steer) use i-buttons for keys. Each machine was orginally shipped with a set of keys - each one had a different maximum speed capability. Black slow 5 mpg, yellow medium 8 mph, and red maximum 12.5 mph. These i-button keys could be reprogramed to give you any speed you wanted up to the 12.5 mph and any turning speed you wanted. The color was only an indicator, though you could program a red key to be dead slow. Other key colors are available and programing can only be done by someone who has a laptop and the right program and hardware to do it.

Gen Two machines (control shaft / lean steer frame moves side to side) come with 2 infokeys. These are set with two speeds, a turtle mode and a normal (rabbit mode.) Again the maximum speed is 12.5 mph or anything up to that. The nice thing about the gen two machine is you can take your infokey and program in what ever speed you want for the rabbit or turtle mode by manipulating the infokey buttons from very slow up to a maximum of 12.5 mph. No outside computer, program or hardware required. Many tour companies program their machines at 8 or 10 mph for rabbit mode and dead slow for turtle mode for training.

Though the Gen One machines are great, the Gen Two machines are a much better machine and are more fun to ride. Gen One machines seem to be preffered by the Segway Polo Players, but you can play polo on any Segway you want.

If your budget is $2500 - go the extra $500 and by Dhuggers machine that he just listed for $3K - it will be well cared for and an excellent buy - especially since he is including shipping.

[bentbiker]

If your budget is $2500 - go the extra $500 and buy Dhuggers machine that he just listed for $3K - it will be well cared for and an excellent buy - especially since he is including shipping.
I PM'd him suggesting the same thing, but I guess he hasn't logged on since yesterday morning. What a missed opportunity.

[Bob.Kerns]

None of the keys mentioned ever change speeds.

Speed is changed on all machines, in all modes, by simply how far you lean... If you lean more, you go faster, if you lean less, (closer to standing straight up) you go slower or stop...

Actually, to be utterly pedantic -- the more you lean, the more you accelerate. The longer you do that, the faster you go.

The keys tell the machine when to make you stop leaning!

[segaddict]

The infokey as found on the gen2's cannot change the speed. The only speed changing you so on the gen2 key is by putting it in turtle mode (limiting the speed to, I believe, 6mph or taking it off turtle mode with a speed limit of 12.5). On a gen2 you use the leaning of your body back and forth to change the speed between 0mph and 12.5 mph. The keys on the gen1's just set your maximum speed as well! You cannot adjust your speed on a gen2 using the key. It is all done by your body, however speed adjustment is something most get used to fairly quickly!

Jeremy Ryan

The generation 2 actually has a speed limiter that can be programmer to reach a maximum speed anywhere between 1 mph and 12.5 mph. This is slightly more complex than pressing a button.

Personally, there is no comparison and the gen2 is way superior, but if you want to airline travel gen2 is NOT the way to go.

John

[KSagal]

Actually, to be utterly pedantic -- the more you lean, the more you accelerate. The longer you do that, the faster you go.

The keys tell the machine when to make you stop leaning!


I am not so sure of this. Acceleration implies an increase in speed. If you lean forward at 2 degrees, you will accelerate from 0 to a fixed speed, and if you maintain that 2 degrees, you will reach a terminal velocity of a speed that is set by the software.

If you lean forward at 4 degrees, you will accelerate from what speed you are traveling at to a new speed. If you maintain 4 degrees, you will maintain that new speed, which will be faster than the speed you maintained at 2 degrees...

While you will accelerate from a starting speed to the new speed as determined by the amount of lean, you will no longer accelerate beyond that speed, and will instead maintain it.

Therefore, you will accelerate and then maintain a certain speed, based on the amount that you lean. I think it is reasonable to shorten this to simply say you will go faster if you lean more. (up to the point that the machine will not allow more speed) If you try to lean farther, it will simply stop you from leaning further.

The machine will still maintain a particular speed for a particular lean angle.

If you maintain the angle of your lean, and it is less than the maximum speed that the machine will allow, it will not accelerate. You can maintain a speed for a long time, and will be affected by battery range, and other issues, but you will not accelerate because you hold the lean longer...

[Bob.Kerns]

I am not so sure of this. Acceleration implies an increase in speed. If you lean forward at 2 degrees, you will accelerate from 0 to a fixed speed, and if you maintain that 2 degrees, you will reach a terminal velocity of a speed that is set by the software.

If you lean forward at 4 degrees, you will accelerate from what speed you are traveling at to a new speed. If you maintain 4 degrees, you will maintain that new speed, which will be faster than the speed you maintained at 2 degrees...

While you will accelerate from a starting speed to the new speed as determined by the amount of lean, you will no longer accelerate beyond that speed, and will instead maintain it.

Therefore, you will accelerate and then maintain a certain speed, based on the amount that you lean. I think it is reasonable to shorten this to simply say you will go faster if you lean more. (up to the point that the machine will not allow more speed) If you try to lean farther, it will simply stop you from leaning further.

The machine will still maintain a particular speed for a particular lean angle.

If you maintain the angle of your lean, and it is less than the maximum speed that the machine will allow, it will not accelerate. You can maintain a speed for a long time, and will be affected by battery range, and other issues, but you will not accelerate because you hold the lean longer...

No, if you don't accelerate, and your center of gravity is not over the wheel, you'll have a net torque, and will rotate in the direction of the lean. So long as you're leaning forward, it has to go faster and faster. That's the only way to balance you.

You can't maintain a lean forward at 12.5 MPH any more than you can at 0 MPH.

(Except for a very small effect from wind resistance, but that's really, really tiny. How much lean do you notice standing on the sidewalk with a 12.5 MPH wind in your face? I can't quickly locate a Reynolds Number value for the human body, clothed (or naked, for that matter) so I won't try to calculate the angle, but I expect it's significantly less than one degree).

(That's the simplified inverted-pendulum explanation. It's actually a bit more complex since there's also torque around the axles, but that's also in the direction of increasing your speed).

It's easier to understand if you draw a force diagram.

The net result is, you'll go faster and faster as long as you lean. When you stop leaning and stand up straight (or it makes you by tipping back), it'll keep you at a constant speed. Depending on how much you leaned for how long, that may be full speed ahead, or zero, or even backward.

I think you can handle drawing the force diagram and working it out, but if you, or onlookers want, I can walk you through the physics.

I can understand how it might FEEL like you're leaning forward. The speed limiter contributes to that, but there's also the whole "naive physics" thing, where our brains process things a bit different than reality. It's a much-studied point -- your expectation is exactly what our brains are programmed to expect. This is a perfect example.

(The term "naive physics" was coined in 1978 by Patrick Hayes in the Naive Physics Manifesto. I can't find an online copy to point you to, unfortunately, but you can find thousands and thousands of citations. It's been studied both from the standpoint of Artificial Intelligence and Psychology. I can't say either field has come to any useful result from all that, but I think you can sum it up as "our brains process things a bit different than reality". In part, I think it's an adaptation to handling events that happen faster than our perceptions, which is more the domain of neuroscience, than psychology).

[Edit: It's also widely exploited in the field of hand animation. Think Roadrunner cartoons...]

[KSagal]

I'm still not getting it...

If you do not shift your weight forward of the center of gravity (the definition of 'lean' in my posts in this thread) than you will not move the segway forward...

If you hold the lean at a consistent angle (I was using 2 and 4 degrees as an example, and if you say they are wrong, I have no problem with that) but it is less than the angle needed for the segway to achieve 12.5 mph, it will accelerate to a set speed, and stop accelerating. It will continue to move forward but will not continue to accelerate.

I understand the word accelerate to mean the increase in speed of an object... More specifically, the rate at which the time an object traveling a fixed distance will take is decreasing. If the time it takes to travel that same fixed distance is increasing, they are decelerating. If they are traveling that fixed distance at a consistent rate of time, then there is no accelerating or decelerating.

My understanding of the way a segway works is not the same a theoretical physics. Since there are actions the segway itself is taking to react to the operator's inputs, force calculations are not enough.

What we are talking about here is the difference between what the segway sees and feels when a person leans, and what an observer sees and feels when seeing a person on a segway, and how that particular segway reacts...

My understanding of what you are saying is that you are only talking about the forces that are being put upon the segway by the person leaning, I am talking about the person leaning, those forces, and the resultant segway's reaction.

I am a nuts and bolts guy. I know that if you do not lean you will not move the segway. I also know that if you lean at a consistent rate, the segway will not continue to accelerate beyond a particular point, and that point will change if you lean more or less.

Of course, I may be all wet. But you have not convinced me of it yet.

[KSagal]

I just thought of a new way to describe my thoughts...

A person is not the same as the hands on a clock. If a person were to watch the hands of a clock, they will see that the second hand takes the same amount of time to 'fall' from 12 o'clock to 1 o'clock as it does from 2 o'clock to 3 o'clock... That second hand has a constant velocity, and no acceleration.

A person, doing a face plant, if viewed from the right angle, will travel a similar path, as their head moves from 12 o'clock to 3 o'clock. The difference is that if a person leans forward, the time it takes to fall from 12 o'clock to 1 o'clock is far longer than the time it takes to fall from 2 o'clock to 3 o'clock. In other words, they are accelerating as they fall. The deeper into the fall they are, the faster they are moving...

If a person had a quick acting speedometer on their nose, they might be moving 4 mph as they pass 1, 14 as they pass 2, and potentially 40 as they approach 3. (I made up these numbers, they are not the real rate of acceleration, but will suffice for my needs)

If you were to have the ability to move the person, feet, hips and everything, in the direction their nose moved from the 12 o'clock to 1 o'clock and were able to do it at 4 mph at the point their nose was falling past 1, then it would arrest their acceleration, and the would maintain a perpetual fall. As long as you exactly matched the forward speed of their body to the rotational speed of their nose, they would not accelerate nor decelerate, but maintain a constant velocity...

What say you to this?

[Bob.Kerns]

Quick response -- I'll try to do better later.

To arrest a person's fall, you have to apply force.

Thanks to F = m * a, the only way to do that is by acceleration. Velocity won't do it. You can analyze the situation identically whether v = 0 or v = 12.5. To visualize the latter situation, think of someone videoing someone from another Segway.

One more way to slice it: The contact patch on the tire can provide two components of force. The force up, if not aligned with your center of mass, produces a torque, leading to face plant city.

But add in the horizontal force, and you can balance everything with a torque around your CG in the other direction. But F = ma! So the whole system (you, Segway, your groceries) accelerates.

In any static situation (static in the sense that the situation is not changing -- there can be constant motion), the sum of all the force vectors, and the sum of all the torques (also a vector quantity), must be zero. Otherwise, you'll have acceleration or rotation. Rotation = face plant.
The only place velocity yields a force is with viscosity, e.g. wind resistance, or similar electromagnetic phenomena, where kinetic energy is being dissipated in a way that increases with velocity. (Simple friction doesn't depend on velocity).

The Segway speed limiter stops the lean by simply accelerating the powerbase a bit more than enough to balance your lean -- bringing it and your feet forward, thus eliminating the lean!

No matter how much you TRY to lean at that point -- it has control, because you don't have anything to push on, but it does. You try to bring your CG forward -- it brings the contact patch forward to match, and a little more so it can bring the speed back down to 12.5 (or whatever speed it thinks you should be limited to).

[KSagal]

Quick response -- I'll try to do better later.

To arrest a person's fall, you have to apply force.

Thanks to F = m * a, the only way to do that is by acceleration. Velocity won't do it. You can analyze the situation identically whether v = 0 or v = 12.5. To visualize the latter situation, think of someone videoing someone from another Segway.

One more way to slice it: The contact patch on the tire can provide two components of force. The force up, if not aligned with your center of mass, produces a torque, leading to face plant city.

But add in the horizontal force, and you can balance everything with a torque around your CG in the other direction. But F = ma! So the whole system (you, Segway, your groceries) accelerates.

In any static situation (static in the sense that the situation is not changing -- there can be constant motion), the sum of all the force vectors, and the sum of all the torques (also a vector quantity), must be zero. Otherwise, you'll have acceleration or rotation. Rotation = face plant.
The only place velocity yields a force is with viscosity, e.g. wind resistance, or similar electromagnetic phenomena, where kinetic energy is being dissipated in a way that increases with velocity. (Simple friction doesn't depend on velocity).

The Segway speed limiter stops the lean by simply accelerating the powerbase a bit more than enough to balance your lean -- bringing it and your feet forward, thus eliminating the lean!

No matter how much you TRY to lean at that point -- it has control, because you don't have anything to push on, but it does. You try to bring your CG forward -- it brings the contact patch forward to match, and a little more so it can bring the speed back down to 12.5 (or whatever speed it thinks you should be limited to).


I think you just agreed with me. If you consider a 'lean' as a specific amount of weight out of balance, and a person were to lean that much out of balance but not attempt to go more out of balance (lean a certain amount and hold it, as opposed to continuing to lean where they will eventually fall) then it is possible for the segway to apply forward force to the platform, via the friction on the road with the contact patch of the tires, and equalize the lean or out of balance condition, and when it equalizes, the segway will be moving at a constant speed, and there will be no acceleration (which would arrest the fall) or rotation (which is the continuation of the fall).

The only other time you can lean forward with no acceleration that I can think of would be when you do so in front of a very large pile of jello. But that goes into your viscosity argument. ( As I skydiver, I have experienced 200mph+ winds upon myself, and the viscosity of air at any reasonably atainable speed is just not going to stop this ole' fat boy in mid fall...)

[Bob.Kerns]

I think you just agreed with me.
Nope. But we're narrowing in on it.

If you consider a 'lean' as a specific amount of weight out of balance, and a person were to lean that much out of balance but not attempt to go more out of balance (lean a certain amount and hold it, as opposed to continuing to lean where they will eventually fall) then it is possible for the segway to apply forward force to the platform, via the friction on the road with the contact patch of the tires, and equalize the lean or out of balance condition, and when it equalizes, the segway will be moving at a constant speed, and there will be no acceleration (which would arrest the fall) or rotation (which is the continuation of the fall).

The only other time you can lean forward with no acceleration that I can think of would be when you do so in front of a very large pile of jello. But that goes into your viscosity argument. ( As I skydiver, I have experienced 200mph+ winds upon myself, and the viscosity of air at any reasonably atainable speed is just not going to stop this ole' fat boy in mid fall...)

The only ways to equalize the lean or out-of-balance condition are:

Continue accelerating so the upward & horizontal components of the force from the contact patch sum to a vector that goes through the CG, or
Remove the lean. The vertical vector goes through the CG, and no horizontal forces; hence, no acceleration. And no lean.


(Of course, you could do something between -- remove some of the lean, and accelerate less.)

So you can "equalize the lean" by removing it, or by accelerating. No other choices are available, outside of plowing into a block of jello, as you so aptly put it.

I figured as a skydiver, you could relate to how much faster you'd have to go for wind resistance to be a significant factor. The wind resistance increases as the square of the velocity, so you really don't see much effect at all at low speeds. At 10% of terminal velocity, you'll only see 1% of the force. That works out to be about 0.57 degrees of lean. (I'm not sure what value of terminal velocity to apply to someone standing on a Segway -- I'd guess 125 MPH would be close, so something in the ballpark of a half degree of lean would be about all you'd obtain from that.

[KSagal]

Nope. But we're narrowing in on it.




The only ways to equalize the lean or out-of-balance condition are:

Continue accelerating so the upward & horizontal components of the force from the contact patch sum to a vector that goes through the CG, or
Remove the lean. The vertical vector goes through the CG, and no horizontal forces; hence, no acceleration. And no lean.

So you can "equalize the lean" by removing it, or by accelerating. No other choices are available, outside of plowing into a block of jello, as you so aptly put it.

I figured as a skydiver, you could relate to how much faster you'd have to go for wind resistance to be a significant factor. The wind resistance increases as the square of the velocity, so you really don't see much effect at all at low speeds.


So you are saying that it is possible to accelerate and not increase in speed?

If not, how is it possible to maintain a speed of 10 mph on a segway?

[Bob.Kerns]

So you are saying that it is possible to accelerate and not increase in speed?

If not, how is it possible to maintain a speed of 10 mph on a segway?

No. You understand correctly (from the definition of acceleration as the rate of change in velocity) that that would make no sense.

I'm not sure why you think I said that, so I can't usefully respond to that first part.

As for the second -- it's possible by standing up straight with no lean, once you reach 10 MPH. Briefly lean forward a tiny amount to pick up some speed if you lose a bit of speed (say, a gust of headwind). Briefly lean back a tiny amount of you pick up a bit (overcorrection, or a tail wind).

So your feedback control is around that balance point -- and it's vertical, not leaned. (Again, ignoring wind resistance).

You might want to re-read my previous post -- it looks like I edited it after you read it; I wasn't quite quick enough.

[KSagal]

No. You understand correctly (from the definition of acceleration as the rate of change in velocity) that that would make no sense.

I'm not sure why you think I said that, so I can't usefully respond to that first part.

As for the second -- it's possible by standing up straight with no lean, once you reach 10 MPH. Briefly lean forward a tiny amount to pick up some speed if you lose a bit of speed (say, a gust of headwind). Briefly lean back a tiny amount of you pick up a bit (overcorrection, or a tail wind).

So your feedback control is around that balance point -- and it's vertical, not leaned. (Again, ignoring wind resistance).

You might want to re-read my previous post -- it looks like I edited it after you read it; I wasn't quite quick enough.


Wait a minute! Can I go back and fill in holes I left in my posts that you pointed out? I did not know that was in the rules! ;)

I still cannot completely agree. If you could lean to get to speed, then stand directly above the CG to maintain speed, you are describing a perpetual motion machine. I will accept that you need to lean more to get to speed than you need to lean to maintain speed, but I cannot accept that you are backing off the lean to full vertical, or you would coast to a stop.

There has got to be a bit of weight in front of the cg for the seg to move... Of course, a segway at speed is not level. I suppose if you consider vertical in this case to be a line from the contact patch of the tires, thru the cg, and continuing up, than you could stay in line with the cg and still move, but that line would not be the same a vertical, it would lean forward a bit...

Edit: Correction. A line from the contact patch, thru the cg of a forward leaning segway would not lean forward, but backward, as the contact patch is in front of the axle. A person standing perpendicular to the platform would indeed be leaning forward of the cg...

Edit 2: I just realized that a person standing in front of that backward leaning line (Contact point which is in front of the axle thru the cg and up) could be standing vertical. Since the segway is leaning forward, they could be leaning backward relative to perpendicular to the platform but stil vertical and forward of the line...

[KSagal]

You were supposed to come around to me, not me toward you!

Sheesh! Don't think for a moment I will not be just as arrogant about other stuff....

Nicely done...

[Bob.Kerns]

Wait a minute! Can I go back and fill in holes I left in my posts that you pointed out? I did not know that was in the rules! ;)

Sorry -- I was trying to improve the message for your benefit before you read it, since I didn't think of some details to add until after I hit "Submit". Sorry to make you read it twice.


I still cannot completely agree. If you could lean to get to speed, then stand directly above the CG to maintain speed, you are describing a perpetual motion machine. I will accept that you need to lean more to get to speed than you need to lean to maintain speed, but I cannot accept that you are backing off the lean to full vertical, or you would coast to a stop.

There has got to be a bit of weight in front of the cg for the seg to move... Of course, a segway at speed is not level. I suppose if you consider vertical in this case to be a line from the contact patch of the tires, thru the cg, and continuing up, than you could stay in line with the cg and still move, but that line would not be the same a vertical, it would lean forward a bit...

OK, with this "perpetual motion" argument, you're taking us into very detailed territory, because we're talking about small forces -- like wind resistance, and rolling resistance of the tires. We've already established that wind resistance requires some lean. The tires are a more complex picture, but a tiny amount of lean is necessary there to counter the torque the motors have to put out to overcome it. (So it's not so complex at that level, just when you try to work out the forces involved at the tire).

Again, tiny fractions of a degree. Very different from your statement that you lean a certain amount, and it picks up speed until your speed balances you out. You'd need a LOT of speed for wind and rolling resistance to to balance out even a 2 degree lean, and you can lean a lot more than that. Until it decides not to let you anymore.

BTW, it's only a perpetual motion machine if you actually get free energy out of the system. It's an *ideal* system, if you ignore small loses, and get continuous motion with no energy input when you don't lose any energy either.

There are no ideal systems, either! At least, none that you can observe, though at a subatomic level they can exist until observed.

But unlike perpetual motion machines, ideal systems are a useful simplification for analyzing the overall behavior of a system. Sooner or later, though, anyone with an engineering frame of mind is going to want to look at how the system departs from the ideal, just as you did.

But it helps to keep the thinking straight, and focus on the ideal first, and then add in additional factors, preferably one at a time.

So normally, we ignore wind resistance, rolling friction, and jello, until we've worked out the idealized behavior. And then we say, "but what about...?", and find out that "vertical" isn't quite "vertical" because there are other small torques and horizontal forces.

They still all add up to zero net force, and zero net torque, for constant velocity and angular velocity. You just have a few more terms in the equation.

[Gihgehls]

If you have a gen1 machine this is really easy to demonstrate. First you have to improvise a counter balance, like I have in the picture below. This removes operator response from the equation.

http://i82.photobucket.com/albums/j273/hellphish9/photo-22.jpg

Now, if you walk the Segway to a level area, it should hold nearly still. It will actually tilt a bit and correct itself without moving forward because the tiny forces required at this stage aren't enough to overcome the rolling resistance of the tires. Now, if you push the Segway forward it will move forward for quite a ways before eventually stopping due to rolling resistance, but lets look at what is happening.

The Segway does its best to stay level. This is rule #1. It doesn't care about keeping a steady speed or holding still. Its main concern is staying level. I'll try to explain what is happening by breaking down the process into discrete steps, sort of how the CU boards work. (in actuality, the sampling rate is different than the motor command refresh, so this is only an estimation)

In the first tick of the clock, we push the handlebars forward. Segway feels the tilt.

In the second tick, the wheels move forward just enough to correct the tilt, bringing the platform level and moving the entire system forward.

Now the Segway (and case of waterbottles) has forward momentum and the wheels are stopped. So in the next tick, the momentum (instead of my hand) tilts the platform forward again. Segway sees this. (so, for a fraction of a second, the wheels were locked and the entire machine rocked forward, with the rolling resistance absorbing some of the energy.)

Fourth tick, the wheels are commanded again to move foward, but not as far as before. Rolling resistance has slowed the whole unit down in between ticks. The correction has been made and the plaform is level again. The wheels hold firm.

Next tick, forward momentum carries the whole mass forward again, pivoting again on the locked wheels, some energy again being absorbed into overcoming the tires.

This goes on until we are back at the first step, with the segway holding mostly still, making small corrections that don't take it anywhere.

[KSagal]

Nice.

I do not see how waterbottles on a pushed segway address if a person who rides a segway wants to keep it moving at 10 mph needs to lean forward or not...

But I do enjoy hearing you talk, too.

Have a nice day.

[Bob.Kerns]

Nice picture and demonstration.

It's not quite true that the Segway tries to stay level, though that's a good starting model. In fact, the faster you go, the more it tips back (speed limiter). Pushing the handlebars forward won't make it go, either, if you're standing on it. It'll end up making you lean back.

I've been trying to figure out a good way of describing it. The best I've come up with is that it tries to maintain a particular angle, depending on speed. That captures the immediate Segway part of it.

But when you add the human into the equation, it gets more subtle. Because as I said, if you push on the handlebars, it tips forward a bit, you tip back a bit. And then, it moves forward a bit, moving you back even more. And all you did was move forward a few inches and come to a stop, with a different weight distribution (more spread out), but still aligned with your CG over the contact patches.

Actually moving forward involves pushing back with your feet to rotate your weight forward. It's a lot like trying to describe how you enter a spin or a jump in figure skating, actually. In both cases, it's not that you just rotate. In order to rotate, you have to do a sequence of actions, with different moments of inertia. We do this so instinctively while walking or segging that it's really hard to think about what we do.

In fact, I'm not entirely sure exactly how we do it. I understand the space of possible ways, but what we specifically do is subtle. Walking is a LOT more complicated than it looks from a physics standpoint, too. In fact, it's more complicated than anything we've discussed here so far.

Or standing. Since my legs don't work well, I do most of my balancing with my upper body, which is how you learn to do it as a skater. But rotating around any axis is not a simple action. It's a sequence of actions that result in a change of position. You can't just create angular momentum.

[KSagal]

Nice picture and demonstration.

It's not quite true that the Segway tries to stay level, though that's a good starting model. In fact, the faster you go, the more it tips back (speed limiter). Pushing the handlebars forward won't make it go, either, if you're standing on it. It'll end up making you lean back.

I've been trying to figure out a good way of describing it. The best I've come up with is that it tries to maintain a particular angle, depending on speed. That captures the immediate Segway part of it.

But when you add the human into the equation, it gets more subtle. Because as I said, if you push on the handlebars, it tips forward a bit, you tip back a bit. And then, it moves forward a bit, moving you back even more. And all you did was move forward a few inches and come to a stop, with a different weight distribution (more spread out), but still aligned with your CG over the contact patches.

Actually moving forward involves pushing back with your feet to rotate your weight forward. It's a lot like trying to describe how you enter a spin or a jump in figure skating, actually. In both cases, it's not that you just rotate. In order to rotate, you have to do a sequence of actions, with different moments of inertia. We do this so instinctively while walking or segging that it's really hard to think about what we do.

In fact, I'm not entirely sure exactly how we do it. I understand the space of possible ways, but what we specifically do is subtle. Walking is a LOT more complicated than it looks from a physics standpoint, too. In fact, it's more complicated than anything we've discussed here so far.

Or standing. Since my legs don't work well, I do most of my balancing with my upper body, which is how you learn to do it as a skater. But rotating around any axis is not a simple action. It's a sequence of actions that result in a change of position. You can't just create angular momentum.


Bob, you are a much nicer person than I am...

I am constantly amazed at just how small the world is... I have good leg strength, but due do a reconstruction of my right knee from an army injury, I have very little latteral stability in my right leg, for the last 30 years...

As a result, I have learned to walk and balance very differently than a person who does not have this particular issue... I frequently find myself using my upper body movements for balance, and of course, cannot pivot well on my feet or use the geometry and mechanics I was born with...

And just to prove how dense I am, I plan to lean forward as I walk to my car when I leave work in a little while:rolleyes:.

[Bob.Kerns]

Bob, you are a much nicer person than I am...


Not sure what prompted that, but thanks. I think?



And just to prove how dense I am, I plan to lean forward as I walk to my car when I leave work in a little while:rolleyes:.

When you get back, tell us how you did it. How the forces all worked -- to keep you upright, and to move you forward.

I could do the analysis, given motion capture data, but I couldn't begin to capture the experience of walking, let alone translate it to words. Math, yes.

I haven't measured your density, but I do know you're complicated!

[KSagal]

Not sure what prompted that, but thanks. I think?

When you get back, tell us how you did it. How the forces all worked -- to keep you upright, and to move you forward.

I could do the analysis, given motion capture data, but I couldn't begin to capture the experience of walking, let alone translate it to words. Math, yes.

I haven't measured your density, but I do know you're complicated!


I took the walk with no problem... Two people asked me if I hurt my back:o

It is kind of like running down hill. You just lean forward and then try to keep your feet under you...

As far as my density, I was referring to my stubbornness, but I am rather thick on several levels...:rolleyes:

[Bob.Kerns]

I took the walk with no problem... Two people asked me if I hurt my back:o

It is kind of like running down hill. You just lean forward and then try to keep your feet under you...

As far as my density, I was referring to my stubbornness, but I am rather thick on several levels...:rolleyes:

Oh! Are you OK?

You know,when you're walking, you're continually alternating between being off-balance one way or the other. It all has to average out...

I'm sure you've seen some toddlers who can't seem to walk at all -- just stand, or run, nothing in between. Sometimes it's harder to walk than run.

[wweens]

Thanks for all the information. From what I've been able to tell I'm not sure that anything less than the X2 would fit my needs. I have a large backyard with a very steep hill. It's all I can do to get my 21 HP Troybilt up it, altho it's a little weak in that it doesn't have a gearshift so won't pull hills like geared lawn-tractors do. The pathway up the hill is decomposed granite so it can be a little 'slippery'. I need to try some Segways, and I may try to locate one in the subdivision I live in (Pecan Plantation in Granbury, Texas) and try it on my hill. I think I'll pass on the guy's HT for $2200 because I don't know enough to make even that big of an investment. I'll keep researching, and I really appreciate the help I've received here. No PM have been sent to my email address. It may be that I haven't posted enough to be able to have that option.
Louis