03-11-2013, 04:43 PM | #31 | ||
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Most single front wheel trikes of any sort have stability problems in high speed hard turns. There are some that have vertical movement and active suspension for all the wheels, to compensate for this. But that would require a totally different machine to what we call a segway. I do wonder. There are lots of possibilities. Quote:
You could add this to a segway without a total and complete redesign. I do not believe you can add some of the other concepts and still have a segway or something we would recognize as one.
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03-11-2013, 06:05 PM | #32 |
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I wouldn't suggest or even imply changing the Segway as we know it unless Segway Inc. and purists feel minor design or engineering changes make it better from a performance perspective and ultimately enhancing the glide. I would 'speculate' a machine to compete with the T3 to be a totally different class of Segway.
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03-11-2013, 07:22 PM | #33 | |
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If the public safety market wants T3-like transporters, Segway is probably capable of offering something similar but better.
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03-12-2013, 12:24 PM | #34 | |
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You're thinking of things as if the platform and the three wheels were rigidly connected. But that does not have to be the case. They can be linked so that the load is always shared between front and back wheels, with the center of gravity always "above" (relative to net acceleration) a point between front and back wheels. This is really no different from what the Segway does now, except (a) instead of balancing over the axle, it would involve balancing over an arbitrary point between axles, and (b) instead of rigidly connecting to the axles, at least one of front or back would need to be a non-rigid connection. (This non-rigid connection could be active or passive). Remember, there's a computer on board. There is no need to rely on castoring to align the third wheel in the proper direction. You can compute the correct position based on the turn rate, and force the third wheel into that position with a servomoter. Have you ever driven a shopping cart with a wheel that didn't quite make full contact, but kept wobbling back and forth? You really do NOT want that.
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03-12-2013, 10:26 PM | #35 |
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The point that seems to be being disregarded in this thread is the significant benefit and importance of the current Segway PT dynamic balancing system. Its benefits are:
1. Zero turning radius when needed 2. Combined acceleration/braking/steering control 3. Dynamic balancing over two side-by-side wheels 4. Smallest possible footprint The T3, for example, has NONE of these attributes which results in its being significantly more awkward to handle: 1. >0 turning radius 2. Separate controls for acceleration/braking/steering 3. NO dynamic balancing which results in a MUCH less stable machine, especially when climbing and descending hills. I really wouldn't want to make a hard turn coming down a steep hill at speed, for example. 4. Larger footprint than a Segway PT If Segway scraps any of the PT's attributes for the sake of a third wheel, they'd be throwing the baby out with the bath water. Soooo, why and how would they add a third wheel sensibly? I'm guessing a third wheel would serve to provide stability for when the machine is operating very slowly or when it is stopped or parked. Why else would it be needed? This is why I think it should be in back and be a caster so that it could simply caster to follow the two main wheels. It would be on an arm or hinge which would lift it up once the machine went above a certain slow speed so that Segway-style dynamic balancing could be actuated for the two main wheels. One distinct advantage of the existing PTs is their stability fore and aft while ascending and descending hills. The driver remains vertical and the platform remains essentially level. This is not the case for the T3. It would also tend to accelerate going down hill where the PT doesn't.
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03-12-2013, 11:11 PM | #36 | |
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And I can't tell, thanks to there being no clear terminology, if you've gotten my point about the third wheel and dynamic vs active castoring. IMO, it should NOT just "follow along", but should be electrically placed in the position it SHOULD be if castoring worked ideally. Which it doesn't. My apologies if I'm getting redundant here. I can't tell if I'm making a muck of the explanation, or not. Remember the SegTrax? That balances the platform, with an entire tank tread on each side. More dramatic a difference than a 3rd wheel. Now consider a triangular frame connecting the three wheels. Now attach two pivots to that frame, above the triangle, between front and back, at the level of the Segway's wheel axles. Now, drive the wheels forward and back to keep the platform level. Now you *almost* have a Segway. The one difference is that when you drive the wheels of a Segway forward to catch up with the platform, the torque you apply to the wheels also tends to tip the platform back. So we either have to be more aggressive about accelerating the platform, or apply a torque back to the platform. Springs would be one possibility, so would an active system with a servomotor. Bottom line, Segway doesn't have to give up any "Segwayness" by adding a third wheel -- except the part about it falling over if you turn it off. Balancing a platform does not require exactly two wheels -- but two wheels requires balancing. Anyway, I think I've run out of ways to explain it. I hope at least one makes sense to people. One thing you probably DO lose with 3 wheels -- turning radius. You can turn around the midpoint of the two wheels. But if the third wheel is further away from that point than the current rear corner of the platform (which seems likely) you'll need a bit more room to turn than presently. It would sure beat the T3 though!
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03-12-2013, 11:34 PM | #37 |
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Despite all the supposed advantages of the dynamically stabilized 2 wheeler and the supposed disadvantages of the non-dynamically stabilized 3 wheeler, the T3 fits the needs of a segment of the public safety market, drawing off sales from Segway Inc. If there are customers that want a 3 wheeler, its in Segway's best interest to offer one.
"Segway Director of Global Police and Government Business Chip MacDonald said the new vehicle is not a replacement for the company’s current line of two-wheel public safety patrollers, but a natural extension of it that’s designed to fulfill additional roles in a market the company created." Segway might be better off giving the public safety market what they want rather than offering them only what current EPAMD enthusiasts want.
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03-13-2013, 04:05 AM | #38 | |
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In practice, you come into questions of cost. I *think* self-balancing 3-wheeled could be done around their price point, but that's a lot harder to evaluate sitting here.
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03-15-2013, 05:24 PM | #39 |
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I think it would be cool if it stood up on two wheels when you started moving. Going down a curb would be much easier if you are balanced on two wheels.
Slow down and it rocks down on three wheels. It will be interesting.
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03-15-2013, 06:32 PM | #40 |
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I'm not an engineer and not qualified to do any technical speculation. But I've said from the first time I was on one that it needed retractable landing gear. The stand is fragile simply because if it was stiff it could/would catch when you start up and cause big trouble.
I am not a fan of 3-wheeled devices unless they can deal with the potential for tipping inherent with a front third wheel. I'd rather see it be the "landing gear" concept for stability when not moving. The fact that it is being designed for police/security work makes me suspect that whatever is included will allow an officer to step off and let the Seg wait for his return. We shall see! Patience!
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