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(...) Not so obvious. If you increase the surface the pressure per surface unit decreases proportionnaly (at least on hard surface)... Actually I would expect little or no variation in traction power. Philo (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) Hmmm - that's unfortunate...but if the 'right' strategy is to go with a non-slipping robot, the measurement of sliption is really a lot less important. (...) Yeah - so many of those basic mechanics equations are only approximations - yet they (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) hmm. This sounds like a good project... (...) All things being equal, I'd put my money on the robot with ten spinning wheels, over a couple (or even ten) stationary ones. I'd also mechanically connect all the motors together, so they drive a (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) As you note in your mini-cooper example, *if* you can keep the wheels from "spinning out", but instead are always in rolling contact with the ground, static friction is what's important... and generally, the static coefficient of friction is (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) That makes sense. (...) Yeah - I agree. So we have to sum some force vectors here. If our robot is pulling to the left, we have a horizontal 'drive' force to the left and a force in the tow rope going off to the right - plus a force due to (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) Dave, Actually I am very happy and grateful. I am getting a crash course. Couldn't have asked for more. Raj. (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) Steve Hassenplug, Sorry, my mistake. Thank you for the Wiki link and all your help. Raj. (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) The problem is that this is measuring the static friction ("stiction"). That's the wrong thing to measure if your strategy is to jam all the motors full on and progress forwards (we hope!) with all wheels spinning. To measure the dynamic (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) I would have expected that compression would be a good thing because it would increase the area of the 'contact patch' - which increases traction - which is a good thing - right? (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) A rather inventive young man that I know did try exactly that - using the ribbed tubing from the Mindstorms set inside the Mindstorms motorcycle tire. It's a good fit, and a good idea, but I'm not sure how effective it was. (...) One simple (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) It does happen - if you use more that 2 motors or if you try to use a RC motor. The driver circuit limits current around 500mA, and at that rate it is not long before going in thermal shutdown mode. (...) No, you won't see smoke... RCX motor (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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Philo, That's interesting, and looks to explain why it is that I've never been able to observe the RCX output going to thermal or current protection cutoff? I've one largish sumo type bulldozer style robot with 4 treads that can easily push 4-5 (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) Actually it does - barely. With the increased current, RCX output voltage drops, so does motor stall current. See these compared charts: (2 URLs) Philo (19 years ago, 7-Jun-06, to lugnet.robotics, FTX)
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(...) Thought provoking question. It led me to the conclusion that when the bot is generating it's maximum possible drawbar pull (as limited by the motor and drive train), the weight on the undriven front wheels (I'm assuming a rear wheel drive (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) Yeah - bad for a tractor with front-wheel steering - and a need to steer - not so bad for a robot with either no steering or rear-wheel skid steering. This robot really doesn't care if it's front end gets light - but for a tractor it's a major (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) (Or vice-versa!) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) Sure, I understand the argument. But this old farm boy has both a few hours in the driver's seat of a farm tractor, as well as a couple of engineering degrees, both of which prompted my cautionary statements. Let me start by saying that I (...) (19 years ago, 7-Jun-06, to lugnet.robotics)
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(...) I don't think Dean was talking about torque from the rope tipping the robot; I think he was talking about the fact that a raised attachment point for the rope can result in a downward component of the tension, increasing the force down on the (...) (19 years ago, 6-Jun-06, to lugnet.robotics)
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(...) Quite true. My bad. -dave (19 years ago, 6-Jun-06, to lugnet.robotics)
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(...) I think you need another pair of gears on one of the wheels to reverse its direction. If you are going to use a rotation sensor to measure the slippage then you need to realise that the sensor is notoriously poor at very low speeds. You'll at (...) (19 years ago, 6-Jun-06, to lugnet.robotics)
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