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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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| | Re: Newbie needs Help (diff sensor)
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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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(...) What I'm saying is that if the robot is moving along at (say) 3 inches per second - then the drive wheels will get most traction if they are turning at a speed equivelent to 3 inches per second. If they are rotating faster than that (because (...) (19 years ago, 6-Jun-06, to lugnet.robotics)
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Some varied thoughts here: (...) I might be wrong, but my understanding of the Lego differential gearing is that if both shafts are turning at the same rate and direction, the outer gear/shell will turn at the same rate as the axles. Only when the (...) (19 years ago, 6-Jun-06, to lugnet.robotics)
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(...) Raj, There's a bit of confusion here. I believe the above quote actually came from Steve Baker (posting only as Steve). As Steve Baker pointed out, there is a difference between kinetic (sliding) friction and static friction. ((URL) In the (...) (19 years ago, 6-Jun-06, to lugnet.robotics)
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(...) Ummm.... that's not the way I remember the mechanics. There is a torque created that is force on the drawbar times the drawbar height from ground. That torque will lift your front end. Doubling your own drawbar height halves your pulling (...) (19 years ago, 6-Jun-06, to lugnet.robotics)
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(...) One rotation sensor and a differential will allow you to compare the rotation of two wheels. If the driven wheel and the undriven wheel come in the two sides of the differential, and the rotation sensor is connected to the drive ring, then the (...) (19 years ago, 6-Jun-06, to lugnet.robotics)
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