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I've been puzzling over this one, and I still don't really understand it: Why can a bot with tank treads do a turn in place, while a bot with four wheels geared together so that the front and back wheels on each side always move together can not? My (...) (25 years ago, 26-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) [snip] (...) You are close here. Tank steering is often called "skid" steering because tank tracks are optimized for traction parallel to direction travelled and have little traction in a tangent direction. A look at the tread pattern will (...) (25 years ago, 26-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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This isn't an answer, but why not just make a three wheeled bot. You can place the third pivot wheel inside the radius of the two outer wheels, and you'll have a bot that turns in place. Most of my bots are of this design. Here is a crude ASCII (...) (25 years ago, 26-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) I don't know the other LEGO tracks, but the CyberMaster tracks confirm everything you said. They look like this (fixed font): | ----| |---- | |---- | | ----| | ----| |---- | |---- | | ----| | ----| |---- | Also, they are deeper in the center (...) (25 years ago, 26-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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I was wondering the same thing until a little while ago, I saw a large (i.e. industrial-sized) remote control vehicle in use by the UK fire service to fight fires in hazardous areas. The vehicle uses solid low- grip rubber tyres and four wheels that (...) (25 years ago, 26-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) Add on: Also important in all this is the distance the tracks are apart. The further apart the less friction they have, since the radius is larger. Same happens with wheels. Laurentino Martins [ mailto:lau@mail.telepac.pt ] [ (URL) ] -- Did (...) (25 years ago, 26-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) Why is this? The further apart they are, the greater r*cos(theta) is going to be for any given theta. Seems like that would make for more turning resistance, not less. (25 years ago, 27-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) Because the wheel base length shrinks in relation to the turning radius. It is this distance that causes the friction. The further this point is from the imaginary circle that the treads describe, the more perpendicular friction there is. As (...) (25 years ago, 27-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) I'll try to explain this with an ASCII picture, but I'm make no promises about the quality... Please use a fixed font (as you always should in newsgroups) Legend: #### - Lower part of the track (the part that touches the ground). OOOO - Inner (...) (25 years ago, 27-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) That makes sense - thanks! (25 years ago, 27-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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It makes for more. Don't ask me why, it just does. It kind of reminds me of a great old banjo player i know. When i asked him to break down the way he used his picking hand he said, impatiently, "WHAT'S THERE TO SHOW?! EITHER U JUST PICK UP THE DAMN (...) (25 years ago, 28-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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U R My hero (next to my dad). Only problem w/him is that he never explains anything!!! : ) Michael Aaron (...) (25 years ago, 28-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) Sure. Based on other comments I've received I'm guessing my previous explaination was a little obtuse. (No pun intended... angles, get it.) Ok, let's see if I can explain this without any pretty pictures. It is getting to be time for bed so (...) (25 years ago, 28-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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(...) [lots snipped . By all means, look at the original message! ;-) ] (...) Beautiful stuff! That's what I call an explanation. "progeeks", indeed... :-)) Thanks, Paul! (Incidentally, you're not using a pseudonym? ;-) Best regards, Martin (25 years ago, 28-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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Jon Shemitz skrev i meddelandet <379E1AC5.53445703@m...ch.com>... (...) further apart the less friction they have, since the radius is larger. (...) (ASCII Art warning - fixed font on) Just compare these two designs: #-# ! ! X ! ! #-# and (...) (25 years ago, 31-Jul-99, to lugnet.robotics)
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| | Re: Mechanical question
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This thread already offers a lot of interesting explanation about the thrack slip, but on the wheels part you may want to have a look at: (URL) in menu: going in circles Animations explain how side slip in wheels is (practically) zero as long as (...) (25 years ago, 9-Aug-99, to lugnet.robotics)
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