Subject:
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Mechanical question
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 26 Jul 1999 19:15:38 GMT
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Reply-To:
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JON@MIDNIGHTBEACH.saynotospamCOM
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Viewed:
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904 times
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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 *expectation* was that the two
were basically identical, but that clearly is not the case. The 'tank'
turns easily; the 'car' just sits there making motor straining sounds.
Is it that the tank treads are harder rubber than the tire wheels, and
so resist sideways motion less?
Or is it that the wheeled version is concentrating all the sideways
force at four points, while the treaded version is spreading the same
force over a much larger area?
Or is it something else entirely?
--
http://www.midnightbeach.com - Me, my work, my writing, and
http://www.midnightbeach.com/hs - my homeschool resource pages
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Message has 6 Replies:
 | | 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)
| | | 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)
| | | 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)
| | | 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)
| | | 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)
| | | 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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