Subject:
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Re: 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 19:57:22 GMT
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Original-From:
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alex wetmore <alex@phred.org#antispam#>
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Viewed:
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715 times
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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 drawing of the footprint (you'll need to view it in a
fixed width font)
# * #
# * #
# #
# #
# #
# #
So the # wheels are the large ones that come with Mindstorms. The ** are
much smaller wheels. This gives three points of contact (so its stable),
but the point of contact made by the smaller wheel is inside the turning
radius of the larger wheels.
My first robot was built this way, and was designed not to fall off of
tables. It was quite cool to see it come up to the very edge, then spin
around (with parts of the robot, but not the wheels themselves, off of the
table) and finally start driving away.
alex
----- Original Message -----
From: Jon Shemitz <jon@midnightbeach.com>
To: <lego-robotics@crynwr.com>
Sent: Monday, July 26, 1999 12:15 PM
Subject: Mechanical question
> 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
> --
> Did you check the web site first?: http://www.crynwr.com/lego-robotics
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message is in Reply To:
 | | Mechanical question
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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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