Subject:
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Re: "synchro drive"
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 4 Feb 1999 04:05:03 GMT
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Original-From:
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Doug Carlson <DCARLSON@NET-ihatespamINFO.COM>
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Viewed:
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985 times
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I'm not sure I follow the problem in the design I used.
One feature which isn't spelled out on my page is that each wheel
is offset from the center of its turntable by a distance equal to the wheels
radius.
When the turntable turns (while the vertical drive shaft is static) the wheel just
runs
in circles equal to its diameter and the vehicle doesn't move at all.
If you drive both the steering and main drive systems at the same time the whole
vehicle
runs in a circle (while still 'facing' the same direction) the diameter of which
can be changed
by the the ratio of main drive speed to turning drive speed. So you can 'turn' on
a point or
any radius you might choose.
One other benefit of this offset design is that the wheel contact point is not
'scrubbed'
as would be the case with a center mounted wheel when the turntable rotates.
I have also read of a design using a differential between two wheels per
'turntable' to
equalize the load on the wheels.
This was difficult to build with LEGO so I stayed with the current design.
BTW - somebody thump me in the head if I'm way off here :-).
Also, I do have a .dat file for Ledit/Ldraw of this design. I just haven't
finnished
pollishing it up for instructions yet. Just let me know if you would like it as
is.
-- Doug
John A. Tamplin wrote:
> I am working on building a platform using the idea from the "Syncho Drive"
> (no flamewars about what to call it -- that is what the original poster
> had so I am sticking to it).
>
> The problem I am having is that turning one "leg" induces a turn in the
> shaft used to supply power to the wheel. I thought it would be easy to
> use a differential to subtract the induced rotation from the shaft, by
> gearing the differential body to the turntable. However, I am running
> into a problem trying to achieve this since the inner gearing in the
> turntable is too small to get the power shaft and some other gears in,
> and the outer gear is 56t.
>
> Poor ASCII drawing to follow:
>
> A
> |
> _|_ B
> | |
> | |
> ------- C
> |
> {-------------------}
> D[=====================]
> |
> |
> (to wheel via crown gear)
>
> A is the input power from the drive motor. B is the 16t gear on the
> differential, C is the 24t gear on the differential, and D is the 56t gear
> on the outside of the lower part of the turntable.
>
> I need to take one complete rotation of D and transform that into half a
> rotation in the same direction on either B or C. That will result in no
> turning of A just from turning the turntable, making turning and drive
> independent.
>
> The problem is that 56=7*2*2*2, and none of the standard Lego gears have
> any way to generate a 7:x ratio. I am sure I can use another
> differential to subtract two other ratios to get 7:1, but this is quickly
> getting painful (not to mention the efficiency losses).
>
> Am I missing something simple? Does anyone have any bright ideas?
> Doug's version appears to ignore the problem of turning introducing
> movement, but I would like to correct that.
>
> John A. Tamplin Traveller Information Services
> jat@Traveller.COM 2104 West Ferry Way
> 256/705-7007 - FAX 256/705-7100 Huntsville, AL 35801
>
> --
> Did you check the web site first?: http://www.crynwr.com/lego-robotics
Doug Carlson
dcarlson@net-info-com
carlson_doug@htc.honeywell.com
http://www.net-info.com/~dcarlson
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 1 Reply:
 | | Re: "synchro drive"
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| (...) Wish it was mine. :-) (...) I just used the 12T miter gears. 1:1 with the wheel offset equal to the wheel radius.I was just lucky that it fit the turntable so well. (...) I think the point of this platform is that it's handy to always have a (...) (26 years ago, 5-Feb-99, to lugnet.robotics)
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Message is in Reply To:
| | "synchro drive"
|
| I am working on building a platform using the idea from the "Syncho Drive" (no flamewars about what to call it -- that is what the original poster had so I am sticking to it). The problem I am having is that turning one "leg" induces a turn in the (...) (26 years ago, 5-Feb-99, to lugnet.robotics)
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