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In lugnet.robotics, Philippe Hurbain writes:
> I received two new 9V mini-motors from S@H, that was of the new variety
> described by Mark Riley (http://news.lugnet.com/robotics/?n=19204).
A friend brought a newly bought DACTA set, 9793 Mindstorms for schools, today
and it contains two 43362 motors. These are not the same:
http://www.lotek.nu/misc/43362.jpg
The one without the "backholes" spins like the older geared motor, for aprox
six seconds given a twist on the shaft, the other one for but one second...
The mystery deepens...
::spooky music fades into the night::
Best regards,
Tobbe
http://www.lotek.nu
(remove SPAM when e-mailing)
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Hi Tobbe,
My guess is that your friend actually got one 43362 and one 71427, the
latter beeing enclosed in a 43362 case. If you look at 43362 enclosure photo
(http://www.philohome.com/motors/case.jpg), you see that there are 4 plastic
pins in corners that are used to secure 71427 core to the box. So Lego can
use the same case for two different products ! The proof to that: the two
black holes on back are missing from the freely running motor while they are
required to hold the brushes of 43362 core motor.
This is not a good thing for your friend : the weight of these motors is
somewhat different (28g vs 42g), 43362 rotates slightly slowlier and stops
sooner. This probably render a simple differential drive equipped with both
motor types almost unusable (needs to be tested though !)
Philo
www.philohome.com
> A friend brought a newly bought DACTA set, 9793 Mindstorms for schools, today
> and it contains two 43362 motors. These are not the same:
> http://www.lotek.nu/misc/43362.jpg
>
> The one without the "backholes" spins like the older geared motor, for aprox
> six seconds given a twist on the shaft, the other one for but one second...
>
> The mystery deepens...
>
> ::spooky music fades into the night::
>
> Best regards,
> Tobbe
> http://www.lotek.nu
> (remove SPAM when e-mailing)
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In lugnet.robotics, Philippe Hurbain writes:
> Hi Tobbe,
>
> My guess is that your friend actually got one 43362 and one 71427, the
> latter beeing enclosed in a 43362 case. If you look at 43362 enclosure photo
> (http://www.philohome.com/motors/case.jpg), you see that there are 4 plastic
> pins in corners that are used to secure 71427 core to the box. So Lego can
> use the same case for two different products ! The proof to that: the two
> black holes on back are missing from the freely running motor while they are
> required to hold the brushes of 43362 core motor.
Ah!
> This is not a good thing for your friend : the weight of these motors is
> somewhat different (28g vs 42g), 43362 rotates slightly slowlier and stops
> sooner. This probably render a simple differential drive equipped with both
> motor types almost unusable (needs to be tested though !)
My friend wont bother much since the boxes are for education at hiw workplace.
I conducted a quick test with one 71427-002 and one 43362 (with new internals),
put them back to back with a 8462 wheel on each axel and a 9V small battery box
being pused in front of them. A _very_ simpel dif. vehicle. As suspected the
vehicle wont drive in a straight line and it's the new motor that lags behind
causing the vehicle to turn. It's not a very tight turn though. The path
describes an arc, like a ')' being 6.7 meters "high" and 1 m wide. Don't know
the math to turn this into a turning radius. Perhaps I should have used gearing
to make the difference between the two motors more visible.
It feels like this is not a big difference though, I bet two of the old motors
would have done about the same arc...
/Tobbe
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Tobbe Arnesson wrote:
> I conducted a quick test with one 71427-002 and one 43362 (with new internals),
> put them back to back with a 8462 wheel on each axel and a 9V small battery box
> being pused in front of them. A _very_ simpel dif. vehicle. As suspected the
> vehicle wont drive in a straight line and it's the new motor that lags behind
> causing the vehicle to turn. It's not a very tight turn though. The path
> describes an arc, like a ')' being 6.7 meters "high" and 1 m wide. Don't know
> the math to turn this into a turning radius.
It's 6.11125 meters.
> Perhaps I should have used gearing
> to make the difference between the two motors more visible.
Yes - it's hard to tell because the difference in speeds will depend on
the load on the motors - loading them either more or less would alter
their characteristics relative to each other.
> It feels like this is not a big difference though, I bet two of the old motors
> would have done about the same arc...
Yes - I think so. Really, every robot that's required to drive more or
less straight needs software to measure it's course and correct for small
motor differences.
Between the dozen or so (supposedly identical) Lego motors I own (all of
the older kind), I see an 11% speed difference between the fastest and the
slowest (with no load other than a rotation sensor).
http://www.sjbaker.org/steve/lego/motor_speed.html
If you had told us the distance between the wheels of your test robot,
we could come up with an estimate of the speed difference between them
and see just how unreasonable this is.
Personally, I'd call Lego an explain that your motors are not the
same and that this makes your robots misbehave - and I'd bet good
money that they'll come through and offer to replace one or both
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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