Subject:
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Re: Heavily modified 8880 chassis, succesfully motorised and solar powered.
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Newsgroups:
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lugnet.technic
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Date:
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Sat, 15 Feb 2003 19:40:29 GMT
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Viewed:
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2140 times
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In lugnet.technic, Gillis Hommen writes:
> It's just that according to this page:
> http://www.philohome.com/motors/motorcomp.htm the new style lego motors'
> efficiency is only 54% at 9v (or even 47% for the 'newer' (?) style V9
> motor)...which is not even close to 90%...
Well, I can't argue with that... But in your application, going from a motor
with 30% efficiency to one with 54% efficiency will help a lot. You will
also gain some efficiency by simplifying your gearing since the new motors
are already geared down.
> I'd have to connect the 2 motors in serial
??? Why would you do this? I'm not an electronics expert, but connecting
motors in series seems strange. The speed of a motor is proportional to the
voltage across it, so I think you would get drastic speed variations between
two motors in series. This was discussed on the newsgroup a while ago:
http://news.lugnet.com/robotics/?n=19878
Someone actually tried connecting two motors in series (it is possible with
Lego, just a bit awkward) and this is what he found:
http://news.lugnet.com/robotics/?n=19880
If you connect two motors in parallel, they have the same voltage across
them, so their speed should be much more closely matched. I guess they draw
more current in this case, but such is life...
> Connecting two motors without a diff
> is do-able, but in serial, one of the motors will probably get more voltage
> than the other, which makes the 'tandem connection' less optimal.
Right. In parallel this won't be a problem.
> You're totally right about the weight though. The motor I'm looking to buy
> weighs in at some 160grams, much more than 2 lego motors.
And don't forget cost :)
Actually, if your main focus is efficiency, why would you even use the
supercar chassis to begin with? I think you could increase your efficiency
dramatically just by using a highly simplified chassis with minimal gears
and parts. It would be lighter and have less losses due to friction.
Rob
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