Quote:
Originally Posted by rootar
stum the 3d drawing as many or more amps on 18.5v compared to the 2.5d would only be true if you had extremely high gearing that REALLY REALLY loaded the motor, but only 40mph isnt anything for either of these, so the 3d will definetly draw les amps than the 2.5d on the same voltage. its only marketed as a 70amp motor while the 2.5d is a 78, this is at max voltage but you must take into account when running on the same voltage the 3d Will be more efficent on 5s and up, now getting down down below 5s i dunno how they react as much to the slower rpm because that would be a
large gear up to run the 3d at 40mph on 4s
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What it really comes down to is what motor best suits the application. If you are using ~15 volt packs, you don't want a low turn 4,000 kv motor just to go 30 mph and you don't want a high turn 1,000 kv motor in order to go 60 mph.
Keep in mind that just because a motor draws less amp geared to go a certain speed, doesn't mean it is more efficient. Efficiency directly relates to how well a motor can hold it's rpm. Otherwise, torque is basically proportional to current no matter what. You could have two 2,000 kv motors and even if one is 50% efficient and the other is 90% efficient, they both will have the same torque per amp. However, the 50% efficient motor will be spinning much slower than the 90% efficient motor. And btw, you can treat a 1,000kv motor with twice the pinion gear size as being equivalent to a 2,000 kv motor, and refer to the torque at the wheels instead.
Another example, if you gear a 1.5D for 40mph, it will create lots of wheelspin and will get up to speed very quickly. It will also draw a lot of current to do so, but not because it's inefficient. The excess amperage directly correlates to the explosive acceleration that the 1.5D will have in constrast to the 3D also geared for 40 mph. Such comparsion with the 2.5D and the 3D will be more subtle.