Beppe, I agree with you. No load ratings are almost worthless. I also agree that 1 amp is insufficent for the SC07, NC4, NC6, or similar hi-performance motors.
However, stall readings are also erroneous since they do not occur in normal use. Accelerating from a stop is not the same as stall, in a DC motor. Stall implies that the motor can NOT turn, and thus the current draw is a product of resistance and voltage. However, if the arm CAN turn, the first inrush of power will cause the arm to begin rotating and stall current will never be realized. There will be a brief spike that tends TOWARD the stall current but it will never reach that level and will last only for a very brief time (milliseconds at most). If the supply is a good one, the starting current can actually be satisfied by capacitors on the output.
Using your example, 12V in a 3 ohm armature, I would expect typical current draws to range in the lower half of the stall band, even on mag cars - up to 2 amps max, with a VERY brief spike to perhaps 3A on initial startup. Also, at full speed, the motor will draw much less than 1.3A (reverse EMF will bring the current draw to near zero on ANY motor at maximum speed). Even with heavy magnets, I doubt the SC07 will draw more than .5 to .75 A at full speed.
BUT... you are correct! One amp is NOT enough for motors in this range! They will need at least 2, and preferably 3, amps to properly display themselves and have a slight excess current available.
The best measure we could ever hope for would be a standardized system whereby motors were rated at moving a set mass, under set conditions, over a given distance or time, with acceleration and speed measurements, and current draw, available using fixed voltage levels. This would give us real world numbers that might actually mean something. At the moment, motor specs are virtually worthless, and only the experiences of others are truly indicative of a motor's actual performance.
However, stall readings are also erroneous since they do not occur in normal use. Accelerating from a stop is not the same as stall, in a DC motor. Stall implies that the motor can NOT turn, and thus the current draw is a product of resistance and voltage. However, if the arm CAN turn, the first inrush of power will cause the arm to begin rotating and stall current will never be realized. There will be a brief spike that tends TOWARD the stall current but it will never reach that level and will last only for a very brief time (milliseconds at most). If the supply is a good one, the starting current can actually be satisfied by capacitors on the output.
Using your example, 12V in a 3 ohm armature, I would expect typical current draws to range in the lower half of the stall band, even on mag cars - up to 2 amps max, with a VERY brief spike to perhaps 3A on initial startup. Also, at full speed, the motor will draw much less than 1.3A (reverse EMF will bring the current draw to near zero on ANY motor at maximum speed). Even with heavy magnets, I doubt the SC07 will draw more than .5 to .75 A at full speed.
BUT... you are correct! One amp is NOT enough for motors in this range! They will need at least 2, and preferably 3, amps to properly display themselves and have a slight excess current available.
The best measure we could ever hope for would be a standardized system whereby motors were rated at moving a set mass, under set conditions, over a given distance or time, with acceleration and speed measurements, and current draw, available using fixed voltage levels. This would give us real world numbers that might actually mean something. At the moment, motor specs are virtually worthless, and only the experiences of others are truly indicative of a motor's actual performance.
