Do you have a datasheet of the BLDC-motor?
The specs are linked to in the OP...
how many pulses were created per revolution?
Its a 4 pole 3-phase BLDC - that means 12 per motor revolution, so 600 per gearbox
output shaft revolution
25 Nm at the output of the 1:50 gearbox means
25 / 50 ) 0.5 Nm on the motor-shaft. That is not too much
No it doesn't quite mean this, it means the gears are rated to 25Nm for momentary periods,
and its 15Nm continuous (given in the specs). The efficiency of the gears may be
as low as 60% or so for a multistage planetary gear, so expect less performance than
naive calculation suggests.
For large reduction ratios the mechanical limits of the gears often dominate the output
torque rating, in fact its not impossible to destroy a gearmotor if the motor torque isn't
limited by the controller for whats safe for the geartrain. Here the gears appear to be
well matched and will handle the nominal output of the motor (just). They may not
handle motor stall torque though - a trap for the unwary.
The motor itself is 220W, 0.6Nm, 3500rpm, clearly given in the specs in that link.
220W is a lot more power than any stepper I've seen, if you need that torque at speed,
a stepper won't be a plausible substitute to this servomotor.
quite common steppermotors do have 3 Nm.
That's hold-in torque, dynamic torque is much less, perhaps 10 times less at full speed.
That's a large NEMA23 or more likely NEMA34 too.
So a gearbox of 1:10 would create 30Nm.
Not at speed though, only for holding fast.
for 70 rpm this means the stepper-motor runs at 700 rpm which is quite doable.
So what is the acceleration that you need for the 60 degree turns?
The question is: how much torque does the BLDC create when rotating at a lower speed for your 60 degree turns
A stepper-motor has the highest torque at low RPM.
DC motors, brushed or brushless, have the basically same torque at any speed as its set by the current.
a closed loop stepper-motor can do fast acceleration
If you need high acceleration a proper industrial servomotor (long thin rotor) is the way to
go as these have the lowest inertia to torque ratio.
best regards Stefan