E30-400 Motor Evaluation

The electric mower motor I got off craigslist had a 12in blade on it. That motor was rated for 24V, 4300RPM, 1.3N-m. I suspect it was pretty undersized for doing any real grass cutting, but whoever manufactured it had to size it at least somewhat appropriately.

Our three blade mower design has 12in blades on it. So in theory, any motor larger than the craigslist motor should be sufficient. But because I’m a perfectionist, I don’t want to just barely exceed these parameters. I want to knock them out of the park.

E30-400_Chart
Performance curves for the AmpFlow E30-400 DC motor.

For the same torque values as the craigslist motor, the E30-400 motor will rotate at about 5000RPM, consuming 700W while operating at about 77% efficiency. That translates to a blade tip speed of 15700ft/min, or 80% of the maximum allowable tip speed.

At the same speed as the craigslist motor, the E30-400 outputs about 2.8N-m of torque. That’s more than twice what the craigslist motor is rated for. Not bad.

The best part? Three of these guys only cost $354.41. And that’s after shipping, with insurance. The holy grail indeed.

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