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I need a small air compressor for a robotics application. I currently have one of those 12V tire inflators (200 psi, 1 CFM or so) that is sized well for this purpose (sample image below).

However, in the future I would like to replace this with a lighter compressor with similar specifications (for weight savings). Most of the weight of these compressors is a large DC brushed motor (the whole big silver cylinder in the photo below), while the actual compression module is relatively small. These motors are roughly 350W peak (30A, 12V from spec sheet). Similar DC brushless motors (by wattage) are <150 grams. Certainly they might be at a higher RPM, but even with gears this would still be a lot smaller.

Is there any reason that these huge (3-4 kg) brushed motors couldn't be replaced by tiny brushless motors? If so, why can't I find such devices anywhere? It wouldn't be cost effective for these cheapo inflators (you need more complex controls for brushless), but it seems like there would be enough demand for lightweight compressors for someone to manufacture a few.

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If so, why can't I find such devices anywhere?

In a word - Cost.

Running some quick searches for 300W DC motors, the brushless motors were typically 3x - 5x more expensive than their brushed counterparts. And as you pointed out, brushless motors require additional and more expensive controls than a comparable brushed motor.

It's worth pointing out that small compressors like the one you asked about are commodity grade products. Profit margins on them are slim and purchase decisions are frequently driven by cost alone. It is the rare consumer who would consider paying a significantly higher amount of money for a comparatively smaller benefit of decreased weight.

And I think you're overestimating the demand for lighter weight compressors. Most places that I'm aware of that are using compressors purchase them infrequently, and they tend to be fixed installations where the weight of the compressor doesn't matter that much. And for the cases where weight and portability is a concern, cost becomes an over-riding factor.


That said, would you be able to replace the existing motor with a brushless motor? Presuming you have the ability to create the additional controls and gearing to go along with using the brushless motor, I don't see why not. And for what I suspect is going to be a relatively low utilization rate, you're likely going to see an equivalent lifespan of the product.

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