OT How important is steel jacket on DC motor?

Magnetic flux path. Won't work without it.

John

Won't work _as well_ without it. Will probably still work. Certainly won't work as well.

The motor will spin faster for the same voltage, it will produce less torque for the same current, and it's torque/watt dissipated figure of merit will go down. If you're looking at performance vs. weight, it's probably better left on.

Why not just find a slightly smaller motor?

That might have saved one of my motors. I just love to remove stuff I see as unnecessary.

Thanks.

I will if this one ends up being overpowered. Given my limited design capability, I can't tell yet.

I'm guessing it won't spin at all, but just make smoke. The reluctance of the magnetic path will go up by two or three orders of magnitude.

John

How do you intend to support the magnets, bearing and brushes?

Usually the outer cylinder has multiple functions, one is to complete the magnetic path, another is mechanical to ensure the magnets are held with a small air-gap to the armature and also as way of mounting the bell-ends that support the brushes and the bearings.

Sometimes I have seen an additional sleeve that goes over the outside to improve the magnetic path - that can be removed without stopping operation.

kevin

The motor casing.

In fact, I was planning to clarify that now just in case John Larkin misunderstood what I meant. Whatever you want to call it, to me it looks like an extra layer of steel that doesn't completely cover the motor casing.

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I think you're thinking about a different motor than I'm thinking about. The battery powered drill motors that I have seen have a thin steel (probably less than 20 mil) can backed up with a thicker band (around 25 mil or so) that looks like mu metal. So if you took off the band then it'd still work, just not so well.

Kinda like this one:

You used to be able to buy the bands as a retrofit for electric-powered RC model cars; I think now you would just get a brushless and go twice as fast, instead of getting a little bit of steel and going 10% faster.

Yes, if you took away _all_ the iron then the motor would suffer greatly, but since it's usually the iron that holds the magnets, you'd probably notice that something was wrong...

So what's the motor that you're thinking of?

OK, if you leave some of the magnetic path in place. Doesn't sound like it will save a lot of size or weight, though.

John

You got it, thanks for the picture.

The motor I have is from a Bosch 36 V hammer drill. The band is more than a bit of steel (.05 inches, 1.2 mm, thick), but I would be surprised if a brushless motor would be much better for the application. They hardly skimp on materials, for example the included batteries are exceptionally sturdy 36V two amp hour lithium-ion with a 3 LED charge level indicator. The battery charger has a fan in it.

FWIW. That Bosch 36 V hammer drill is being dumped for (USA) $170 total at the online merchant Tool Authority and a few other places on the Internet). It's $575 at Home Depot with tax. I guess Bosch is dumping them for a good reason, but I dunno exactly why. Nothing obviously wrong with the tool. Great deal IMO if you have the cash and need a 36V motor and accessories.

I don't know about John Larkin, but I'm wondering about taking that band off of my DeWalt 36V motor (I vaguely recall doing that). Glad I asked before doing that again. Oh well, since I've misplaced the band, now I have an excuse (however weak) for not using that DeWalt motor.

Thanks to Kevin for the first correction, I probably should have said "additional" or "extra" in my original post.

Methinks theHeavy Metal Jacket holds it together...