Cordless drill?

Looking at cordless drill I noticed one which stated on it that it produced 32Nm of torque at 2000RPM. This seems a lot are they being optimistic.

None of my drills have it marked on them.

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2 years ago

I was just looking at,

http://www.dewalt.co.uk/powertools/productdetails/...

Advertisers have sort of a weakness for hyperbole; i.e. writing that makes their products seem bigger, faster, more powerful, etc.

A typical motor torque-speed curve, for a DC motor,

http://lancet.mit.edu/motors/motors3.html#tscurve

has the shape of a line with negative slope, intersecting torque axis at Tmax, intersecting speed axis at Smax, and it is not too hard to prove the maximum power such a motor can deliver, is

Pmax = (1/4)*Smax*Tmax

Although, even with those generous assumptions, the numbers Dewalt is quoting give a Pmax of around 500 watts, (1/4)*(60 rad/s)*(38 N*m) = 570 W, which to me seems far too high, by about a factor of 10.

rickharris (author)  Jack A Lopez2 years ago

It may be that dewalt (and others) are talking about different things to me

-The attached graph is the spec for the motor used on our electric car. It states unequivocally that the torque is 1.15Nm -

This is a motor I know to be large, operating on 24 volts and drawing 20 amps. (500 watts). This doesn't start to compare with the drill motor even considering the drill motor has a considerable gearing down.

2 years ago

Yeah. I think the advertisers lost a decimal point somewhere. Maybe intentionally?

Supposing the motor is geared for a maximum (no load) speed of 575 rev/min = 575*2*pi/60s = 60 rad/s, and maximum torque of 3.8 N*m (rather than 38 N*m), then

Pmax = (1/4)*(60 rad/s)*(3.8 N*m) = 57 W

and that number is a lot more realistic for a cordless drill.

rickharris (author) 2 years ago

Thanks guys - best answer to you all but the stupid system won't allow that.

steveastrouk2 years ago

6.7kW ?

What batteries were they ?????

rickharris (author)  steveastrouk2 years ago

according to this web site

http://www.translatorscafe.com/cafe/EN/units-conve...

60 Nm converted to Hp/hour is as below.

Is their conversion right?

60 newton meter = 0.00002235036816667 horsepower hour

2 years ago

I used torque x speed in rad/sec = power....

The spec I'm reading doesn't claim 60Nm at 2K, it claims a stall torque of 60Nm

rickharris (author)  steveastrouk2 years ago

My thoughts as well - It was a dewalt - This is the spec

even worse this claims 60 Nm

I wonder what they are measuring.

Vyger2 years ago

How many people does it take to hold it?

Thinking about those gas powered ice augers with the 2 people spinning around while the auger remains stuck in the ice.

rickharris (author)  Vyger2 years ago

It's a standard Dewalt cordless - the spec is from their web site

http://www.dewalt.co.uk/powertools/productdetails/...

Something seems wrong.

iceng2 years ago

That's 9 HP, way too much for a cordless hand drill !

rickharris (author)  iceng2 years ago

My thoughts as well - It was a dewalt - This is the spec

even worse this claims 60 Nm

I wonder what they are measuring.