×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Cordless Drill Torque at Speed

Cordless Drill Torque at Speed

Cordless Drill Torque at Speed

(OP)
Is there a way to find out the approximate torque of a cordless drill at a certain speed? All of the manufacturers I have found only list max torque and then speed ranges. Is the max torque when the unit is stalled?

Thanks,
Mike

RE: Cordless Drill Torque at Speed

I'd assume that the max torque is at zero speed.  Brushless motors usually retain their torque through out their speed range except at the highest RPMs where the motor inductance-resistance keeps the current from rising to maximum.

RE: Cordless Drill Torque at Speed

I thought DC motors had 100% torque at any speed, except for loses due to friction or limits of current as speed increases, so sried is right on.  look at http://www.teslamotors.com/index.php to see the ultimate torque on a DC motor.

RE: Cordless Drill Torque at Speed

I know that my DeWalt - fully charged - could break a wrist if you aren't careful!!

RE: Cordless Drill Torque at Speed

(OP)
I am looking at a 28 volt Milwaukee Electric Tool drill: V28 1/2 in. Hammer-Drill #0724-20. The low speed setting is up to 600 RPM, the high speed setting goes to 1800. The manual lists low speed torque as 600 in.lbs. and the high speed at 300 in.lbs.

I am trying to get an idea of how much power this drill can actually put out. Might it put out 1 hp? Say 35 in.lbs. of torque at 1800 RPM or 300 in.lbs at 210 RPM?

I have never worked with such a beefy drill but would love to hear from someone who has and the manufacturer (and other drill makers) has not been very helpful.

Thanks,
Mike

RE: Cordless Drill Torque at Speed

A pulley, a string and some weights.

RE: Cordless Drill Torque at Speed

I was thinking a drum, a strip of crocus and a fish scale

RE: Cordless Drill Torque at Speed

Usually a DC motor at constant voltage has maximum torque at stall and zero torque at maximum speed, with a linear relationship between them. So if you assume the torque and speed ratings are the maximums, you can find that the low-speed torque is 600in-lb - N * in-lb/RPM.

RE: Cordless Drill Torque at Speed

Get a pencil and some graph paper and plot the two sets of data  speed-torque where the y coordinate is speed and the x coordinate is torque. Now draw a straight line thru the points and that is the curve for a DC motor. The x and y intercepts reprresent the stall torque and no load speed respectively.

RE: Cordless Drill Torque at Speed

(OP)
So you are saying that at the midpoint the drill puts out 300 in.lbs of torque while the shaft is turning at 900 RPM? That seems high to me.

RE: Cordless Drill Torque at Speed

mechengineer18, I think you've mixed up the numbers between the two curves. The high speed curve would give results of 150 in.lbs at 900rpm at the midpoint.

RE: Cordless Drill Torque at Speed

(OP)
Thanks geekEE. My head wasn't in the game.

RE: Cordless Drill Torque at Speed

While it is true that DC motors will develop maximum torque THEORETICALLY at zero speed, in reality this is not done.  To design an efficient motor, the motor resistance needs to be low.  If one allowed full stall current to flow the result would probably be

Demagnetized motor magnets

Blown Power Transistors

A Battery taken to it's knees

Brushless motor controllers sense the motor current and limit the current to a maximum value.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources