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UWO

Viewing 11 posts - 21 through 31 (of 31 total)
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  • #365282
    Toolshead
    Pro
    In the Rice Fields, South TX

    http://www.dewalt.com/featured-articles/power-tools-what-does-torque-rating-really-mean.aspx really seems pretty clear.

    Which is more powerful – a Ferrari or a Ford truck? Depends if you’re after speed or trying to get out of the mud.

    This rating seems to combine the two ratings into a meaningful number, the same as volts times amperage equals watts.

    No, it doesn’t show just speed or max-out torque by itself, but seems to come up with a number taken at multiple points. You could vary either parameter by changing the gearing, depending on what the manufacturer wanted to claim, but not both at the same time.

    Makes more sense to me than tools rated by what battery they take.
    Or maybe I read it wrong.

    #365367
    jzmtl
    Pro
    Montreal, QC

    It matters more on a vehicle because you want speed in some of them, whereas on a drill torque matters more so than speed, plus one engine could have twice the redline RPM than another while drills all have more or less the same RPM range.. But even with cars both max HP and max torque are listed in specs. With Dewalt as the only user of the unit, it’s about as useful as if Ford starts saying their trucks produces 369 turnmajigs.

    I think the European system where both stall torque and running torque is listed is the best.

    #365396

    It’d be even better if we actually had torque-RPM curves that also showed temporary overload conditions wherein the motor is thermally power limited after the peak power, like these:

    http://www.ajaxcnc.com/images/servo%20stepper%20torque.jpg
    http://www.animatics.com/images/kb/torquecurve.png

    And after the gearbox, too.

    I could have 1kW motor coupled to a high RPM flywheel, it’ll be awesome the moment the tool bit hits material since it’ll probably thermally form off the inertia of the flywheel, but then the gutlessly low torque, high revving motor will basically lose the capability to spin the flywheel from a stall until the tool is disengaged and freed from the workpiece.

    As detached from handheld powertools as that example sounds: Impact drivers and wrench work in a similar kind of fashion, they use the momentum of the hammer to store the energy until the torque load is reached to cause the hammer to slip and disengage from the anvil, where the motor can spin it back to speed again before it strikes, engages and then slips as it runs out of energy to drive the bit. A driver using the same motor with a different reduction ratio can beat the impact driver for driving bolts that it can muscle in since it doesn’t have to lose that energy.

    In the case of the impact driver, you’re seeing the “hard torque” rating with the nice big numbers, even if they fundamentally share the same motor or motor power class as another driver or drill. Different gear reduction ratios on the motors to generate different torque and RPM output to match the application. I believe in impact drivers the output RPM to the hammer is usually double or higher than the drills since it relies on spinning the hammer to RPM to gain enough rotational speed until it strikes again instead of relying on the torque of the motor to directly drive the tool into the workpiece. The direct drive mode being representative of the soft torque stage in drill/drivers until the impact driver starts reaching the torque spec where the hammer slips and allows for the impact mechanism to function.

    Kind of a generalization for most of that, but that gets it down pretty well. That gets more information on the capabilities of the tool by than 300 turnwatts or whatever they plan on rating those in the future.

    #365408
    DirtyWhiteBoy
    Pro
    Honolulu,, Hi.

    I’d say 90% of people around here think Dewalt is the Ferrari of power tools. I’d consider them a Tercel…

    I think ponto got it nailed.
    It’s not their products I dislike it’s their policies I hate!!!!

    #365425
    jzmtl
    Pro
    Montreal, QC

    Heh, a torque curve would be too much to ask, I’d be happy with stall and running torques.

    #365462
    theamcguy
    Pro
    Fayetteville, NC

    Specs are nice to compare different models with each other, but nothing compares to real world reviews like found on BTP.

    Automotive Pro
    Fayetteville, NC

    #365514
    Toolshead
    Pro
    In the Rice Fields, South TX

    What bothers me on this is the articles referring to UWO and MWO as ‘standards’. DeWalt has a passing mention of ‘performance standards’, but not that it’s THE standard.

    A standard tells you how something is measured, under what conditions, the accuracy and precision required, and a bunch of other stuff to make sure every item tested has repeatable results.

    International organizations devise these standards. It’s OK to report speed in furlongs/fortnight if you want, but it’s in addition to the standard of miles (km)/hr if you are measuring speedometers.

    I searched ISO (International Organization for Standardization) and ANSI (American National Standards Institute) for UWO and MWO – no results found.

    That doesn’t mean that DeWalt doesn’t have its own method developed to consistently measure things (their own and competitor’s), it’s just not a recognized standard so you get the same number no matter where in the world and by who it’s tested.

    An analogy – One stereo system is rated 100 watts RMS output per channel with maximum 0.005% harmonic distortion from 20-20,000 Hz, with 0.2 volts input. Another stereo is rated at a gazillion watts output ‘peak’ or ‘instantaneous’ power, distortion isn’t measured, with a single tone injected at the stereo’s most efficient point with the maximum voltage you can to avoid smoke. Whatever reading you get in that fraction of a second before melt-down is what’s reported. Which is a more accurate representation of the item for how you use it?

    I’m amazed at people that can interpret power curves and interpolate all the factors involved. X times Y = number seems pretty easy, as long as X and Y are measured identically.

    #365696
    jdw1865
    Pro
    Dewey, OK

    I went back and looked at the DeWalt. Thought about it some more. And did what I started to do at the vwry get go. I bought a Bosch.

    #365714
    theamcguy
    Pro
    Fayetteville, NC

    I went back and looked at the DeWalt. Thought about it some more. And did what I started to do at the vwry get go. I bought a Bosch.

    So what Bosch driver did you end up getting?

    Automotive Pro
    Fayetteville, NC

    #365825
    jdw1865
    Pro
    Dewey, OK

    PS-41 the 12v impact driver. My old 12v driver batteries bit the dust and even the after mkt ones were almost 3/4 as much as a new driver with batteries.

    #365865
    jzmtl
    Pro
    Montreal, QC

    You are gona love it, it’s my most used tool of them all, more than the drill and more than the 18v set. I even used it on tiny machine screws to disassemble/assemble stuff before I got a Makita screwdriver.

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