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  • #31
    Originally posted by Dawg View Post
    i think Milkwaukee just delivered what you were looking for in regards to lower RPM and higher torque. The RAD (V28) in lower in rated at 400 RPS and 1081 in lbs. of torque. Compared to DeWalt's 400 RPM and Does anyone know what the ^$&*@&$# a "Unts Watts Out" is? Is this something that DeWalt invented? Why? I also just notice that DeWalt only has 2.0 amp hrs of run time in their Li-Ion batteries.


    http://www.dewalt.com/us/articles/ar...rdless&ID=1487
    Thats their explanation. I believe its common for this being the standard way to measure them in europe. As mentioned a continuos graph would truly be the ideal way but for now its better than torque ratings which are worthless. All they do is tell at what point the drill will stall in the lowest gear.

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    • #32
      No, Watts or the UWO measurement is not something DeWalt "invented". Torque ratings are not even the slightest bit useful - they're typically the peak torque measured as the drill is stalled on a torque wrench i.e. the drill is chucked on to the torque wrench and the trigger is pulled full blast. The torque will peak at a maximum very briefly and almost immediately drop down due to the intense heating of the motor and battery. Typically, the torque will drop down to a continuous sustained amount that is significantly lower than the peak torque.

      All this peak torque measurement does is allow the manufacturer to print the largest torque number without technically "lying"... per se. But because this peak torque only happens within a very short blip of time, it really bares little representation of how the drill works a continuous task.

      That being said, DeWalt's stab at this UWO rating seems to be a generally good concept, because it should give you a better idea of how the tool performs in the real world. If every manufacturer used a standard rating scheme that better represents real tool performance, it would be much easier for the end user to find the tool with the power that they need.

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      • #33
        How does Unit WAtts out = a better representation?

        I always thought electric/battery powered motors had their peak torque from 0 RPM's all the way to, say 1000-1500 RPM's. And after that torque dropped off.

        What I'd be interested in, are the gear ratio's of the gears/transmissions found in drills.

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        • #34
          Scott

          You need to contact a senior tech working in tech support at the factory. The right person there should have the loads of testing info on file.

          All of this makes me wish I knew someone with a small PRONY BRAKE (name of inventor) . They required a skilled operator of which I am not. They are great for loading and measuring torque and RPM. Then using the right math formulas you can obtain HP. Next to make a graph with about 10 points on it and then use a "French Curve" (drawing tool) to connect the dots. Power tools companies need to quit the marketing hype and post a true power curve. Most serious engine manufactures post such along with a torque curve. That's the way to compare A with B and really know the difference. I think when it comes too drills they are scared to publish such info.

          Now the more simple and lower cost way is to get several drills and several new bits in the same sizes and brand. Next you find lots of the same material and in different types and run side by side drilling tests. I'm sure you get my thoughts here. Real life testing under real life conditions. Now just get me my money tree so I can buy loads of different drills and bits along with stuff to drill loads of holes in. The fun starts. Anyone want to help drill loads of holes?

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          • #35
            Torque and Power Graphed

            http://www.robinamerica.com/engines/...g=eh36_crv.gif

            This will take you to a power and torque graph for a small gasoline engine made by Subaru - Robin. This is what we want is for power tool companies to publish for their tools. Please remember that engines have a limited running speed range.

            If interested click the link under it which will give you more info to read about.

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            • #36
              Except power/torque curves for electric engines are very different than gas.

              Originally posted by Woussko View Post
              http://www.robinamerica.com/engines/...g=eh36_crv.gif

              This will take you to a power and torque graph for a small gasoline engine made by Subaru - Robin. This is what we want is for power tool companies to publish for their tools. Please remember that engines have a limited running speed range.

              If interested click the link under it which will give you more info to read about.
              Electric engines can actually produce their max torque at 0 rpm (stall)...gas engines can not. However, these very high torques come at a price of very high current and heat to the motor. Without stall protection, you can burn up an electric motor quickly. This was an issue Consumer Reports exposed with the Milwaukee 28V LiIon drill.

              These high stall torques can also be safety issues...this is where people usually break their wrists when the tool digs in, and yanks itself free and around....not to mention what can happen to the thing you are working on.

              It would be nice to know the max. torque that an electric drill can handle without meltdown or clutch damage (another problem at high stall torques.) It would also be nice to know that a drill had stall protection that would prevent motor, clutch damage...or wrist damage.

              It would also be nice to know the efficiency of the motor. This can be measured in work done per battery power. Based on the bearings and motor technology, there can be a big difference in efficiency. A high wind motor, will have less torque, weigh more, handle less max. current, but be more efficient. Motors will be more efficient at one speed...than another....which could lead to a different optimization for drilling or driving. A brushless motor is considerably more efficient and will not lose power with age like a brushed motor (don't know anyone who uses brushless for power tools though.) Brushed tools can vary the motor "advance" to offer more efficiency in forward than reverse. If I recall, brushless motors can actually vary the advance by speed and direction...which helps with their efficiency.

              There is a lot more to motor technology than many people realize. It would be nice to see some advances there...as opposed to just a race for the biggest battery.
              Last edited by Disaster; 11-08-2006, 08:47 AM.

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              • #37
                True about that electric motors and especially brush types have max torque right as they stall out. With an engine other than double acting steam engines, that there is a torque rise from idle speed up to a given RPM and then a fall off.

                As for overload protection for a portable power tool some do have it, but very few that I have seen. It would be a good idea to include such, but then the tools would cost a bit more to make.

                If any of you really want to find out about electric motors you might try contacting NEMA www.nema.org and and ask what publications they have which you can purchase. Another place for info is Power Tools Institute, Inc. http://www.powertoolinstitute.com They are big into safety but should have other info and some good reading for all power tool users.

                I think all of us need to remember that because of stockholders demanding profits that most manufactures are really into making big $$$ and not posting loads of info that the DIYer would know little about. I did read about a drill one time that has a flashing light overload indicator. A few drills and angle grinders have slip clutches but they are more for user protection than to protect the tool for being run overloaded.
                Last edited by Woussko; 11-08-2006, 06:52 AM.

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                • #38
                  Because peak torque only gives you the extrapolated performance of the motor, again, not what the motor does under continuous loading conditions.

                  Peak torque is at 0 RPM, maximum power output (i.e. this "UWO" is around the half "no-load" RPM. So if your tool does 600 RPM full blast with no load, the maximum power output occurs when you load the drill down (with trigger fully depressed) to 300RPM.

                  True it would ultimately be better if they put out the whole speed-torque performance graph for the tool, but they also can't be too confusing or else people won't get it at all. Having one blanket number/rating that describes whether a tool is a completely better performer than another is impossible. But if you find the type of measurement that best represents most applications, then that's probably the better way to go.

                  Originally posted by Scott K View Post
                  How does Unit WAtts out = a better representation?

                  I always thought electric/battery powered motors had their peak torque from 0 RPM's all the way to, say 1000-1500 RPM's. And after that torque dropped off.

                  What I'd be interested in, are the gear ratio's of the gears/transmissions found in drills.
                  Last edited by Sceeter W Wheels; 11-08-2006, 05:31 PM. Reason: Additional comments

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                  • #39
                    http://www.dewalt.com/us/cordless/powerrating/?p=5
                    Here's some more info. I know its dewalts site but their explanation is accurate.

                    Comment


                    • #40
                      I was surprised that DeWalt came out with that article because it's quite technically correct in the priciples they're explaining. I can't vouch for their measurements of other companies drill power comparisons, because I don't have the means to verify them, but the measurements seem reasonable.

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