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  • Good News/Bad News as usual...

    ...in my life; sigh.

    This picture clearly depicts several things:

    1) As many experts have said on the forum, a "2 hp" treadmill motor ain't in no way even slightly close in size & power to a real motor. Notice the difference in purposefulness (is that a word?) between the manly real motor and the wimpy TM. Man was I impressed!

    2) Even I can get a decent deal on ebay. I won this new (other than a few scratches) Baldor 1750 rpm 3/4 hp PM DC motor for a bit over $140 shipped to my door....that's the good news.

    3) Bad news? I have no idea where in the HECK I'm going to mount this monster on the ORAC lathe. Reminds me of the time I helped a buddy swap a 327 Chevy into a '59 Opel Record station wagon.

    The original was a 1/2 hp AC motor that must've been small for its power rating. I can't believe I never even tried to visualize how much difference there is in the size of the 2 motors. Embarrassing really.

    I'm pretty determined to use it because most of the ORAC references I've come across on the web mentioned that it definitely needs more power. I guess I'll have to fab some kind of structure to mount it way above the original location to allow the carriage and it's rear mounted stepper motor to clear it when it moves close to the chuck.

    I have the original ORAC heavy sheet metal base and intend to keep it to have a place to mount all the control electronics and there's just not a lot of extra space on the motor end. Sigh again. Time to put on my Tennessee engineering hat and see what I can come up with

    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  • #2
    I bought 2 5HP DC motors & 4 controllers on ebay from hoosier racing tire & I bet the motors go over 200# ea. I bought 12 3HP 3phase Balders that are 115# ea.
    "Let me recommend the best medicine in the
    world: a long journey, at a mild season, through a pleasant
    country, in easy stages."
    ~ James Madison

    Comment


    • #3
      Welcome to the asylum!

      But you will find a way.

      Dave

      Comment


      • #4
        Big motors are nice,,similar to finding a big woman.

        Comment


        • #5
          Originally posted by sasquatch
          Big motors are nice,,similar to finding a big woman.
          Yea, they both eat more!
          "Let me recommend the best medicine in the
          world: a long journey, at a mild season, through a pleasant
          country, in easy stages."
          ~ James Madison

          Comment


          • #6
            Simple... Rig-up a base plate, and mount the new motor just like you have it positioned in your picture.
            Buy a longer belt.
            EUREKA !!!!

            Comment


            • #7
              Well, here's part of the difference- TM motor, 2 hp, must run at 5k+ rpm to get that kind of power. Baldor, 3/4 hp at 1750 rpm, could run all day at that level. Probably could produce 5 hp intermittently if loaded down.

              Now put a D cell beside that pair of motors. That will represent a model airplane electric motor. About 3/4 horse, 60,000 rpm-
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

              Comment


              • #8
                I notice the plate mentions CCW rotation, that could be just for the polarity indicated or that the motor is Uni-directional, it may pay to check that if you want to use bi-directional?
                If you can access the brushes, this should tell you.
                Max.

                Comment


                • #9
                  As Darryl says.......

                  MOTOR SIZE IS NOT NECESSARILY RELATED TO POWER.

                  Motor size is DEFINITELY related to torque.

                  I have worked with 250HP PM motors that were a bit smaller than your larger motor seems to be in the picture.

                  The 250HP was at 60,000 rpm........ does not take a lot of torque at that speed to get to 250 HP.

                  A treadmill motor is usually at least 4000 rpm "natural" or "base" speed, and may be 5000 rpm or more. You would expect to see a size relation similar to the speed ratio, so an 1800 RPM motor would be somewhere at least 2x larger than a motor of the same power at 4000 rpm.

                  I have no idea if the treadmill motors really put out anything close to the claimed power (I suspect that is "peak HP" or some other such nonsense), but I know for sure they don't do it at the same speed as the bigger motor.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    I went through a bit of what you're experiencing with HP ratings on DC motors. What has been said here is correct in regards to rpm vs horsepower rating. I had a 3/4 HP AC on my Logan, so I thought, what the hell, a 1 1/4 HP DC ought to be just fine....right??? Wrong. Even with a good Leeson controller, I smoked the brushes on it 3 times before I finally admitted defeat. Managed to fall into a 3HP Baldor DC, and it rarely shows any signs of strain. The belt usually starts squealing long before the motor slows down.

                    A Baldor 3HP DC by itself is usually not found in a bargain basement, but score one of those high-end, Cadillac style treadmills at a yard sale, and you're in heaven. A 2HP may well do the job, but you can't beat that extra HP when you're bearing down on it. Well worth the extra price.
                    Wayne

                    Comment


                    • #11
                      I have the 2.5 hp tm motor on my lathe, and I've never found it lacking for power, although I don't push it. My power supply can't deliver that much power anyway, so I don't know what it could really do. But I'm sure that if the power supply was capable of delivering, say 20 amps at 100 volts or more, the motor would put out that much power. There's going to be some heat stress, not only in the armature but in the brush assembly, but I think you could push it for a few tens of seconds at a time.

                      That won't be a continuous power rating of course, but it would do it on demand. It's not the type of motor that would 'dump' on you like an induction motor that reaches its torque limit, then loses all rpm. A PM motor is more like a universal motor where the torque is highest when the rpm is lowest.

                      I think if you could find the performance curves for the tm motor, you would see what is achievable for power on an intermittent basis, and I think you'd find that the rating is substantiated. It bears repeating again that this is not a continuous rating. Be interesting though to see what a continuous rating might be for these motors. Another factor would be the various ways in which that could be raised to a higher level. A separately driven fan to ensure a minimum continuous level of airflow through the motor would be one, and re-designing the brush assembly to reduce brush heating would be another. Splitting the brushes to give more than one brush per side, each with its own spring, would be another.

                      Here's an interesting idea- don't know if it's been done except on a very small scale, but it's an ac motor with permanent magnets. No rectifier, just straight ac going in, no brushes- although an inside-out version could use slip rings to feed ac to the rotating armature. The motor would have to be brought up to speed, then the point of rotation matched with the ac waveform, then it runs. It would lag as it was loaded, but would not lose any rpm, and it would be synced to the ac frequency.

                      In a sense, the RC electrics are like this, although the supply is DC. The current pulses alternate and are fed according to sensor input or rotation sensing. They are 3 phase but are not induction types at all. At a stretch, you could say they are driven by VFDs.

                      The difference with my 'ac permanent-magnet' motor is that there would be no electronics handling the current, except maybe for on and off relay which would be activated once the rotor rpm was up and the rotor was in sync.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                      Comment


                      • #12
                        Originally posted by atty
                        I went through a bit of what you're experiencing with HP ratings on DC motors. What has been said here is correct in regards to rpm vs horsepower rating. I had a 3/4 HP AC on my Logan, so I thought, what the hell, a 1 1/4 HP DC ought to be just fine....right??? Wrong. Even with a good Leeson controller, I smoked the brushes on it 3 times before I finally admitted defeat. Managed to fall into a 3HP Baldor DC, and it rarely shows any signs of strain. The belt usually starts squealing long before the motor slows down.

                        A Baldor 3HP DC by itself is usually not found in a bargain basement, but score one of those high-end, Cadillac style treadmills at a yard sale, and you're in heaven. A 2HP may well do the job, but you can't beat that extra HP when you're bearing down on it. Well worth the extra price.
                        Atty,
                        What are you using for the controller on the 3 hp Baldor DC? I just happen to have one sitting in the shop but haven't been able to find a decent deal on a controller.
                        Thanks, Wilhelm

                        Comment


                        • #13
                          Originally posted by darryl

                          Here's an interesting idea- don't know if it's been done except on a very small scale, but it's an ac motor with permanent magnets. No rectifier, just straight ac going in, no brushes- although an inside-out version could use slip rings to feed ac to the rotating armature. The motor would have to be brought up to speed, then the point of rotation matched with the ac waveform, then it runs. It would lag as it was loaded, but would not lose any rpm, and it would be synced to the ac frequency.

                          In a sense, the RC electrics are like this, although the supply is DC. The current pulses alternate and are fed according to sensor input or rotation sensing. They are 3 phase but are not induction types at all. At a stretch, you could say they are driven by VFDs.

                          The difference with my 'ac permanent-magnet' motor is that there would be no electronics handling the current, except maybe for on and off relay which would be activated once the rotor rpm was up and the rotor was in sync.
                          What you have done is re-invent the synchronous AC motor. The usual type has a wound rotor, creating the "magnetized rotor" , but the effect is the same if you use a PM instead of the wound field.

                          You lose the ability to adjust the reactive component, which you can do by adjusting the field current in the regular synchronous motor.
                          1601

                          Keep eye on ball.
                          Hashim Khan

                          Comment


                          • #14
                            Originally posted by MaxHeadRoom
                            I notice the plate mentions CCW rotation, that could be just for the polarity indicated or that the motor is Uni-directional, it may pay to check that if you want to use bi-directional?
                            If you can access the brushes, this should tell you.
                            Max.
                            The fine print on the sticker says to reverse direction you just reverse the 2 wires so I assumed it was designed to be reversible. I sure hope so.

                            I hooked it up to a KB controller last night and it runs very smooth & quiet. The loud AC hum I'm used to hearing from the TM motor with KB controller is noticeably quieter as well. I guess that's due to greater mass of the bigger armature? I checked the shaft and it's nice & straight as well. I'm happy with mthe purchase.

                            I woke up today thinking about the mounting issue and am thinking the best solution will be to mount it completely outside the base assembly on the back side with a long belt. I'll probably mount an idler to dampen out any possible belt oscillations. I'm pretty sure the 10 groove Poly V or Micro V belt is one & the same as the ubiquitous "serpentine" automotive belts so getting a belt should be fairly easy.



                            Getting a sheave for the motor is another story though. Far as I can figger, I need a 10J280 sheave and the only online sources I've found so far are huge volume sellers that don't sell in onesie-twosies. I found the specs so I could grind a toolbit and make a sheave but'd much rather buy one at a reasonable price and not spend a day making one if I don't have to.
                            Milton

                            "Accuracy is the sum total of your compensating mistakes."

                            "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

                            Comment


                            • #15
                              Originally posted by darryl
                              Here's an interesting idea- don't know if it's been done except on a very small scale, but it's an ac motor with permanent magnets. No rectifier, just straight ac going in, no brushes- although an inside-out version could use slip rings to feed ac to the rotating armature. The motor would have to be brought up to speed, then the point of rotation matched with the ac waveform, then it runs. It would lag as it was loaded, but would not lose any rpm, and it would be synced to the ac frequency.
                              .
                              As mentioned this is a synchronous motor, this was popular some decades ago in large motors 100hp and up, the motor was ran up to minimum slip as a normal induction motor, the slip was read out via a winding on the rotor and a pair of slip rings, when the slip freq was around 5 cycles, DC was injected via the slip rings and from then on it ran as a synchronous motor (zero slip).
                              The other type of AC wound rotor motor is/was used extensively in crane hoist control, the generated three phase out from the rotor was rectified and controlled by resistor bank by the crane operator therefore varying the rotor current, you could actually hold a lift load with a stationary motor this way.
                              Max.
                              Last edited by MaxHeadRoom; 04-27-2012, 11:34 AM.

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