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DC motors on the rotors for a prerotator?

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  • #16
    A favorite motor from back in my Battlebot days was the Magmotor. It has since been renamed the Amp Flow motor. The A28-150 should do everything you ask. There may be others, but that would be my first choice for a brushed motor right now.
    "Nothing screams poor workmanship like wrinkles in the duct tape!"
    All opinions are my own, I've been wrong before and I'll be wrong again. Feel free to correct me if I am.
    PRA# 40294

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    • #17
      Battlebots...kewl. No wonder you have a keen interest in motors. I always wanted to build one myself....bucket list item I suppose it will go in.
      Now I will look into this motor and see what controller and batteries to use. Thank You for the suggestion.

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      • #18
        The Vyper ESC is a possibility, You can probably get away with running it at 10s Lipo with a 5 Ah battery good for 50c peak. I'd expect 4-8 prerotations/charge depending on how fast you ramped it up.
        "Nothing screams poor workmanship like wrinkles in the duct tape!"
        All opinions are my own, I've been wrong before and I'll be wrong again. Feel free to correct me if I am.
        PRA# 40294

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        • #19
          wow i am surprised @ how small & powerful those Amp Flow motors are. $$ as well. Somehow I thought to do this prerotator set up would be under $500. The motor alone starts there and then the controller and batteries. 1K+....hummm. Any other alternative ways to acquire these Amp Flow motors @ a discount or used sources you might be aware of.

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          • #20
            The issue with a brushless outrunner motor at zero or low speed is really an issue with their controller and the timing of the signals to the motor, a sensored controller is probably best for pre-rotor application compared to a sensorless one.

            Also keep in mind that most electric pre-rotators are using some sort of soft-start to limit torque during the initial application of power, the "inefficiency" in the starting torque of an outrunner motor may very well be desirable for that soft-start.

            At one time we were building a gyro with a pre-rotator using the Turnigy 100cc motor but the project was never finished. My take on it was the cost and operational limitations weren't desirable compared to a good mechanical drive or go-ped system.


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            • #21
              Ebay for a used motor. Lower your power requirements by spinning up slower and accepting a lower top speed. Brushless is cheaper mostly because you have more choices, but the start from zero is problematical. You could go with a cordless tool motor. Smaller cheaper and lighter but less top speed. They are trial and error because you can rarely get good specs on them. David McCutcheon told me about someone that used a small scooter motor with reasonable success. There is a thread here: https://www.rotaryforum.com/forum/ge...re-rotor/page2
              "Nothing screams poor workmanship like wrinkles in the duct tape!"
              All opinions are my own, I've been wrong before and I'll be wrong again. Feel free to correct me if I am.
              PRA# 40294

              Comment


              • #22
                Originally posted by Jazzenjohn View Post
                Ebay for a used motor. Lower your power requirements by spinning up slower and accepting a lower top speed. Brushless is cheaper mostly because you have more choices, but the start from zero is problematical. You could go with a cordless tool motor. Smaller cheaper and lighter but less top speed. They are trial and error because you can rarely get good specs on them. David McCutcheon told me about someone that used a small scooter motor with reasonable success. There is a thread here: https://www.rotaryforum.com/forum/ge...re-rotor/page2

                I have found more sources thankx to the links. Most excellent. I have a razor scooter pancake motor that needs a new controller. However the built in controller looks to be more of a compact package @ http://www.electricscooterparts.com/motors24volt.html
                Very grateful to you JJ sir! I will have to post my results and progress. Now to mate a battery like with a plug in style on a cordless hand drill so changing batteries will be a snap. Motor w/internal controller,snap in battery pack, thumb throttle on the joystick. This could work nicely. Or NOT! TBD.

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                • #23
                  Jazzenjohn
                  I'm thinking of putting these items together, what do u think the Ampflow A28-150 will do rrpm wise?

                  AmpFlow A28-150 Motor_____________________________(robotmarketplac e.com)__ $344.00
                  Kobalt 24-Volt Max Power Source Adapter _______________(Lowes)________________ 19.99
                  KOBALT 24V Max Power Tool Battery Charger ___________(Lowes)_________________ 39.98
                  Kobalt 24-Volt Max 6-Amp-Hours Lithium Battery __________(Lowes)________________ 80.00
                  CTR Electronics VEX pro Talon SRX Speed Controller _____(robotmarketplace.com)___ 89.99
                  36V/48V/60V/72V Thumb Throttle with Power Switch LED voltage display for ebike____(EBAY) $12.95

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                  • #24

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                    • #25
                      The Talon looks like a good controller, especially for the price. My only concern is whether it can handle the current draw of the Amp Flow motor. Same for the batteries. The specs are usually pretty vague about that stuff. If it can, that would be a pretty convenient package. If it can't, you will soon know what the inside of the Battle Box smells like.
                      "Nothing screams poor workmanship like wrinkles in the duct tape!"
                      All opinions are my own, I've been wrong before and I'll be wrong again. Feel free to correct me if I am.
                      PRA# 40294

                      Comment


                      • #26
                        Thank's for all the great info we have some great minds in here, but they are talking about placing the motor directly on the rotor, one on each side to balance the weight, has anyone seen this before, or is it just a bad idea? I have never heard something like this, its definitely outside the box. Powering them would be a trick but not undoable. It is not my idea, but something the class thought might work.
                        David Bacon

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                        • #27
                          Hi Dave,
                          Everything I have seen or read about putting motors on the rotors ended up being unfeasible and some what complicated.The conversation has morphed into what it is now talking about electric motors to do the pre rotating.And you are right, there are some great resources here. Some better than others I say, but never the less I have learned a thing or two about gyro's from those willing to help get r done! Like Jazzenjohn. His knowledge of motors was very helpful in my determinations thus far.

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                          • #28
                            Dave, if you are suggesting that they would use the motors, one on each side, to friction drive a disk or drum, or drive a large gear, then I personally haven't seen that configuration. There has been some working setups using props which provides a nearly torqueless prerotator. Offhand, the only problems I see with that setup are the ability to configure it to the different hub bars people use, and the wireless setup or commutator drive to supply power to the motors. Neither issue seems insurmountable.
                            "Nothing screams poor workmanship like wrinkles in the duct tape!"
                            All opinions are my own, I've been wrong before and I'll be wrong again. Feel free to correct me if I am.
                            PRA# 40294

                            Comment

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