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Thread: Open Source Pre-Rotator Project Description

  1. #11
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Hi Chris!
    There are excellent non-electric prerotators for sale by vendors. There is only one manufacture who created a 7 lb electric prerotator for lightweight blades. But he has instructed us not to sell it has 3 out of many burned out a wire and or chip by the human over driving the amps and could not hear the waring beep to back off on the power knob.

    We are taking the human out of the procedure other than PRESSING a start switch and it will turn itself off by the Bendix popping off at a set RRPM speed = 250 or+ depending on the motor. Once the controller sees there is no load any longer because the Bendix is spinning too fast it will shut itself off automatically. There is an emergency stop switch that you FLIP not push just in case.

    We can just add any sensor we want and program it for adding many safety responses, like a robot'/autopilot working the rerotator, we know how to turn it off in case of a roll over or blade flap on take-off. Because an MUC drives these state of the art AC 3 phase motors we can add sensors in the future or now and patch everyone system for free upgrades over the years of improving it.
    You will able to add different motors in the future and just down load a patch for the software and install it and you are done!

    All of this and much more DETAIL will start being added by the end of next week to the private threads.

    What we need now are internet researchers! To look for all the difference motor candidates so we can write up our project requirements and get them to educates us on these motors and why theirs is best suited.

    That way once all the other groups are staffed we can get right to work on evaluating the best 2 or 3 to test.

    Much more coming but in the volunteers Private working forums...

    We also would like suggestions for other safety features like shutting off the fuel on a roll over or over a impact over a certain 'G' level etc.

    We can add just about anything by just adding the sensor and code needed.
    Last edited by JOHN ROUNTREE 41449; 01-04-2015 at 07:46 PM.
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  2. #12
    ALLEN BRADLEY AND SEIMANS CONTROLE BOTH HAVE SOFT START CONTROLES AND MOTORS.
    MIGHT BE A PLACE TO START. ALSO CNC MACHINE CENTERS DRIVE DC MOTORS TO MOVE THE TOOLS AND TABLE AROUND. HOPE THIS HELPS. I KNOW JUST ENOUGH TO BE DANGEROUS.




    A car starter motor is typically an extremely powerful dc motor. When operated at no load they will draw about 30 to 50 Amps and spins in excess 7000 rpm and continue to build revs if they continue without load before they explode due to extremely high revs. When starting an engine they typically draws about 300 amps and when stalled even 500 amps .They are not designed to operate for a long time ie for cranking an engine .They produce more torque even further by the reducing gear of the flywheel by lowering revs and gaining more torque.They are so powerful that they can be used for a small go kart with an impressive acceleration if they are geared right. This way they can be operated for a much longer time since the starter has a much less load on it before it needs a rest. Imagine a starter cranking an engine against compression and to propel a 100 kg of a small go kart. The only problem is that you need some sort of a high ampere deep cycle batteries or lithium batteries to last longer because ordinary car batteries are not designed to be fully discharged unless you want to go for 200 meters and fry the battery. Imagine how powerful they are : power (Watts) is amps x voltage so 300 amps x 12v =3600 Watts so 1 hp is 746 Watts so 3600 w divided by 746 W = 4.8 hp approx of the starter motor alone . You can gain more torque by a reduced gear like the flywheel by reducing revs but gain torque , that's why a car starter motor can move a car on a gear with a low speed of course.

  3. #13
    Joe. I have an electric prerotator. Its off of a Toyota. Approx. 1200watt. I'm familer with both of the motor control companies. Never have a soft start that is 12v capable. I'm working ng on other solutions as we speak.

  4. #14

    A Different Method

    There comes a time to scrap all the existing methods and start completely fresh. As far as the gyro prerotater I think the time is here.
    What I am about to suggest is a radical change and I think most people will want to ignore it because it will take some time and money
    to make it work on a existing bird but here goes in spite of my reservations. Please think it out in detail before throwing the whole idea out.

    First thing to consider is there is a real lack of selection in 12 volt motors and motor controls. Plus things like starters are darn heavy and
    tend to draw 100 plus amps so they require 2 gauge or heaver wire.

    Lets throw all that difficult to get heavy stuff out!!!.

    all the 36 48 or 72 volt stuff is also in short supply and kind of expensive plus getting some odd ball voltage on a gyro is a PITA!!
    So out the door with that!!

    First we may want to get a light weight battery that can supply HIGH current so lets think about lithium based batteries maybe something
    like what is shown here. http://antigravitybatteries.com/

    I am aware that some folks think that lithium batteries can be a fire hazard but I will address that latter. Now lets move on.

    There are plenty of 110 and 230 volt motors and available in both single and 3 phase. They are generally lower cost and easy to get.
    so lets think about a 110 or 230 volt system.
    First we will need a inverter. Due to the fact that electric motors are not delicate electronics they will basically run on any
    any kind of dirty crappy electricity that you throw at them so a expensave true sine wave inverter will not be required. One of the cheep
    inverters that produce a square wave will be fine.
    Maybe something like this http://www.sonicelectronix.com/item_...a-CPI1575.html
    Or maybe this
    http://www.ebay.com/itm/1500W-Car-DC...item1e94c56a7b

    It adds 8 pounds in weight but look at how much weight we are going to save on a battery!!!
    Plus that inverter could be handy for other things but we will think about that latter.

    Now we need a motor. Something compact, light weight, easy to get, not to expensive and
    a bit of gear reduction would be nice. Maybe something like this.
    http://www.homedepot.com/p/RIDGID-1-...vZc27fZ1z141kh

    It will be lighter than most starters probably 10 pounds or so.

    Now for a little known fact. Most power tools have what is called a universal motor. That means that they will run on
    AC or DC basically what ever kind of trash that you throw at them.
    Because of that we can use a industrial motor drive that will give us adjustable current limit, Adjustable torque limit,
    Adjustable acceleration and adjustable maximum speed so lets try something like this.
    http://www.automationdirect.com/adc/...e/GSD5-240-10C
    or this
    http://www.surpluscenter.com/Electri...OT-11-2269.axd

    Or if we feel the need for something 3 phase we could try this.
    http://www.automationdirect.com/adc/..._VAC)/GS1-21P0

    I understand I have left a number of details to work out but this could be a starting point.

    Now comes the time to pick this apart and see where I have had oversights.
    Last edited by Marc Oestreicher 42290; 01-16-2015 at 08:30 PM. Reason: Add more detail

  5. #15
    I A few more thoughts on the subject. It seems to have been recently shown in a thread at the RWF that trying to prerotate to
    a super high speed before starting a takeoff roll is pretty much a waste of time but applying a small amount of torque with the
    prerotator while rolling is helpful and will shorten the takeoff distance.

    http://www.rotaryforum.com/forum/sho...ght=prerotator

    The motor control that I gave a link for in the post before this should make it simple and reliable
    to control the amount of torque from the prerotator.

    From what I can see with the super small prerotator motor
    and short takeoff distance that is working for the folks at Aviomania they have also found the same thing to be true.

    Bottom line is that I estimate that the electric drill in the post above should be strong enough.

    If more power is needed to spin up the rotor on a large 2 place machine 2 drills could be operated side by side with
    connecting gears on the output shafts but I really don't see that being needed.

    Also to make this arrangement work at the correct RPM a smaller ring gear than what is normally used would
    be needed as well as a larger gear on the bendex.
    Last edited by Marc Oestreicher 42290; 01-16-2015 at 08:15 PM.

  6. #16
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Brilliant!!! Give Cathy a big kiss for me and thank your for always being there for me with your calls about my health when I disappear = you guys ROCK!!

    Actually Marc, you and PRA are on exactly the same page in this regard that is exactly one of the 1st we will test as a starting reference for power, load, cost, future expansion and maintainable of replacement parts.

    I believe the only difference in opinion or methods is that PRA know methods to use 36 48 or 72 volt stuff with existing lithium batteries and we will test a super-capacitor mixed lithium batters pack! But would prefer to keep this in the Private volunteer need to know section until tested!

    So we have many more options than just the first. There new motor are powerful and lightweight and a control er can be written with any MPU chip that creates a PWM (Plus Width Modulation) {sign-wave] to drive it!

    Once you add the chip you might as well use it and add all kinds of safety features and gauges like: Rotor blade RPM gauge needed anyway to make sure you never over power your load. Only increasing power after it hit the next lever of RRPMs,
    Accelerometers for = if you roll over on blade flap it shut the engine and fuel off for you in an instance of a second.... Etc, etc, etc.

    Once you add a chip and filtered power supply for it; for any purpose that cost is a major portion of the cost.

    So why not add just a little more and write a motor controller program add only a few more components to the same power supply need to run the MPU?

    We are just now starting to request volunteers and need more volunteers before we can test anything!!!

    They are almost too many option today so the easy way is as you suggest buying and testing the LIGHTEST candidates!!

    So far there is nothing but testing stopping any or all of these solutions = sky is the limit!!! Hahahaha Heehehe
    Last edited by JOHN ROUNTREE 41449; 01-16-2015 at 08:31 PM.
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    PRA31 - Vice President of S.D. Rotorcraft Club
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  7. #17
    Greetings from a newbie. I've been interested in gyros for over 20 years, have learned a LOT from your PRA forums, am now retired so have some time though not much money, am very much a do it yourself guy (which goes hand in hand with not having much money), nevertheless hope to start work on a gyro when the weather warms, (have a garage full of tools). Have been looking at rotorheads a lot lately just for fun, particularly at jump starting. As far as pre-rotators are concerned -- my drill drivers have an amazing amount of torque for such a small motor - any chance it could be enough, even if 2 required? -- my snapper mower has a really simple transmission, a steel disc powered by the engine and a clutched rubber tire connected to the wheels. The rubber tire moves across the disc for infinite speeds, and the friction is enough to power the mower very well. Easy to make and low maintenance. Does the pre-rotator really need gears and chains? Maybe a flat bottom on the pre-rotator plate and a rubber wheel on a drill to move across it would power it? Maybe might need a larger diameter plate for more leverage to get it started? Would probably be as light as you could get. No doubt you've got somebody there smart enough to figure out if it could be possible. For somebody like me it would have to be trial and error and I don't have anything similar to trial with, and why spend time and money creating some kind of a test apparatus when you guys have wizards to figure such things on paper? Cheers. Jim

  8. #18
    John part of my reasoning on the parts selection is in the crazy industrial world that I live in almost
    everything needs to get done right now with off the shelf parts that are instantly available any time.
    Bottom line is that my old habits are hard for me to break.
    Also I just happen to have some DC motor drives laying around.

    On the same subject if you are in the mood to tie enough batteries in series to get 72 volts a few
    more can be added to get 110 volts DC There again drill motors are happy with AC or DC and
    as a rule of thumb it is less expensive to build a controller for higher voltage instead of higher current.

    I guess that I am a high voltage addict. It seems like almost everything that I work with is 460 volts.

    In my defense with 460 3 phase on a large motor it only takes 1.2 amps per horse power. Sure keeps
    the wire bundles nice and small. LOL

  9. #19
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Quote Originally Posted by Joe Sherer 42678 View Post
    ALLEN BRADLEY AND SEIMANS CONTROLE BOTH HAVE SOFT START CONTROLES AND MOTORS.
    MIGHT BE A PLACE TO START. ALSO CNC MACHINE CENTERS DRIVE DC MOTORS TO MOVE THE TOOLS AND TABLE AROUND. HOPE THIS HELPS. I KNOW JUST ENOUGH TO BE DANGEROUS.




    A car starter motor is typically an extremely powerful dc motor. When operated at no load they will draw about 30 to 50 Amps and spins in excess 7000 rpm and continue to build revs if they continue without load before they explode due to extremely high revs. When starting an engine they typically draws about 300 amps and when stalled even 500 amps .They are not designed to operate for a long time ie for cranking an engine .They produce more torque even further by the reducing gear of the flywheel by lowering revs and gaining more torque.They are so powerful that they can be used for a small go kart with an impressive acceleration if they are geared right. This way they can be operated for a much longer time since the starter has a much less load on it before it needs a rest. Imagine a starter cranking an engine against compression and to propel a 100 kg of a small go kart. The only problem is that you need some sort of a high ampere deep cycle batteries or lithium batteries to last longer because ordinary car batteries are not designed to be fully discharged unless you want to go for 200 meters and fry the battery. Imagine how powerful they are : power (Watts) is amps x voltage so 300 amps x 12v =3600 Watts so 1 hp is 746 Watts so 3600 w divided by 746 W = 4.8 hp approx of the starter motor alone . You can gain more torque by a reduced gear like the flywheel by reducing revs but gain torque , that's why a car starter motor can move a car on a gear with a low speed of course.
    Good observations!!!
    PRA- Director
    PRA- Volunteer Coordinator

    PRA31 - Vice President of S.D. Rotorcraft Club
    http://www.Pra31.org

    U.S. Agent for Aviomania Aircraft... the most stable gyroplane on the market today.
    See: Aviomania USA http://www.AviomaniaUSA.com

    OEM Dealer for MGL Avionics - glass cockpit EFIS for Experimental aircraft Ask about DISCOUNTS for PRA MEMBERS

  10. #20
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Quote Originally Posted by Marc Oestreicher 42290 View Post
    John part of my reasoning on the parts selection is in the crazy industrial world that I live in almost
    everything needs to get done right now with off the shelf parts that are instantly available any time.
    Bottom line is that my old habits are hard for me to break.
    Also I just happen to have some DC motor drives laying around.

    On the same subject if you are in the mood to tie enough batteries in series to get 72 volts a few
    more can be added to get 110 volts DC There again drill motors are happy with AC or DC and
    as a rule of thumb it is less expensive to build a controller for higher voltage instead of higher current.

    I guess that I am a high voltage addict. It seems like almost everything that I work with is 460 volts.

    In my defense with 460 3 phase on a large motor it only takes 1.2 amps per horse power. Sure keeps
    the wire bundles nice and small. LOL
    Yo bro you are brilliant!!!

    One of these are going to be the best solutions that fits all prerotator needs!!!

    Thank you for all the links too... This really jumps start us! Now I just need some web-researcher and I think we can get started..


    Cannot wait to start testing... This is going to be fun!
    PRA- Director
    PRA- Volunteer Coordinator

    PRA31 - Vice President of S.D. Rotorcraft Club
    http://www.Pra31.org

    U.S. Agent for Aviomania Aircraft... the most stable gyroplane on the market today.
    See: Aviomania USA http://www.AviomaniaUSA.com

    OEM Dealer for MGL Avionics - glass cockpit EFIS for Experimental aircraft Ask about DISCOUNTS for PRA MEMBERS

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