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Electric pre rotor Soft Start

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  • #16
    Originally posted by madwinger View Post
    Alan, thanks for this picture. If you could answer a few questions for me I would appreciate it.

    1. Did you have to make the bracket that holds the starter or are these available and if so where?

    2. Do the starter gears on all motors just mesh up with the ring gear on the rotor or do they have to be changed?

    3. I assume that the Bendix in the starter pops up just like it would in a car?

    4. I dont think my has a larger enough gap between for the adapter plate. did you have to do something to raise the rotor head?

    5. I have 24' Dragon Wings. I read a lot about a Toyota Starter. Is that the starter I want?

    6. Not related to the per-rotator but what does the spring assembly the top of your push rods do or prevent? I have never seen that and as curious.

    Thanks again.


    I saw the picture and was wondering about the springs in the controls... is this to dampen vibs? Or to soften control inputs?

    John Morgan
    Private A-SEL
    "PeachState Rotorcraft Club"
    Owner/builder: The Subinator
    (Single Dominator/Subaru)


    • #17
      the way we did the soft start was to buy a $10 fender starter relay and used a 1/8 ss welding rod 9" long hope you can make out the pic!
      Attached Files


      • #18
        Hi PDCLAY,
        I have made quite a few of these pre-rotators of which you mentioned.My design was featured in the Homebuilt Rotorcraft mag.(which no longer exists),a few years back.Don Parham did an article about my soft-start system. I am a 30-year expert on this matter.My
        business is rebuilding starters,and alternators.
        I was also the first one to design the small 100-amp Delco CS 121 alternator to fit on the Subaru EJ 25(Sparrow Hawk).Phone me @Straco Rebuilers 618-532 4846,and I will explain
        how the soft-start works,and I will fax you simple instructions to do it yourself!
        Big Dawg


        • #19
          If I assume 3 hp (mechanical) to start the rotor, then the car starter requires about 6 hp (electric) from the battery. It is 500 amps / 8 Volts. To supply 500 A, the car battery (12 volts) will weigh almost 30 lbs. Or 36 lbs including the starter motor.
          Usualy we need 50 Hp and 500 lbs of expensive technology to lift 180 lbs of pilot. So it is 10 hp and 100 lbs that really cost this launcher.
          Sorry for the fly in the soup.

          If the battery does not give 500 A, then needless to find a bigger launcher or better gear ratio.
          Last edited by Jean Claude; 10-27-2013, 10:22 AM.


          • #20
            JC, donít you believe that the most inefficient method of flight that is possible should also have the most inefficient method of rotor starting that is possible?:D


            • #21
              A rotor becomes almost decent when it flies faster. But the lack of attention to the dead weight and parasitic drag is very expensive.


              • #22
                A helicopter rotor is almost decent JC; the efficiency of a mechanical transmission being 90%+. However, the pneumatic transmission of a gyroplane rotor, the product of propeller efficiency and rotor windmill efficiency being less than 50%, can never be decent.


                • #23
                  Chuck, loss difference between helicopter and gyro seems no so great to me.


                  • #24
                    JC, we both agree that fat gyros are silly.


                    • #25
                      Lots have happened on the Little Wing and in life.

                      The Little Wing 5 is tied down at the Lincoln Airport outside of Sacramento, CA.
                      Only one system needs additional attention.
                      The electric pre-rotation inline fuse.
                      I am up to popping 200amp ANL fuses. I have the correct size wiring for this amount of amperage,
                      the recommended auto starter and I am pulsing the switched heavy duty solenoid.
                      But it's the spiked initial amperage draw with such a high inertial load of the 28ft rotor disc.
                      Any suggestions???


                      • #26
                        Pre-Rotation Circuit Breaker problems.
                        I just tried hand propping the rotor blades and pulsing the solenoid switch, I called it quits the second time I popped a 300A circuit breaker between the battery and the solenoid.
                        My current circuit is, positive battery to 300A breaker to HD solenoid to mast starter. Starter negative to battery negative. Solenoid on two cab panel switches in series.
                        I see a soft start diagram on this Forum. It looks like that individual ran a completely separate medium voltage line from the starter into the cab through a switch and then a non breaker-ed line thru the firewall to the solenoid. Then across the solenoid terminals he has a resistor wire.
                        I'm not an electrical guy, but ... If you only added a switch on the original hot lead to the starter and that switch was in the cab, then put a resistor wire across the main solenoid leads, You could switch the main hot lead in the cab and run the starter across the resistor wire on the solenoid, than switch on the solenoid and run higher amperage thru the solenoid straight from the battery???
                        I really don't want to put a high amperage switch and reroute parts of the hot lead in the cab on its way to the starter.
                        Is there another option?
                        If not, OK. What type of wire, gauge, material, length and it will need to be insulated, it's in on the fire wall.
                        Brad N954BH


                        • #27

                          What type of starter motor are you using?

                          Does it have a built-in solenoid to carry the current?

                          Does it have a built-in mechanism to pull the Bendix into place or does it rely on motor spin to engage the Bendix?


                          • #28
                            If you blew a CB after giving the blades a flip you have either a locked or misadjusted bendix or the wrong kind of fuse (Should be a slow blow not a fast blow) or a bad motor or some other fundamental problem that won't be solved by a soft start. I'd suggest you take the blades off and try again. The motor should have no difficulty spinning without the rotor. I don't see any good reason for a fuse in the circuit, and in any case would put it After the solenoid and not between the battery and the solenoid.
                            "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