Announcement

Collapse
No announcement yet.

OT Huge gear reduction

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • OT Huge gear reduction

    How is it done? Just boggles my mind, 20,000 or so to 400rpm. That is some serious machining.

    Our fire season is really just starting and we provide some space for the forward attack crews here. This baby just came in this morning, nice looking unit. Talk to the pilot, it’s an A-Star 350D. Actually thought by the sound it was a Bell 212 which frequents us, just a wee bit lighter on the thump.

    But then again I think the thump depends on the pilot, sometimes, its rattle the windows in a big way and hang on to anything you don’t want shaken, other times its just noisey and I have to go to work dear, their here. And with the pads less than 80 yards from the house, you know it.

    Although yesterday another new job came in, similar to this but way more aerodynamic looking and 4 blades with a fan. Nothing I have ever seen or heard before, more of a whine to it, must be new, sure looked like it. Next time it comes in I will get a pic and talk to the driver.

    Anyway, thought some of you would like the pics, have always wanted to fly one of these, childhood dream. There’s a good chance they may be heading out on patrol and will try to get another of it lifting off this afternoon.

    Cheers, Bob





    Last edited by Quetico Bob; 06-20-2009, 04:56 PM.

  • #2
    20K to 400 is only a 50 to one reduction. That's pretty easy to do. A double compound planetary gear set will do it nicely.

    See these videos of one I made using SketchUp. (Not my model)

    ~1 MB

    Proper operation http://ixian.ca/video/plgear.wmv

    What happens if you forget something

    http://ixian.ca/video/plgearnp.wmv
    Free software for calculating bolt circles and similar: Click Here

    Comment


    • #3
      QUOTE” What happens if you forget something” QUOTE

      Priceless, first time I went up with a friend in his Taylor Craft he asked me, Do you know what the purpose of the propeller is? Obvious answer but, I have never thought I knew the obvious….Why I asked?

      It keeps the pilot cool, cause when it stops you should see the sweat!

      First and last time I flew a plane was with him, rest his sole.

      Cheers, Bob

      Comment


      • #4
        Originally posted by Evan
        20K to 400 is only a 50 to one reduction. That's pretty easy to do. A double compound planetary gear set will do it nicely.

        See these videos of one I made using SketchUp. (Not my model)

        ~1 MB

        Proper operation http://ixian.ca/video/plgear.wmv

        What happens if you forget something

        http://ixian.ca/video/plgearnp.wmv
        I must be a little dense today. What color does what? Input? Output?

        Comment


        • #5
          The inner gear the centre carrier and the outer housing are all part of the action. What happens depends on what is allowed to rotate and what isn't.

          Trying to explain it is very difficult. Play with it for a few minutes in SketchUp and it becomes clear, which is the point of the model. It is a Sketchy Physics model.

          Bob, the helicopter you saw with the tail fan is probably the Aerospatiale Gazelle.

          Free software for calculating bolt circles and similar: Click Here

          Comment


          • #6
            QUOTE”the helicopter you saw with the tail fan is probably the Aerospatiale Gazelle”QUOTE

            Hard to tell, this one had 4 blades and don’t remember the rib over the tail section. But I only drove by it about a dozen times in passing looking at it from the front. Never stopped to really take a close look as they were supposed to be stationed for several more days. Thought I had some time.

            Tell you one thing, I have never seen such a tight turn at speed and altitude coming to the pad, an amazing machine. Betcha this thing would put John Travolta and his disco moves outta business.

            It will be back as it’s a regulars owned aircraft.

            Cheers, Bob

            Comment


            • #7
              Tell you one thing, I have never seen such a tight turn at speed and altitude coming to the pad, an amazing machine. Betcha this thing would put John Travolta and his disco moves outta business.
              I don't know about the blades, maybe a newer version? The Gazelle is one of the fastest helicopters and is also fully aerobatic, very unusual for a helicopter.



              http://www.furyhelicopters.com/conte..._StoryShip.htm
              Free software for calculating bolt circles and similar: Click Here

              Comment


              • #8
                ...or the Aerospatiale HH-65? They have a distinct constant whine with a lesser thump on approach and more of a smack-thump passing by. (i live under the flight path to a hospital landing pad a few hundred yards away)

                Comment


                • #9
                  Evan

                  On the planetary gears we have them on machines at work, I have worked with the company 15 years now, and have had my hand at going at every part on the machines, and the planetary gear gave me some trouble at first. Lucky for me we have a neat way of looking at a machine right beside the one broke down for how it should be, I also got a spare planetary to examine how it works, it's hard to comprehend in that video, however once you understand they are very simple, and superb in reliability. We replaced some steel gears inside with nylatron, then implemented across the entire job, it worked great if anything locked down the nylatron gear would strip instead of raking havoc with the entire gears, bearings, and most of the time the outside ring gear.

                  Our setup is one that is driven by a shaft on the inside center, this in turn transfers energy/movement to another set of gears, and yet to one more set that drives on the outside face with two "implements" ( have to be some what discrete company is real high on "treason") this allows the two implements to be timed via a 360* rotation.

                  Long rambling post, I just wanted to say it's really hard to comprehend a planetary without having it in your hands to work with, and then it takes a few minutes to see just exactly how it works, reduction can be whatever you dream of on a planetary.

                  Comment


                  • #10
                    Here's a fun animation of the Prius planetary drive. The Prius has two motors and this is how they are coupled to the final drive. This is a case where the planetary gear has two drivers.

                    http://homepage.mac.com/inachan/prius/planet_e.html

                    Comment


                    • #11
                      Originally posted by dp
                      Here's a fun animation of the Prius planetary drive.
                      This one is even more fun: http://eahart.com/prius/psd/ -- it has sliders which work. The drive is a fascinating electro-mechanical hybrid itself.
                      ''It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.''
                      Last edited by aostling; 06-21-2009, 01:00 AM.
                      Allan Ostling

                      Phoenix, Arizona

                      Comment


                      • #12
                        Originally posted by aostling
                        This one is even more fun: http://eahart.com/prius/psd/ -- it has sliders which work. The drive is a fascinating electro-mechanical hybrid itself.
                        It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.
                        This one does a good job of showing the relationship between the electric drive and the engine/generator combination.

                        Did the sliders not work for you on the other link? The were fine here. it's a pretty boring demo if they don't work

                        Comment


                        • #13
                          Just download SketchUp and the Sketchy Physics plugin and there are hundreds of mechanical models to play with. With the SP plugin the main distinguishing feature of the $500 pro version vanishes. Right now I am just finishing debugging some code I wrote to produce fancy fully triangulated meshes for CamBam that will export DXFs that are compatible with ShetchUp.

                          I will post more later in a new thread.
                          Free software for calculating bolt circles and similar: Click Here

                          Comment


                          • #14
                            Originally posted by dp
                            Did the sliders not work for you on the other link?
                            No, the sliders were stuck for me -- needing a Flash 6 player which I must not have loaded my mac.
                            Allan Ostling

                            Phoenix, Arizona

                            Comment


                            • #15
                              OK, I just saw proof that something is screwy with this BBS software. This has been happening for a while to me and a couple of other people have made comments about not seeing a post at all until later.

                              The post by Alan, #14 was already on line and I had already read it. It took me several minutes to post my post which should be after his but instead was inserted ahead of his as #13.

                              This explains some posts that appear to be non sequiters and really poses a problem in a some discussions. My post followed Alan's by at least 3 minutes.
                              Free software for calculating bolt circles and similar: Click Here

                              Comment

                              Working...
                              X