Announcement

Collapse
No announcement yet.

3DRV and KB3 Mast Composition - Lightening the ultralight

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

  • 3DRV and KB3 Mast Composition - Lightening the ultralight

    Hi:

    The KB3 ultralight is a KB2 with a 72 inch mast, still using the 2 x 2 x .125 6061-T6 and could use a 6" drop keel. 7 pounds.

    The 3DRV was a drop keel ultralight with a 60 inch mast, using 2 x 2 x .1875 6061-T6 (8.78 pounds) and a 6" drop keel. 72" mast would be 10.5 pounds.

    So, I want to increase the mast length of the mast on the 3DRV but decrease the weight.

    IF the KB3 2 x 2 x .125 mast was good enough at 72" why would not a change to the mast on the 3DRV be just as good?

    Both designs use the same kind of cluster plates, and there might even be a Hornet drop keel integration here.

    The Same engine or nearly the same engine was used on all three (503 or 582). I really want to swing a 68" - 72" prop with enough clearance to not worry about slicing through the support for the tall tail.

    i could use the double 2 x 1 x .125 for an increase that would put it at 8.78 pounds. 40K pounds of strength, is way more than the 254 pounds the thing would weigh even at 4.5 g....and given the possible lateral challenge, it will still hold up.

    Opinions?

    Curtis Scholl

  • #2
    The 40K pounds of strength you mention is probably the tensile strength of 6061-T6. There is far more tensile strength there than is required. If you take the cross sectional area of a 2x2x.125 tube you get 7.5"x.125"- or .9375 sq. in.x 40,000 lb/sq/in. = 37,500 pounds. Bending strength and especially the roll over strength of the mast are more of a concern for me. I personally use 2x2x.125 tubing for the mast. The bending loads are closer to the limits of the material than tensile loads. Bending loads from the engine thrust are about 300 pounds in the middle of the beam, but the beam is rarely handling the load by itself in most triangulated frames. I don't think a bending failure is likely for a typical triangulated frame using the engines we typically use, presuming you don't drill a bunch of holes for the engine mount. Once you start drilling holes in the middle of the mast, all bets are off!! Roll over is another issue entirely too. I've seen the aftermath of several rollovers and any drilling in the area of the middle of the mast or near where your neck is when seated in the gyro is very bad idea. I'd much rather have a single 2x2x.125 tube with no holes over 2 separate 1x2x.125 tubes that are drilled for a shoulder harness at shoulder height. The Gyrobee and other designs often have a single hole for the seat back angle braces at or near the top of head height. The Hornet has 2 holes well above head height. That doesn't bother me nearly as much. Just my opinion Curtis, others may disagree.
    "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


    • #3
      That is just fine. Yes you are correct sir. I neglected to allow for the reduction of length by the wall thickness. .I remember our discussion about that the holes in the mast. I am trying to insure the best arrangement with no holes.. BTW how are things going on your Hornet build. I have been meaning to call about yours and the apprentice.
      Last edited by curtisscholl; 09-11-2017, 02:15 PM.

      Comment


      • #4
        OF the three ultralight Gyros, Hornet KB3 and 3DRV, the only one that does not put holes in the middle of the mast mast is the 3DRV. The engine mount is accomplished with cheek plates drilled for bolts in front of and behind the mast. The only holes drilled are for the rotor head cheek plates and the cluster plates down at the keel, and again down near the cluster plates for the seat mount, but even that could be eliminated with a little ingenuity. I am going to use the 3DRV arrangement.

        Comment


        • #5
          Holes for cluster plates at the bottom and for the rotorhead at the top are fine. The Hornet, the KB-3,and the Gyrobee can all be constructed without holes for the motor mount. I don't know if I've seen a 3DRV so I can't comment on that model. Here's how I'm doing it on the new gyro.
          "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


          • #6
            The pic illustrates the clamp pressure. That is similar to the 3DRV engine mount system in that the bolts do not go through the mast, but are in front and behind holding cheek plates for the engine mount..
            Last edited by curtisscholl; 09-14-2017, 09:34 AM.

            Comment


            • #7
              That isn't the only attachments for the mount. It continues forward and bolts to the seat back angle braces and there is a vertical support from the back of the engine mount down to the rear keel.
              "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


              • #8
                Sweet arrangement.

                Comment


                • #9
                  Hey John,

                  I have bee looking at the pictures on your facebook page. You have come a long way. Engine is installed. Lots of progress.

                  Comment

                  Working...
                  X