2/16 Brain Dump and To-Do

  1. BUMPERS I spoke tonight with Katrina about our plan to get wooden bumpers with attached noodles to her ASAP. If Tyrese can saw and dovetail two sets of new ones (glued over a form to ensure perfect 90º this time) I will drive them to her during the week. The wooden bumpers should have studs and T-nuts built into them before upholstering. We need to purchase an appropriate amount of the the appropriate material. Here’s my estimate of the fabric required for one (of four total) bumper “bracket”, including a generous 2.5″ seam allowance all the way around.Width: (5 +2(2.5) + 2.5) = 15″ by
    Length (35 + 2(8) +4(2.5) +2(2.5) = 66″So we need 2 yds of red and 2 yds of blue, unless the bolt is more than 66″ wide. In that case we only need 1 yd each.

    She will also need to obtain thread & some white paint for stenciling the numbers.

  2. ENDGAME Rules clarification needed: If we attempt to “drive” up the wall (the “Heyduke maneuver”), will the string be violating the 15″ extension restriction when the chassis rotates? If so, we need to winch from a point very close to amidships…Harry and I ran some tests using the tape measure, a length of Dyneema and a mock-up idea for using “orgami training wheels”. The “orgami” consisted of a square of printer paper, folded on both diagonals to form a 8.5″ X 8.5″ 45-45-90º triangle, creased along its altitude. The resulting “Klingon ship” shape was attached to the end of the tape measure so its wingtips dragged along the wall surface. This was a good scheme to defeat the tape’s tendency to twist itself and buckle on its way up. The weight of the Dyneema is low enough that the tape had no trouble getting it to reach the target height. We need to be very careful not to overshoot and hook the goal opening however; maybe a diamond-shape Klingon ship cut from a stiff plastic report cover will make such fouling impossible.Next, we need to install a lightweight but strong hook to the spine of the Klingon ship, and decide how we want to “set the hook”. Harry suggested that backing down the ramp could do it very simply. Let’s try that, or try rotating the whole robot by jacking up the far end with the BPU prior to hook deployment, then lowering it back down after the hook is in place. A third possibility is to employ a simple “Hempelmann” linkage to deploy the hook. (A “Hempelmann” is a German toy for toddlers of a jumping jack figure who dances when you yank on his string.) One such linkage would pull the Klingon wingtips down & closer together, making the whole arrangement do a push-up off the wall.

    A successful hook needs a sufficiently long shank to prevent it from rolling off the chinning bar. In other words, the hook needs to envelop somewhat more than 180º of the pipe, from its tip to the point of its attachment to the winch cord, while also presenting much more than one pipe diameter of “open” side to catch the pipe. 200 – 225º seems a likely range to ensure that swinging doesn’t cause a disaster.

    The winch gearbox needs to be “folded” from its current too-linear layout if it is to fit in the small space allowed. I spoke with David Ragone (who sounds eager to quit struggling with the flywheel shooter) about applying some of his newly acquired geartrain expertise to build it.

    Some likely arrangements for the climbing winch have the following characteristics:

    1. Tape measure is upright and on top, spooling out clockwise.
    2. Winch is below and spools out in the same linear direction as the tape while turning counterclockwise. The natural directions of the gear drive will facilitate this, but means that the idler roller is below the tape.
    3. A Mini-CIM motor drives the winch/tape pair through a 3:1 reduction, but should nevertheless be capable of extremely high tape speeds when it has no load (>12 feet/second), so an encoder and speed control seems imperative.
    4. After the hook is set, tension in the Dyneema should release the tape drive rollers, so the tape will be free to rewind
      The winch has to stop when sufficient height has been attained.

    Let’s shop for more wide tape measures. I think we will be chewing them up!

  3. CATAPULT If we narrow the catapult somewhat by using just a single release mechanism on one side, would that create enough space down its edge for the climbing winch? I don’t yet have a clear picture in my mind as to where it would fit around there…

Leave a Reply