April, 2007

  • Eric Gunnerson's Compendium

    Electric Helicopter 101


    I've been spending some time doing research on RC electric helicopers, and thought I'd share the highlights.

    I'll do this by describing the two that I own and the one that I'm considering getting.

    First, there's the Picoo Z.

    Good stuff:

    • Inexpensive ($50 ish)
    • Easy to fly
    • IR control
    • You can fly inside your office

    Bad stuff:

    • 2-axis controller. Basically, you control the speed of the main rotor and the tail rotor. You can hover and spin the tail around, but not move forward or backwards (well, you can a bit in the the turns). If you weight the front a little, you can get it to slowly move forward.
    • Eats batteries
    • Hard to get away from your 12-year-old daughter

    Blade CX2

    Good Stuff:

    • RTF (that means "Ready to Fly")
    • 2.4 GHz digital controller (a nice upgrade over the old-style radios)
    • 4-axis controller
    • Stable (ie relatively easy to fly (I was going to write "easy to fly", but it's really not)
    • Gyro-based heading control. Basically, the electronics automatically attempt to keep the copter pointing in the same direction.
    • Counter-rotating dual rotors (ie not tail rotor to break)
    • Pretty-red color

    Bad Stuff:

    • It has heat issues. The electronics and the motors heat up as you work through the charge in a battery, which means that the trim settings change, especially the trim on the yaw control (ie which way the nose is pointing (I'd call this "tail rotor control", but there's no tail rotor (on a real copter, you'd call this control the "anti-torque pedals", but there are no pedals on my controller)).
      Anyway, what it means is that you start with the yaw torque all the way to the right, and then end up with it all the way to the left at the end of the battery.
      The fix is to a) put a heatsink on the motors, b) remove the case on the electronics and c) cut out the top of the canopy so the rotorwash cools the electronics
    • Two motors are twice the complexity
    • Yaw is controlled by slowing down one of the rotors, which means the copter drops if you spin it around quickly.
    • No inverted flying
    • Hard to fly when it's breezy

    Blade CP

    The CP is a "real helicopter", while the CX is a "easy-to-fly toy".

    Or at least that's what I've been told...

    There are two big differences from the CX (AFAICT).

    The biggest one is the design of the 'copter. The CP has a single main rotor and a tail rotor, and therefore doesn't exhibit the bad behavior when spinning around.

     The second is that the CX is designed to be much more agile, so it's harder to fly.


    Neil spoke of not being able to replace batteries. I replaced the battery on my daughter's air hog last weekend, and it works fine now. The Picoo Z battery is a 50mAH battery - this looks like a nice replacement. One of the disadvantages of the low-end RC models is that they charge their batteries too fast (so that it's more convenient). In general, you want a charge that takes about an hour to complete, but the Picoo charges in about a third of that (or quicker), which cuts down on the battery life substantially.

    There are directions here on how to open the body, and then it's simply a matter of soldering the new battery. Make sure you get the polarity correct.

  • Eric Gunnerson's Compendium

    A short little ride


    I wrote about the Seattle Randoneeur group last fall when they did the Populaire.

    And I think I probably wrote something about the relative insanity of riding a 1000K course.

    So, how about 2519 miles in 22 days down the continental divide on a single-speed mountain bike?

    The Way of the Mountain Turtle

  • Eric Gunnerson's Compendium

    Things that don't seem possible


    The Kaye effect (aka "Leaping Shampoo")

    From "Good Math Bad Math"

  • Eric Gunnerson's Compendium

    Hacky way of doing changing bitmaps on a button in WPF


    I came up with a hacky way of doing "hover" and "press" buttons in WPF recently. There are a couple of nice examples on the web, but I was looking for a way to do it purely through XAML. If there's a nicer way to do it through XAML (or if there are big drawbacks to this approach) please let me know.

    So, here's what I did.

    1. For the button, create a button template (very easy to do in blend...) that has an image in it, and hard-code that image to use the default bitmap. I also hardcoded the size to the image size.
    2. Add triggers for the IsMouseOver and IsPressed events to change the image to the appropriate hover or pressed bitmaps
    3. Apply the template to the button.

    Okay, so it's not very general in that it hardcodes the behavior for the specific button, but it was really cheap to do.

     XAML looks something like this: 

         <ControlTemplate TargetType="{x:Type Button}">
           <Border x:Name="Border" Padding="{TemplateBinding Padding}" VerticalAlignment="Stretch" BorderThickness="2,2,2,2" CornerRadius="5,5,5,5">
            <Image HorizontalAlignment="Right" x:Name="image" Width="24" Height="26" Source="prev_rest.png"/>
           <Trigger Property="IsMouseOver" Value="true">
            <Setter Property="Source" TargetName="image" Value="prev_hover.png"/>
           <Trigger Property="IsPressed" Value="true">
            <Setter Property="Source" TargetName="image" Value="prev_down.png"/>



  • Eric Gunnerson's Compendium

    Midlife + 3.010958


    Okay, so it turns out that I was confused. It's not real helicopter training - I'll be flying this instead.

    It's fairly easy to hover - easy enough that I'm not sorry that I don't have training kit (a set of poles and balls that keep the copter from flipping over). It's going to take some time, however, to learn how to deal with flipping the controls (left == right, right == left), when the copter is facing me ("tail out" in rc copter jargon). Battery life is 10 or 12 minutes, which is plenty for how skilled I am, as it's fairly intense work.

    Disadvantages? Well, the more advanced model, the Blade CP, can do this:



  • Eric Gunnerson's Compendium

    Midlife + 3


    As some of you already know, I'm at the point in my life where it becomes expected to have a crisis - more specifically, one of the mid-life variety.

    In fact, many would say, that at the advanced age of 43, I'm past the point where I should be thinking about such a thing, and should be deep into crisis mode. I've been ignoring the many, but this last week I found out that an acquaintance at work is buying a Tesla...

    And, so, I've decided to take on a challenge. A *real* challenge - none of this "ride 200 miles in a day" stuff, but something with the potential for serious bodily harm.

    I'm going to learn to fly a helicopter. Perhaps not the most practical thing to do - especially given the cost and expense - but that's really the whole point of a such a crisis.

    I'm not sure exactly what model I'll be training on, but it might be this one...


  • Eric Gunnerson's Compendium

    Animated stereogram


    Animated stereogram

    I've always liked stereograms because they're one of the few cases where being seriously nearsighted is advantageous - because of my poor eyesight I am used to looking at things that aren't in focus.

    From Bad Astronomy

  • Eric Gunnerson's Compendium

    Eric's Ski tips for the 2007 season...


    We're at the tail end of the ski season here. I skied yesterday - in conditions that were less than exciting - and next weekend is probably the last time of the year, assuming the weather is worth it.

    Over the past 7 years or so, my wife and I have taken a set of ski lessons (all at the excellent Olympic Ski School, teaching at Stevens Pass). We started because our daughter was going to be in real lessons, and we needed a reason (explanation) for why we weren't going to watch her during lessons. (for the young parents who haven't figured this out yet, having mom/dad hang around is a pretty good way to compromise your child's improvement).

    Those lessons have taken me from a pretty good intermediate skier, skiing all the blues and groomed blacks well and surviving ungroomed blacks to skiing pretty much everything in good snow conditions (though I'm not great in the bumps). Which puts me somewhere in the advanced/expert region.

    Normally, when a new season rolls around, I forget the things I worked so hard to learn the last year and spend a few weeks skiing below where I want to ski. Which is why they are "Eric's ski tips" - they're for me, so I can read them next October. But I'll try to phrase them generally...

    Stand tall. While it's okay to be compressed a bit, you need to compress at the knees, not bend at the waist.

    Hands in front. This is about feeling the front of your boot, and not getting your shoulders rotated.

    Block, then poll plant. This is probably my biggest insight of the year. I tend to be a fast skier (I topped out at 45MPH on a recent day according to my GPS), which is a lot of fun on groomed stuff, but not what you want on fresh or chopped up stuff. And I've often had trouble controlling my speed in those situations. This year, we were doing some pole plant exercises, and they weren't working for me at all. My instructor had me borrow his (shorter) poles, and what do you know, my poles (which were sized using the "old school" approach of a 90 degree angle at the elbow) are too long for the kind of skiing I do. I went two sizes smaller (a full 10cm), and saw a major improvement. They don't get in my way and they make it easier for me to reach downhill. So, now that I have the new poles, I can adjust my timing to block (a bit like what you do with a hocket stop) at the end of the turn, pole plant while in the block, and then release in the new turn.

    Feet apart. This is mostly about getting angulation - if your feet are next to each other, it's hard to get any curve (aka angulation) into your lower body - all you can do is bank. That's fun on groomers, but will prevent you from doing short turns, and if your ski loses an edge, you fall down.

    Look downhill. I usually don't have trouble with this.

    Balanced weight. On the groomed, when making big turns, you end up with the vast majority of your weight on the downhill ski. In shorter turns and especially in ungroomed snow, you need to have a balanced weight between the two - somewhere in the 60-40 to 70-30 range. This does a few things. First, it keeps your downhill ski closer to the surface of the snow (you're using more surface area). That puts you in the lighter snow, and it also means that the weight transfer from turn to turn is less, so you can do it more easily and quickly.

    Inside knee. Another big insight for me this year. Getting the proper angulation through the turn is controlled by what you do with your inside knee rather than your outside knee. If you get it to the inside, your outside leg has to follow.

    Here hoping these help out next season...

    Oh, one bonus tip.

    My long-suffering Volkl vertigos had reached the point where they couldn't be tuned, so I ponied up for new skis, and boots. The Soloman X-10s are wonderful - more floaty than the volkls, but still stable at speed. The soloman boots are also very nice - they have a softer flex than my old nordicas and also have more space in the angle box to allow some angulation in the angles. Finish that up with some nice custom footbeds, and that's a setup that are very comfy and don't have to be tight to perform well. If you're an intermediate skier, the benefit to be had from good boots, custom footbeds, and higher-end skis (in that order) is well worth the investment.

    Oh, and woo-hoo! No cracked ribs this year!


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