Tuesday, September 29, 2009

Campitch 1 Monocopter Pt2

On Sept 19, I went to fly with the Alamo Rocketeers over in China Grove.
Since my truck is broken, I went on my Harley Sportster with whatever I could carry in a knapsack. It's been a long time since I did that. You're limited to rockets that are either small enough, or that disassemble. Sturdy is important too. The Campitch 1 is certainly small enough once the flybar is removed.
The hard part is getting by while leaving a new 25LB field box at home. It helps to have friends.

The CP1 sitting on a borrowed pad, loaded with a D12-0

After ignition it's only spun 180 degrees and the wing is already extended for ascent at least part way. The pads' rod angle adjuster is slipping.

That's the wing in the foreground after bouncing off the ground, and tossing up a small cloud of orange soil.

The hub is falling after making a respectable altitude, wingless.

No major damage to speak of, but the cam follower pin was sheared off where it came out of the reinforcement plate on top of the wing. The pin was essentially a 2-56 steel bolt. I've already done repairs and replaced the 2-56 with a 4-40 socket head bolt, and widened the
camtrack slot to take it.

In retrospect it's not too surprising that something happened, given the number of MC's that come apart under centrifigal loads. I would've been much less surprised if the 2-56 pin was simply bent but still there. While I was at it, I installed the heavier return spring I had pre-selected as a possible upgrade. I never liked the limited wing attachment method on this model. A secondary safety attachment would be nice, but how to do it without making the next failure worse?

Sunday, September 27, 2009

Campitch 1 Monocopter Pt1

This is the Campitch 1.  The 1st of 2 recently finished
monocopters. Both monos employ quite different wing
control mechanisms, but I decided to build both at once
because most of the construction is routine enough to be
a bit boring and I always mix too much epoxy  anyway.  

The Campitch 1 uses a system similar to that of the
Rotary Space Ship that I posted about back in March of
this year. When the vehicle begins to rotate, centrifigal
force causes the wing to slide outward on its' pivot rod,
as it does so, a pin on top of the wing root follows a
cam track causing the wing to rotate from down pitch to
up so that it can ascend.  Once the motor burns out, the
mono will slow it's spin until a spring can retract the
wing, returning it to down pitch so that it can autorotate
for a gentle landing.   No stopping, no falling.  

Now, I've done away with the burn string that the
Mousetrap requires.  After I work the bugs out on D12's,
I'll be able to fly it on my own small moonburn sugar motors.

Monday, September 21, 2009

It was a Gorey Show [sorry]

I can't remember the last time I was hot to go to a museum.
The Cosmodrome when I was in Kansas for LDRS 12?
That was a space related museum, no surprise there.
This time it was the McNay art museum here in San Antonio.
I've driven past it a 1/2 a million times without knowing it
was even there, this time we were pulling in. What snagged
me was a traveling exhibit of the art of Edward Gorey.
We aint in Kansas anymore, for sure.
We managed to get down there on the final day of the exhibit
and it was great. There were plenty of prints of course, a
mere drop in the bucket from a prolific artist, but mixed in
were occasional originals, and pencil layout sketches. One of
the prettiest displays was a cabinet with hand drawn and
watercolered envelopes that Edward sent to his mother over
the years. I'll spare you further descriptions, the book covers
above are adequate examples. The Doubtful Guest above was
my intro to Ed Gorey, it was read to me/us when quite young,
but then I grew up with hippy school teachers.
My brother and his Sylvia were the ones who went with me,
in fact drove me as I had no transportation at the time. Last
weekend was my birthday and they gave me Ed Gorey's
Amphogorey Again, a compilation.  Love it.

The website below is a .net, but it's actually a .com.
Other than that go to Amazon for books or simply Google,
there's plenty of E.G. out there.

Sunday, September 13, 2009

Flying a better Mousetrap

I've been flying monocopters since 1988. I've also seen
other people fly them. They all shared two common
problems, the first is getting them to stay in one piece
throughout the flight despite the high rotational loads.
I've seen a few fly apart, including some of my own.
Anyone who hangs in there a while, can conquer this
sooner or later.
The second problem is the subject of this post. When
a monocopter's motor shuts off, they typically stop
spinning and fall down. Some falling monocopters will
reaquire spin, either backward or upside down, hopefully
before impact,and make a safe landing.

In short, after getting monocopters to go up reliably, the
next trick is to get them to come back back down safely.
I've seen other recovery methods tried with varied success,
but the coolest will always be autorotation, ie; true 
mapleseed recovery. Spinning up, and spinning back down,
without stopping, without falling.

Last fall, I built the 1st step on this quest. I call, it the Flying
Mousetrap. It somewhat looks the part. Mousetrap has a
wing that pivots around the center of lift. There's a spring that
pulls the wing to descent angle, and a length of string to hold
the wing at ascent angle until the motor [D12-3] ejection burns
it through. This gives a timely transition after slowing to
autorotaion speed, but without falling or reversal. The string is
actually dental floss, it's easy to work with at the field, and it
comes in a neat dispenser WITH a built-in cutter.
Minty fresh too.

I don't consider this to be the best approach to the problem.
It's a simple up/down system instead of being reactive, and it
limits the choice of usable motors to ones with suitable delay
and an ejection charge.  Since I make my own sugar motors,
I would prefer a system that can use them, and they're all
capped.  However, I figured this would be a good first step
that others might prefer.

The 1st flight video was posted by friend John Lee at the time.