Two vs Four

To All:

If you've got a major back pain but absolutely positively HAVE to be
able to walk you use FOUR canes. This turns you into a quadraped.
Two of your 'legs' just happen to be wood. (Or aluminum, PVC or
whatever) But it doesn't matter what those two new legs are made of.
Your body mass is now supported by FOUR 'legs' rather than two... or
three. The only place where you'll have trouble is in the check-out
line.

Did that come across? Your body's mass is now supported by FOUR limbs
rather than two. Of course, the two canes don't carry as much of a
load as your two real legs but when it comes to BALANCE your two
pseudo-legs are about as good as the real thing.

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So what does this gotta do with aeroplanes?

I thot you'd never ask :-)

The landing gear, as a system, represents a significant portion of the
cost when you are trying to build a bucks-down airplane. Cheapest way
to go is to use a stiff-legged landing gear like they used in the
Piper "Vagabond" or the homebuilt "Fly Baby." In effect, the rubber
TIRE becomes the entire 'landing gear.' Of course, that only works
when the tire is large enough.

Want a cheap tire & wheel? You can get a 10" tire & wheel for a 5/8"
axle for less than $5 (!!) (see the closing NOTES). And along about
here you'll discover there's a bit more to your alighting system than
energy absorption. For example, if your tire is too narrow it's
liable to sink into the soft earth and simply stop rotating. Of
course, the airplane will continue rolling right along... but with the
wheels locked to the earth, the airplane will prescribe a graceful
outside loop, prying the wheels free of the soft earth as the airplane
comes to rest on its back, a position that's more embarrassing than
dangerous. Roll it back up-right, buy yourself a new propeller and
you're pretty much good to go, if you're willing to ignore the risk of
a cracked crankshaft or damaged rudder hinges.

The lesson here is that your landing gear must have a significant
'foot-print.' And that means you want a big, fat tire.. such as those
used on the Vagabond or the Fly Baby. Of course, big fat tires cost
more than little skinny tires. As in a LOT more.

But wait! If we put TWO of those little skinny tires together we'll
end up with a 'foot-print' that's almost as big as that of a big, fat
tire. And the price is still durt cheep.

Okay, let's take a look at what we got. We order FOUR of those Harbor
Freight pneumatic ten inch wheels. They cost less than five bux each,
plus the shipping. We rig a 5/8" cross-shaft and put one of those El
Cheepo wheels on each end. Now we've got a foot-print that's bigger
than the Beanstalk Giant and there's a good chance our cheep landing
gear won't sink in and flip us over on our back.

Of course, it would really be swell if we had a landing gear that DID
address energy absorption. And since we've already started with those
cheap 10" wheels let's stick with them and see what we can come up
with.

First off, let's get rid of attaching two wheels to each landing-gear
upright. Instead, let's make a kind of upside-down teeter-totter that
pivots in the middle and has TWO of those El Cheepo ten-inchers on
each end. For energy absorption we'll strap the front part of the
teeter-totter to the landing gear upright with some bungee cord. Now
when the aft pair of wheels kisses the earth the weight of the plane
will cause the teeter-totter to pivot around the mid-point until all
four wheels are on the ground. NOW we've got a landing gear that's
got a foot-print the size of a DC-3 and the whole damn thing only
costs about $20 per side.

Weight? Probably kinda heavy; the wheel part is stamped steel and
we've got the upright and the teeter-totter to think about.
Cost? Cheap, as in Durt Cheep. Each wheel is only five bux. The
bearings are trash -- we'll want to replace those as soon as we
receive the wheels.
Brakes? Nothing comes to mind other than scrubbers -- the sort of
thing that rubs against the rubber tire. But as for foot-print, we've
got an alighting system that's good for everything from beach sand to
muskeg.

One of the big down-sides is that this arrangement is only good for
something like the Teenie Two. But wait a minute... what if we were
satisfied with only TWO wheels per side. Then we could go ahead and
rig it for a tail-dragger such as Bert Sisler's 'Cygnet' or any other
similar design.

For now it's just a thought. I was about to cut metal when they
decided I had cancer. Ever since then I've been sorta preoccupied.

-R.S.Hoover

NOTE: 10" pneumatic tire w/tube $4.99, 30900-0VGA (10" Inner Tube
$3.49 38354-4VGA)

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PS -- As for my canes, I've got two of them. The first one is named
'Kane' and is made out of aluminum.
The second came along after my wife saw me struggling to keep up with
her in the parking lot outside the cancer/x-ray place. Once you get
inside they got wheel chairs and an elevator and all kinds of good
stuff but the trick is getting there, which is damn hard to do with
only one cane or Kane.