The little pill-bottle altimeter got me inspired. But the test chamber seemed
way too expensive and high-tech for me. So I've built a three-dollar altitude
test chamber.
Parts:
Spaghetti sauce jar (free with sauce)
25 feet of aquarium air line tubing ($2.00, though I could have gotten away
with a shorter piece)
Aquarium air line T valve ($1.00, actually not a valve but a fitting)
Glass of water (borrowed from kitchen, free)
Eat spaghetti until jar is empty, clean spaghetti jar and lid.
Drill ~0.175" hole in spaghetti jar lid.
Epoxy one end of T "valve" into lid. Allow to cure.
Cut 1-2 foot length of air line and attach to one of the ends of the T "valve."
Cut a 6-foot length of air line and attach to remaining end of T "valve."
Set altimeter test chamber on table.
Set glass of water on floor.
Immerse end of 6-foot line in glass of water
Very gently suck on 1-2 foot line. Use tongue as valve to maintain vacuum.
Height of water in 6-foot line above water in glass indicates pressure
distance. Height of water is roughly 0.0012 of the altitude simulated in the
test chamber. The exact value depends on the barometric pressure and
temperature at launch, but on a nice day at low altitudes, the numbers seems to
be in this neighborhood. This simple tabletop experiment allows about a 3-foot
high column of water which allows calibration up to 2500 feet.
It is very easy to suck this much vacuum with your mouth, though it takes a
little effort to control the water level.
For higher altitudes you can use the remaining tube either looped around a tall
object or hanging down to a glass of water down a stairwell.
Anyway, I thought this fit the spirit of the pill-bottle altimeter.
Peter Alway