Tubing Racks Complete

Tammy & Bob H finished building and installing the racks to hold the carbon fiber tubing today, in time for the tubing coming by sea freight that we expect at end of October/start of November.

Prototype airspeed test

We did a quick sanity check on the prototype airspeed indicator board, riding the trike and pacing with another bicycle since we don't have a way to display the ground speed of the trike setup yet.  The airspeed indicator uses a small pitot/static tube with an analog output, then converts that to a digital signal for the display.

There is some digital noise that makes the airspeed pretty inaccurate near zero, but once it gets into the region of interest above about 5 m/s it is pretty stable and appears to agree within a few tenths of a meter per second with the cyclometer on the other bicycle (though it seemed to read slightly lower than the bicycle gauge).  (Note on video #2, the trike rider Geoff is calling out m/s, the cyclometer on the bike is in mph -- the conversion is 2.24, so 6 m/s is about 13.4 mph -- we ran several more tests than the videos shown.)

In a few weeks when we have this hard mounted to the trike and also have a separate speedometer set up for the trike, we'll be able to log both and compare, and make adjustments if necessary.

Here's some photos and video:

Getting ready to test the prototype airspeed indicator

Geoff turns on the prototype airspeed/altimeter setup

Starting the test

Pacing with another bike to compare speeds

Altimeter test

Geoff built a breadboard version of the circuit for the ultrasonic rangefinder we'll be using as the altimeter for the DaSH plane.  Here is video of a test:

Shelves and Welds

"Shelves":

We are building racks to hold the long carbon fiber tubes, the longest of which is 8.5 meters.  Tammy got the first two vertical supports up over the last week.  In about a week and a half we'll add 6 more supports like these, so they will be ready for the tubes coming by sea freight and arriving at the end of this month (October '12):

6 more vertical supports like these will be added to make the full set of racks for 8 m tubes

Welds:

We continue to practice welding both mild steel and aluminum, so that we can weld the superstructure for the trike and the trailer for the airplane out of steel, and the seat frame for the airplane out of aluminum.  Steel we pretty much have down, but welding aluminum is a lot tougher, and we are just getting experienced at it.

We are getting better at, though, and by playing with the frequency and A/C arc balance settings, we have managed to make some acceptable welds.  With a little bit more practice, we should be ready to go.  Here is an example of a decent weld on the very thin tubing we are planning to use on the seat (1/2" OD, .035"wall thickness).  (compare with a few blog posts ago when we were making lumpy messes...):

A good weld by Yohann on 1/2" OD, .035"wall Aluminum tubing