Wednesday, July 23, 2014

"Terror in the Sky" Airfest (updated with a discussion of tolerances in design)

Braving the 100 degree humiture, I traipsed out this afternoon to a local park to fly a couple of low tech water rockets and my Blade 180-QX Quadcopter. My drone piloting skills suck...hence the name of the 'launch'.

Things started poorly when I realized I hadn't reloaded the battery in my camera. And I had gotten all fancy by bringing out the tripod. Rats!

Water rocket-wise, I mainly wanted to see if the 1980's vintage hand held water rocket, which I adapted to the Quest launcher, would be suitable for the grand rocketeers.



As expected, this small volume pressurized fast with my electric pump.  Faster than I had hoped for. 50 psi was the lowest I could get it and I ran up to 100 psi.  The performance was unimpressive and I am a little scared to run those pressures around kids. So, this will be retired.  At least the old rockets are tough. My kids bounced this one off the pavement more than once before the pump gave out. The new models are not nearly as robust...at least not the $2 variety. This was a CATO, not a lawn dart:

20140719_104728

I also brought a 1L rocket with the Quest fins and bumper. This is where things went down hill.

I had recently bought some replacement nozzles knowing I was going to chop one up for the rocket shown earlier.  Well, something was up with the nozzle/launcher.  I flew several times at 80 and 100 psi. Most of the time, it wouldn't release without some nudging from my thumb. Not good for seeing the flight or staying dry. Glad I brought safety glasses. Once it launched spontaneously at 100 psi. Then it needed nudging again. I'm going to measure the nozzle and maybe lube it lightly?

At that point, the heat got to me and I scrubbed the quadcopter practice. Probably was a little too windy for this novice anyway.

UPDATE:  Well, I investigated the Quest nozzle issue further. This is all qualitative since I couldn't detect any differences with my calipers. Variations were beyond what I could reliably measure.

  • Original nozzle that came with the kit and is now on the red rocket above.  This is clearly the loosest fit.
  • The one that was on the other rocket that I flew. This was much tighter as it was full seated in the launcher. It slides in and out much better once it was lubed.  Is it loose enough?
  • The second new nozzle that I tried slides in and out easily. Very close if not the same as the original.
  • The third new nozzle was the tightest of all! I removed the O-ring and is was still just as tight. Enter the Dremel. Now that it is ground and lubed it its loose. Loose enough?
It appears there are variations in the molding process, possibly in the thousandths of an inch. My next solo outing will include testing all three of the new nozzles.