May 17, 2004
We worked late on Saturday and I spent Sunday at the Wired NextFest event, so this is just a quick update.
Small vehicle work
We cut open the small vehicle motor to replace the hot
catalyst pack. The bottom retaining
plate had bowed down a fair amount, but there wasnt anything burned
inside. Activity was down, so we
replaced it with completely fresh material.
We used a thicker retaining plate with a deeper weld, 600 grams of
rings, and welded the top retainer in place under 2000 psi
gauge (4000 pounds) pressure.
It turned out that this didnt help the engine, so we cut
the top off to remove the cold pack monoliths.
The top one was ok, but the second monolith had some burned sections,
and had very little catalytic activity.
This almost certainly happens during the low flows at warm up. We have selected the two best monoliths out
of our used sets (we have fresh 7, but no more fresh 5.5) to rebuild the
We added a little more weight to the small frame to balance
it more precisely. Dry weight is around
420 pounds now.
The software is all complete and simulated for doing our
boosted hops, which we hope to test next weekend at our remote site.
Big vehicle work
We got the big vehicle completely converted over for a big
engine with jet vanes. This consisted of
several major tasks: landing gear supports, engine mounts, engine plumbing, jet
vane mounts, and the jet vane protection box.
All told, we wound up saving about 20 pounds over the four separate
engine configuration, but we are probably going to put several more pounds of
bracing into the lading gear support.
We have some concern that the 1/8 thick vanes and ½ thick
shafts may not be strong enough, so I have ordered 3/16 stainless and ¾
shafts that we can replace them with if necessary. We will still try and hover it with the
current hardware, which will give us some good limit data if they do bend.
I still need to do a few hours of wiring and configuring to
get everything ready to fly, but we did a water test to check for leaks.
The vehicle is almost three feet taller, which makes loading
We seem to have a moderate leak through both the throttle
and cutoff valves. We usually seem to
scuff the ball valve seats after we drill vent holes in the ball valves. This isnt a major problem, but the engine
will start heating up earlier than we want, possibly contributing to short
When I opened the throttle to drain the water out, it
started making a funny noise, and the flow wasnt very fast. We repeated this several times, and reached
the conclusion that we had probably left a wad of paper towel in the inlet of
the valve when we mounted the engine. We
are going to have to pull the engine off and take the valves apart to get this