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Small vehicle work, Big vehicle work

May 17, 2004 notes:

May 17, 2004 notes:

 

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 wasn’t 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 didn’t 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 engine with.

 

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 propellant slower.

 

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 isn’t a major problem, but the engine will start heating up earlier than we want, possibly contributing to short catalyst life.

 

When I opened the throttle to drain the water out, it started making a funny noise, and the flow wasn’t 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 out.

 





 






 
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