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Nov 28 meeting notes

Nov 28 meeting notes:

Location: Long Range Systems

In attendance:

John Carmack
Phil Eaton
Russ Blink
Neil Milburn
Darin Smith

Next meeting: next Thursday at Long Range, hopefully with 10L of 90%

We fixed all of the plumbing for the VTVL vehicle.  Last week it was leaking all over the place, but we plugged everything up.

We had been using Teflon paste on the NPT threads in the distribution manifold, but we replaced them with Teflon tape and fixed those leaks.  We aren't sure if it wasn't tightened enough before, or we didn't use enough paste, or we didn't let it dry long enough, but it works fine now.

 The flexible hoses had a couple things wrong with them.  The primary thing was that we weren't tightening the hose ends tight enough.  There were lots of warnings about not over tightening, but we weren't getting nearly enough.  I brought feeler gauges and we cranked them all down to spec.

That fixed most of them, but we did still have two ends leaking a bit, so we re cut the hose and did a better job of seating the sealing olive.  We cut a small piece off and removed the steel braid completely so we could closely see how far it was expected to fit into the olive.  It is difficult to get it as far as it should go with a finger, so we wound up pushing it against a wall, which got it seated properly.

We tried cutting the hoses with a hand dremel instead of Russ's big metal cutter.  It did cut without splaying the braid at all, but it took a lot longer.  We will probably continue to use the big cutter in the future, as it doesn't seem to have been a problem on most of the hoses.

We hooked everything up, and the system works perfectly now.  We were still controlling the PWM driver board directly through the laptop parallel port, but I am almost done with a radio controlled interface.

We may want to look at using metal hard lines for some things in the future.

We experimented with an NOS annular fogger nozzle.  It is designed to mix N2O and gasoline, but we just plugged one of the inputs.  It turns out that the N2O input is only a single stream, but the gasoline input spreads over eight little orifices.  It does divide the flow up fairly well, but it doesn't atomize as well as I was hoping.  It is fairly long and would complicate the plumbing, so I don't see it as a strong enough benefit to use.

I am still interested in exploring other types of spray nozzles, and we might want to try drilling our own like-doublet spray nozzles.  We still don't have a good handle on exactly how important atomization is.

Russ has one more blank plate we can drill for the small engine's catalyst pack forward plate.  We are going to try about eight .020" holes in a radial pattern about halfway out.

I got the flow control valve from McMaster-Carr, and it looks pretty interesting.  Unlike a cavitating venturi, which gives a constant flow for a range of back pressure, but changes based on source pressure, this valve flows fairly constantly irrespective of both source and destination pressure.  This would be a very, very nice thing, as it would eliminate the blow down variability as well as the chamber pressure startup transient.  However, it is only rated for 200psi pressure, and has a flexible washer of dubious peroxide compatibility.  The body itself is beefy stainless, so it isn't going to burst, but the flexible part may break under high load.   It has 3/8" fittings, so Neil is going to get us some adapters down to 1/4", then we can do some tests with it.

I am still going to order the 50ml/s cavitating venturi from Fox Valves.   It will be about $500 with AN fittings.

I brought a can of high temp spray paint for the test stand, but we ran out before finishing.  I'll grab a couple more cans tomorrow.

I brought in a set of four .040" metering jets for the VTVL engines, and a few other sizes for experimental use.

I have a bunch more 3 and 1/8" fittings on order.

I gave Darin my extra Basic Stamp experiment kit, so he should have the accelerometer working next week.

I will modify the flight simulator to try and work with some idealized accelerometer inputs this weekend.

Phil reported that he talked with someone who knew someone that had built a VTVL jet powered platform, and had flown it using RC helicopter gyros, so that sounds like something we should also look into.  Darin had found a supplier a couple months ago, so we will go ahead and get one for experimentation.

Still no word on the magnetometers.

Phil is going to make a self contained battery pack for our launch valve controller, so we don't need to clip it to a battery when we are using it.

Neil should have the components for the dumb rocket next week, so we may get to do some tank fitting soon.

The silver screen order from India has been confirmed, so we should be getting that soon.

I am going to try to get more of the metallic foam from Bob in the next couple days, so we can get that plated again.  We are going to try sintering it on after plating this time, because there was clear erosion from our earlier tests.

We need some Teflon tubing and clamps or pumps to transfer the 90% next week.

Our 12v vacuum pump seems to be weakeing.

Russ needs to get another full nitrogen bottle.


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