up-may8a.htm Small-Pogo Project


Small-Pogo Project


Status Updates


May, 1998

May 1, 1998

Squared the attachment bulkhead on the bottom of the shroud assembly (includes shroud, vanes, and upper portion of the lower center body. Completed the bulkheads and ribs for the lower center body. Glued two of the six ribs to one bulkhead using the lathe to keep them square.

May 2, 1998

Mounted four of the six stringers (ribs) for the lower center body assembly. Mounted the fuel tank, throttle servo, and battery. Still need to mount the on/off switch, battery charge connection, receiver, and skin and it will be ready to reassemble and test. I started cutting the vanes for the upper body.

May 3, 1998

Used sheet aluminum for part of skin. This was used to mount the switch and the charger connection. By countersinking the holes in the stringers and using wood screws the aluminum pulled in so that the screw heads are flush with the surface. Looks cool if I do say so myself. I still need to finish the plastic skin over the rest of the lower center body assembly.

May 5, 1998

Completed installing the avionics and skinning the lower center body assembly. It is now ready to be bolted to the shroud assembly. The shroud assembly needs to have the remote glow plug connector re-mounted and the trim tabs installed and it's ready for flight.

May 6, 1998

Too cold and wet to work outside. And this is supposed to be the desert? Well, we blame everything else on El Nino so we might as well blame this on it too.

May 7, 1998

Good progress today. I fabricated and mounted the trim tabs. There are four of them and are nearly the size of the rudders so it may be overkill but at least it shouldn't be too little. I mounted the lower center body to the shroud assembly. To get to all the interface mount screws I had to de-skin the lower center body assembly but have already started to re-skin it. Another half hour should do. Next is mount the remote glow plug connector, the engine, and the landing strut assembly.

I also cut the vanes for the upper body assembly and glued them to the upper center body. I'll be fabricating small mounts to attach the vanes to the center body assembly and that portion will be complete. The rocket launcher itself will be a separate bolt-on assembly, designed specifically for whichever rocket is to be used.

First free flight is getting nearer, possibly Sunday. There will be no parachute because I haven't figured out how to mount it yet and I'm not real happy with what I have. Nor do I think for these tests that it will be needed. For much higher flights it will be needed.

May 10, 1998

Completed reassembling the vehicle, sans upper body assembly, and ran the engine in the vehicle test fixture. It was too windy even for the rotation test. Otherwise, everything seemed fine. With the rebuilt lower center body and the heavy landing gear I'm concerned about the weight growth, though I haven't weighed it yet.

May 11, 1998

(0700) The wind is calm and will, hopefully, stay that way. I won't be able to test until about 0900 or 1000 when I can get some help with the camera.

(1000) By 0800 the winds were too strong to fly. They were almost too strong for the turntable test but I managed to get that in. Here is a picture of how it looked on the table. I placed the plywood on top of the turntable to give the vehicle a more stable platform to rest on. The test went well. I was able to remove two of the four trim tabs and even then they were almost straight by the time I had the vehicle trimmed. This also says that the rudder control is not very robust, though it may not need to be. In fact, it may be best to have it like this so I don't overcontrol it during flight.

May 13, 1998

(0930) Yesterday was windy (about 40 mph) with sprinkles. Last night it poured down rain and I'm hoping the garage didn't leak (it usually doesn't). This morning it was 40 degrees on my front porch, cloudy, and sprinkling. There was snow on all the hills. Right now the temperature is up to 41, windy, and the sky goes between rare sunbeams and rain. Looks more like Portland, Oregon, in winter than the Mojave Desert in mid-spring. I heard down at the Skillet this morning that Lancaster had some snow flakes on the West side and that there has been a mud slide out by Gorman. No chance for flying today unless a miracle occurs.

May 14, 1998

(0830) The miracle occurred this morning. The winds were near calm and the sky above clear (45 degrees F and clouds on the horizon). I got started about 0700. Getting set up I ran into, of course, several glitches.

I finally got the vehicle running and took it out about 0800. The engine ran up but just tipped over again, popping the balloons and dinging up the blade (which I had just put on after breaking the last one). It had weighed in at just over 5.5 lbs, which is heavy but should have lifted off easily. I put it back on the bench and replaced the blade with an 8 pitch (as opposed to the 6 pitch I had) and ran it again. After about a 30 second delay the engine jumped in speed to maybe twice what it was at first (and in the field) and it tried to lift off the bench. When I tried to shut it down the servo wouldn't respond.

My analysis is that, because I didn't have the battery fully charged, the throttle servo didn't command full throw and I had insufficient thrust. I'm now waiting for the battery to charge up and will stay with the vehicle on the next run until I know I have full power. Another lesson learned is to dry run the tests ahead of time (but then, everyone knew that).

May 14, 1998

(1030) Got in a second run. This time all the pieces were in the right place but the thrust was too low. The vehicle weighed 5.25 lbs with 6 oz (half a tank) of fuel. It did not try to lift off until I had tuned the engine and the fuel was nearly gone. Once it started to lift it tipped over and played weed-whacker. Still running, I picked it up and tried again. Again it just tipped over and chopped up some more weeds. The engine should have been putting out about 7.5 lbf thrust. The blade is, again, dinged up.

To get the thrust up I'm going to have to bite the bullet and order some 11.5 inch blades in various pitches to try to get the engine to pull more thrust. This time I'll actually measure the thrust with a scale. As a backup I can always borrow back the OS-.61 I had originally borrowed. It's a better engine, runs at higher RPM, and has more horsepower. I would really hate to damage it, though, by flying it through the weeds. I can also buy a bigger motor like a .90.

To get the weight down I'm going to replace the very heavy landing gear with something much lighter, though I don't know what yet. I'll also lighten the lower center body by drilling the frame. The four balsa longerons had enough strength and I replaced them with six birch (or something) longerons plus heavier bulkheads. Drilling was commonly used on motorcycles to lighten the frames when they were made from heavy steel tubing.

The weather is expected to get bad again tomorrow and stay that way for a few days which will give me time to make the necessary modifications. I also want to extend the rudders, they seemed to have too little authority. And, of course, the batteries are charging.

May 15-23, 1998

No activity. Planning on building a thrust stand to test various propellers.

May 24-31, 1998

No activity.



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