Secure harness

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Top of harness

Have thought for a while to secure the top of the safety harness to the metal frame that holds it up. Up to now that triangle steel “ring” was just sitting in the top of that bar, BUT

Today I made two little steel cables with thimbles on the end. Drilled little holes in the tube exactly where thimble sits, and by pushing a pin through there, the harness is secure and can’t fall of the frame anymore 🙂

Hold down strap
Hold down strap

Cylinders are honed

😊 Picked up the honed cylinders today from “Motor Reconditioners” here in Christchurch NZ !

You can feel that the wear is gone ! And looking at picture below you can see the typical honed surface almost like rough sandpaper style grooves, circling around the inside of the cylinder. Sort of looks bad in this picture, but its good !!!

Went to Richard, the piston man from “Proturn Engineering” straight afterwards, so he could measure them and finalize the design. Hope to hear from him tomorrow or the next day !!!! so I can see what they look like (on the computer screen) before they are ordered in the States !

Honed cylinder

Lesson 32, fast taxis, circuits

A bit of a Southerly this morning, beautiful day ! KNZ all back operational. The problem we had last week, apparently is not so unusual. With all the fast taxing, the plane bounces a bit and the float in the carburetor drops down at every bump, allowing the fuel level to rise a bit more, every time when this happens. This higher level, makes the mixture richer.

By making a drain at some higher level I think, this is now fixed. But if it ever happens, while on the ground, I just close the fuel valve for a little while to drop the level in the carb 🙂

OK back to today. Did 3 fast taxis. During one “we” were told of by one of these GA guys who think they own the airstrip…. When I started that fast taxi, we couldn’t see any traffic and didn’t hear any radio calls, but by the time we were about at the end of the runway, he was behind us and having to do a “go around”. Its just a matter of sharing the facilities I suppose!!

After that it was time for circuits. The one main thing I learned was raising the tail after landing before taking of:

When landing you flare by pulling the stick more and more to raise the nose, until it stalls and lands. Then for taking off again, you apply power, and go faster and faster. One, for now unnatural thing to do, is pushing the stick forward, to raise the tail. This automatically gives you full vision ahead and because the speed increases, directional control is a bit better. Then when fast enough, you pull the stick and off you go, in the air…

So yes Dave showed me this once, and I did it later, getting better and better. Still more practice required, but I know what to do now and know what it feels like, so yes happy with today’s lesson !!!  🙂

Oh yes during one of my landings, I got a compliment over the radio: “nice landing Gert” so that was nice !

All cylinders are off

 

All 5 cylinders off

Took the last two cylinders of today. Wow, never realized, but yes in a radial, after stopping the engine all the oil drips down to sit in the sump and inside the two bottom pistons on either side of the sump.

But anyway, I will be dropping of the remaining 4 cylinders at an engine conditioning workshop “Motor Reconditioners” here in Christchurch today so they can be honed, so yes progress made towards “as new” cylinders and NEW pistons 🙂

 

And yes, glad a have a good oil drip tray !!! Thanks Sam 🙂

Lesson 31, Fast taxi and KTO

Hi, today bright and early I was going to have a lesson in the Kitfox at 0900. After the fuel check and the plane inspection I ran the engine for a few minutes to warm it up, while waiting for Dave. All went well.

As soon as Dave arrived, we hopped in and I did a fast taxi on RWY25 all going well, lots of short pedal bursts. But seconds later taxing back the engine started dropping power, up to a point where full throttle was just enough to keep it going. After a good look, we think its the choke that’s not working, and basically priming the engine continually, making it run very rich…… Hopefully its fixed soon 🙁

Dave told me to hop in another plane, a Karatoo, owned by Mike 🙂   KTO

I did one fast taxi, followed by a take-off and flew to the Loburn training area, did a few turns. Also we tried a stall, but the plane didn’t stall. it was the engine that stopped !!!!!!!!!! Scary to see a  prop in front of you that doesn’t spin anymore. But luckily we had a starter motor…. phhhh

A few more tricks and back home with an overhead join and a good landing !  🙂

Lesson 30, fast taxis

Yeah had another lesson at 9 this morning. Perfect day for it, sunny and no wind.

First I did a few, 4 I think fast taxis. This to start to get  the feeling of the directional control in a tail dragger. You need to adjust the rudder in short burst all the time as long as you are moving, to keep going straight. To much rudder for to long and you over adjust and you go the other way.

I was thinking, it’s like driving backwards in a car with a trailer, continuously correcting, and if you don’t pay attention, the trailer will “disappear” to the side……

Yes that’s what its like !  🙂

After a few taxis, I felt it was getting better, but yes needs lots of practicing.

After that we just went full speed, doing the same rudder stuff and took off, to our practice area, for a few turns, left and right, and back with a overhead join, and landing, followed by one more circuit.

So yes very happy the way its all going.

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Above Dave my instructor on the right, with his next student Tosh on the left in front of the Kitfox ZK-KNZ

Why a high compression ratio gives more power

After Wayne showed  me an example of how more hp is created with a higher compression ratio, I found this explanation by David Vizard, where he compares two engines with extreme different compression ratios:

For a moment, let’s imagine that both the 15:1 and the 2:1 cylinders start off at TDC with 1,000 psi. As the piston of each cylinder moves down the bore, the drop in pressure follows a distinctly different line. The 15:1 cylinder drops pressure much faster than its 2:1 counterpart because of its more rapid change in volume. It only has to go down the bore a short way for the original volume to have doubled, whereas the 2:1 cylinder must travel almost half way down the bore to double its original volume. At the bottom of the stroke the 15:1 cylinder has dropped down to about 25 psi above atmospheric whereas the 2:1 cylinder is still at some 260 psi. In simple terms, the high-compression cylinder, when the exhaust valve opens at BDC, is only dumping 2.5 percent of its original pressure whereas the 2:1 cylinder is dumping 26 percent.

Very interesting !!

Combustion chamber mold

Last night I made some Plaster of Paris, pored it in a plastic container and put my Plasticine “combustion chamber” in, upside down.

This is what I got this morning 🙂

Mold of combustion chamber
Mold of combustion chamber

What I plan on doing , is glue a flat piece of something to it, covering the face where the piston would sit in TDC position.

Then I can pour water in through the “spark plug” hole and measure exactly how big it is. It should work as long as the seal I intend to glue on it is in the same position as the top of the piston.

“a few days later”

Yes, have measured the combustion chamber volume. Its even bigger, its 204 cc ( = 12.45″ cube )

This gives me a compression ratio of  (50.115 / 12.45) + 1 =  5.0 .  Very low, almost unheard of !!!

Resulting in a lot less power then expected with the original compression ratio of 5.4