First Flights

page created: May 19, 2000 last edit oct 17 2000 (header: link to drawing)

October 17, 1999 3:43 PM

Ted,
Today I test flew the .51 carb in which I had the L-shaped drum groove straightened using a Dremel cut-off disk. The spring will keep the barrel pressed against the guide pin.
I obtained better transition than with the standard, old type drum, in fact, the engine behaved quite nice with instant trottle response. The displacement angle in the low trottle range is very slightly less than the
rest of the rotation (contrary to the ST L-modification). The carb was set up as per ST instruction and needed only minor adjustments at the field. Cold, windy dry weather, just above freezing. Had one dead-stick during inverted spin after a Lomchevack because mixture was not rich enough , I think due to colder weather. I re-adjusted the mixture, and had no further problems during the rest of the day.
I now wonder why on earth, ST introduced the modified drum motion pattern, as it clearly seems just the opposite of what they set out to do: "get a leaner mid-range".
Point to consider:
Instead of modifying the expensive Cline unit, why not try a complete walbro carb if you have one in your scrap box. Close both high and low speed needles, fit a nipple to the membrane chamber for crankcase pressure, fit a fuel outlet nipple on the regulated pressure chamber, braze a nipple on the membrane cover plate vent hole. It should take less than an hour's work. See Article " a Regulated fuel supply for details" 

Regards, Pé


20-oct-99 0:16

Hello Pe:

I'm glad your modification on the rotor barrel groove worked. I will keep your idea on file for using a Walbro carb on the ST2300. Unfortunately, I don't have any spares. But, there's plenty of swap meets coming up. I received a reply back from Bob Pastorello on using the Cline regulator with the ST2300. He is an FAI pattern pilot in the US and has a ST2300 in his EMC2 pattern plane. He gave up on the Cline regulator after having the same problems I had with mine when using the stock carb. He tried 2 different engines in 2 different planes with the Cline regulator and couldn't get it to work properly. Finally, he moved his tank forward so that the clunk is about 14 inches from the spraybar, removed the Cline regulator and uses muffler pressure. At first he was using the stock muffler and then switched to a head pipe with some kind of silencer. He says that his motor now runs great and never quits. I will have to give it a try too!

Regards....Ted


29-oct-99 

Hi Ted, 

I finally finished my own set-up so I can do my part of contributing. 
I finished mounting the ST2300 in the 20 lbs piggy back test bed (A high wing ClarkY plane with 2.4 meter span), spent money on a new Walbro carb, made a pump out of it and modified the carb fuel pressure regulator back plate to take exhaust pressure. The pump is fitted alongside the engine mounting lugs with the regulating membrane hanging down, so no exhaust residue will pool on it. My engine is with the cylinder angled 45° down, and fitted with the backplate to a stand-off plate, which in turn is equipped with three pillars which mount on the real back plate, which is fitted to the fuselage with rubber grommets. I had to choose this construction, because the ST is so much smaller. Also had to re-design the throttle linkage. After brief runs to set the idle mixture about right, decided to wait until tonight with the first in-plane test-run of this motor. 
Up to now the engine only has run on the test stand, but not run beyond 1/2 throttle on 20% castor fuel. ( This allowed me to set the high speed needle such, that the engine would not become overly rich and die)
test results:
I could let the idle mixture as it was, the motor ran just rich on full throttle with the needle 4 turns open from closed. At 3/8 throttle, the engine dies because of rich mixture (no nitro); But what a powerhouse! It seems to run stronger than the 30cc it replaces, even at rich settings. 
Not daring to fly a plane with a built-in dead stick condition, I took out my Dremel right away, and straightened the L-shaped drum displacement groove just like I did on the ST.51. By then it was too late to do some more testing. Now it is past midnight, so in the morning I intend to do some high speed running-in prepatory to flights/checks in the afternoon. 

Will keep in touch, 
Pé


Saturday, October 30, 1999 4:21 AM

Hello Pe: 

I don't understand why your throttle barrel has an L-shaped groove? Mine is straight on the ST2300. 

Regards.....Ted


30 oct 1999 

Hello Ted, 

That seems to be a new phase that ST is going through in order to solve their mid-range problem. 
I also had it in a .51, and that engine too died at 3/8 throttle and became a wonderful runner after mods. 
I test ran the engine in my back-yard this morning. On a rich setting, it pulled a steady 12.5 pounds on a 18x8 Menz prop (one pound in excess of the 30cc engine!), Mid-range when throttling down showed a steady decrease in RPM, when going up a slightest 4-stroking tendency. That might be anything ranging from new engine to plug or fuel 0% nitro. With this setup I am very confident of flight testing this afternoon. The weather is reasonable. 

Pé

Saturday, 30-Oct,-99 4:00 PM
Subject: first flights

Hi Ted, 
Just burnt a quart of fuel running in the G20 this afternoon. The guys at the club were really watching closely, as this engine has aroused a lot of interest and some are planning to buy one. 
1) the Walbro pump worked flawless; never had to touch the high end needle all day. 
2) low end not quite right. in this engine it is hard to figure out whether it is lean or rich. Pinching indicated a lean setting, and I had one flame-out on a touch-and-go because of that. Opening the idle needle 1/16 turn cured that! May have to tweak some more. 
3) It surely is not a guzzler! I flew along with a Saito 1.20 and he used more fuel than I did. 
4) take off runs of about 60 feet got the 20 lbs airborne, climb-out 40 degrees; Impressive! 
5) I did not start leaning the engine yet, so the engine did not show its full potential, and I cannot say whether the added exhaust pressure to the regulator is the ticket home. It seems that the engine likes it hot a bit, because then, throttle response is flawless. After puttering along a bit, it needs to get up to temperature again. May be the OS-F plug, will try an Enya-3 tomorrow, when I will test-fly the Venetian blind add-on flaps at fixed angles, for slow flight fast climbing. Will be a boring up to the ceiling, down to the deck, touch down, up, down etc. But the change in loads will make the engine run in pronto, as well as give me an impression of it's reliability. Will adjust the mixture a bit leaner than today, but still using 20% oil, no nitro. 

BTW, what fuel do you run in it? ST is not at all clear about the fuel to be used in their brochure. As usual, they state quite different things for Italian, English and German markets. 

Pé


Sunday, October 31
Re: first flights 

Hello Pe: 

Glad you're having good luck with your ST2300. I have been using Cool Power 15% nitro fuel and Omega 15% nitro fuel. Cool Power is all synthetic oil (maybe 17%), Omega is about 15% synthetic oil and 2% Castor. I'm also using an OS-F plug. The hot plug keeps me from going dead stick when the engine starts gurgling in the midrange. The only time it quits is when it's too lean somewhere. I had one flight today, and then my Bisson muffler lost its threads, so I had to tap it oversize for an American size screw. The muffler is a dumb design where the screw threads into the aluminum muffler. The vibration ate up the aluminum threads. I would rather they had used steel locknuts to capture the muffler. I'll try again tomorrow. 

Good luck...Ted 

Sunday
Hi There Ted, 

We had a windy day today, fair weather, and wind blowing rather straight down the runway. Drove about a quart through the engine, about 10 touchdowns, one flame-out while leaning out the high speed end. It sure is sensitive in set-up. Still, midrange has a tendency to load up, prohibiting instant throttle response after a while of puttering along. If settings are not on the lean side, the engine will accept more throttle sooner or later, which is not quite acceptable, though for my kind of flying does not matter very much. I now have four options: 
1) drill a hole as you did 
2) Square the barrel bore in the drum 
3) adjust the barrel translating groove angle some more 
4) Block one exhaust tube to increase exhaust pressure (which I do not like) 
I am inclined to start with option 3). 

Today, I added external airfoil flaps to the wing inboard section (per NACA report No. 614) they have 20% chord and .025% gap, while being set at a mere 5° deflection (both wing and flaps are Clark-Y). the flaps extend spanwise a bit beyond the ailerons. Lift-off at an incredible 6 feet! Trim is hardly affected, though throughout the flight envelope, and depending on angle of attack the plane wanders between nose heavy and tail heavy. It will spin, but recovers lift immediately after dropping the nose into the spin. Did Cuban 8, chandelles, endless loops, Immelmans, square loops, tail slides, stall turns, wing-overs. All with that 20 pound plane. I could roll it on a wing-tip, add max elevator and swing it around to turn on a dime at almost zero speed. With the wind we had today (force 4 Beaufort), it flew backward at 1/4 throttle and nose up attitude (tail heavy; speed makes it nose heavy, all predictably gentle). Mind you, this is a 94" span plane. 

Pé 

(Remark: The plane in this configuration turned out to be a floater, which later had to be solved, also because of severe yaw instability with the piggy back saddle mounted)

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