bjr_93tz

Hope you noted the position of the moon, so you can orientate the motor correctly for starting when you take it out to the field

Seriously, best of luck. IIRC some Austrian guy re-porting OS .61's 25+ years ago helped bring to F3A one of the finest engines ever made. Maybe OS just need another push.

airborne2.4

Timble,
Yep, lol. I probably will get a 30cc Breitling MXS-R from Red Aero a long time before I place an order for the GT33. If the GT33 doesn't turn out to be a winner, then I pick up a Syssa

MTK

In my very limited running of the OS and extensive running of the Syssa, I can make some general statements from experience:

The SAP needs to turn fast. Don't try for less than about 8400 rpm. It requires a smaller prop to turn that fast like a 16x12 on pipe. It's a terrific sport engine but just doesn't have what we are looking for in Pattern. I think it would have been fantastic back in the heyday of the 140RX, 8 or 9 years ago since it has more raw power than the 140RX

Having said that, modifying a spark plug to accept a glow plug and running an Avgas-MeOH mix is one option I will look into. I suspect the exhaust duration is just too long but we'll see

The OS33GT on the other hand, develops it's power at lower rpm. Due to its compression ratio and Bore:Stroke ratio and timing, it can turn considerably more prop. It is better suited for Pattern needs today. I am currently turning an 18x12 in mine but I know it can turn as large as a 20x10 prop more suited for 40-45 cc engines. The 18x12 really moves my Temptress around very well, better than the 16x12 I was using on the SAP. I can state with certainty that it moves Temptress around better than my Webra 160 ever did. The verticals and diagonals are where I see a very big difference...

I am expecting that the learning curve will be tamed and I will get great runs under my belt. I also expect the engine to become a lot more user friendly as it breaks in

DagTheElder

MTK

Take a look

3D Hobby Shop 71 AJ SLick- OS GT 33 gas motor

Best regards

Sorry for the wrong line to link

www.youtube.com/watch?v=R8YA0bwLaBw

JRgraham

My Feedback: (1)

MTK, Thanks for sharing all this information on the GT33. It seems that OSis on the right track with petrol. (you know how americans love stuff like GT something on an engine model!!)

Maybe Ioverlooked it in here somewhere, but any idea what your sound level is... about??

Ifeel that petrol will really evolve as soon as someone designs a carburetor four our needs. Walbro is great, for sure.. but Ithink its fairly clear there is much room for improvements. (for one, they are not designed for our R/C style servo linkage.. Iknow, thats a pettycomplaint.. but still)
OSseems to be the most likely to do this, if Iwas to imagine who would first. Ithink it only makes sense.

Or am Iwrong to think that the walbro is not the most perfect carb, that needs no improvements?? It seems that is the next leap for petrol RC engines.. a carb designed for for these r/c engines.

Anyways, thanks again for the reports!

TimBle

fuel injection is entirely possible. Even direct fuel injection is already available on outboard engines.

MTK

Mel,

Sound level of the 33GT (piped, soft mounted, 2 blade 18x12 carbon-wood hybrid prop) is probably around 94-95 dB. It probably would pass the sound test. I have a 3 blader I am developing that should reduce the dB a bit... Final word not yet developed. The engine should have the guts to turn an 18x10 3 blader at useful rpm and good mid range response with this much load

Walbro is amazing for what it does but to me, needs either a mid range needle, a servo controlled low speed needle or both. Servo controlled low speed needle is not new of course and will tend to complicate things a bit but Pattern people want crisp response at any setting. That's one way to do it as my good friend Jersey Jim Martin has said time and again. That's straight forward implementation; not a difficult thing to do. I am not sure an OS developed purpose carb is a good thing unless cost could be controlled at a reasonable level. I am actually surprised their 33 is as cheap as it is

You are very welcome. We are in this together so we should help one another and learn from each other

airborne2.4

So, is it to soon to say that the OS GT33 is a winner? http://www.youtube.com/watch?v=GHPK-WvNyGo

MTK

I squeezed out of work yesterday and got in a little flying. Last day in Jan, 50 degrees but windy, not terrible in north Joisey for January

Used the starter on the OS and had no problems. Two solid flights some 30 minutes of flying, and a little closer to break in. I'm still using the 18x12 hybrid; even in 20 mph wind the engine pulled great. Half throttle for everything it seemed.

Have also started to finish the 18x10 3 blade. We'll see how the weather co-0perates in next couple weeks.

Edit, Feb 5:

Got 3 in this weekend....Cool conditions and a bit breezy, but I am only interested in the engine's performance, and not the flying necessarily. Flying full Masters schedules with all the vertical stuff included. But have only got 2/3rds gallon through it so far

The engine is beginning to really impress me. After the early problems, it seems that it has settled down. Starter starts are really simple

MTK

These terrific days keep on coming it seems. This has got to be one of the warmest, nicest winters up here in the NE in quite awhile. Every day brings us closer to spring.

Took the day off (B'day) to go out and play. Five X 15 minute solid flights. I finally got to try the 18x10 Mezjlik 3 blader and 19x11 apc which is all the rage for YS170 users. The 33GT had no problem with either prop. In fact neither prop was overloading the engine in any particular way which tells me there is still room for more load. Actually the 18x10 3 blader was a lighter load than expected and more pitch would help. Both props produced a lot more speed than I have ever had on Temptress. Both props were quieter than my 18x12 hybrid

Right now the 19x11 is the prop of choice. I will dial the engine in on this prop and fly it a few dozen times and try to tone it down a bit. The 33GT is trully impressing me with its apparent limitless appetite for big loads and its overall output

CustomPC

How loud is it with the pipe?

My club has just introduced noise restrictions.
I was all set to put together a Giant Big Stik with GT33 but now have reservations due to the noise. If the pipe is significantly quieter i may still go ahead and build one.

MTK

My set-up is not a sport set-up. It is extremely quiet by your typical muffled glow/gas standard....... more like large 2 stroke glow set-up on pipe (Webra 160). But it takes a lot of prep to get it that quiet. A soft mount, full cowling and large, pattern props are must do's

TimBle

How does the OS 33 handle the schedule?
Are you able to accelerate on a vertical line after snap?

airborne2.4

Up line, down line, 45 degree line. Tumbles, rumbles, shake it and throw it at the OS GT33, looks like she can handle it lol
http://www.youtube.com/watch?v=EaYlGd4lcR8

MTK

How many snaps on the vertical up line? Even at half throttle where I have to fly it, the model will do several snaps going up before dropping off. A blip of throttle has it back on the line, and if I go to full, she'll take off like a rocket. The plane is 11 pounds, BTW, if anyone is thinking this is a light plane.....

I am quite pleased with the piped performance, finally, after all the crap at first. To me, having played with several engines in this displacement size, up to the 40ZDZ and Mintor 38, the OS is the best of the lot by wide margin. I am buying another for a new project

MTK

The AW Edge is small compared to the pattern planes we fly. The OS on muffler or can works well on this smaller airframe but it can handle a bigger airframe. And if you use a pipe, holy merde!!

TimBle

excellent MTK. Looks like I will opt for the OS 33GT based on your findings.

MTK

Timble please remember that I have never used the muffler that comes with the engine. My set-ups are piped only.

I am also finishing up a 19x12 and 20x10 hybrid for this engine. I will have some info soon

TimBle

Yes I am aware that you are using a pipe. Its the way I will go as well.

airborne2.4

The OS GT33 out performs the Mintor 38?

choihjin

My Feedback: (1)

Dear Matt;
I have not flied my Smaragd with OS GT 33 in these cold windy days. But I did another Gas/Glow converted DLE 20 on Accipiter.
It will be helpful for conversion.
It works more than I expected:
http://youtu.be/Cyquiy6UTDo
http://www.rcuniverse.com/forum/m_80...m.htm#10983505

Regards

MTK

I am not surprised. Glow plugs work because of the platinum/methanol catalytic activity. I also believe that a bit more output could be had from any gas engine with a little extra oxygen in the fuel.

The most important thing for us in Pattern is getting useful mid range. If methanol gives a better responding mid range then it will be worth quite a bit to the few of us who still use wet fuels.



I finally got a few numbers using my brand new TNC tach. I checked the engine's low end, mid throttle where I fly normally, and top end. I got the following:

Low end was reliable (19x11 apc 2 blade) down to 1750; engine only has 1 gallon through it so far so this may get a little lower, but it is low enough. Sounded like a YS 170 on low throttle...very neat sound

Half throttle stick, same prop, gave me approximately 6575-6780. Temptress will do everything in Masters pattern at half throttle

Full 7450-7600 average; The tach also records the hi or peak values and at full throttle the engine would occasionally hit 7800. So full throttle gives me an average of around 800 rpm more; that's what I have in reserve. Now I know why the engine drives Temptress to ballistic speeds.

Acceleration is instant even with this large load up front but it was 41 degrees today so cooling was not a factor. I leaned the low end needle a hair and it helped a little bit. How it does in warmer weather waits to be experienced

MTK

Hey folks, just read Clarence Lee's column in MAN....He has a very short piece in there about the 33GT. He claims he got 5.4 HP out of this engine at 7000 rpm on stock muffler. If that's true, then the engine better turn a heck of a lot more prop than a 19x11.

It has to be a misprint; I think he meant 4.5 HP....I believe that's likely.

TimBle

yeah 5.4hp out of a 33cc is quite a lot of stress and would make it one of the highest specific power output engines in the world at 122Kw per litre!!

clivemc