reynolds74

Hey guys,

what do you think about the 90 CC in development?? Could be interesting??

I've asked some information already to our friend CRRC but still no reply about... so, as I'm really interested in that engine (that I suppose could be twin), I would like to invite him to let us know something more about it. May I have you support?

Bye.

Andrea

RustyTumbles

Well I flew the extra today and I was very disapointed. The engine ran fine on the ground peaking at 7300rpm. Then as soon as the wheels were off the ground the rpms dropped off alot. The first time I went to take off it did it and I aborted the takeoff and put it back down. I taxied back in and did a run up. All was ok!! I taxied back out and took off, it struggled into the air where it sounded really rich. One circuit and I landed, taxied back and shutdown. I took it back to the pits and started it again. It ran fine once again. WHAT IS GOING ON?????

I think the carb diaphram maybe getting a false reading from the airflow around it. So I took the cowl off and flew it again. It was a little better but not much, just enough power to do basic aerobatics. I have taken the plate of the carb diaphram and I have soldered a piece of copper tube to it where I can run some fuel line inside the fuse where the air is static. Do you guys think this will work??

The underside of the plane was very dirty with unburnt fuel so I think I am onthe right track.

RustyTumbles

Here's a few pics of the carb mod I did this afternoon. Hopefully it works but I won't know until next sunday when I fly it again.

fwman1

My Feedback: (22)

I like to do conversions. I have made making the mod you did a part of my normal setup procedures. It's easier to just eliminate it as an issue at first, rather than wonder if it is the problem later. You might try a different velocity stack if your mod doesn't work. It's possible that lower air pressure is pulling gas out the carb as you pick up speed. Do a search and you'll find all kinds of opinions on whether it should face forward or back. Myself, I'm a face forward kind of guy. Good luck. You'll get it. If it runs good on the ground it CAN be made to run good in the air.

Roger

reynolds74

If I remember in the correct way, some time ago I've seen a modified stack for the Zenoah 45 to turn 90 degrees backward the carb, to avoid changes in the air pressure. Maybe could be useful.

Bye.

Andrea

Jim Branaum

My Feedback: (3)

Bigsport,
The problem is the carb pump that delivers enough fuel except in a vertical climb when the engine is burning all you can give it. Few of us gas burners pick up and hold the plane vertical for long enough for the carb to run dry. I was taught that if the engine sags slightly on the up line, it is slightly too lean on the top end. It may only be a blade width too lean, but that can give the results you seem to be reporting. Your modification to the plate will work and is a good idea for many applications. I frequently baffle my engines to insure cooling and to prevent turbulence around that static port. Being cheap and lazy, I use 1/4 foam board cut to fit and glued with foaming polyurathane for my baffleing.

I am thinking about getting one of these GF45I engines to compare against my 1/3 GP Pitts which is flying with a BME 44 right now. The all up weight is within a few ounces and the claimed rpms are higher which should make the bird fly better. The question is where to put the comparison report and how detailed does it have to be...

RustyTumbles

Thanks for the help guys, I will try this mod and go from there. Maybe it could be the stack also?? Where can I find the zenoah G45 stack?

Jim Branuam,

You can post the comparison here and you can make it as detailed as you wish. The more info on this engine the better!!

reynolds74

Hi Bigsport,

if you refer to the stack I was talking about, I'm looking on the net if I'm able to find it. I checked this afternoon in my old catalogues. It wasn't a mirage, it does exist. In Italy has been sold by the Zenoah importer (i'm not sure he's still importing the Zenoah), but for sure this item sould be available somewhere in Germany. If I can find it , I'll post the link immediately.

Bye.

Andrea

reynolds74

I've found it.
You can find all the details in :

http://www.toni-clark.com/index_en.htm

Just download the catalogue for the Zenoah 45 and 62 accessories. You can find all the details at page 13.

Bye.

Andrea

RustyTumbles

Thanks for that. I'll see if I can track one down here!

Octopus RC

My Feedback: (2)

I have some pics that Chinese model fans hung the plane with the GF45I . I also have the video .

RustyTumbles

CRRC,

Are these guys flying with or without the velocity stack on the motor? If my carb mod does not work the stack is the next place I'll be looking for the cause of the problem.

I have got the 22x10 3w prop balanced and bolted to the motor. I am hoping to fly again on friday if the weather is good. Fingers crossed it works this time.....

reynolds74

I've seen that the velocity stack for the Zenoah have a cylindric shape instead of the one used by CRRC that have a cone shape. Does this have any influence on the air pressure?
Anyway, for what I can see around, almost all the people who's using a gas engine to do aerobatics have the carb air inlet besides the firewall, to allow the carb breathing in a such of a calm airbox.
Maybe this modification, turning the carb 90 degrees backward, could be useful.

I have a question: does the carb position have any kind of influence for the engine running? I mean, if it's rotated left or right or upside down, does it matters?

Bye.

Andrea

Jim Branaum

My Feedback: (3)

From what I was taught, the primary purpose of the velocity stack was to contain the small splatters of fuel when the throttle was opened suddenly. The various shapes used are attempts to get the theoretical additional benefit from the stack and its shape.

The position of the carburetor should have no influence on the engine operations if the static hole in the fuel pump is protected or piped elsewhere.

RustyTumbles

Some engines like the ram air effect and others don't. Also the static port for the diaphram pump can have a large effect on the mixture if is pressurises durring flight. I have done some research here on rcu and some people have the port routed to the carb inlet to sense the pressure at or near to the throttle butterfly. I will try that if the fuse routed pipe doesn't work.

reynolds74

Bigsport,

I've seen your mod to the carb, adding a line, but I still don't understand which effects this mod will have (due to my poor experience with gasoline engines). Can you explain me again?

Bye.

Andrea

RustyTumbles

Basically on the carb diaphram cover plate a piece of copper tube is soldered to it and sealed around the bottom of the tube, so no air from in the cowl can get in. Next a piece of tubing is attached to the copper tube and routed into the fuse. The idea is to prevent the pressurised air inside the cowl getting into the static port of the diaphram cover plate and forcing the diaphram onto the needle at increasing the fuel flow, and therefore making the engine run extremely rich. So the diaphram is now only subject to the static air pressure inside the fuselage. So in theory it shouldn't turn rich when the cowl becomes pressurised with ram air. If it does the problem is else where? And my guess would be the velocity stack. But we will see on friday when I fly again.

Jim Branaum

My Feedback: (3)

Bigsport,
At a high level, your theory is correct. However most gas burneres I have used a simple elbow pointing to the rear of the air flow solved the over preassure problem on the diaphram. Your routing a line back to the inside of the fuselage is overkill, but it will work.

RustyTumbles

I guess will see tomorrow when I fly it!!!! I'll get some more numbers on the 22x10 prop as well.

aiken779

hello bigsport,

how your edge 540t price? and where can buy it cheap on yous.
I hope make a friend of us, can't we?

regards

RustyTumbles

Try the PA web site www.precisionaerobatics.com or www.troybuitmodels.com for the edge. It think they are about $850 AUD.

reynolds74

Thanks Bigsport,

now I've understud.
I'm only thinking that if the cowl is opened to insure enough cooling effect, that means more than the front inlet area, there should be no air in pressure inside the cowl, only air that is passing by, so the effect is not noticeable.

Anyway, please let me (us) now what about your next runs...

Thanks.

Andrea

Jim Branaum

My Feedback: (3)

Normally, we want two times as much exit area as inlet area to insure proper engine cooling. Many baffle the engine reasonably tightly to reduce the excess air being brought into the cowl. This insures that there is no high pressure area within the cowl. Some of us go as far as to provide three times the exit area as inlet area to insure cooling even at low throttle settings on hot days.

TooLy

You should email crrcpro and he will answer you.

RustyTumbles

I have finally got the GF45 going nicely. I took it out today. The first flight was the same as sunday so the carb mod didn't improve anything. However when I landed I grabbed the plane on did another run up. It was reving out nicely but then I put my hand in front of the carby to block the prop wash and it dropped a few hundred rpm. So the I put my hand behind it and it picked up a few hundred. So back to the pitts we went to make a scoop. I found some cardboard in the car and cut it to size and cable tied it to the velocity stack. Started it up again and tached it. We got an extra 400rpm static!!! So I taxied back out and took off, it ran well and had more power than before but was still a little rich. I have since been leaning the low end needle after each flight and it is coming on nicely. Even got some prop hang time from it. But my day came unstuck when I ran out of fuel. I almost got it back to the strip, just caught the edge of the long grass and it flipped over stripping both elevator servos. I was just having a ball and forgot how long I'd been flying.

All flying today was done on the bolly 21x10 as the engine wouldn't spin the 22x10 any more than 5500rpm. It may spin it at 6000-6500rpm once fully run in but I won't try it again for a while.

I will be removing the cardboard scoop and filing the velocity stack so the fron't edge is lower than the rear. I will report again once I fix the plane, make some adjustment, and fly her again.