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Gohbee Aviation Stinger 30-90 > Gohbee / TZ / Raptor 90 Heli with BME modified G90 Gas Engine
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

I thought i would start a new thread detailing my first foray into fuel helis. Specifically, I will be putting the new BME G90 converted supertigre G90 into a Gohbee / TZ 90 (basically a very well cloned and arguably improved raptor 90) machine.

Why do this? Simple for me. I want to fly a large machine without the mess, cost, and all the support equipment associated with glow models. Its the main thing thats been keeping me away from fuel models until now. Since i have never flown a 90 sized ship with a glow engine (outside the simulator) I'm hoping that i will still get great pleasure out of this machine. In the blissful ignorance of not knowing the amount of power others can get from a nicely tuned .91 glow engine, I picture myself grinning to myself all the way to and from the field, flying 40 minutes on a tank at a fraction of the cost , and going home to a beer and my gal without having to hose the oil off my model before i can relax.

Ok, back to reality... Here is what i have and what's on the way.

* 1 x 90 sized heli kit
* 1 x BME G90 Gasser with muffler and CH ignition system
* 1 x 2 cell 3500mah Lipo pack
* 1 x 6V KoolFlight Systems Ultimate BEC
* 1 x Arizona dual output voltage regulator
* 1 x MA RevMax RPM Limiter
* 4 x Futaba 9252 servos
* 1 x Futaba 9254 servo (tail)
* 1 x CSM SL720 gyro
* 1 x SAB 710mm Blades
* 1 x V-Blades 105mm tail blades
* 1 x Futaba PCM 2048 G3 14 channel RX
* 1 x Futaba 14MZ Radio (Yeah, I couldnt help but list it)


This is my first fuel machine so this should be quite a learning experience for me. Worst case scenario is that i sell the engine to someone wanting to throw it in a 60 and get a OS .91 and fly the thing how it was meant to be flown. In the meantime im going to think happy thoughts and dream away about how cool this is going to be.

Please feel free to chime in with comments, info, suggestions, or if you just want to point and laugh at me that's ok as well.

Ill update this thread (if there is any interest) with build pics, flight vids, and more information as i progress. For now im just waiting on Mr. Postman.


Update Section:

Here's what i still have left to do:

* mount revmax sensor
* install fuel tubing and fuel magnet
* connect tail linkage

Getting VERY close to getting this thing in the air now!


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Disclaimer: This thread is for informational / entertainment purposes only and is not a commercial endorsement of any of the products mentioned. I and/or any companies i am affiliated with do not sell fuel models and have no plans to do so now or in the future. This is a merely an ongoing documentation of my own experiences as an individual.
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A day without sunshine is like, well, night.
03-07-2006 Over year old.
HOMEPAGE  
 
 
FLYINFOOL
Veteran
Location: Cudahy, WI

I for one will be interested in how this works out, and would love to see any pics or vids that you have.

My initial thought is that you will want to run 680 blades with that engine.
The head on that heli is about 35mm wider than most other helies that I have checked. So the 680's will fly like 700's on a fury.
The consensus that I have gotten from the other thread is that this engine is somewhere between a 70 and a 90 in power.


Jeff Borowski
Gohbee Field Rep
0133TD
03-07-2006 Over year old.
HOMEPAGE  
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Jeff,

Thanks for the tip on the blades. Whats the main problem with the larger ones? Just that they may tend to want to bog the engine more from the size? Or will i have actual problems with the length and the tail rotors or boom? I already have the 710's on the way so i plan on trying them first as long as there is clearance to run them and then if they dont work out i will take you up on your suggestion and go with v-blades or something similar in the 680 length.





A day without sunshine is like, well, night.
03-08-2006 Over year old.
HOMEPAGE  
 
 
SkateFreak
Key Veteran
Location: Cambs UK/Luton

Hey.
I have to say i'm very intrested to see how this turns out myself!
Best of luck and i'll be watching all the way

-Jvr

Non-3D heli pilots are planker spys trying to bring down the heli community from the inside - Topher
03-08-2006 Over year old.
 
 
Raptorgasser
Heliman
Location: Sweden , City . Eskilstuna

Hello, AnnihilaT

Interesting project, and welcome to be one of the new generation gasser flyer. It will be werry interesting to hear how much power you got out from this concept if it is 3D power out.

I hawe now flying my conversion more then one yaer and i am werry happy abut the fuel cost saving my conversion have done.

i flying 35 minute on my 450cc fueltank.

Please send us pictures and also video clip from flying if it possibly.

Regards

/Bengt Larsson

Flying my Raptor 60 on Gasoline (Raptorgasser)
03-08-2006 Over year old.
HOMEPAGE  
 
 
Dr. Fibinotchi
Key Veteran
Location: Sioux Falls SD

keep the 710's

I agree with the blades load a little more on this heli and it will use up a little more power becuase the disk it bigger, but it may give you a good comparison with the nitro guys with the 710's as well. If you can pull 11 collective at 1700 your in the groove if not 680 it. Let us know what you can pull at 11 degrees with either blade.



-Cody

good luck in your adventure and keep us posted.

All that a man achieves and all that he fails to achieve is the direct result of his own thoughts
03-08-2006 Over year old.
 
 
FLYINFOOL
Veteran
Location: Cudahy, WI

There is no clearance issue with the 710 blades. Mechanically they will be fine.
My only concern is bogging the head due to insufficient power.
Even my Os 91PS on 30% has difficulty maintaining the head speed during hard maneuvers with the 710 blades. I have tried MAH and V blades.

With the 710's on a Stinger you will have 132 more square inches of disk area than a Fury with 710's and a 91 engine, that's a lot of extra work for the engine.

But since you have the 710's coming, try them, the gas engine might have more torque than the glow. I don't really know.


Jeff Borowski
Gohbee Field Rep
0133TD
03-08-2006 Over year old.
HOMEPAGE  
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Jeff, Thanks for clearing that clearance issue up (har har)

from what i understand, more torque is one of the best things gas engines are known for but thats just what ive been told. No personal experience to speak from here

Sab blades and revmax came in today! Which actually brings me to a question.

The revmax came with only 1 magnet and i understand ill need 2 for gas engines... I also was told by REVMax that i can use the standard sensor that comes with the revmax and attach it to the gas engine so that it use the stator for reading engine rpm. Anyone tried this before? Is this the best way or should i mount 2 magnets?





A day without sunshine is like, well, night.
03-08-2006 Over year old.
HOMEPAGE  
 
 
flytech
Veteran
Location: Sunland, CA

go anni!

hey so what are you planning to do w/this bird? style flying? scale eventually?
03-08-2006 Over year old.
HOMEPAGE  
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Dunno! First big bird so lets see how it flies i guess and if it will do some 3D thats what ill be doing with it. If not maybe a camera ship.





A day without sunshine is like, well, night.
03-08-2006 Over year old.
HOMEPAGE  
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Sorry for such a noob question but im coming from electrics where its all volts * kv rating / main gear teeth * pinion teeth...

anyway.... I just checked on the gearing ratio for the TZ 90 i have and it appears to be 1:7.7:4.72

Can someone explain that to me in dummy terms? How does one figure out the pinion tooth size and the main gear size from these numbers and furthermore shouldnt there only be 2 numbers? Whats the first one?





A day without sunshine is like, well, night.
03-08-2006 Over year old.
HOMEPAGE  
 
 
FLYINFOOL
Veteran
Location: Cudahy, WI

Weather you run 1 or 2 magnets depends on the RPM that you are going to run.
I thought the the TJ pro needed to see at least 9,000 magnet pulses per minute, I don't know if the Rev Max has this same requirement. Either way My guess is that you will be running a lot more than 9,000 RPM.
If you can use the magnet that is built into the engine then 1 magnet on the fan would work equally as well.


Jeff Borowski
Gohbee Field Rep
0133TD
03-08-2006 Over year old.
HOMEPAGE  
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Ok i have now been educated and know that 7.7 is the main gear and the other number is the tail gearing. So if i can run this engine at 13,000 - 14,000 in an ideal world we are looking at 1753 or so RPM before loss in the gearing etc. If im lucky i guess it will be somewhere around 1650. Not sure how that will be for 3D. Would be much happier with it around 1850. Since it doesnt look like these helis are so easy to change pinions on and still get them to mesh with the main gear, how do you guys go about doing when you want to gear something up or down? With electrics the motor can be slid forward and backward for proper mesh with the main gear but this is a whole new world it looks like. What would one do to try and gear this up for 1850 or so on the head?





A day without sunshine is like, well, night.
03-08-2006 Over year old.
HOMEPAGE  
 
 
FLYINFOOL
Veteran
Location: Cudahy, WI

The frames are slotted for the pinion stack and the engine mount so there is some room to slide things back and forth for different gear ratios.

Based on the info that you gave so far your gear ratio should be somewhere between 7.0 and 7.5.
The 7.0 may be a little harder because it will need a 13 tooth pinion that is not yet available.


Jeff Borowski
Gohbee Field Rep
0133TD
03-08-2006 Over year old.
HOMEPAGE  
 
 
Dr. Fibinotchi
Key Veteran
Location: Sioux Falls SD

hmm..

what is the max hp and torque curver on this engine? What rpm does the engine max out at.


Set it 75-100 rpm more on the head and lock and load for 3d....

All that a man achieves and all that he fails to achieve is the direct result of his own thoughts
03-09-2006 Over year old.
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

I believe its 2.7HP@14,000 RPM. 15CC.

Quote 
The 7.0 may be a little harder because it will need a 13 tooth pinion that is not yet available.


And what about using a 85T main gear from a raptor 50 with a 12T pinion? This would give a 7.08:1 ratio. That would be damn close, no?

Would the 85T raptor 50 main gear be a bolt on replacement for a 90?





A day without sunshine is like, well, night.
03-09-2006 Over year old.
HOMEPAGE  
 
 
FLYINFOOL
Veteran
Location: Cudahy, WI

That would be darn close.
If you go to the 85 tooth main gear I think that the tail drive gear will hit the clutch bell.
With the 91 tooth main gear the tail drive gear is within .005 of hitting the clutch bell.
If you go to the 85 tooth main gear I think that the tail drive gear will hit the clutch bell. The tail drive gear is also an 85 tooth R50 main gear.


Jeff Borowski
Gohbee Field Rep
0133TD
03-09-2006 Over year old.
HOMEPAGE  
 
 
RescueHelicopter
Veteran
Location: Portland Oregon

so how will this engine preform compared to the webra 91?

view my aerial photography pictures www.somethingforever.com
03-11-2006 Over year old.
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Franconia2
Heliman
Location: Shrewsury, MA

Gearing

After 16 flights on the BME G90 conversion, the sweet spot on this engine seems to be 11,500 to 12,500.
Supre tiger rates the glow version at 14,000 but the gas conversion is different. BME changes the con rod, and piston and gas runs a bit different than glow. Also, the plane guys are running this engine at 12,000 so it seems to be tuned and timed to this rpm range.

I think a 6.8 to 7.0 gear ratio is needed to get this puppy to run at max power for 3D. This ratio will get you 1800 or so for headspeed, with the tourgue of a gasser, this hs should be enough for 3D.
So it looks like a 13T pinion and 90T Main Gear.
I'm running this engine on an X-Spec frame with a 12T, 93T main does anyone know where I get a 13T pion gear or 88-90T main? Can they be modified to run on a Hirobo?

Dave
03-12-2006 Over year old.
 
 
KrtekHeliman - Location: Czech -
AnnihilaT

Raptor 60 + BME 0,90 + Falkon Ignition


detail : http://www.maxir.ic.cz/fotogalerie/...benzin/foto.htm
Krtek
03-12-2006 Over year old.
 
 
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Gohbee Aviation Stinger 30-90 > Gohbee / TZ / Raptor 90 Heli with BME modified G90 Gas Engine
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