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Thunder Power RC . Real Raptors . Mikado Modellhubschrauber

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Gasser Model RC Helicopters > Throttle and Pitch curve starting points
 
 
tkn0spdr
Heliman
Location: Indian Harbour Beach, FL USA

Okay, I've got an ASI Mongoose (similar to a Vario Acrobat).
I'm new to the whole gasser thing and I'd like to get suggestions for where to start with my throttle and pitch curves.
Also, some ideas on how to learn what to watch and listen for in order to be able to tune it past a starting point.

I'll try to offer as much info as I can and will supply whatever is missing if you just let me know.

1. 810mm main blades
2. JR X9303 2.4GHz radio
3. ASI recommends -4, +5.5, +11 and 1350-1400 head speed.
4. Gear ratio, I'll have to get this info tomorrow.
5. Zenoah G260 engine.

Thanks,
David
http://www.FloridaPets.org
06-18-2008 02:18 AM
 
 
xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

Pitch curve set it liner, set it mechanically for your setup
Throttle curve ( just to help you get started,, you need a tach to get it right,,)
1: 0
2: 8
3: 18.5
4: 29
5: 41
6: 54.5
7: 100

As for tunning a gas engine, read here,, Everything you need to know is in this topic,,
http://www.runryder.com/helicopter/...?top=1213754240

Not for sure what gear ratio the air/star is but it might be 9.0:1 that is what my Vario Benzin Trainer is,, Hope this helps,,

John Crotts
www.soonerhelicamproductions.com
06-18-2008 03:00 AM
HOMEPAGE  
 
 
tkn0spdr
Heliman
Location: Indian Harbour Beach, FL USA

Okay, so...

4. Gear ratio 85t main and 23t pinion - can 3.695 really be right?
06-19-2008 01:38 AM
 
 
xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

Well does it have the belt drive?? for the main gear...

John Crotts
www.soonerhelicamproductions.com
06-19-2008 02:33 AM
HOMEPAGE  
 
 
tkn0spdr
Heliman
Location: Indian Harbour Beach, FL USA

The drive shaft from the engine has a belt that goes to another gear on the bottom of the shaft with the pinion on it that meshes directly with the main gear that spins the head. How do I calculate the ratio?

Thanks,
David
06-19-2008 03:05 AM
 
 
xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

Thats a good question, David,, and I'm not for sure,,, Post about this in the Vario fourm,, I know that hootowl, and others will be able to answer this,, Sorry I cant be of any help here,, XGM/VGM

John Crotts
www.soonerhelicamproductions.com
06-19-2008 03:07 AM
HOMEPAGE  
 
 
jschenck
Elite Veteran
Location: La Vista, NE.

I'd split this into two calculations: calculate the speed that your countershaft is spinning via ratio from the main gear to the countershaft. Now you can calculate the engine speed via the ratio from the countershaft to the engine.

...yep...
06-19-2008 05:21 AM
 
 
jschenck
Elite Veteran
Location: La Vista, NE.

ok, I think I understand what the real point here was - how do you calculate the actual gear ratio, not just the engine speed vs. headspeed.

final_ratio = (countergear/pinion*maingear/countergear)

e.g. from a Raven

55/26 * 60/14 = 9.06

...yep...
06-19-2008 05:33 AM
 
 
xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....



John Crotts
www.soonerhelicamproductions.com
06-19-2008 05:38 AM
HOMEPAGE  
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Ratio is also engine speed / head speed. Tach it. If the numbers don't match you did something wrong.

Ace
What could be more fun?
06-19-2008 05:45 PM
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
ASI recommends -4, +5.5, +11 and 1350-1400 head speed.


You absolutely need a tach to set the throttle curve. The throttle curve shown is from another machine and probably will not give the same results. Once you develop the curve I will update the graph.

If you follow the suggested ASI recommendations for -4, 5.5, 11 degrees the numbers will be 0,21,42,63,75,100.



Ace
What could be more fun?
06-19-2008 09:26 PM
 
 
shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

Easy ratio .

Mark your engine drive pulley with a marker pen,Mark or identify one rotor blade and its position relative to the heli.Turn the rotor so the blade comes back to its exact starting point after one turn,counting the amount of turns the engine pulley makes until it reaches the start point.This will give you your ratio.Say one complete turn of the blade (360)to maybe seven turns of engine drive pulley.7to1.
06-21-2008 09:28 PM
 
 
Fixit
Key Veteran
Location: UK

Download this program free called winheli, it's a calculator for gearing, head and engine speeds, fuel ratio and so on.
Great little program for the dummy, like me

http://www.birdcagesoft.com/winheli/
06-21-2008 09:48 PM
HOMEPAGE  
 
 
tkn0spdr
Heliman
Location: Indian Harbour Beach, FL USA

That's a good way to get you close, but I don't suppose you can eyeball 6.8:1 too easily.

Cool program, Do they make it for a Mac?

Thanks,
David
06-21-2008 09:57 PM
 
 
Fixit
Key Veteran
Location: UK

Quote 
Cool program, Do they make it for a Mac?
Don't know I'm Pete
06-21-2008 10:01 PM
HOMEPAGE  
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
but I don't suppose you can eyeball 6.8:1 too easily.

You can if you take the time to count out 10 turns of the rotor. (68 on the engine) As close as you have to be...

Ace
What could be more fun?
06-22-2008 12:12 AM
 
 
shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

EASY RATIO

I realise this method is not a precision method because when i made a check using this method ,i made it 6.75.1 and in my heli manual it was actually 6.77.1.split your engine flywheel into quarters(0.25,0.50,0.75,1,0)you can get pretty close .When helping at a field ,say with governor set up you may not have access to a PC.
06-22-2008 07:24 AM
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
i made it 6.75.1 and in my heli manual it was actually 6.77.1

he;,he, You think 2 hundreths will make a difference? I would guess your tach is not that close. Your talking frog hairs.

Ace
What could be more fun?
06-22-2008 03:35 PM
 
 
shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

Easy Ratio

I know Ace bird.i was just playing,You dont need a calc to get damn close.
06-22-2008 05:04 PM
 
 
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Gasser Model RC Helicopters > Throttle and Pitch curve starting points
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