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Old Jan 26, 2003, 11:41 PM
now that's a wattmeter...
simingx's Avatar
Singapore
Joined May 2002
1,136 Posts
Is there such a thing as motor being too powerful/prop being too big?

I installed a Mega 16/15/5 with a Master Airscrew 7x4 (gas) prop on my Wattage F-22, gave it a launch... and round it went, rolling RIGHT INTO the ground 2 meters in front of me! No amount of right aileron could save it
It has a broken stabilator now... I wonder if the torque produced was too much for it to handle?
The motor is turning the prop at about 12,500 RPM.
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Old Jan 26, 2003, 11:45 PM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
Sure, it can happen.
..a
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Old Jan 27, 2003, 01:40 AM
slope'n the Colombian Andes
ShredAir's Avatar
Colombia, Antioquia, Girardota
Joined Mar 2001
4,698 Posts
Sure. If the tail wags the dog or the prop spins the plane... )

Dieter Mahlein,
http://shredair.com
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Old Jan 27, 2003, 02:20 AM
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shaneyee's Avatar
Singapore
Joined Aug 2002
758 Posts
Sounds like what happened to my PicoJet the first time I flew. I launched it upwards with a moderate throw like a parkflyer and it stalled and ate dirt so fast I couldnt even blink -just a few metres in front of me. Dont think it was the torque but rather a stall. You have to throw it hard and straight ahead. Next time we fly and if KP brings the Picojet around .. I'll show you how I throw it. You use as much strenght as you would throwing a football or a softball.

Shane

ShredAir: Thats really outrageous...
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Old Jan 27, 2003, 05:45 AM
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vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,703 Posts
Yup. If the plane stalls at full throttle, torque nearly always turns it against prop rotation under power, so it looks like a nasty tip stall whether it is or not. The key is to have the model going fast enough so the ailerons actually work


You aren't going to ever run into torque problems on direct drive.

However, if you have put in a heavier or more powerful motor, sometimes its wise to re-check downthrust/upthrust and CG.
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Old Jan 27, 2003, 08:10 AM
Single-task at best...
tim hooper's Avatar
Telford, UK
Joined Feb 2000
7,500 Posts
I think the potential problem is worse on a pusher set-up, as there's no propwash over over the control surfaces to give authority at low airspeeds.

tim
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Old Jan 27, 2003, 11:47 AM
Ascended Master
Sparky Paul's Avatar
Palmdale, CA
Joined Oct 2000
13,499 Posts
Prop too big, motor smells bad after flight.
F-22.. BAD airplane for models!
The verticals get blanketed by the large wing.
Unless you have a LOT of speed all the time, it will do exactly what you saw, all the time.
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Old Jan 27, 2003, 11:09 PM
Registered User
Folsom,Ca,USA
Joined Apr 2001
992 Posts
Yes, the torque of a powerful motor can sure do that.

As Sparky said, the problem is even worse in pushers as there is no prop blast over the control surfaces to help at low ( launch ) speed.

When you go into high power systems, you NEED to have things like dual rates on the transmitter so you can have large throws for low speeds and switch to smaller ones for flying. As you found out, "flying" throws may not be able to handle the takeoff torque.

Try launching at partial throttle and throwing it as hard as you can.

Hope its repairable.

Dave
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Old Jan 28, 2003, 08:28 AM
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United States, NY, Spencerport
Joined Oct 2001
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Have you checked to make sure your ailerons weren't reversed? If the ailerons were reversed, the more you tried to correct the roll, the worse you made it.
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Old Jan 28, 2003, 08:36 PM
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Thomas Nelson's Avatar
Calgary, Alberta, Canada
Joined Sep 2002
2,910 Posts
I have a similar setup on my smallish pusher ...

Quote:
Originally posted by simingx
I installed a Mega 16/15/5 with a Master Airscrew 7x4 (gas) prop on my Wattage F-22, gave it a launch... and round it went, rolling RIGHT INTO the ground 2 meters in front of me! No amount of right aileron could save it
It has a broken stabilator now... I wonder if the torque produced was too much for it to handle?
The motor is turning the prop at about 12,500 RPM.
A few less rpm. Same prop - in fact I've used an 8x3.8 as well. 24" WS, 20.6 ounce AUW. Same pusher config. Same stabilator control - no ailerons. No right/down thrust. Approximately 17 ounces static thrust. Never a hint of torque problems during launch. And I don't heave it nearly as hard as my TwinJet.

A maneuver I enjoy watching (more than flying) is to do a slow circuit at eye level & at high AoA and then punch it for a steep, slow climbout. Again, never experienced any appreciable torque reaction with this application of full throttle.

I dunno if this helps or not. But I plan to use EXACTLY the same motor/prop combo as you in the next iteration of my '27, and nothing I had read or experienced to THIS point was suggesting that I would be making a mistake.

I'm always ready to learn, though! If others think this really is a torque problem, I may need to rethink things.
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