Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Torque question

Reply

Old 09-30-2009, 01:20 PM
  #1  
mk1spitfire
Senior Member
Thread Starter
 
mk1spitfire's Avatar
 
Join Date: Oct 2007
Location: south, UNITED KINGDOM
Posts: 1,208
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Torque question

Ive had horrid rolling to the the left on a nitro delta before but more recently on a pimped electric funjet,clocking 120mph airspeed.

The little bugger likes rolling left alot when I apply power.

Ive used a mix, throtle to aerlon, now at 16% but in a vertical dive she still wants to bank left. May need more mix

I heard that torque decreases with rpm but ask what effects does torque have on acceleration? increase/decrease?

Also what counter acts the torque for level flight, wing area, length of wing??

Cheers
mk1spitfire is offline  
Reply With Quote
Old 09-30-2009, 01:45 PM
  #2  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

Make sure that you don't have any left thrust accidentally built in. The easiest way to check is to bolt a flat stick on in place of the prop and use that as a reference. A tiny amount of right thrust is far better than a tiny amount of left.
The lateral CG should be checked also, if you could pick a side to be heavy, it would be starboard, definitely not the port.
The biggest torque reaction will be the instant you release a plane running full throttle into the air. That's going to be where the most stored energy is built up, or when the plane is in a perfect hover and then you can get it to torque roll.

Of course more wing span and area will buffer the torque response. The reaction is only momentary and not something that you trim the ailerons to correct.

This advice is assuming that you are working with tight controls and a tight airframe that holds it's allignments in flight.
combatpigg is offline  
Reply With Quote
Old 09-30-2009, 02:06 PM
  #3  
mk1spitfire
Senior Member
Thread Starter
 
mk1spitfire's Avatar
 
Join Date: Oct 2007
Location: south, UNITED KINGDOM
Posts: 1,208
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

Thanks

Its a pusher plane. I'll check the thrust angle.

As an electric model, full throttle is used in bursts unlike my nitros where its wot all the way.!!

I have found the mix to work. Before it was like flying an untamed bull.

I hope its not a aerodynamic twist in wing, but it looks pretty good.

Ok will try flat stick, I guess I just measure or mark the stick at different positions????

I have aditional carbon spar in airframe
mk1spitfire is offline  
Reply With Quote
Old 09-30-2009, 02:59 PM
  #4  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,629
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

Torque follows a curve like horsepower, and usually peaks at lower rpm than the max power point.

Acceleration comes from thrust versus mass, thrust comes from power and the efficiency with which it is converted to thrust, and power is torque times rpm. Maximum acceleration potential is at maximum power rpm coupled to the optimum prop for the airspeed. Engine "A" may have more peak hp than engine "B" at the same peak rpm for both of let's say 16,000rpm. But, if engine "B" generates more torque at say 11,000 rpm than engine "A" does, then engine "B" can swing more prop load at 11k than engine "A" can, even though engine "A" can swing more prop at peak power rpm than engine "B". So if you prop them for 11,000 rpm at WOT with similar props, engine B will out accelerate engine A. If you prop them both for 16k at WOT, then engine A can out accelerate engine B assuming the prop choices in both cases are within reason.

If the roll gets worse at speed it is twist. If it worse at launch then it is side thrust. In an nutshell anyway. From experience a tiny bit of with-torque thrust offset can cause mayhem with higher power models with short wingspans - as in left thrust on regular tractor deltas. Aero and inertial damping is small. But roll tendenceies that change with speed are aero induced. You can have some of both which is a fair way to have fits.

MJD

MJD is offline  
Reply With Quote
Old 09-30-2009, 03:50 PM
  #5  
mk1spitfire
Senior Member
Thread Starter
 
mk1spitfire's Avatar
 
Join Date: Oct 2007
Location: south, UNITED KINGDOM
Posts: 1,208
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

thanks.

Ha I think I'm allready having a fit.

Im going to check the thrust angle.

roll changes with speed, yes, aero induced, Humm I dont want to hear truth.

Unless I dynamically slope soar it without power, how will I know wether its aero or engine?
cut motor at speed and see if she levels?

I think I have roll at launch and at high speed, its horid flying a constanly rolling plane.

The mix is helping I guess but masking it.

Is right thrust primary objective to over come torque?


mk1spitfire is offline  
Reply With Quote
Old 09-30-2009, 04:24 PM
  #6  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,629
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question


ORIGINAL: mk1spitfire
Unless I dynamically slope soar it without power, how will I know wether its aero or engine?
cut motor at speed and see if she levels?
Is right thrust primary objective to over come torque?
Yes, that is a great idea - get it up to speed, then chop power. No change in roll rate - all aero. Lots of change then look at thrustline.

When in doubt set it 0-0, esp on fast aircraft where they spend so much time WOT. Hovering aerobatic things with big props and low rpm feel the need most.

On my Demon when it had left thrust, once it was up to speed there were no detectable symptoms. At launch before the wings got on step it was a worry. It got around 180 degrees on me once, I mean in a left turn back towards me not rolling. But running the pylon props launch authority was nowhere near as good as say a sport 9-7 which chugs out of your hand.

MJD
MJD is offline  
Reply With Quote
Old 09-30-2009, 04:49 PM
  #7  
mk1spitfire
Senior Member
Thread Starter
 
mk1spitfire's Avatar
 
Join Date: Oct 2007
Location: south, UNITED KINGDOM
Posts: 1,208
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

When in doubt set it 0-0, esp on fast aircraft?

It will be hard to fly knowing it will roll left with mix out, assuming full throttle and then cut,once its banked over would I expect it to roll back to level flight or stay in the last position of rolled bank when i cut power????

Is right thrust primary objective to over come torque?
mk1spitfire is offline  
Reply With Quote
Old 09-30-2009, 05:17 PM
  #8  
Mike Connor
Senior Member
My Feedback: (5)
 
Mike Connor's Avatar
 
Join Date: Jan 2002
Location: Tulsa, OK
Posts: 2,025
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

There is torque, spiral slipstream and P-factor that try to make the airplane turn left. Most noticeable at high power and a high angle of attack like in climb out. I suspect you have an airframe issue but definitely consider some of the good suggestions so far.
Mike Connor is offline  
Reply With Quote
Old 09-30-2009, 06:18 PM
  #9  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

How much effort does it take to make the wing panels on this plane twist? If the airframe isn't tight, this problem will never go away without resorting to bandaid type compensations.

The torgue reaction after launch gets absorbed by the plane, the pilot corrects...then the plane should go where it's pointed until the next time that the plane has to absorb another hit of torque applied. Most of the time there is enough airspeed to help buffer the inflight torque reactions.

There is a constant low level of torque that causes planes to roll left faster than right.

This force is cancelled [I suppose] by a very minute amount of aileron trim.
combatpigg is offline  
Reply With Quote
Old 09-30-2009, 06:26 PM
  #10  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,629
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question


ORIGINAL: combatpigg
This force is cancelled [I suppose] by a very minute amount of aileron trim.
I'm sure that is correct, and I imagine on a light aircraft with torquey engine if you do a fast fly-by then chop, it might twitch right. But it must be insiginificant because we never seem to grumble about it. I bet pattern fliers do, they probably have a correction algorithm that mixes it out depending on the rate of throttle down when switch "M" is in the middle position.

MJD




MJD is offline  
Reply With Quote
Old 09-30-2009, 07:04 PM
  #11  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

If you send a real short span plane with a flimsy airframe [like a Blink] on a surging run with a hot TD, it will torque itself around like a funny car when the driver stabs the gas pedal, but it'll still stay the course.
combatpigg is offline  
Reply With Quote
Old 09-30-2009, 11:18 PM
  #12  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,629
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Torque question

Like when it rolls half over to the left on hand launch on a VA...? [X(]

MJD
MJD is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service