Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > General Electric Discussions
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

General Electric Discussions Talk about topics related to e-powered RC flying

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 09-13-2011, 09:39 PM   #1
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 3,014
View mclarkson's Gallery4
Thanked 181 Times in 179 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default Correct me if I'm wrong: Torque Roll

I think I've messed something up here. Correct me if I'm wrong.

I recently modded my UMX J-3 Cub with a UMX Mustang motor. (I was sick of breaking prop shafts and this is a common mod.)

Most people use a Mustang prop, but I went with a 3-bladed Corsair prop mainly to avoid the prop clearance issues that come with the big ol' Mustang prop. Others have posted that they run the Corsair props.

But ... the prop spins clockwise when viewed from the front. This means - doesn't it? - that the plane will want to respond by rolling to the right.

However, the motor is mounted so that it is angled to the right (and down). In my case, though, this is exacerbating, rather than compensating for, the torque roll. Am I right?

Cuz this thing is a pill. It really, really, really wants to roll hard to the right on launch/take-off.

I want to check my thinking before I cut a bunch of foam out of the motor mount area and screw the plane up forever.

mclarkson is offline  
  Reply With Quote
Old 09-13-2011, 09:42 PM   #2
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,488
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

If the prop spins clockwise when viewed from the front (i.e. opposite to normal convention) then yes, you are going to have to set left thrust instead of the more normal right thrust.

downthrust will remain down though

Steve
JetPlaneFlyer is offline  
  Reply With Quote
Old 09-13-2011, 09:45 PM   #3
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 3,014
View mclarkson's Gallery4
Thanked 181 Times in 179 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

That's what it seemed like to me. Didn't think about it much until the plane wouldn't fly.

Does this mean that the Corsair prop is built to spin 'backwards?' I can't have it mounted wrong; it screws on.

mclarkson is offline  
  Reply With Quote
Old 09-13-2011, 09:50 PM   #4
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,488
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

I dont have a Corsair but according to the photos on this page: http://www.parkzone.com/Products/Def...rodID=PKZU1680 it has a conventional prop that spins anti-clockwise when viewed from the front.

Are you 100% sure that you haven't got the direction that the prop is actually turning in wrong?
JetPlaneFlyer is offline  
  Reply With Quote
Old 09-13-2011, 10:12 PM   #5
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 3,014
View mclarkson's Gallery4
Thanked 181 Times in 179 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

Well ... not 100% I guess. I'm looking at it now, and it looks like I *could* screw it on from the other end.

But I've mounted it so that the numbers are in the front. That's how I always mount my props and how I've understood they are always designed to go (unless you're putting them on a pusher.)


Attached Thumbnails
Click image for larger version

Name:	j3-corsair-prop-2.jpg
Views:	205
Size:	50.6 KB
ID:	152914   Click image for larger version

Name:	j3-corsair-prop-CU.jpg
Views:	205
Size:	9.6 KB
ID:	152915  

mclarkson is offline  
  Reply With Quote
Old 09-13-2011, 10:20 PM   #6
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,488
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

That does appear to be a reverse rotation prop.. Strange how the photo on the Parkzone web site shows a standard prop?.. we are talking the same plane here aren't we?

Even if you did mount it reverse (which you haven't) the rotation direction would remain the same for forward thrust.
JetPlaneFlyer is offline  
  Reply With Quote
Old 09-13-2011, 10:23 PM   #7
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,488
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

You didn't by any chance get that prop off the starboard engine of a PZ Mosquito did you

Looking at the PZ web site that's the only place they use a reverse rotation prop, and it's a three blader, and it looks just like yours.
JetPlaneFlyer is offline  
  Reply With Quote
Old 09-14-2011, 05:20 AM   #8
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 3,014
View mclarkson's Gallery4
Thanked 181 Times in 179 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

I can't find the packaging. I was in the LHS and said, "Gimme a Corsair prop," and this is what they gave me. But I'm starting to suspect you're right.

mclarkson is offline  
  Reply With Quote
Old 09-14-2011, 08:37 AM   #9
Catalina
Member
 
Join Date: Jul 2009
Location: Sydney, Australia
Posts: 185
Thanked 10 Times in 10 Posts
iTrader: (0)
Friends: (0)
Default

Looks like a reverse prop to me as well. I have used them with no issues but my motor mounts have always been straight so had no issues. Your motor mount is angled to reduce the affect of torque roll with a normal prop. So yes you are compounding the problem. Just buy another $5 prop to fix all issues.
Catalina is offline  
  Reply With Quote
Old 09-14-2011, 11:36 AM   #10
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 3,014
View mclarkson's Gallery4
Thanked 181 Times in 179 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

I've ordered a Corsair prop. Hopefully all will be well (once I reverse the wires.)

mclarkson is offline  
  Reply With Quote
Old 09-14-2011, 12:11 PM   #11
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 6,193
View solentlife's Gallery47
Thanked 266 Times in 263 Posts
Club: Founder Member Ventspils RC Club. Ex Waltham Chase and Meon Valley Soaring.
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Outstanding Contributor Award  125mph Speed Demon 
iTrader: (0)
Friends: (15)
Default

Like most things in life - there's usually a simple answer !

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
- Subscribe my Youtube: "solentlifeuk"
solentlife is offline  
  Reply With Quote
Old 09-26-2011, 09:10 AM   #12
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 3,014
View mclarkson's Gallery4
Thanked 181 Times in 179 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

I put a non-reversed prop on the plane, and it flies much better now!

mclarkson is offline  
  Reply With Quote
Old 09-26-2011, 07:50 PM   #13
Glacier Girl
Kamikaze Ace
 
Glacier Girl's Avatar
 
Join Date: Aug 2005
Location: Sunny Florida
Posts: 1,940
Thanked 149 Times in 139 Posts
Club: Badius Boys Flying Club Inc. Outlaw Flyers World Wide
Awards Showcase

1kW 
iTrader: (0)
Friends: (6)
Default

And a bit of advice, couple actually. Don't always believe the rule of thumb.
Not all props have the numbers on the front. The one used on the Parkzone Corsair, the park size, not the micro, is one that can bite you. Properly installed the numbers are on the back of the blade.

Ask me how I know.

#2 don't confuse torque roll with P factor.

Prop P factor is the forces (on a normal rotation prop) that makes the prop pull to the left and up. That's what your down and right angles on the motor are used to compensate for.

Torque is the force used to turn the prop, bigger the prop, the more torque it takes to turn it. And in turn, the more the airframe has to counter it.

You'll see torque roll as a type of condition, where the torque of spinning the prop is used/fought to make the plane roll on the prop axis. Do a roll to the right and it's easier as the torque is helping roll the plane over. Try it going left and you have to over come the torque to roll.

Prop P factor (again normal set up)is always trying to pull the nose up and to the left.
Torque is trying to twist the airframe to the right/clockwise, when viewed from the rear.

When I die, I want to go like my Grandfather did, in his sleep...... Not screaming like the passengers in his plane.
Glacier Girl is offline  
  Reply With Quote
Old 09-26-2011, 08:36 PM   #14
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,488
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

If we are getting technical then it's not actually P-factor that's responsible for most of the yaw experienced due to the prop rotation. P-factor is not a cause at all of nose up pitching, that's a different issue altogether and related to stability, trim and other factors.

Most of the left yaw you might experience and the main reason for right thrust is helical prop wash creating a sidewaws force on the vertical stabiliser. P-factor is only an issue where there is a large difference between the line of the prop axis and the direction of travel, like in high alpha flight or on a taildragger during the take off run. In normal level flight P-factor isn't an issue.

From Wiki:

This is an attempt to answer the frequent question "Why is my airctaft turning left all the time?".
This occurs only in aircraft with propellers at the front of the aircraft. And yes, it does occur in real life. Four distinct phenomena cause the effect, all causing the aircraft to turn in the same direction. They are:

Prop wash

A propeller pushes air not just horizontally to the back, but more in a twisting helix around the fuselage (clockwise as seen from the cockpit). As the air whirls around the fuselage it pushes against the left side of the vertical tail (assuming it is located above the propeller's axis), causing the plane to yaw to the left. The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i.e., at high power and low airspeed, which is the situation when starting the takeoff run.

Propeller torque effect

Torque effect is the influence of engine torque on aircraft movement and control. It is generally exhibited as a left turning tendency in piston single engine propeller driven aircraft.
According to Newton's law, "for every action there is an equal and opposite reaction," such that the propeller, if turning clockwise (when viewed from the cockpit), imparts a tendency for the aircraft to rotate counterclockwise. Since most single engine aircraft have propellers rotating clockwise, they rotate to the left, pushing the left wing down.
Typically, the pilot is expected to counter this force through the control inputs. To counter the aircraft roll left, the pilot applies right aileron.
It is important to understand that torque is a movement about the roll axis. Aileron controls roll. Prop torque is not countered by moving the rudder or by setting rudder trim. It is countered by moving or trimming the aileron.
This correction induces adverse yaw, which is corrected by moving or trimming the rudder (right rudder).
On aircraft with contrarotating propellers (propellers that rotate in opposite directions) the torque from the two propellers cancel each other out, so that no compensation is needed.
Further Reading: Propeller Torque Factor

P-Factor

P-factor is the term for asymmetric propeller loading, causes the airplane to yaw to the left when at high angles of attack.
The descending right side of the propeller (as seen from the rear) has a higher angle of attack than the upward-moving blade on the left side and provides more thrust. This occurs only when the propeller is not meeting the oncoming airflow head-on, for example when an aircraft is moving down the runway at a nose-high attitude (i.e. at a high angle of attack), as is the case with tail-draggers. Aircraft with tricycle landing gear maintain a level attitude on the takeoff roll run, so there is little P-factor during takeoff roll until lift off. In all cases, though, the effect is weaker than prop wash.
According to What You Need to Know About Aerodyanics... by Franklin Gutierrez.

Gyroscopic Precession

This is the tendency of a spinning object to precess or move about its axis when disturbed by a force. The engine and propeller act as a big gyroscope. However, gyroscopic precession is likely to be minimal in a typical aircraft.
Gyroscopic precession is frequently confused with p-factor.
JetPlaneFlyer is offline  
  Reply With Quote
Old 09-26-2011, 10:15 PM   #15
mclarkson
Super Contributor
 
mclarkson's Avatar
 
Join Date: May 2010
Location: Wichita, KS
Posts: 3,014
View mclarkson's Gallery4
Thanked 181 Times in 179 Posts
Awards Showcase

Scratchbuilders Award  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

Oh, my. I'm just happy I got my prop sorted out.

mclarkson is offline  
  Reply With Quote
Old 09-26-2011, 11:47 PM   #16
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,488
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

Originally Posted by mclarkson View Post
Oh, my. I'm just happy I got my prop sorted out.
Pleased to hear that you did get it sorted, happy flying
JetPlaneFlyer is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > General Electric Discussions

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Lengthen nose for correct CG SBS_Pilot Hi-Performance and Sailplanes 20 05-29-2011 07:09 PM
unsheduled roll kevinm General Electric Discussions 9 05-13-2011 02:00 AM
Could a EDF torque roll? or Why did I just total my Gripen? K CLOSE Electric Ducted Fan Jets 12 01-29-2011 03:36 AM


All times are GMT +1. The time now is 08:22 PM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.37538 seconds with 53 queries