Toe out, Neutral or Toe in?
09-22-2015, 08:08 PM
#1
Toe out, Neutral or Toe in?
Hey Gang
I am starting a project converting an old "Big Stick" ARF that I rescued several years ago, from a modeler that got in over his head. He had tried to teach himself to fly R/C solo, and eventually cracked up the original kit. Sweet deal for me; kit, OS .61, sport radio and a few other bits for $100.00
The fuse was a total loss, but the wing was untouched. I immediately put the plane on a diet, built a new fuse narrowed by a 1/2 inch and shortened, height-wise, by the same. I did a built up empennage with laminated (outline) vertical stab and rudder. I wanted to clean up as much drag on this bird, so I added drooped (Hoerner) the wing tips and all control surfaces were tapered down to a 1/16 inch. The final touch was a enclosed engine cowl with a slippery cheek. See below.
That rescue was about seven years ago and now I want to do something completely different (shameless Monty Python ref.). So, my plan is for an electric conversion and I want to go "twin". I have several electric motors laying around and have two 35 outrunners with no better place to be. I would like to get some input on how to set them up.
My fading memory of an old sport twin I had back in the early 80's was, to have a degree, or so, of toe-out on each motor and a degree, or so, of down thrust on each. A couple of folks at my field seem to think there should be toe-in or just neutral with down thrust only. Toe-in does not make any sense, from my training.
Another question while on this project. Has anyone ever run two brushless motors with one ESC? I have a couple of 100 Amp ESC's and the motors are rated for 30Amps each. The 100 amp ESC is pretty bulky so two of them would be, well, bulkier. Seems as long as I keep all the leads the same length... I have heard that long leads between the ESC and motor causes problems, but I have no trust in the source of that info. I don't want to spend more bucks if I do not have to.
What say-eth the brain trust of the Universe?
Peace, Wolf
I am starting a project converting an old "Big Stick" ARF that I rescued several years ago, from a modeler that got in over his head. He had tried to teach himself to fly R/C solo, and eventually cracked up the original kit. Sweet deal for me; kit, OS .61, sport radio and a few other bits for $100.00
The fuse was a total loss, but the wing was untouched. I immediately put the plane on a diet, built a new fuse narrowed by a 1/2 inch and shortened, height-wise, by the same. I did a built up empennage with laminated (outline) vertical stab and rudder. I wanted to clean up as much drag on this bird, so I added drooped (Hoerner) the wing tips and all control surfaces were tapered down to a 1/16 inch. The final touch was a enclosed engine cowl with a slippery cheek. See below.
That rescue was about seven years ago and now I want to do something completely different (shameless Monty Python ref.). So, my plan is for an electric conversion and I want to go "twin". I have several electric motors laying around and have two 35 outrunners with no better place to be. I would like to get some input on how to set them up.
My fading memory of an old sport twin I had back in the early 80's was, to have a degree, or so, of toe-out on each motor and a degree, or so, of down thrust on each. A couple of folks at my field seem to think there should be toe-in or just neutral with down thrust only. Toe-in does not make any sense, from my training.
Another question while on this project. Has anyone ever run two brushless motors with one ESC? I have a couple of 100 Amp ESC's and the motors are rated for 30Amps each. The 100 amp ESC is pretty bulky so two of them would be, well, bulkier. Seems as long as I keep all the leads the same length... I have heard that long leads between the ESC and motor causes problems, but I have no trust in the source of that info. I don't want to spend more bucks if I do not have to.
What say-eth the brain trust of the Universe?
Peace, Wolf
09-22-2015, 08:51 PM
#2
I have set up a couple of glow twins and used 2 deg of out thrust on each engine so if you had an engine out situation the running engine with out thrust would want to pull the nose in line and be more in control. Some advocate doing this on the Right engine only as the left engine rotation ( when both engines are running in the same direction) prop wash and torque of the left engine would be sufficient to keep the plane on track.
In an electric application I'd leave it at zero as your not worried about loosing an engine..
Pete
In an electric application I'd leave it at zero as your not worried about loosing an engine..
Pete
Last edited by Rocketman612; 09-23-2015 at 04:59 AM.
09-23-2015, 02:42 AM
#3
As to twins: http://www.rcuniverse.com/forum/twin-multi-engine-rc-aircraft-192/10913690-twin-tips.html#post10919987
As to ESC: Each brushless motor needs its own ESC since it replaces the mechanical commutator (collector and brushes).
Long leads between battery and ESC cause problems as well.
As to ESC: Each brushless motor needs its own ESC since it replaces the mechanical commutator (collector and brushes).
Long leads between battery and ESC cause problems as well.
09-23-2015, 10:36 AM
#4
Join Date: Oct 2002
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Yep to electric not needing the toe out which IS the right direction. Your flying line buddies are likely thinking about conventional landing gear setups where I like to use a degree or two of toe-in.
With an electric twin you gain the option of playing with mixes if your radio has them and running the two throttles off separate channels mixed to the throttle stick. You can then mix in some percentage of rudder to the throttles and get "power rudder" with the motors being linked to the rudder stick. It aught to make for some snazzy "out there twin only" maneuvers that no one has a name for....
With an electric twin you gain the option of playing with mixes if your radio has them and running the two throttles off separate channels mixed to the throttle stick. You can then mix in some percentage of rudder to the throttles and get "power rudder" with the motors being linked to the rudder stick. It aught to make for some snazzy "out there twin only" maneuvers that no one has a name for....
09-23-2015, 05:51 PM
#6
Thanks for all the input, all good points. I think I will run the out thrust, there is always the possibility of one of the motors/ESC crapping out. I already planned to counter rotate the props, since it simply a matter of switching a couple of wires. Just not thrilled about buying more ESC's.
Hey Ustik.
I haven't heard of the Battery to ESC leads being problematic, I thought it was the ESC to motor side. What is considered "long"? I will have about 10"-12" between the Battery and ESC's.
keep those cards and letters coming.
Wolf
Hey Ustik.
I haven't heard of the Battery to ESC leads being problematic, I thought it was the ESC to motor side. What is considered "long"? I will have about 10"-12" between the Battery and ESC's.
keep those cards and letters coming.
Wolf
Last edited by BD5wingnut; 09-23-2015 at 05:57 PM.
09-23-2015, 07:41 PM
#8
Join Date: Oct 2002
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The key to remember if/when you lose a motor is to initially go into a shallow dive or at the very least push over to level to pick up speed. Where one prop operation goes bad is when the ability of the rudder to yaw the model is less than the yaw torque from the prop still running. So keeping up some good flying speed so you don't actually need full rudder to maintain a straight ahead path is the key. If you MUST climb on one prop be sure you don't let the speed bleed off. As you find you're needing to hold full rudder to maintain a straight heading nose down a little to let the speed come up.
The toe out is an aid but it still doesn't cancel out the yaw torque of the running prop. Speed management is still key.
If you use that rudder to throttle mix I described please be sure to PM me with the results or a link to the thread with the results. I'd love to read about it and what it let's you do.
The toe out is an aid but it still doesn't cancel out the yaw torque of the running prop. Speed management is still key.
If you use that rudder to throttle mix I described please be sure to PM me with the results or a link to the thread with the results. I'd love to read about it and what it let's you do.
09-24-2015, 09:51 AM
#10
Some modelers report no problems with long leads but it's recommended to install additional electrolytic capacitors (470 microF / 35 V) every 4" to 8" or even 10" between the leads. So 12" would be problematic. ;-)
09-25-2015, 09:44 AM
#11
Bmatthews
Unfortunately my DX6i does not have the capability, I think. Not really into the 3D thing anyway, I am more into Olds-Cool pattern with big boomin loops and a "box" that fills your view. Would be interesting to see what can be done mixing rudder with separate throttles.
I am sure the "Stik" has plenty of rudder to counter any induced yaw. Hopefully, there will not be a need.
Unfortunately my DX6i does not have the capability, I think. Not really into the 3D thing anyway, I am more into Olds-Cool pattern with big boomin loops and a "box" that fills your view. Would be interesting to see what can be done mixing rudder with separate throttles.
I am sure the "Stik" has plenty of rudder to counter any induced yaw. Hopefully, there will not be a need.
09-25-2015, 10:06 AM
#12
Peace, Wolf
10-01-2015, 08:38 AM
#13
You missed that smiley in my post? Seems 10" or even 12" would not be problematic. And the EEs say the caps compensate the inductivity of the long leads. There is no during current in them (no AC either) but pulses what can make for phase shift and reactive power and whatnot. I'm a ME and don't know either... ;-)
10-13-2015, 04:12 AM
#15
My Feedback: (43)
If you do a lot of quick throttle changes often, then the long battery leads become a problem. Normally, you only do these types of throttle changes when hovering for 3d junk, or I have seen some guys that love to blip the throttle while taxing. It sets up ripple voltage and when that gets too high, it will kill the caps in the ESC. I have run 18" battery leads on a 4s 100 amp EDF and never had a bit of trouble.
