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-   -   Limited normal nose wheel travel wiht max for ground handeling (http://www.rcuniverse.com/forum/rc-jets-120/11647272-limited-normal-nose-wheel-travel-wiht-max-ground-handeling.html)

CRye 04-18-2018 08:10 AM

Limited normal nose wheel travel wiht max for ground handeling
 
Getting to near the edge of the pavement after a landing roll out seems to happen with some frequency and the you have to either power through the rough or make the walk of shame.
I am trying a DX18 mix and curve to give max nose wheel with full rudder deflection and still keep the normal takeoff and landing nose movement narrower.
since the nose is mixed to the rudder anyway I set 5 point curve.
I set the inner points for normal and then a flat curve till near max rudder and then max the nose wheel. with some slow on the nose you can go max rudder momentary without much nose past normal. Makes what I call a bat wing curve.
max
.
-----------
0
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.
max
As you try to set the outer end of the flat part of the mix move the control stick until you see "add a point" go off and then move back till it shows again. Apparently the DX18 has a limit on how far out you can set a curve point.
Anyone else using this? If so any bad results?
PS you cannot add any expo that creates a really wild nose movement going back and forth. And slow has almost the same effect of expo.
??
Charles

Dansy 04-18-2018 09:40 AM

I have 2 rates for the nose wheel, 45* each side when I'm taxing, this is associated with my cruise Flight mode, on take-off or landing flight modes (flaps), I reduced this significantly...just enough to be able to correct the start of a cross wing takeoff/landing. And of course I also mix out the steering with gear up..on gear down my steering has a 10 seconds delay before it move.

Len Todd 04-18-2018 10:04 AM

If you have the correct length of servo arm and steering horn, there should be no problem getting the nose gear to turn as much as the fuse/gear will allow. Then, once you have enough mechanical travel, you can use dual rates to have a Taxi Rate and a Flying Rate on the nose wheel. Of course, when flying, the gear controller has the flying rate of the steering deactivated. Or, ... You can even put that maximum nose wheel rate on a separate switch so that it does not change with your other dual rates you use for flying (e.g. Landing Rates and Flying Rates, etc.). But, ...

I just have dual rates: One for take-off and landings and another for flying. Once I am back on the ground,, I switch over to the flying rate to get a smaller turning radius. At that point, the gear controller has the steering activated. But, again, once I have the mechanics set up right, I don't even need the other rate for turning.

If you are having trouble getting down in the center of the runway, use your spotter to help you gage where you are at. Have the spotter tell you with one word whether you are "short" or "long." Once you get thru that a few times, you begin to get the right perspective and not need the spotter coaching you. When I get on a fairly active flightline, I always have the spotter helping with landing positioning and announcing where the other planes are at, etc. After all, the spotter is not there to just watch you fly a plane around.

raron455 04-18-2018 10:23 AM

I will tell you what works for me in all mine,,,go into the servo speed option, and select the nose steering servo. Add about 1.75-2 to it. What that does is Adds a delay to the steering which drastically reduces the rapid movement causing you to drift and slide and over compensate down the runway , you still retain all of your travel at your set end points so when you taxi and you turn you get full movement it just doesn't happen as quick. This works perfect for me to help hold the centerline while on the ground. My ultra flash used to look like the General Lee swerving all the way across the runway until I started doing this and now I do it on everything I own with a front wheel.

Len Todd 04-18-2018 10:34 AM


Originally Posted by raron455 (Post 12424131)
I will tell you what works for me in all mine,,,go into the servo speed option, and select the nose steering servo. Add about 1.75-2 to it. What that does is Adds a delay to the steering which drastically reduces the rapid movement causing you to drift and slide and over compensate down the runway , you still retain all of your travel at your set end points so when you taxi and you turn you get full movement it just doesn't happen as quick. This works perfect for me to help hold the centerline while on the ground. My ultra flash used to look like the General Lee swerving all the way across the runway until I started doing this and now I do it on everything I own with a front wheel.

That is an excellent idea! My UF is a bugger to handle on the ground right after landing. I am going to give this a whirl.

opjose 04-18-2018 01:38 PM

Great idea... (runs to grab TX....)!

ravill 04-18-2018 01:47 PM

Gyro, baby, gyro.

Keep all your travel and never never touch another darn switch on take off. :cool:

olnico 04-18-2018 10:36 PM

Just do the same stuff as real size aircraft.
Have the nose wheel partly mixed to the rudder stick for max landing speed deviation allowed ( usually about =-15 degrees ).
The remaining of the travel ( about +-50 to 70 degrees ) should be located on a tiller ( typically a volume knob on the transmitter ).

At typical landing speeds, a deflection of over 15 degrees on the nose tire will just result in a flat. The rubber adhesion will not be sufficient for the cornering action commanded. The higher the landing speed, the smaller the nose tire diameter, the harder the tire rubber, the more noticeable the cornering limitation becomes.
Also, at high speeds the cornering action might over-torque your servo if too weak/ or too much travel is required.

As said above by Raff', a great option is to place a gyro in heading lock on the steering channel and electric brakes.
Our LG15 electric gear controller does exactly this. It has a gyro on the yaw axis only dedicated to the ground operations ( gear extended ).
This has two actions:
1. control the steering servo in heading lock
2. Control electrical differential braking in heading lock.

Point 2 reduces the nose wheel cornering force dramatically for high speed/ small nose wheel equipped airplanes.

https://www.ultimate-jets.net/produc...ear-controller

The other benefit of a gyro equipped gear controller is that you do not have to bother with the gyro gain mixing/ sharing between rudder and steering. Your flight gyro is a different box and completely decoupled from your ground system gyro ( gear controller ). You can easily program completely different gains between the rudder and the steering servo. At the end of the day, this makes sense as they are completely different controls and have a different point of action on the plane ( one is above the roll line, the other one is below the roll line, one has a decreasing action with decreasing speed, the other an increasing action with decreasing speed ).

In practice, assign the steering servo to a separate channel, controlled by a volume knob ( and assigned to a gyro line if willing to do so ). Then mix in a bit of rudder to that channel.

CRye 04-19-2018 10:03 AM

Thank all,
Hey Ronnie, I am already shaking the couch and saving coins for gas $ to HOTMAC!!!
Yep this all began with your programming my Aurora out and, of course, I had to mess with the theory on my now knockabout flyer the mighty Boomerang.
Cheers
Charles
Out of all these new systems I have learned perhaps I will dis spell the rumor that I don't even fly. But if it was one or the other I would pick pit time at fly ins and fly at home.

Zeeb 04-19-2018 10:28 AM

My friend got me started on reducing the nose wheel travel substantially when the flaps are down, so far seems to work fine. I guess that might not be the best idea if a model does not require some flap extension for takeoff, but so far everything I've flown needs the flaps.

RCISFUN 04-19-2018 03:20 PM

Flight Modes:
Take off and landing flaps = very low rate movement
Normal Flight Mode i.e. flaps up = higher rate movement to make tight turns

Landing gear up = disable steering servo


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