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-   -   nose gear (http://www.rcuniverse.com/forum/questions-answers-154/11341688-nose-gear.html)

fredsedno 12-23-2012 11:16 AM

nose gear
 
Gentlemen, A question about slanting a nose gear forward rather than straight down or slanting aft.
I'm thinking something like 10 to 15 degrees. Would there be any advantage for use on a grass strip?
How would vertical and horizontal forces be affected on touchdown? The general consensus seems to be " won't work".
Have any of you pilots tried this? I trust your input. fredsedno

invertmast 12-23-2012 12:25 PM

RE: nose gear
 
There are quite a few aircraft with forward slanting nose gear..

DO-335, ME-262, King-Air, Cessna 150/152/172/182/206/207/210 just to name a few...

vicman 12-23-2012 01:31 PM

RE: nose gear
 
If you are familiar with motorcycles at all, the image of a chopper style should do much to help you understand what a forward rake does for handling. None of the performance or racing bikes use much rake for this reason. Basically the wheel will want to tip to one side. This also happens with some negative rake but it doesn't cause any pressure when the wheel trails like the amount of push it takes to make a turn with positive rake.
Same applies with a tailwheel. Taildraggers like the P51 utilize the neutral steering and ease of rolling when the tailwheel is not locked into the rudder.

red head 12-23-2012 02:08 PM

RE: nose gear
 
Pretty much what all the above have said. One thing you would have to watch real close is that you don't get it so far forward that it will hit the prop when it springs back in place on a landing . ( that's hard on nose wheels, I know ) I know that you aren't supposed to land on the nose wheel !!!!! lol

I've had a couple with slight forward tilts and they were fine , I just wouldn't tilt much . ENJOY !!! RED

Gray Beard 12-23-2012 05:19 PM

RE: nose gear
 
I have had the front LG leg bent back too much and just flipped it around so it had a forward rake, no problems. A few degrees isn't going to hurt anything.

da Rock 12-23-2012 05:58 PM

RE: nose gear
 
It should work as long as your steering servo can take the impact and load.

When the wheel is pivoted normally, there is little load on the servo gears. When the wheel is castered behind the axis, there is a load that not only tries to return the steering to center, but bears somewhat on the servo gears. The load won't worsen the steering situation, but will increase the power the servo is going to ask from the battery. Electric motors draw more juice when the load on them goes up.

If you caster the wheel in front of the axis of rotation, the same increase in draw is going to happen as when the caster puts the wheel behind the steering axis. Only thing is, the force on the wheel is going to try and increase the steering you're asking for. If anything goes wrong with your forward rake (negative caster) setup, it's going to try to go even 'wronger'.

Why do you want to do what you want to do? There may be another way to get what you want.

BTW, race car engineers play with caster all the time. It was used in the old days to help the cars into the turns. And it makes all cars want to go straight. In racing, the drivers really wanted the normal (trailing) caster. Every so often, someone would try what you want to try. The drivers discovered that the steering fought them in an unnatural way. And the car acted like it had a mind of it's own. And had lost it's mind. They often decided while loading a wrecked car on the truck to go home early that they'd learned an expensive lesson.

Oh yeah, if you do it, make sure your steering tiller arm is strong enough to deal with more than usual load. And consider grinding flats where the gib screws clamp down. Also, think about what power servo you're using and if maybe metal gears would be a good idea. Bowden cable might be a better choice for the pushrod also. All that is what we should do even if the setup is 'normal'. But shouldn't be overlooked for anything with caster.

da Rock 12-24-2012 09:28 AM

RE: nose gear
 
To simplify...

When the footprint of the tire is directly in line with the strut, it takes no effort to steer the tire and steering doesn't load up the 'steering wheel'.

The footprint is the rubber touching the road. The strut is usually aligned with the axis of rotation. Where that axis points with almost all our nose wheel landing gear would be right through the footprint. The steering wheel of a model airplane is the servo.

When the footprint is in front of or behind the axis of rotation there is caster present. Caster always loads the steering wheel when the tire is steered. It has been known to break race driver's hands, wrists, and arms. It usually doesn't. ;)

red head 12-24-2012 01:39 PM

RE: nose gear
 

Quote:

ORIGINAL: Gray Beard

I have had the front LG leg bent back too much and just flipped it around so it had a forward rake, no problems. A few degrees isn't going to hurt anything.
By turning the nose gear around you would probably be loading the nose gear spring in the wrong direction. Probably wouldn't hurt anything, but it would be backwards. ENJOY !!! RED

jester_s1 12-25-2012 07:02 PM

RE: nose gear
 
With the amount of forward rake you're talking about, there would be in increased risk of stripping servo gears on a rough landing. Any hit that isn't perfectly centered in the direction the tire is facing will try to turn the tire full left or right.

I'm curious too. Why do you want to do this? Is it in order to move the nose gear forward so as to have more stable tracking or is it because you have been bending the gear back on landings and think this will help it?

fredsedno 12-27-2012 01:02 PM

RE: nose gear
 
Thanks one and all. All answers were informative and appreciated.
Sorry for the delay in respondingdeer season, oh yuh,and Christmas.
Actualy I really don't want to make this alteration. I had a "knuckle" nose gear.
Tower#lxfv50 that bends aft on nearly all landings [grass] some as much as 20*on not so perfect touch downs. The knuckle[spring] is appx. 1inch below the bottom of the nose gear. The bend occurs where the gear goes into the nylon bearing for support. There has been no damage to the aircraft in all events. Looks like an innovative design,perhaps the gear wouldn't bend if the "knuckle" were closer to the bottom of the fus. fredsedno

Gray Beard 12-31-2012 04:36 PM

RE: nose gear
 
You do know most hobby shops sell replacement nose gears and they are a lot better steel then what comes with a plane.

fredsedno 01-02-2013 09:33 AM

RE: nose gear
 
Greybeard, This gear is an after market product, seems to be a quality mfg. part. The design is nothing like I have seen before.
This item is made by a well known and respected business. Just checked Tower, price seems to have doubled in the past six months.
The design fascinates me and I intend to try again. Possibly the steel is not spring tempered properly. fredsedno

jester_s1 01-02-2013 09:01 PM

RE: nose gear
 
FWIW, if you're bending up the nose gear something is wrong. All the nose gear is designed to do is give the front of the plane a place to sit while it rolls around on the ground. If you're bending them then you are either nosing the plane in on landings (likely stalling the plane before getting to the ground) or you are using too small a nose wheel on a rough runway.


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