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byoungplumbing(at)gmail.c
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 Posted: Wed Feb 16, 2011 8:09 am Post subject: landing gear toe in - out |
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OOOOOKKKKKK
i need to apologize to the list... in the past the question has come up as to what the value of toe in - out was necessary. many on the list have said you need some toe in,, and my response has always been copied from the kolb builders manual. which states in short, neutral, if you have to err, err on the side of toe out. from my experience this week that is wrong. toe in is needed,, but how much is still evading me.
while driving the kolb around on snow and ice,, i would notice that when 1 tire was on a slick spot and the other on dry surface, my mkiii would jump in the direction of the tire on the ice, now i had believed my gear to be quite neutral when i last visited the subject 9 years ago.... but this experience convinced me i was toe in by quite a bit. and more sophisticated measurements has confirmed that. now i am using the solid tapered steel legs i bought from kolb. and the camber has always been off since i installed them new, so i have decided to do something about it. so i did some work on the calculator to decide how much i wanted to bend the gear legs down to correct the camber, then how much i wanted to bend the gear back to eliminate the toe in,, figured the angles to do both with 1 bend. after bending the camber is perfect, and i left a tiny bit of toe in, and figured before i tried bending more i would try it. it felt as if i was driving down the railroad track on the railroad ties. it was near impossible to look out the windows to see and keep things straight down the runway,,, but what i think was happening is the rolling resistance would flex the gear backwards, till i was in a toe out position,,, that would increase the rolling resistance, bend back more till the wheel would loose traction then the gear would spring forward, the wheel would slide, skip, roll, bounce, all at the same time and do it at 30 times a second. or there about.
long story, but i will start bending some toe in back in the gear, bit by bit,, and keep trying till i get a smooth roll out. in the past if i inflated my tires to 15 lb or so, it could get a bit darty, but if i kept the tire pressure at 8 psi or so, there would be enough flex in the side walls to roll correct. so i will be doing the test with 15 psi in the tires and try and get the toe in so that when the gear flexes back, the tires will be tracking true. so i am thinking my final be will be back near where i started.
when i come up with some final answers i will post to the list... one last thought, when i had the alum, gear legs it seems that they flexed less than the spring steel legs. so my results may not fit everyone's needs. but my lessons and experience may help.
boyd young
mkiii utah.
[quote][b]
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Wed Feb 16, 2011 8:35 am Post subject: landing gear toe in - out |
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when i come up with some final answers i will post to the list... one
last thought, when i had the alum, gear legs it seems that they flexed less
than the spring steel legs. so my results may not fit everyone's needs.
but my lessons and experience may help.
boyd young
Boyd Y/Kolber:
I always use a lot of camber and a tad of toe in.
Heat treated (48rc) 4130 gear legs are more flexible in all directions than
7075 aluminum legs, especially the extra long legs on the stock MKIII.
Braking will cause the main gear to toe out. Toe out spreads the gear legs
and reduces camber.
My gear legs are 24" total with 18" outside the gear leg sockets. Don't get
near the flex with the short stubby legs.
john h
Titus, Alabama
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Ralph B
Joined: 14 Apr 2007
Posts: 367
Location: Mound Minnesota
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| Posted: Wed Feb 16, 2011 9:14 am Post subject: Re: landing gear toe in - out |
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Boyd,
The gear is toed in slightly on both my Firestar and Kolbra. It taxies fine on both aircraft and have not noticed the type of problem you are seeing. When either aircraft is picked up by the tail and moved backwards, the gear spreads out and it looks like I had a very hard landing. I will usually put my back to the cockpit and lift underneath. This will spring the gear back to their original position to make it look like it's not spread out like that. If one side is not sprung back, it can make your wings look like they are not level even if it's sitting on level ground.
Ralph B
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Ralph B
Kolb Kolbra 912uls
N20386
550 hours
Last edited by Ralph B on Wed Feb 16, 2011 9:25 am; edited 1 time in total |
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byoungplumbing(at)gmail.c
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| Posted: Wed Feb 16, 2011 9:24 am Post subject: landing gear toe in - out |
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I always use a lot of camber and a tad of toe in.
john h
Titus, Alabama
>>>>>>>>>
john and kolbers
been doing a lot of investigating the last couple days... it seems the best i have learned about camber,,, it that it should be positive, on an empty plane,,, but when the plane is loaded to grose wt,, they should be netural. i guess the book furtherer clairified that they should be netural at the normal loading of the plane,,, example,, if you normaly fly at 80 % gr, wt. then you should set it at netural at that wt.... if occasional you are at 60 or 100 % you would be only slightly pos, or neg, camber. this will maximize the tire wear. likewise the 'toe in' should be equal to the amount the wheel pulls back due to the rolling resistance,, which will vary depending on the flex for and aft in the gear leg, and the loading of the plane. kind of hard to measure at 50 mph... guess you go by feel at that point.. everything else is just a starting point. trouble in a kolb,,, once it is set,,, its kind of hard to change.
boyd young
mkiii utah
[quote][b]
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Ralph B
Joined: 14 Apr 2007
Posts: 367
Location: Mound Minnesota
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| Posted: Wed Feb 16, 2011 9:36 am Post subject: Re: landing gear toe in - out |
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| Quote: | kind of hard to measure at 50 mph... guess you go by feel at that point.. everything else is just a starting point. trouble in a kolb,,, once it is set,,, its kind of hard to change.
boyd young
mkiii utah |
This obviously is one of the shortcomings of Kolb aircraft. It's a guessing game on toe-in. What I did for the Firestar is to adjust it to neutral to begin with and then equally toe in on both sides. With the aluminum gear, it tends to toe out quite a bit with added weight. Once the gear leg hole is drilled, there's no re-drilling, unless you get another gear leg. One advantage to this type of gear, is that it can be removed easily. That's got to be a big plus.
Ralph B
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Ralph B
Kolb Kolbra 912uls
N20386
550 hours |
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byoungplumbing(at)gmail.c
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| Posted: Wed Feb 16, 2011 10:09 am Post subject: landing gear toe in - out |
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Boyd,
The gear is toed in slightly on both my Firestar and Kolbra. It taxies fine on both aircraft and have not noticed the type of problem you are seeing. When either aircraft is picked up by the tail and moved backwards, the gear spreads out and it looks like I had a very hard landing. I will usually put my back to the cockpit and lift underneath with my hands. This will spring the gear back to their original position to make it look like it's not spread out like that. If one side is not sprung back, it can make your wings look like they are not level even if it's sitting on level ground.
Ralph B
| Quote: | >>>>>>>>>>>>>>>>>>
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what type of gear legs do you have?
other than my camber being way off... it drove ok before i started.. except when i was on ice. i may end back wher i started with toe in. wish now i had only adjusted camber. hind sight. i am getting too soon old and too late smart
boyd
[quote][b]
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neilsenrm(at)gmail.com
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| Posted: Wed Feb 16, 2011 11:13 am Post subject: landing gear toe in - out |
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Boyd
It sounds like I have the same solid steel gear legs. I really like the gear but don't like the look of negative camber. Where/how did you bend the gear and did you remove the gear to bend it? I clamped a staight 2X4 between both axles notched for the brake attachment while installing my gear legs so I think they are neutral. But they flex under load so much that things could change.
Keep us posted
Rick Neilsen
Redrive VW Powered MKIIIC
On Wed, Feb 16, 2011 at 11:03 AM, b young <byoungplumbing(at)gmail.com (byoungplumbing(at)gmail.com)> wrote:
[quote] OOOOOKKKKKK
i need to apologize to the list... in the past the question has come up as to what the value of toe in - out was necessary. many on the list have said you need some toe in,, and my response has always been copied from the kolb builders manual. which states in short, neutral, if you have to err, err on the side of toe out. from my experience this week that is wrong. toe in is needed,, but how much is still evading me.
while driving the kolb around on snow and ice,, i would notice that when 1 tire was on a slick spot and the other on dry surface, my mkiii would jump in the direction of the tire on the ice, now i had believed my gear to be quite neutral when i last visited the subject 9 years ago.... but this experience convinced me i was toe in by quite a bit. and more sophisticated measurements has confirmed that. now i am using the solid tapered steel legs i bought from kolb. and the camber has always been off since i installed them new, so i have decided to do something about it. so i did some work on the calculator to decide how much i wanted to bend the gear legs down to correct the camber, then how much i wanted to bend the gear back to eliminate the toe in,, figured the angles to do both with 1 bend. after bending the camber is perfect, and i left a tiny bit of toe in, and figured before i tried bending more i would try it. it felt as if i was driving down the railroad track on the railroad ties. it was near impossible to look out the windows to see and keep things straight down the runway,,, but what i think was happening is the rolling resistance would flex the gear backwards, till i was in a toe out position,,, that would increase the rolling resistance, bend back more till the wheel would loose traction then the gear would spring forward, the wheel would slide, skip, roll, bounce, all at the same time and do it at 30 times a second. or there about.
long story, but i will start bending some toe in back in the gear, bit by bit,, and keep trying till i get a smooth roll out. in the past if i inflated my tires to 15 lb or so, it could get a bit darty, but if i kept the tire pressure at 8 psi or so, there would be enough flex in the side walls to roll correct. so i will be doing the test with 15 psi in the tires and try and get the toe in so that when the gear flexes back, the tires will be tracking true. so i am thinking my final be will be back near where i started.
when i come up with some final answers i will post to the list... one last thought, when i had the alum, gear legs it seems that they flexed less than the spring steel legs. so my results may not fit everyone's needs. but my lessons and experience may help.
boyd young
mkiii utah.
| Quote: |
get="_blank">http://www.matronics.com/Navigator?Kolb-List
ttp://forums.matronics.com
_blank">http://www.matronics.com/contribution
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byoungplumbing(at)gmail.c
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| Posted: Wed Feb 16, 2011 2:03 pm Post subject: landing gear toe in - out |
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Boyd
It sounds like I have the same solid steel gear legs. I really like the gear but don't like the look of negative camber. Where/how did you bend the gear and did you remove the gear to bend it? I clamped a staight 2X4 between both axles notched for the brake attachment while installing my gear legs so I think they are neutral. But they flex under load so much that things could change.
Keep us posted
Rick Neilsen
>>>>>>>>
Rick yes i had to remove the gear,,, my son bought a pipe bender that goes up to 2 inch,, the bending was easy,, but wish i had left toe in alone and only did the camber.
b oyd
[quote][b]
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undoctor
Joined: 21 Oct 2008
Posts: 212
Location: Bethelhem, PA
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| Posted: Thu Feb 17, 2011 8:05 am Post subject: landing gear toe in - out |
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railroad track on the railroad ties. it was near impossible to look
out the windows to see and keep things straight down the
runway,,, but
what i think was happening is the rolling resistance would flex
the gear
backwards, till i was in a toe out position,,, that would
increase the
rolling resistance, bend back more till the wheel would loose
traction
then the gear would spring forward, the wheel would slide, skip,
roll,
bounce, all at the same time and do it at 30 times a second. or
there
about.
Boyd/list
This brings to mind years ago when they first started putting radial
tires on
the steering axles of 18 wheelers. For a while we had our jobs cut out
for us to
keep the it in one lane. The rig would lurch right, then left; kind of
where ever it
wanted to go, and the driver was left with the task of getting safely to
our destination.
Through experimentation and testing they found that the toe in normal for
years with bias tires didn't work with radials. I believe the amount of
weight
had something to do with it. The greater rolling resistance with bias tires
pulled back on the steering and suspension, causing the wheels to roll
parallel. But with the reduced rolling resistance of radials, the toe
in remained
intact, consequently the steering axle wheels "argued" with each other which
one was in charge at any given moment.
The resolution of this problem was welcome for those of us who fought with
it for thousands of miles!!
Good luck getting it right. Hope this info gives you some insight, like
experimenting
with tire pressure, which is easier to change than bending, and not
nearly as "permanent."
Dave Kulp
Bethlehem, PA
FireFly 11DMK
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