taildragger toe-in vs toe-out AGAIN

OK, I've researched this a fair bit and am still hearing two definite
different views. One one hand you have those that swear you need
toe-out and then on the other you have (among others- these are the
few I'm certain about) Cessna 100 series, Huskies, and Pitt's that all
are set with slight toe-in by the factory. Granted these are set
without weight on the aircraft and the toe-in may change slightly when
under load.

I think it boils down to what wins when you start to go into a turn
with a taildragger- does the toed-in outside wheel "drag" and thus
want to straighten you back out or does the toed-out outside wheel get
weight transferred to it and tend to straighten you out (vs tightening
the turn)?

Anybody with some definite answers based on physics? There's lots of
emperical and experiential opinions out there, anybody with some more
factual answers to the argument?

J oa

On 14 Nov 2003 10:07:59 -0800, (Joa) wrote:

OK, I've researched this a fair bit and am still hearing two definite
different views. One one hand you have those that swear you need
toe-out and then on the other you have (among others- these are the
few I'm certain about) Cessna 100 series, Huskies, and Pitt's that all
are set with slight toe-in by the factory. Granted these are set
without weight on the aircraft and the toe-in may change slightly when
under load.

I think it boils down to what wins when you start to go into a turn
with a taildragger- does the toed-in outside wheel "drag" and thus
want to straighten you back out or does the toed-out outside wheel get
weight transferred to it and tend to straighten you out (vs tightening
the turn)?

Anybody with some definite answers based on physics? There's lots of
emperical and experiential opinions out there, anybody with some more
factual answers to the argument?

J oa

What's wrong with putting the wheels on straight?

What's wrong with putting the wheels on straight?


Or not even fixed - like crosswind gear?

Seems to me that there might be a few parameters to many to make a "scientific"
generalization. This may be an area where it's best to just go with the
conventional wisdom, hope it works, and if it doesn't, do a bit of
experimenting.

The conventional wisdom does not work with my brand of 'dragger, but then it's
kind of odd. Q

There's lots of
emperical and experiential opinions out there, anybody with some more
factual answers to the argument?

I've pondered this thing myself. Problem with tail draggers (actually a
characteristic of aircraft and their need to have flexible gear way out on
spindly aerodynamic legs) is that toe out could change to toe in depending on
the load. This also changes during the transition from ground to flight. Worse
yet (the big problem with my plane) is the toe change as I bring the tail up on
take off or transition down during landing. Suffice to unscientificlly say that
20 years in the automotive alignment business has shown me that cars with toe
out tend to be a bit more twitchy than those with toe in. Have no idea if that
translates to aircraft because taildragger pilots EXPECT the plane to try to
swap ends.

Jim

On 15 Nov 2003 00:22:09 GMT, (JFLEISC) wrote:

There's lots of
emperical and experiential opinions out there, anybody with some more
factual answers to the argument?

I've pondered this thing myself. Problem with tail draggers (actually a
characteristic of aircraft and their need to have flexible gear way out on
spindly aerodynamic legs) is that toe out could change to toe in depending on
the load. This also changes during the transition from ground to flight. Worse
yet (the big problem with my plane) is the toe change as I bring the tail up on
take off or transition down during landing. Suffice to unscientificlly say that
20 years in the automotive alignment business has shown me that cars with toe
out tend to be a bit more twitchy than those with toe in. Have no idea if that
translates to aircraft because taildragger pilots EXPECT the plane to try to
swap ends.

Jim
+++++++++++++++++++++++

TOE IN is a NO-NO for tail draggers.
Just the reverse of cars.

Read the archives.
This has been beaten to death.
Many times.


Barnyard BOb -

On Fri, 14 Nov 2003 19:12:31 -0600, - Barnyard BOb -
wrote:

On 15 Nov 2003 00:22:09 GMT, (JFLEISC) wrote:

There's lots of
emperical and experiential opinions out there, anybody with some more
factual answers to the argument?

I've pondered this thing myself. Problem with tail draggers (actually a
characteristic of aircraft and their need to have flexible gear way out on
spindly aerodynamic legs) is that toe out could change to toe in depending on
the load. This also changes during the transition from ground to flight. Worse
yet (the big problem with my plane) is the toe change as I bring the tail up on
take off or transition down during landing. Suffice to unscientificlly say that
20 years in the automotive alignment business has shown me that cars with toe
out tend to be a bit more twitchy than those with toe in. Have no idea if that
translates to aircraft because taildragger pilots EXPECT the plane to try to
swap ends.

Jim
+++++++++++++++++++++++

TOE IN is a NO-NO for tail draggers.
Just the reverse of cars.

And many cars actually DO have a toe out spec.
The ideal is for the wheels to roll 100% straight down the road.
Depending on steering geometry, they will try to toe out, or in. The
spec is to set them toed in if they tend to toe out, and out if they
tend to toe in, so that the natural forces pull the wheels towards the
straight ahead position. GENERALLY, vehicles with front wheel drive
tend to have toe out specs. ( Austin mini (old) was 0.062 inch toe
out) - but more and more you are seeing spec of 0 +/-.
The position of the tie rod, either ahead of or behind the steering
axis had some effect, as does the position of the intersection between
the KPI and the wheel centerline (camber).

Positive camber contributes to a toe-out tendancy ( that's why cars
tend to pull to the side with the most positive camber) (also think
about the handling of a bicycle)and Negative caster has the same
tendancy.
On an aircraft landing gear, the camber is self evident - and the
"effective" camber changes with load, and is effected by "unballanced"
landings (one wheel first). If the landing gear has "caster" it
changes between tail-up and tail-down attitudes. The different
combinations of uneven loading and landing attitudes will all effect
the "toe" behaviour of the wheel - so it is dangerous to make a
statement that either toe out or toe in is NECESSARILY more desirable
on a particular plane.


Read the archives.
This has been beaten to death.
Many times.


Barnyard BOb -

On 14 Nov 2003 04:12 PM, - Barnyard BOb - posted the following:

TOE IN is a NO-NO for tail draggers.
Just the reverse of cars.

One of the instructors at the local A&P school tried to convince me
otherwise, unsuccessfully, I might add.

----------------------------------------------------
Del Rawlins-
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/

"- Barnyard BOb -" wrote in message

translates to aircraft because taildragger pilots EXPECT the plane
to try to
swap ends.

Jim
+++++++++++++++++++++++

TOE IN is a NO-NO for tail draggers.
Just the reverse of cars.


It depends on whether you have a front or rear wheel drive car,
toe-out for front wheel drive and toe-in for rear wheel drive,
generally speaking anyway. Just because I can't think of a car with
something quite different doesn't mean that it isn't the case, just
that I can't think of it.:-))
--
---
Cheers,
Jonathan Lowe.
/
don't bother me with insignificiant nonsence such as spelling,
I don't care if it spelt properly
/
Sometimes I fly and sometimes I just dream about it.
:-)


Read the archives.
This has been beaten to death.
Many times.


Barnyard BOb -

It depends on whether you have a front or rear wheel drive car,
toe-out for front wheel drive and toe-in for rear wheel drive,
generally speaking anyway. Just because I can't think of a car with
something quite different doesn't mean that it isn't the case, just
that I can't think of it.:-))

OK, just to add more fuel to the fire. As I said I had 20 years of doing car
alignments with repete customers so I got many chances to see "long term"
results. If a car "needs" some sort of "preset" (toe in or toe out) to
compensate for what will happen when it is driven then experience has tought me
that something is generally loose that needs fixing first. Customers want two
things; First they want the car to go down the road straight when they take
their hands off the wheel. (don't ask me why the hell they are taking their
hands off the wheel, I couldn't figure that one out). They also want their
tires to wear evenly. End of story. Tried many manufacturer's recommendations
over the years but zero toe in always proved the best to keep them happy and
coming back.
The inner side of the right tire always seems to wear more on my RV. Don't know
why and don't care. Rotating them and flipping them on the wheels each odd year
gets me 200 hours out of a set. Can't complain; cheap tires and it's the most
stable tail dragger I've ever landed. (my tail wheel springs are snug and the
wheel is the old non-pivoting type. couldn't tell you if that's good or bad)

Jim

On 18 Nov 2003 00:51:52 GMT, (JFLEISC) wrote:

Customers want two
things; First they want the car to go down the road straight when they take
their hands off the wheel. (don't ask me why the hell they are taking their
hands off the wheel, I couldn't figure that one out).
Jim

It's not that they want to drive with their hands off the steering
wheel Jim, it's that they don't want the car pulling to one side or
the other. I don't like that either. When I find that happening to
my car it drives me to distraction. I don't want to have to hold
constant pressure on the steering wheel to make sure the car is
tracking straight down the road (unless the road is crowned, or there
is a steady side wind).

I used to do alignments too. I remember one guy who came in with a
Datsun 2000Z and was complaining about it pulling to one side. Z
cars, like many Japanese cars and a lot of cars now, don't have any
adjustments for castor or camber. All I could do was adjust toe-in,
and that would not correct for a pulling condition. So I took the car
out on the road to find out if it really was pulling. The wind was
blowing strongly directly out of the west that day and the interstate
heads north and south. The car veered to the left when heading south,
and veered to the right when heading north. It COULD NOT be a
mechanical pulling problem or the car would have veered only one way.

I explained that the high winds were simply blowing his car to one
side. He didn't believe me. I suggested we go for a test drive. He
drove. We went south on the interstate, I told him to let go of the
wheel. Sure enough, it veered left. I pointed out the bending
treetops, which were showing us which way the wind was blowing. We
turned around and headed north. Same thing, let go of the wheel and
the car now veered to the right.

I explained that there was no adjustment I could make to correct for a
pulling condition, that the wind was causing his problem that day.

I still did not believe me. Drove away convinced I was just trying to
avoid doing a good alignment.

Corky Scott