Mailing List lml@lancaironline.net Message #7448
From: Hapgood, Matt <matt.hapgood@funb.com>
Subject: toe (and I am not talking about feet)
Date: Tue, 7 Nov 2000 11:08:15 -0500
To: 'lancair.list@olsusa.com' <lancair.list@olsusa.com>
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First Union Securities, Inc.

I checked my toe last night. The toe on my plane.

Not the most scientific method, but I think the relative aspect should be
okay.

I measured distance between the main gear at the front side and back side of
the tire (I picked as my reference the second line on the tire tread).  I
know the tire tread isn't necessarily consistent all the way around the tire
- but I would think this is not too far off?

The difference indicated toe-IN of about 1/4".  This sure seems like a lot.
What is a reasonable amount of toe?  And what is a better method of
measuring.  I thought the best method would be to measure off the brake disk
(attach a thin but rigid piece of metal to the disk that extends in front of
and behind the tire.  Do this on both sides and measure the distance at the
front and rear between the main gear.

I can do this and measure - but what is a good range for toe-in?  Of course
the distance will change based on how far away from (in front/behind) the
axle I measure.  So how far away should I measure.

If I extrapolate from my knowledge of car suspension set-up:
Toe out will cause a car to be darty under braking but it will turn well-
not something that would be desirable in a plane!
Toe in increases straight line stability but makes turning kinda sluggish.
This sounds good on a runway!
Too much toe in either direction increases tire wear - how much is too much?

Thanks,

Matt

[When installing my gear I was unhappy with the recommended method of
checking alignment, and so used a pair of four foot aluminum angles clamped
to the wheels as my indicators.  I dropped a plumb-bob from the C/L of
the firewall and the tail and stretched a string along the floor from
front to back to ascertain the C/L of the fuselage.  I put pieces of tape
22" out from the center of the wheel on each end of the aluminum angles
and then measured from the edge of the angle to the A/C C/L perpendicular
to the gauge bar at each tape marker.  I adjusted the toe-in so the
distances at the front markers were 1/8" less than the distances at the
rear markers.  This is a very minimal amount of toe-in, but it's at least
a little, and considering the imprecise method of checking it given in the
manual, far more precise than is probably required.  I am, however, very
comfortable in the knowledge that the track of the mains is as close to
parallel with the fore/aft C/L of the aircraft as it needs to be while
still having a little toe-in available for handling.  I did need to deflate
the tires considerably to allow my "pointers" to be clamped tightly to the
wheels.  I hope this helps.        <Marv>       ]


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