Axle Slot Angle - What Effect?

[Bookmaker]

I have a question for you physics and taildragger experts.

I am working on the landing gear of my AA Nieuport 17 and got to thinking about the angle of the axle slot in the V of the landing gear.

The way the kit is currently designed, the slot angles a little forward at the top when the plane is in flying attitude. This angle resulted when AA modified the gear from the forward legs being vertical to swept back at the bottom. The slot is parallel with the front legs.

My setup, which is basically a copy of Rick Bennett's, produces an angle toward the rear at the top when in flying position. A review of the Hardesty and Rosendahl (sp) drawings shows a slight angle back at the top.

Fokkers, Sopwiths, etc. seem to be vertical.

It would appear to me that the different angles of the axle slots would cause a steering action on landing and takeoff when one side of the axle moves up more than the other.

Does anyone have any data, or comments on this?

Dale

[snj5]

Let's assume the case when they are perpindicular. As the the plane settles and the bungees start to deflect, this adds a bit of camber to the main wheels with respect to the plane. As the plane goes into the THREE POINT ATTITUDE, this camber becomes an effective toe-out, which is stabilizing.

It seems to me, that if the angle is deflected further aft, this adds more toe out, and thereby adds more stability and resistance to ground looping.

[Bookmaker]

That is assuming a split axle like the Sopwiths. The Nieuport has a straight axle. There is no camber change. I don't think. However, if the axle moves forward when compressed, that would seem to cause a steering change since one end of the axle is now forward of the other relative to the centerline of the plane. Opposite steering, if the axle moves back as compressed.

In my set up, if my plane rolls left on touchdown, the left end of the axle would move up and back. It would seem that that would induce a little left steering. Maybe a benefit should the plane swing right, loading the left side of the axle.

Dale

[snj5]

Sorry - forgot it was the Nieuport.
As I sit here and ponder on it, if a ground loop starts to develop lifting the right wing and starting a swing to the right, the asymmetric loading on the axle bungees woul serve to pivot the left gear up and back as opposed to the relatively unloaded right main, giving a degree of toe out with reference to the direction of motion which acts to counteract the swing much more than if the wheel were held straight. The tilted slot acts to tilt the axle in the asymmetric load during the swing.

[Dart]

Hmmm, that's my thinking as well - a slight angle to the rear (from bottom to top) won't hurt and might actually be good; if it were reversed it would be bad.

I don't think you have enough angle to really matter, though. If one is really far into a ground loop position to begin with the slot angle won't be that much of a factor; one is going around.

[RAF56_Ball]

I am way too inexperienced to be certain, but my impression is that most ground loops happen at speeds wehre the tail is usuallydown or on its way? Therefore the slot angle is likely to already be angled aft relative to the ground and a degree or two either way won't change the dynamics much? But this is purely "guess-timation".