3 Axis wheel tracking

[Aerosan]

So to all the boffins, the main wheels on my plane needs tracking and I would like to get some opinions on the matter.
It is a trike cofiguration and I would like to know (looking from the front) should the wheels be perfectly perpendicular to the tar and if not how then.
Then looking from the top, again, should it be perpendicular to the direction of travel and if not how then . I will be interesting to see the different responses.

thanx
San

[Junkie]

ahhhhh.. this is an ugly un in my view...

The prev owner of my Gemini got smart and straigtened the axles, cause he though it looked "kak" and in his words 'I wished I was on another planet' when he tried to land it again - the darn thing goosewalked like a pregnant hippo and he almost wiped himself out

Anyway he set it back with some toe in and camber to what he thought it was and its b4 - well, I can only say it been 'ok' since (99%) - but it WILL catch the inexperienced or unwary out every now and then if landing too slow and not quite straight down the centreline

I pranged the trike the very first time I flew it @ 15hrs as a result of a wild goosewalk - now I come in with positive speed and contact with the ground and then hold off, try to hold off and get too slow

The Gemini has a somewhat narrower undercart across the back wheels - I also replaced the narrow wheels with wider jobies that also seemed to have helped eliminate the wobblies (ya ya i know call me a 'kak' trike pilot) anyway check with your manufacturer before buggering around with it

Oh bye the way - it was the starter turn this weekend to fall off (had to prop star the plane at Wintervogel cause all that was hold the starter on was the cable - crappy Sidewinder & Vibration... goingto get me a C or E box real soon!!!!!

[John Young]

J.U.N.K.I.E 's
Finest used aviation parts in all the Universe
No credit / No returns

Ah, Junkman, so this is how the used parts collection started.

Aerosan – a toe-in setting is a prerequisite for directional stability when rolling. I put it to you that a car is almost impossible to steer in a straight line with a toe-out setting.

If necessary or if you like, I can explain / expand.

Regards
John ZU-CIB

[Aerosan]

Hi gents

Junlman as long as the pilot doesnt fall off alls well that ends well I always say

Yes John Id like it very much if you could do a bit of explaining on the subject. I did some research on the topic once as I used to be the scribe for our Radio controll club and therefore had to do topics for the news letter. But try as I might I cant find the notes I made. I would like to understand the whole story as to propperly do the wheel bits.

Thanx sirs.

Cheers San

[Morph]

Aerosan,

don't you have the manual for your plane? I know on mine the main wheels must have a slight toe-in adjustment. I can't remember exactly how much through.

In my case you use a straight rod/aluminium pole, with a right angle. Use blocks of wood etc to lift the rod so it touches the front of the tyre at axle height. Now use the right angle, plced against the rod and along the outside of the tyre. The attached pic is an extreme example to show you the technique. Adjust the distance between the right angle and the front of the tyre. They must be the same for both tyres and according to your manual.

My plane has tensioning cables going from the axles forward to a point on the fuse. You adjust the toe-in by incresing the tension. If you look at the cable to will see a twist in the threads. Releasing one of the bolts and twist the cable in the same direction and the twist of the threads to increase tension and against the twist to release.

[John Young]

Yes John Id like it very much if you could do a bit of explaining on the subject.

Hi Areosan,

Regarding your request for a more detailed explanation on toe-settings.

Please refer to the sketches below [A, B, C & D] showing hugely exaggerated angles for demonstration purposes.

I stated before that a toe-in setting is required for directional stability. This is described below, viz.

Sketch A

Toe-in setting which creates equal but stable drag from the rear tyres, because;

Sketch B

When “cocked” to the left as illustrated, the right rear tyre will produce the most drag and assist with the directional correction. Note nose wheel input from the “pilot”.

Sketch C

Toe-out setting which creates equal but unstable drag from the rear tyres, because;

Sketch D

When “cocked” to the left as illustrated, the left rear tyre will now produce the most drag pulling the plane off line. In severe cases, the left rear tyre will begin “hopping” which could lead to the very undesirable position of being caught in a “goose walk”.

If you like, I could also provide you with fuller explanations in terms of the effects from camber and castor angles.

Regards
John ZU-CIB

[Aerosan]

Thanx John
nice illustration I must say


Cheers San

[Duck Rogers]

Thanx John
nice illustration I must say

That means he didn't understand anything

[Aerosan]

yes Duckie and youre ugly at least I can learn and understand, but that still leaves you ugly

[Tailspin]

When setting up the wheel alignment on my VP(Taildragger) i was told to have slight toein, as on landing the wheels would be forced outwards and it the wheels are straight then it could cause a goose step or a groundloop, or worse

[John Young]

When setting up the wheel alignment on my VP(Taildragger) i was told to have slight toein, as on landing the wheels would be forced outwards and if the wheels were straight then it could cause a goose step or a groundloop, or worse

Agreed 100%.

Wheel geometry must be set at the correct ride height - that position in the suspension travel at normal load.

Under absolutely no circumstance do you want to encounter toe-out, negative camber or negative castor under full load [full suspension travel] - although in our case, toe-out would be the worst.