Goose-step?

[Bayliner]

Thanks for explaining Splinter.

I remember as a youngster I had one of those old fashioned chopper bicycles, the one with the very small front wheel. When you wheelie the front wheel spins. If you put down the front wheel while it was still spinning the potential for a speed wobble was far less than when the wheel had stopped spinning. I should imagine that this was a result of centrifugal action being, if I may term it this way, turned on or off.

When a plane lands, just before touch down the wheels are not turning. I was just wondering if this could be caused by "chopper wheel syndrome"

[Petrodactyl]

The manufacturer may specify toe-in on the back wheels, but my intuition tells me that if the main gear of an aircraft toes in then the wheel that touches first will try to tuck under the aircraft, whereas if they toe out, the wheel that touches first will bring the other down, which I would think is better. Having been involved with the set-up of the main gear on LM's Waiex, I checked out how the wheel toes out when it is loaded, and this confirmed my speculation.

Please could some of you older and wiser builders give us the benefit of your experience and wisdom with the set-up of main gear geometry.

I would check the whole rear undercarriage assembly - drag-link joints, axle connection and alignment, shock mountings top and bottom, lower control arm pivots, wheel bearings - for play, damage or misalignment. If possible stiffen up the front fork so that it is harder to turn - I have seen small dampers fitted on trike steering.

I know that a pod in a crosswind is more of a handfull - it is harder to get the trike straight in ground-effect just before touch down. Also, the 'cobra bite' might be a factor - in certain conditions the cobra pod seems to produce lift, which can have the effect of rolling the trike.

[John Young]

The manufacturer may specify toe-in on the back wheels, but my intuition tells me that if the main gear of an aircraft toes in then the wheel that touches first will try to tuck under the aircraft, whereas if they toe out, the wheel that touches first will bring the other down, which I would think is better.

Hi,

A toe-in setting is a prerequisite for directional stability.

In the diagram below , the starboard wheel would have more drag and tend to guide the trike back on centre line.

On the other hand (Darren), in [D], the port wheel would have more drag with the toe-out and tend to pull the trike further off line.

Regards
John ZU-sEXY

[Splinter]

The manufacturer may specify toe-in on the back wheels, but my intuition tells me that if the main gear of an aircraft toes in then the wheel that touches first will try to tuck under the aircraft, whereas if they toe out, the wheel that touches first will bring the other down, which I would think is better.

Hi,

A toe-in setting is a prerequisite for directional stability.

In the diagram below , the starboard wheel would have more drag and tend to guide the trike back on centre line.

On the other hand (Darren), in [D], the port wheel would have more drag with the toe-out and tend to pull the trike further off line.

Regards
John ZU-sEXY

Thanx John that makes sense. Spoke to Rainbow and they recommend toe in for directional stability as you said. Spoke to a well known instructor at Springs (once a builder on trikes) and he recommended toe out because of the wheel "tucking" under the aircraft..... The diagram makes it simple.

Splinter

[Bozz]

Following on from the above discussion, how would I adjust the toe-in/out on a windlass?
The rear axles are mounted onto an aluminium down strut with a bungy cord.
I don't think shims can be fitted anywhere. Is bending the axle the correct method and how do you do it?

[Trikenut]

Bayliner: Another example of a goose step is: When you are wheeling a suitcase with wheels through an airport, and it starts to wobble and then jumps from one wheel to the other.
In trikes, I believe that the other way to cause a goose step is when doing a crosswind landing. If you don't do it properly, one of the wheels can hit before the other causing it to goose-step.

[MILO]

Splinter, did you guys figure out what was going on here?

[Splinter]

Splinter, did you guys figure out what was going on here?

Hi Milo. Yes we got the problem sorted thanx to GREAT help from Rainbow! They took the trike and went through every single thing. The problem was in the front steering. The shaft in the front steering was made out of mild steel and would build up rust and residue over time causing some "stiffness" in the steering. When making small steering adjustments on the runway it would "oversteer" as it was stuck and then suddenly turned. The plane has always had a bit of a stiff steering but once the stiffness is not the same all around the shaft it would steer difficult and the suddenly jump to the next stiff point. The "jump" was only a few millimeters (2 or 3) and very hard to notice but it caused a serious problem.

We flew landed on Springs (Tar), Groblersdal (Tar), Hazyview (gravel/grass) and Middelburg (Tar) the weekend in diffirent wind conditions (on the runway and 90 deg crosswinds) and have not hade any further problems.

Regards
Splinter

[Trikenut]

Nice to hear this Splinter!

[Thatchman]

Not the first time that a stiffie has caused problems

Glad it got sorted before anything serious happened.

[Petrodactyl]

Thanks for the explanation, John. I undertand the toe-in logic now.

I have on occasion tightened up the rear steering on our training Aquilla to stop the front wheel being so 'squirrelly' (as they say in the US). From Splinters experience I can now see that this can be overdone. It is always amazing how something seemingly insignificant can have such drastic consequences.

Thanks for giving us the benefit of your experience.

[redrocket]

Hi Manne.
I have seen similar happen to a Windlass.
The instructor was on the trike with his student and called for a tyre change which he was correct with.
The old offending tyres was the extra wide type with tyre pressure too low causing the tyre to float around resulting in either a goose step or if you skrik and gooi juice it keels the whole plane over and you take off with the whole undercarriage at an angle ,one rear wheel on the ground. Just remember to keep the wing tip awy from the floor!!

For the longer ride "go wide" CAN cause problems if the pressure is too low.

Regards
redrocket