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Trike nosewheel castoring

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On most of his training videos, the wonderfully-named Captain Kurt Fister bangs on about how a castoring nosewheel allows the trike to align itself with the wing during the takeoff run. 
Is this indeed a desirable design feature? Does it remove the need for the nosewheel to be steerable by the pilot?

Many thanks

David North

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I think you would be much more in control if you steered it yourself. Otherwise, the trike will turn when pulled by the wing, then go to far since it will require more wing pull the other way to straighten it up. You can also steer yourself deliberately in a direction you want to go.

Just a different point though. Castor is usually there to provide stability ie straight up and the wheel will vibrate about the vertical axis. With some negative castor the contact point between wheel and ground is trailing the point where the steering axis is and thus is "self steering" and stable. This is why all bicycles are like this - not so you can steer hands free, but so they are stable.

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Hi Andy, I’m sure you’re right that it’s desirable for the pilot to be able to intervene. But I think castor geometry a bit like a supermarket trolley would reduce the amount of skill required to get back under the wing. Especially for pilots without the use of their legs.

But I think you’re wrong about bicycle stability - the idea is that if the bike starts to lean, the front wheel automatically steers in the same direction so centrifugal force tends to throw the bike upright again. This is a completely different situation from a trike, which doesn’t lean. 
 

But I shouldn’t pontificate, I don’t even fly a trike or paramotor yet, but hopefully that will soon change. 

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Provided you are moving, a bike will steer just as well with zero castor when you lean. The wheel turns because of the gyroscopic precession. This is why the faster you go, the more stable the bike feels and the harder it is to fall over. 

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42 minutes ago, AndyB said:

Provided you are moving, a bike will steer just as well with zero castor when you lean. The wheel turns because of the gyroscopic precession. This is why the faster you go, the more stable the bike feels and the harder it is to fall over. 

So a Brompton should feel really wobbly, especially when carrying a heavy load? And a 29er should be unmanoeuvrable, especially with a lightweight rider?

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3 minutes ago, Scott Harcourt said:

Parajet’s Falco trike has a neat front wheel setup and has both castor and steering pegs. I don’t know if it is compliant with the sub 70 regs though. 
https://parajet.com/product/the-falco/

That’s exactly the sort of thing I had in mind. For some reason microlight flexwing trikes have usually  had a bicycle-type setup, as do most paratrikes. Seems wrong to me. 

I suspect the Falco weighs a lot more than 70kg, unfortunately. 

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my homemade trike. I have 2 sets of wheels so can swap them quickly for either beach or grass.

20190427_121520.thumb.jpg.f11439153a806dc334b681018602b919.jpg

I added stops on the leg rests to stop feet sliding off....

20180420_124732.thumb.jpg.07595db9a40827805f8344d51a1c3168.jpg

 

 

 

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5 minutes ago, AndyB said:

my homemade trike. I have 2 sets of wheels so can swap them quickly for either beach or grass.

20190427_121520.thumb.jpg.f11439153a806dc334b681018602b919.jpg

I added stops on the leg rests to stop feet sliding off....

20180420_124732.thumb.jpg.07595db9a40827805f8344d51a1c3168.jpg

 

 

 

Looks really good! Nice and simple, I bet it’s very light. Do you think there are any disadvantages in using a paramotor harness rather than having a trike with its own seat and karabiner bars (or whatever they’re called)?

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I rarely look up at my wing when launching as I can feel it so well through the harness. I also still have full weight shift steering so can turn without having to use brakes.

I also still foot launch...because a) it is fun and b) there are not many places I can use a trike. 

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34 minutes ago, AndyB said:

I rarely look up at my wing when launching as I can feel it so well through the harness. I also still have full weight shift steering so can turn without having to use brakes.

I also still foot launch...because a) it is fun and b) there are not many places I can use a trike. 

I don’t think I’m likely to foot launch but even so it might be a good idea for me to buy a complete secondhand paramotor outfit and build a simple trike for it, like yours. Is that a sort of bracket underneath the seat connecting it to the base tube?

 I designed and built a microlight trike many years ago, I’ll post a picture of it if I can find one. 

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On 16/01/2020 at 17:31, AndyB said:

Mine is connected to the side tubes, but there are various ways of doing it,

20180413_130255.thumb.jpg.d2ce09e1c5e84638f387dafa9b9551f0.jpg

During the takeoff and landing roll, don’t you potentially get a big bending moment where the base tube meets the assembly shown in the photo above? And in your earlier photo of the whole trike, what is that black thing that appears to connect the seat to the base tube?

I suppose in some ways it would be good to connect the suspension bars to the base tube, to spread the load, but then you wouldn’t be able to weightshift. 

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While on the ground the black thing is a lightweight plastic spacer that allows me to sit on the standard harness seat. I this position my weight is on the trike wheels. As the wing takes up my weight it lifts me off the plastic spacer so that the only weight on those mounting tubes is the weight of trike.

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4 minutes ago, AndyB said:

While on the ground the black thing is a lightweight plastic spacer that allows me to sit on the standard harness seat. I this position my weight is on the trike wheels. As the wing takes up my weight it lifts me off the plastic spacer so that the only weight on those mounting tubes is the weight of trike.

Plus whatever load is transmitted by your feet, I suppose. 
 

Have you seen the AirOne trike, which is shown on the Scout website? It has some sort of connection from the suspension bars to the base tube but I don’t know how they work. 

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In flight feet dangle down like normal. You don't even know the trike is there.

I've looked at some others. Many seem rather over-kill in terms of connections. I think the difference is whether you are intending to be in flight as per normal with a trike dangling below you......or sat on the trike, which then has to support your weight.  

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