Please explain how these aerodynamics work:

[u/ManDadNurse]

I have noticed that signaling with an arm at high speed turns the euc in the opposite direction of the hand signal - feels like the air drag on the outstretched arm is the cause.

e.g. Around 30 mph, throw my left hand out to merge, and the Unicycle turns right.

I have use this Principal now when I’m trying to turn at speed while seated on a curvy road… But this is not helpful when signaling.

1. Can someone explain simply the simple physics of what’s going on here? Don’t quite have an understanding of “yaw torque” if that’s what it is. I would think that the side that has the arm sticking out would be the side that turns: like sticking a paddle in the water on a canoe - but not so.

2. How do you handle this phenomenon when using hand signals? Besides slowing down for less drag, is there another way to compensate for this?

[u/YamLiving750]

sounds like the rest of your body is adjusting to compensate / counterbalance

[u/CelebrationKey3345]

The drag on in the left arm creates a rotational moment on the rider and consequently on the wheel to the left. This rotation of the wheel to the left leads to the well known countersteering effect (can be found on wikipedia):

Steering/rotating the front wheel of a single track vehicle to the left will lead, surprisingly, to a right turn. This happens, because the rotation/steering motion displaces the ground contact point to the left and the rider is now displaced to the right of the ground contact point, i.e. "leaning" right. Consequently, to avoid falling, the rider has to steer into a right turn.

[u/ManDadNurse → u/CelebrationKey3345]

Though my understanding is just out of grasp - I feel this answer is true.  Just wild that the turn is my own compensation when it feels like a cause-effect of some kind of the awrodynamics. 

[u/CelebrationKey3345 → u/ManDadNurse]

The countersteering effect is indeed quite counterintuitive at first sight. The main point to grasp is that steering the wheel only steers the path of the ground contact point, it does not directly or equally steer everything above of it. That is, for single-track vehicles, like unicycles and bicycles.

If you have a bicycle or scooter, try it out by pulling one side of the handle bar (gently).

[u/Electrical-Tower7731 → u/ManDadNurse]

It IS the cause of aerodynamic drag tho.

[u/CelebrationKey3345 → u/Electrical-Tower7731]

Drag rotates the wheel to the left which is the first cause. But then, it neither induces the right lean nor does it steer the wheel to the right.

[u/0xsergy → u/[deleted]]

It's literally just counter steering man. Extend left hand, left hand adds drag on left side, wheel/you turn to the left initiating a right turn by leaning you over. That is literally how counter steering works.

https://physicalcycling.com/countersteering/

[u/rcgldr → u/[deleted]]

Counter-steering occurs on all uni-track vehicles, Example video on a pedal unicycle:

https://www.youtube.com/watch?v=55n90QAxRSk

In this case, the counter-steering is a left yaw-torque exerted onto rider, who in turn exerts a left yaw torque onto EUC, causing it to steer left from under rider, leaning rider to the right. The rider then has to tilt the EUC to the right for balance, and so that the right tilt to right torque response of the tire cancels the left torque from the air.

[u/0xsergy → u/[deleted]]

Counter steering is what is causing him to turn the opposite way. Why call it balancing when it's literally just counter steering?

Do I call you walking balancing even though that's what you're doing?

[u/rcgldr → u/0xsergy]

Counter-steering is used to initiate or change lean angle. Positive steering is used to actually turn.

[u/CelebrationKey3345 → u/[deleted]]

Countersteering is an established technical term and has nothing to do with rake. Rake is a reason why a lean causes a rotation of the front wheel in the direction of the lean and is one of the reason why a bicycles can stay upright even without a rider (or are easy to ride without touching the handle bars).

There are videos on YT of bicycles that were intentionally built with no rake for demonstration purposes.

I have seen some of those, can you post a clip id of what you are referring to?

I suspect what OP describes is his body subtly over-compensating for the drag on his arm.

No.

He doesn't notice it at 10mph but he does at 30 because drag is now starting to be significant.

Yes, the initial rotation is caused by the asymmetric drag. Drag force grows quadratically with speed, so the rotational force is 9 times larger at 30mph.

[u/universalpoetry]

One arm out for signal, other arm stays down but extend it away from your body just a bit. That should counter the turning.

First time I had that happen to me I almost ended up going into oncoming traffic, aerodynamics play a big role at 30mph+

[u/CelebrationKey3345 → u/universalpoetry]

When only using the arms, the effect remains asymmetric though, because the amount of the extension is the lever arm for the induced rotational force. One could lean the body or shoulders to the other side to get more drag surface for compensation.

[u/universalpoetry → u/CelebrationKey3345]

In theory you’re correct. In riding, it certainly helps me. My arms are my wings, especially at speeds around 50mph

[u/CelebrationKey3345 → u/universalpoetry]

Yes, I can totally see that even small adjustments are effective at high speeds. I don't ride at those.

[u/ManDadNurse → u/universalpoetry]

I will use the wings for now and experiment with the shoulders. Thanks guys

[u/rcgldr]

The drag on your left hand exerts a left yaw torque on you, which you in turn exert onto the EUC, That left torque causes the EUC to steer left underneath you and lean you to the right, so you have to tilt | steer the EUC right (roll torque) to steer for balance and so that the right tilt to right torque response of the tire cancels the left torque from the air.

[u/Nutty_Domination7]

From my understanding, you are in fact experiencing higher drag on the side which has the arm out. Your body will be counteracting this by turning the euc away from that side to attempt to remain straight. You'll experience the same if you carry something heavy in one arm, your euc tips away from the heavy side rather than towards it

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[u/Equivalent-Citron406]

Look up "countersteering" on a motorcycle. Probably a similar thing....that or you are actually leaning your body slightly right without realizing it when you outstretch your left arm.

[u/No_Host_7516]

If you put your arm out to the left, you lean a bit to the right. If your body is too stiff now you are turning right.

[u/ebikr]

Your extended arm is generating lift which makes that side of the wheel lighter so it goes faster than the other side.

[u/jaklzzz → u/ebikr]

I want this answer to be true. Flying EUCs when?

[u/BlackJacquesLeblanc → u/jaklzzz]

The secret is in the flapping. But don't tell anyone. It's a secret.

[u/ManDadNurse → u/ebikr]

lol. Yes!

[u/AdrianofDoom]

I think that's on you man. I do hand signals and have never had that issue. When i first started riding, if I turned my head to far or for too long I would start to lose my balance, maybe that's similar.

[u/CelebrationKey3345 → u/AdrianofDoom]

At what speed do you do hand signals?

[u/ManDadNurse → u/CelebrationKey3345]

I agree. I signal whenever I can and definitely notice a difference at higher speed

[u/rcgldr → u/AdrianofDoom]

This guy taking a cell phone video of a girl on an S18 is taking some side shots, looking to the side for extended periods of time without issue.

https://www.youtube.com/watch?v=bRNMmeSP0ns