Steering bike/trike at speed ?

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Hi all

Why does the steering on any bike/trike seem to get ' quicker ' i.e more sensitive the faster with speed ?

regards Paul
 
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I had this experience today when trying to avoid a pothole.
Just a little tweak on the steering and off the trike went (over-steer), correcting it did a similar thing in the opposite direction. A fatal zig-zag wobble almost developed as corrections were applied.
I guess at speed it just takes so little directional change to "seem" magnified in terms of "I wanted "X", but got "X times a speed-factor". The suddenness and volume of the change causes you to overcompensate the other way I think (well it did to me).
But then it was a new experience being on the Python at an appreciable speed, so I was not well-versed in steering a Python at speed.
 

Radical Brad

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The faster you are moving forward, the quicker you will be forced off course from any steering adjustment. This results in a much larger change in direction of mass, so an equally large opposing force. It's kind of like asking... why does a punch in the face hurt more when delivered by a 300 pound boxer as compared to a 7 year old kid?

Newton explained it well...

Newton's first law of motion states that "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia.

You are amplifying this effect as you increase your forward velocity!

Brad
 
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The faster you are moving forward, the quicker you will be forced off course from any steering adjustment. This results in a much larger change in direction of mass, so an equally large opposing force. It's kind of like asking... why does a punch in the face hurt more when delivered by a 300 pound boxer as compared to a 7 year old kid?

Newton explained it well...

Newton's first law of motion states that "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia.

You are amplifying this effect as you increase your forward velocity!

Brad
So the answer is ride slowly or risk a slap in the chops from a 300 pound 7-year-old :ROFLMAO:
 
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Funny, I have also been thinking about this, not that I am designing for speed. A way around it might be variable ratio steering with low reaction for slight course changes and greater with larger. Cable operation may be the easiest way of providing it with increasing radius pulling on the cable as you turn further.

Food for thought for those who have nothing to do?
 
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Variable ratio would need to work flawlessly every time. A system using something like the cams on a compound bow may give a workable solution though I've never found steering particularly onerous on karts doing the best part of 100 mph, on cars doing more and motorbikes doing the best part of 150 (anyone who saw me fall of the track at Cadwell would disagree). Given the very slow nature of a HPV I can't see the need or benefit. On an immensely fast vehicle there may be some need but outside of land speed record attempts it's currently the preserve of techno cars like the Nissan GTR. I don't really see the problem that requires a solution
 
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Going 30-40kph on a hard sandy or gravel road can provide ample opportunity for oversteering and sideways attitude. I was following someone on a trike once and there was a ridge of loose stones near the edge of the road that he found himself in when trying to avoid potholes. Ordinarily he has no problem but in this case when he tried to avoid what was about to happen, instant 90 degrees to his travel direction and the rear wheel down in a ditch. Unfortunately, I didn't have the camera rolling at the time.
 
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I can see it now. Place an order via the Internet if it isn't down, order a self-drive trike to go and pick it up an bring it home to you. You could even get it to stream a video of the ride as you pedal an exercise machine while watching the video on TV.

Could you bring me a glass of wine please, I'm busy.
 
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I genuinely think variable ratio would put you in more ditches than it will keep you out of as years of fixed ratio reflexes fail to adjust and note the speed before working out the correct steering input. I suspect you'd do a lot of wandering and crashing as the steering reacted differently according to the speed. Over correcting is certainly more likely at speed but it's linked to more than just speed. The rate at which a skid starts is probably just as important as is the reason for the skid such as ice which may spin you completely or a pothole throwing you sideways on an otherwise good surface which will allow you to recover fairly easily. If you have variable steering ratio you're just adding a further variable into an already poor situation. The current vehicles fitted with it have banks of computers controlling not just the steering but also the suspension and individual brakes to keep the car shiney side up.
 
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It probably all depends on your steering input. If it is too sensitive it may be a problem at speed. If not sensitive enough it requires too much input. I don't see that if set up right that it would be a problem. I envisage continuously variable with greater wheel angle change with steering input for only the sharper turns.

I may have to use cable steering yet due to room restrictions and providing variable would be a piece of cake with what I have in mind and it could be easily changed to non-variable if I don't like it. I'm not there yet but should be in a week or two. Will see how I go.
 
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It'll certainly be interesting from a technical viewpoint. I hope you decide to have a go as I'd love to see it in action and I hope I'm wrong and it works for you.
 
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I have seen reports of some velomobiles being a bit too sensitive at speed and the video of one almost going under a truck seems to "smell" of too much correction. Many with so-called tiller steering don't seem to have much steering room inside them but, there may be two parts to their steering.

Tillers are usually operated by moving from side to side, yet tiller steered trikes, some at least, have a universal joint at the bottom of the steering shaft allowing the column to lay down or be moved out of the way for getting in or out. Does that provide for column side to side movement for relatively straight riding and minimal direction change response and column rotation steering for tighter corners with much more direction change response? Of course, when you suddenly need it, you grab what you can at the time - with whatever results that you get.
 
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