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SibSerge · December 4th, 2019, 12:06 AM

Over the years I was giving some thoughts to how two wheeled objects turn and here is my view

The turn is accomplished by the same way as it is accomplished by other (more wheeled objects) and that's by ... you guessed it right .. by turning the steering wheel. Where the difference is in how you keep maintaining the balance while proceeding through the turn.

As the mass of the object sits above the point of contacts with the ground the inertia will try to keep the object on it's original path thus tipping the object over. Counting that force created by the linear velocity to maintain the direction of the turn can be accomplished by different means. On cars and motocycles with a side car turning left it is done by the wheel(s) running on the outside tracks. On motocycles with a side car turning right it is accomplished by the weight of the side car. On two wheeled objects like motocycles or bicycles one can only do it by shifting the weight of the motocycle and/or the rider.

Now contrary to the popular belief the vehicle does not have to be leaned into the direction of the turn. It can lean in the opposite direction as well, as long as you maintain the forces in equilibrium so the vehicle stays balanced. I proved this with both a sidecar motocycle and a bicycle. You can raise the sidecar which leans the motocycle to the left while still turning right.

On a bicycle its easy to do because they are light and the rider mass affects the stability of the system more than that of the bicycle.

Now is the tricky part with two wheeled vehicles. They have a trail which will try to keep them going straight by maintaining the balance "automaticaly" . This is the feature of the suspension geometry that essentially makes them usable. And the faster they go the more force the trail will generate and more difficult it is to upset that balance.

To make the vehicle turning one can do it multiple ways.
1. Shifting the weight to the direction of the turn. This will make the bike leaning and the steering wheel turning in the direction of the turn. From here few things can happen - the trail will try to stabilize the bike by steering the vehicle in a way so the points of contact move under the center of mass. If the weight application point is located high i.e. saddle the bike will be more successful with that as the rider will require more force to stop the bike rotation that will be happening around the axis going in the direction of travel. If the weight is applied lower - foot pegs the rider will be more successful in preventing the trail to stabilize the bike as it will have more leverage not allowing the bike to stabilize.
2. From that point if the rider finds the equilibrium the bike will be making a turn of a constant radius.
3. If the rider "over-applies" the force and keeps applying the force (the rider "wins') the bike will just tip over and collapse.
4. If the rider "over-applies" the force but the bike works faster and overcompensates (the points of contact will move on the other side) with the trail this will now move the weight of the rider onto the opposite side and the bike will now start turning in the opposite direction. This process oftentimes is called counter-steering with weight. I have done is very often on a bicycle when not holding the bars and it does work. From now we go to point number 1. and the process repeats. If they find the equilibrium we end up with #2. I Think #3 is unlikely to happen here. #4 might happen and if this process repeats we will get a so called wobble.
The weight steering is the more effective the higher the ratio of rider to vehicle weight. With bicycles that ratio can be as high as 10:1 but with heavy motocycles it could be in a range of 1:5. That's why it is not very effective on motocyles.

5. Now instead of shifting the center of mass relative to the contact patches we can shift the contact patches relative to center of mass. This can be done by counter steering with handlebars and pretty much we end up with #4 where the bike "won" but not by trailing due to lean but by trailing due to handle bars being turned by the rider.

#5 works really well with heavy bikes and riders as it is way easier to shift the point of contacts below the center of mass than move the center of mass above the point of contact.

I hope that helps... I might be mistaken with my conclusions but so far my observations have been confirmed on various types of vehicles.

December 4th, 2019, 12:06 AM	#6
SibSerge ninjette.org member Name: Sergey Location: Ontario, GTA Join Date: Oct 2019 Motorcycle(s): Ninja ZZR250 (EX250H) Posts: 213	Over the years I was giving some thoughts to how two wheeled objects turn and here is my view The turn is accomplished by the same way as it is accomplished by other (more wheeled objects) and that's by ... you guessed it right .. by turning the steering wheel. Where the difference is in how you keep maintaining the balance while proceeding through the turn. As the mass of the object sits above the point of contacts with the ground the inertia will try to keep the object on it's original path thus tipping the object over. Counting that force created by the linear velocity to maintain the direction of the turn can be accomplished by different means. On cars and motocycles with a side car turning left it is done by the wheel(s) running on the outside tracks. On motocycles with a side car turning right it is accomplished by the weight of the side car. On two wheeled objects like motocycles or bicycles one can only do it by shifting the weight of the motocycle and/or the rider. Now contrary to the popular belief the vehicle does not have to be leaned into the direction of the turn. It can lean in the opposite direction as well, as long as you maintain the forces in equilibrium so the vehicle stays balanced. I proved this with both a sidecar motocycle and a bicycle. You can raise the sidecar which leans the motocycle to the left while still turning right. On a bicycle its easy to do because they are light and the rider mass affects the stability of the system more than that of the bicycle. Now is the tricky part with two wheeled vehicles. They have a trail which will try to keep them going straight by maintaining the balance "automaticaly" . This is the feature of the suspension geometry that essentially makes them usable. And the faster they go the more force the trail will generate and more difficult it is to upset that balance. To make the vehicle turning one can do it multiple ways. 1. Shifting the weight to the direction of the turn. This will make the bike leaning and the steering wheel turning in the direction of the turn. From here few things can happen - the trail will try to stabilize the bike by steering the vehicle in a way so the points of contact move under the center of mass. If the weight application point is located high i.e. saddle the bike will be more successful with that as the rider will require more force to stop the bike rotation that will be happening around the axis going in the direction of travel. If the weight is applied lower - foot pegs the rider will be more successful in preventing the trail to stabilize the bike as it will have more leverage not allowing the bike to stabilize. 2. From that point if the rider finds the equilibrium the bike will be making a turn of a constant radius. 3. If the rider "over-applies" the force and keeps applying the force (the rider "wins') the bike will just tip over and collapse. 4. If the rider "over-applies" the force but the bike works faster and overcompensates (the points of contact will move on the other side) with the trail this will now move the weight of the rider onto the opposite side and the bike will now start turning in the opposite direction. This process oftentimes is called counter-steering with weight. I have done is very often on a bicycle when not holding the bars and it does work. From now we go to point number 1. and the process repeats. If they find the equilibrium we end up with #2. I Think #3 is unlikely to happen here. #4 might happen and if this process repeats we will get a so called wobble. The weight steering is the more effective the higher the ratio of rider to vehicle weight. With bicycles that ratio can be as high as 10:1 but with heavy motocycles it could be in a range of 1:5. That's why it is not very effective on motocyles. 5. Now instead of shifting the center of mass relative to the contact patches we can shift the contact patches relative to center of mass. This can be done by counter steering with handlebars and pretty much we end up with #4 where the bike "won" but not by trailing due to lean but by trailing due to handle bars being turned by the rider. #5 works really well with heavy bikes and riders as it is way easier to shift the point of contacts below the center of mass than move the center of mass above the point of contact. I hope that helps... I might be mistaken with my conclusions but so far my observations have been confirmed on various types of vehicles.