Why do most Raptors lean right when jumping?

[Yamazuki]

Motocross/Dirt bike riders/racers rely on the centrifugal force generated by the rear tire to control their bike during jumps.

Revving the engine and getting the rear tire spinning as fast as possible will cause the front of the bike to rise.
Tapping the rear brake, while the rear tire is spinning, will cause the rear of the bike to rise, pointing the front of the bike downwards.

Obviously, dirt bike riders can adjust their position on the bike to increase the effects of these actions; but typically speaking, if the combined weight of the bike and rider are reasonably equal front to back, and a constant speed is maintained when exiting the jump (neither accelerating or decelerating), the bike will maintain a fairly flat flight path.

I know that a 300lb motorcycle with a 180lb rider is a lot different than a 6000lb Raptor, but one has to assume that a lot of the same forces apply.

But, to what extent?

Is the force created by the spinning, or stopping the spinning, of the rear wheels on a pickup, or the fact that a forward mounted V-block engine's crankshaft spins perpendicular to the direction of travel (contrary to a typical motorcycle engine crank spinning forward), enough to affect the flight characteristics of the truck?

I guess I don't know, but they can fly level.

 

[TwizzleStix]

Wow, lots of great theories here! However, I think the issue is a bit more involved in the layout of the drivetrain.

The "force" utilized in driving the truck is the engine through the drive shaft, rotating in the clockwise direction, facing the rear differential front-to-rear. The torque applied to the rear axle is therefore applying a twisting force to the truck resulting in pushing the left rear wheel (and right front) into the ground.

You can see this force in action when a RWD vehicle with an open differential almost always will spin the right rear wheel and not the left. This is because the torque load is pushing the left rear down harder, so it has more grip. If the vehicle has a LOT of power, the chassis will twist and the left front tire may be lifted off the ground.

When the truck is accelerating up to and over a jump, this torque load applied to the left rear tends lift the left rear while pushing down on the right front such that the right front lands first.

If the driver lifts off the throttle at the instant the truck hits the ramp, the truck will "fly" evenly and land essentially evenly on the front tires. This is why it takes quite some calculations and skill to launch a truck, or any RWD vehicle, such that it "flies" straight/flat to the ground or receiving ramp. In fact, the monster truck drivers understand that the throttle is an essential input to control both the longitudinal and vertical axis while in "flight".

 

[melvimbe]

No. A rigid body is one piece, one part of it can't have more momentum than another part unless the parts separate. Whatever is causing the rotation isn't gravity acting once the truck is airborne.

I don't know. If the object in question had no momentum, yes, but it does in this case, so I'm not exactly sure how this change.

No, they will stop at the same time in the same distance, just as they would fall at the same speed if you threw them off a bridge.

No. The force applied to stop the bike or semi is the same in my example, it's not proportional to the mass of the object. Say the force applied is essentially a brick wall. A bicycle at 50 mph hitting a brick wall will stop the bicycle in zero feet. A semi at 50 mph will go right through the wall. Why, because it has more momentum and thus requires more force to stop the semi than it does the bicycle.

That said, my instincts are conflicting when we are talking about gravity. I get that two objects of different mass, thrown straight up vertically will leave the ground with different momentum, and therefore it requires more force to stop the momentum of the heavier object and return it to earth. If both object reach the same height and return to earth at the same time, then different amounts of force, gravity, has to be applied to each object.

I guess that make sense, as gravity would also need to apply different amounts of force for two objects of different masses to be dropped from a distance and reach the ground at the same time.

True, but irrelevant. Momentum and acceleration are completely different things. You can't swap one for the other.

I wasn't swapping them.

You're mixing up force and velocity. If you launch them at the same velocity, they land at the same time. Depending on how long you apply the force to the different masses, the velocities may differ. The one with the higher velocity will have the longest hang time.

Ok, I think I'm getting it now. I understand the acceleration of gravity is a constant, but I was looking at the force of gravity as a constant as well...which it isn't. Gravity will apply different amounts of force to masses in order to achieve that consistent acceleration. Thus the mass of the object is not relevant, only the velocity.

 

[GordoJay]

I don't know. If the object in question had no momentum, yes, but it does in this case, so I'm not exactly sure how this change.

It's one object. It's rigid. Different parts can't have different momentum any more than they can travel at different speeds.

No. The force applied to stop the bike or semi is the same in my example, it's not proportional to the mass of the object. Say the force applied is essentially a brick wall. A bicycle at 50 mph hitting a brick wall will stop the bicycle in zero feet. A semi at 50 mph will go right through the wall. Why, because it has more momentum and thus requires more force to stop the semi than it does the bicycle.

How do you apply braking force to vehicles? With brick walls? Or brakes and tires? There's a limit to braking force you can apply before the tire starts to skid. Apply that force to each and they stop in about the same amount of time and distance. Doing it any other way leads to confusion.

Ok, I think I'm getting it now. I understand the acceleration of gravity is a constant, but I was looking at the force of gravity as a constant as well...which it isn't. Gravity will apply different amounts of force to masses in order to achieve that consistent acceleration. Thus the mass of the object is not relevant, only the velocity.

Gravity is not a force. Gravity is an acceleration. Force equals mass times acceleration. The force applied to an object by gravity is the mass of the object times the acceleration of gravity. As the mass goes up, the force goes up. We perceive that as weight.

 

[Jeff-Ohio]

Somebody else alluded to this, but you have more weight on the driver's side, so when the truck hits the jump, the shocks on the driver's side would experience more down force resulting in them contracting a tad bit more causing slightly more rebound which would culminate in the driver's side receiving a little more upward force. If that all plays out as described, the truck could land as noted.

 

[mezger]

Motocross/Dirt bike riders/racers rely on the centrifugal force generated by the rear tire to control their bike during jumps.

Revving the engine and getting the rear tire spinning as fast as possible will cause the front of the bike to rise.
Tapping the rear brake, while the rear tire is spinning, will cause the rear of the bike to rise, pointing the front of the bike downwards.

Obviously, dirt bike riders can adjust their position on the bike to increase the effects of these actions; but typically speaking, if the combined weight of the bike and rider are reasonably equal front to back, and a constant speed is maintained when exiting the jump (neither accelerating or decelerating), the bike will maintain a fairly flat flight path.

I know that a 300lb motorcycle with a 180lb rider is a lot different than a 6000lb Raptor, but one has to assume that a lot of the same forces apply.

But, to what extent?

Is the force created by the spinning, or stopping the spinning, of the rear wheels on a pickup, or the fact that a forward mounted V-block engine's crankshaft spins perpendicular to the direction of travel (contrary to a typical motorcycle engine crank spinning forward), enough to affect the flight characteristics of the truck?

I guess I don't know, but they can fly level.

WRT the bikes, yep. For an exaggerated effect, check out what RC car guys do with the cars in the air. Conservation of angular momentum. That said, because the engine's perpendicular to the wheels, as the truck noses up or down, it'll also have a small precession effect which will be very counterintuitive to many unless they've flown taildraggers. Overall, I haven't noticed that mine jumps unevenly. Its attitude for the jumps is the result of a lot of effects including shock damping, how the suspension's loaded, including being on/off throttle/brakes, turning prior to the jump, the shape of the ramp, the size of the woman in the passenger seat....

 

[TwizzleStix]

.....the size of the woman in the passenger seat....

I think this says it all. Don’t take the Honey (boo boo?) along while spanking the ....

 

[Jakenbake]

I think this says it all. Don’t take the Honey (boo boo?) along while spanking the ....

Depends on the co-driver.........I enjoy mine

 

[stevenstommyboy1]

Thank god my Raptor leans right, if it leaned left my Raptor would be a communist.