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sorry forgot i had to explain everything for the new crowd...
I think NERD is in the same boat as me.
Got to remember some of us have been here bitching at each other for over 10 years on these boards, you wont get every joke.
Just let to go man...
However, in terms of physics, it's impossible for a number of reasons. First, you weigh no more sitting down than you do standing up. Second, the spring doesn't rebound either until the suspension is equalized, or until the compressing force (the jump) is removed (so it rebounds in the air). And quite a few other reasons.
The reason the seat-bounce works is because your center of gravity is low, and because you're adding energy to the equation (throttle). Combine those two things, and you maximize the direction-changing potential of the ramp, meaning your bike leaves at an angle closer to the actual angle of the jump.
If the seat-bounce worked by the spring bouncing it into the air, you should be able to compress suspension in your garage by tying the bike down, then cutting the tie-downs, and it would bounce up into the air. But it won't do that. It'll just equalize. First, because there are linkages and dampeners in the suspension to keep it specifically from bouncing, and secondly because a spring cannot return more energy than is put into it in the first place.
That's the argument. Some here can't get it through their heads that you don't literally bounce in a seat-bounce, even though that's what it feels like.
Pit Row
Go in your bathroom and stand on your scale. Now sit on it. You weigh the same either way.
If you hit a jump with stiff legs, it's the same as hitting it sitting down. Look where the pegs are. You sit directly above them in a seat-bounce.
The difference comes from the center of gravity, and the fact that you're accelerating.
Now, on the opposite end of that, just after you reach the sitting position from standing there will be the exact amount of energy released that was gathered during the movement from standing to sitting that will reflect as in increase in numbers on the scale for a short period of time until you are completely at rest in the sitting position.
When you perform this same action on a spring the spring compresses beyond what it would be when you are sitting on it at rest and it then returns to it's at rest state. It's not enough to bounce you into the air because of the damping you speak of but it can make your bike feel "lighter" at the takeoff point for the same reason the scale reads less than what you weigh at rest when moving from the standing to sitting
position on the scale.
Having said all that I actually agree with your basic argument believe it or not. The spring does not "bounce" you off the face of a jump in a greater angle than the angle of the face of the jump. However, when you go from a standing to sitting position you are pre-loading the spring (because you do weigh more when reaching the sitting position from the standing position). If you preload the spring it can't "soak up" the jump and the bike is forced to leave the jump at the angle of the face of the jump rather than at less than the angle of the face of the jump.
Now, I do believe the return action of the spring from a pre-loaded condition does in fact help in a table to table situation. A rider can use the standing to sitting to standing movement to use the spring to an advantage.
Alright. I'm out.
When the "pros" do a seat bounce, why don't they just stand up and use stiff legs?
Let's say we take the same jump Clark did the video on.. Stand up while "seat bouncing" and then sit down while "seat bouncing". Use the same throttle control and speed for each test. The center of gravity thing is the key, I think.. But wouldn't there be more weight on the "spring" if you are sitting down, rather than standing up? That weight distribution thought process comes to mind.
If I understand the message here and in the past, the results would be the same either way.
I remember all the back and forth in the past.. This is just one of those areas where common sense show weigh out over school books..
Post a reply to: LocoMX.com and Clark Stiles telling lies...