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Maybe doing it to be better planted on the seat?
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So you are saying that loading/flexing a bicycle frame in the downward direction is propelling it forward, right? How?
Maybe you thought I meant that you could push on an angled hill and somehow get up it? Sorry, I was assuming having some type of feature to help manipulate your motion. Just like a jump face, your trajectory will depend on a lot including whether or not you seat bounce.
always argued if you push straight down on a damped suspended bike it doesnt bounce back.. We get that.
The reason we set the sag and rebound properly is because if the spring is cranked down to tight and the rear end is rebounding to fast it will literally bounce the rear end over the front end off the face of a jump!
If you start paying attention in photos, it's crazy how often riders feet are off the pegs and in weird positions.
The pump track only works because the rollers cause a difference in height. Time going up the face with being as light as possible with the exact opposite on the back and you end up accelerating.
Flexing the frame on a bicycle has nothing major to do with a pump track. Think about this: you can only put force into a bicycle frame by loading it vertically through the wheels. If the wheels/ground cause a reaction force, how could that propel in you the horizontal direction?
Also, if loading up the bike frame did cause any type of acceleration, you would see truly weird things happen when you flat land bc that is much higher force than you generate on a pump track.
The table to table argument doesn’t involve seat bouncing. All the ones I remember involved standing and most had a slight incline at the end. I also remember how many rear wheels clipped the face of the next table. And are you saying that jumping up and landing on a tabletop can cause a bike to bounce, but Tomac and crew airing it out over HUGE singles and flat landing doesn’t cause the same reaction? Both situations is a flat landing with the riders on the throttle. I’ve seen this with sx and mx suspension with the same reaction.
Here’s the only “moments in time” that matters. Look at the rear shock. Compressed until the same time you see the tire rebound to its original shape,
which is when the rear wheel leaves the ground.
Pit Row
Seat bouncing works because riders time the release of the spring to coincide with their upward momentum, thus pairing their own mass to the bike's. They can just as easily cancel out the spring by standing and soaking up some of the upward momentum with their legs and/or turning the bike at the right time. (Scrub to stay low, seat bounce to go high.)
I'd like to see more pictures like the ones above, done in several passes, some standing and some sitting. I think they would illustrate what I'm saying: that the shock can be purposely compressed more by the rider's judicious application of weight at the right time; that it travels downward until a specific point in time, when it begins to return (and does not remain "compressed" the entire time up the jump face, but rather begins to rebound); and that a skilled rider can time those events to minimize or maximize the upward velocity from the energy returned by the shock spring.
And a pogo stick has no damping to control rebound.
You mention mass of rider. Why? Projectile motion doesn’t care about mass. The bike is bottomed out and doesn’t unload until you’re off the face, so it doesn’t matter if you weigh 150lb or 200lb. All that matters on take off is speed and launch angle. And that’s exactly what seat bouncing gives you more of.
I’ve already posted pics (literally the first video I found on YouTube) and you’re basically ignoring the fact it shows exactly what I’m saying.
Last thing, if it really is the rear shock springing back that causes extra distance, then:
1. Why doesn’t the bike nose over immediately if all the force is being provided from the rear spring?
2. At what point would the shock begin to unload and why do we not see wheel spin at some point on the jump face?
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