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getting more distance?

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The ONLY meaningful factor that determines distance travelled is the velocity vector at the moment contact is broken.  A vector is comprised of magnitude (speed) and direction (the trajectory angle of the net center of mass at the moment the rear tire breaks contact). Yeah yeah...drag to weight impact a little...but we are talking inches...  So when you preload or seat bounce, what happens?  How does the 'vector' change?

 

1.  The bike and rider initially do not assume the trajectory of the jump face, as the suspension loads up.  The wheels of the bike will be following the jump face...but the rider and bike are not. This stores energy in the springs (less that energy which is dampened away by compression damping).

2.  As the suspension stops loading...for an instant the rider and the spung mass of the bike are tracking the jump face.

3.  Later up the face....as the bike rebounds....the bike and rider are rising at a STEEPER angle than the jump face.  By preloading...you exaggerate this effect.  By absorbing, you reduce or even counteract effect.  Scrubbing legit (like Bubba or Trey) is an extreme example of this.  By laying the bike over...you dramatically lower the trajectory of the center of mass.

 

The last phase only occurs at the end of the jump, which explains why preloading can have a HUGE impact on distance.  If the rebounding occurs over the last 36" of a jump face (a reasonable assumption if you watch some film), and that face is 30 degrees steep...and over that distance...the suspension unloads such that the center of mass rises 8" normal to the jump face plane...how much will that impact distance?  If you do some trig...you will find that additional 8" rise over the last 36" boosts the trajectory angle from 30 degrees....to 42.5 degrees.  So...what impact would have have on distance  (defned as return to the plane where contact was broken...ie the jump top).  Lets assume 30 mph, and a baseline 30 degree face angle.

 

30 mph, 30 degree trajectory.  This is what would happen if you have a VERY long jump face...so that the rider/bike center of mass track the face as you take flight:  52 feet

30 mph, 42.5 degree trajectory.  This is the preload example...with 8" normal rebound over the last 36" of the face:  60 feet

 

But what if you stand tall...then aborb...such that you lower center of mass toward the top of the face.  If done properly, you can easily lower center of mass by about 4" over that same distance.  This is the classic absorbing technique.  If you do this, the trajectory angle drops from 30 degrees to 23.66 degrees.  44 feet

 

Finally...what if the rider who is preloading a bit (the more aggressive guy) is also increasing his throttle into the face...and he gains a few mph up the face..so that his velocity is now 32 mph?:  68 feet

 

Rider A goes 44 feet...and rider B goes 68 feet....and at the base of the jump...they were going the same speed.

 

Weight has virtually no impact on this aspect of the dynamic system, because the heavier rider simply stores more energy in the spring...so he gets more energy back.  The only place where weight makes a difference is frequency response.  A smaller rider, even will a lesser spring, whill probably have a rear spring system natural frequency that is higher than that of the heavier rider...meaning he will start to rebound SOONER on the jump face.  (Probably a minor effect....but is also goes towards explaining why bigger riders can hammer the whoops easier....lower natural frequency)

 

So.... the same jump face hit at the same speed...but differing loading and absorbing techniques can make a huge difference. My quess is the OP is intimidated, and he is unconciously absorbing jump faces...while his buddy is pushing down at the right time, and probably adding throttle to put energy into the rear spring...thus causing his trajectory to be altered the other way....

 

This is pretty much what DT was trying to say originally...and he was right.  It perhaps could have been explained a bit more clearly in laymens terms.

 

With regards to Engineers, I can say with certainty that when Engineers screw things up,  the most common cause is their over-simplification of the problem, and this is usually a result of inexperience.  Green Engineers focus on the primary aspect(s) of the system, and then focus on the basicy theory that applies to that part of the system.  The catch is that most systems are so much more complex than is recognized.  I say this as a degreed Engineer (Columbia Univeristy..a top program), who worked in Engineering for over a decade.  My area of focus is rotating machinery...specifically large custom engineered pumps, up to 10,000 HP.....  I now work in technical sales management, but still do a lot of field engineering, because when things go wrong...I get the call.  My customers are pretty much all Engineers....so I know how we/they think.  I see how mistakes get made, all the time.  I made my share....(one of which came within inches of killing someone)  Really good Engineers are often willing to admit when their initial conclusions were wrong.  They are worth their weight in gold...or more.  The problem with many engineers, is they are INTP personality types, who become too attached to IDEAS.  Their egos get tied up in being right, in having the idea, the answer.

 

If you dont want to look up the physcis...and figure out the parabolic trajectory relationships...here is a calculator...

 

http://www.calctool.org/CALC/phys/newtonian/projectile

 

 

point taken about rebound playing a roll. I shouldn't have said suspension won't effect distance. 8/36 is extreme. It makes sense why most fmx ramps aren't constant radius.

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guess what bro, sitting in your chain, right now, gravity is accelerating you downward. Just because you aren't moving, doesn't mean you aren't being accelerated. You have a equal and opposite force acting on you at the same time as gravity. Feel the chair? That is the chair pushing back with a force equal to your mass*gravity. Gravity and chair force balance each other. Pull the chair out, removing the chair force, and you fall on your ass. Gravity doesn't 'appear' all the sudden because you remove the chair, the same way gravity doesn't show up suddenly when leaving a jump lip and disappear when you.

Thanks for showing you lack of middle school science understanding again. It so happens acceleration is defined as a change in velocity. If you are not moving and stay unmoving, as in sitting in a chair, there is zero acceleration. That says nothing of forces, like gravity and the normal force (google if you must) from the chair. Gravity is a force, not an acceleration. The only way it could go away / reappear when stationary is if it were accelation as you insist it is. Perhaps you should read a 7th grade textbook to understand force vs. acceleration and how they are related?

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how do you preload with out seat bounce? jump on your bike on the face off the jump?

Yes, jump you weight into the pegs as the bike compresses into the jump. Right after that it's going to rebound and that's when you jump your weight out of the pegs. Start out real small and easy in order to get it down. 

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Thanks for showing you lack of middle school science understanding again. It so happens acceleration is defined as a change in velocity. If you are not moving and stay unmoving, as in sitting in a chair, there is zero acceleration. That says nothing of forces, like gravity and the normal force (google if you must) from the chair. Gravity is a force, not an acceleration. The only way it could go away / reappear when stationary is if it were accelation as you insist it is. Perhaps you should read a 7th grade textbook to understand force vs. acceleration and how they are related?

hahaha you respond to him needing to read a 7th grade text book after all the stuf he has said here? I bet you dont actually understand half of whats in here and you want to try and clown him? There is acceleration there.. its zero but that is a force. You understand acceleration as movement but it is directly proportional to force. Thats explained in newtons second law of motion. Meaning if one is there so is the other. Maybe you shouldn't have quit school right after 7th grade. He has proven that he is an engineer and knows what he is talking about... he is wrong (imo) with some of his thoughts but he is going off of definition and pryor experience/ knowledge for the theories, but in him being wrong he has made his self right because he has proved what is really going on here. YOU dont u derstand... thats fine but I dont think you have ANY ground to stand on saying he doesnt have an education. Just makes you look stupid. Edited by T-Doshi9

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Yes, jump you weight into the pegs as the bike compresses into the jump. Right after that it's going to rebound and that's when you jump your weight out of the pegs. Start out real small and easy in order to get it down. 

ok thx

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Gary semics is the only guy you should listen to period!...wow this went from how d I get more pop to a physics lesson from a bunch of average goes ...just go do it practice practice

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Gary semics is the only guy you should listen to period!...wow this went from how d I get more pop to a physics lesson from a bunch of average goes ...just go do it practice practice

Definitely did not turn into a lesson on literacy.

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Gary semics is the only guy you should listen to period!...wow this went from how d I get more pop to a physics lesson from a bunch of average goes ...just go do it practice practice

that was already said. I really havent read anything in here that was wrong. Just diff ways of saying the same thing. And one person seems to think a bit diff from the rest. But he is trying to prove himself right so it is what it is. Those average "joes" have already said go ride and redo the susp of his bike. He asked for an explanation and well thats where physics play in... So like it or not every answer here is right and exactly what op asked for.
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the same basic questions come up on what feels like a weekly basis. All the same shit has been covered 1000 times. If that's what you want, go do that. No one if forcing you to read this.   

Edited by Die_trying
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that was already said. I really havent read anything in here that was wrong. Just diff ways of saying the same thing. And one person seems to think a bit diff from the rest. But he is trying to prove himself right so it is what it is. Those average "joes" have already said go ride and redo the susp of his bike. He asked for an explanation and well thats where physics play in... So like it or not every answer here is right and exactly what op asked for.

Based on the simplistic way the question was asked its safe to assume getting more distance in his mind did not entail two stones traveling the same velocity in a vacuum or any other physics related explanation other than a technique worldly known to most riders as loading up his suspension/ preload the linear spring equation with speed traveled degree of lip is not going through his head on approach. So it goes without sayn it didn't need four pages of Wikipedia copy and paste on physics maybe just a link to a YouTube video....probably woulda solved his question without being bogged down by quoted banter

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Based on the simplistic way the question was asked its safe to assume getting more distance in his mind did not entail two stones traveling the same velocity in a vacuum or any other physics related explanation other than a technique worldly known to most riders as loading up his suspension/ preload the linear spring equation with speed traveled degree of lip is not going through his head on approach. So it goes without sayn it didn't need four pages of Wikipedia copy and paste on physics maybe just a link to a YouTube video....probably woulda solved his question without being bogged down by quoted banter

and it was answered like that first then other questions came up. See the internet is pretty cool you can read what you want and not read other stuff. The question was answered on the first page. If you wanted to learn more then read on. If nit click back and move to the next topic. Everything that was said in here was related to topic until someone started crying about not understanding someone else and wants to throw insults about intelligence around. Kinda funny though. Edited by T-Doshi9
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hahaha you respond to him needing to read a 7th grade text book after all the stuf he has said here? I bet you dont actually understand half of whats in here and you want to try and clown him?

 

#1)There is acceleration there.. its zero but that is a force. You understand acceleration as movement but it is directly proportional to force. Thats explained in newtons second law of motion. Meaning if one is there so is the other.

 

#2)Maybe you shouldn't have quit school right after 7th grade. He has proven that he is an engineer and knows what he is talking about...

 

#3)he is wrong (imo) with some of his thoughts but he is going off of definition and pryor experience/ knowledge for the theories, but in him being wrong he has made his self right because he has proved what is really going on here. YOU dont u derstand... thats fine but I dont think you have ANY ground to stand on saying he doesnt have an education. Just makes you look stupid.

 

#1) F=ma is for net force and net acceleration. If there is not net force (forces are balanced) there is no acceleration. Zero acceration does not magicaly turn into a force as you stated. Yes, I 'understand' acceleration as movement, as that is the definition. Per wikipedia, as it is handy: In physics, acceleration is the rate at which the velocity of a body changes with time. Velocity, as in movement. That's the definition of acceleration, period - velocity change. If velocity is not changing, there is no acceration. If you stationary, and gravity is acting on you, then gravity cannot be acceleration or it would not be present.

One form of the kinematics of constant acceleration happens to be a=(V-Vo)/t        acceleration, Velocity at time t, initial Velocity Vo

 

#2) It so happens I'm an engineer too, but I don't have to throw that around as a 'big dick'. I'm not sure if he actually mentioned being an engineer, or if you are assuming that based upon what he posted. Being an engineer really doesn't mean much nowadays. Schols pump out engineering degrees like crazy, and the FE exam really isn't very hard to pass either. And he has not 'proven' he is an engineer, just posted words. No different than anyone else in here. He might be 13, and good at Google for all we know. Everyone in here might be, including you and me. You grammar doesn't say anyhting good about your education, though.

 

#3) He's wrong which means he's right... What are you smoking? My head is so full of fack after reading that...

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#1) F=ma is for net force and net acceleration. If there is not net force (forces are balanced) there is no acceleration. Zero acceration does not magicaly turn into a force as you stated. Yes, I 'understand' acceleration as movement, as that is the definition. Per wikipedia, as it is handy: In physics, acceleration is the rate at which the velocity of a body changes with time. Velocity, as in movement. That's the definition of acceleration, period - velocity change. If velocity is not changing, there is no acceration. If you stationary, and gravity is acting on you, then gravity cannot be acceleration or it would not be present.

One form of the kinematics of constant acceleration happens to be a=(V-Vo)/t        acceleration, Velocity at time t, initial Velocity Vo

 

#2) It so happens I'm an engineer too, but I don't have to throw that around as a 'big dick'. I'm not sure if he actually mentioned being an engineer, or if you are assuming that based upon what he posted. Being an engineer really doesn't mean much nowadays. Schols pump out engineering degrees like crazy, and the FE exam really isn't very hard to pass either. And he has not 'proven' he is an engineer, just posted words. No different than anyone else in here. He might be 13, and good at Google for all we know. Everyone in here might be, including you and me. You grammar doesn't say anyhting good about your education, though.

 

#3) He's wrong which means he's right... What are you smoking? My head is so full of fack after reading that...

 

he was saying I was right about some stuff (gravity, initial velocities determining trajectory), and wrong about the influence of suspensions interaction with a jump face. 

 

gravity, g, is a constant acceleration, 9.81 m/sec^2 . the 'force of gravity', from F=ma, is F=mg.

 

so, with nothing underneath the mass to provide a reactive force, the mass would fall, changing velocity.

 

the person sitting in the chair has an added force. They still have F=mg acting, but in order to not move, they have an equal and opposite force acting on their body: the normal force from the chair. So if the force of gravity equaled mg, the chair force would equal -mg. sum the forces to total F=0, acceleration will equal zero. acceleration g is still acting on the body even when it isn't moving.

Edited by Die_trying
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and it was answered like that first then other questions came up. See the internet is pretty cool you can read what you want and not read other stuff. The question was answered on the first page. If you wanted to learn more then read on. If nit click back and move to the next topic. Everything that was said in here was related to topic until someone started crying about not understanding someone else and wants to throw insults about intelligence around. Kinda funny though.

Wow congrats another hyper inflated over fluffed dick for brains statement. People like you fill this forum up with garbage clogging servers and wasting people's time..and yes the internet is a great place so glad you found a place to escape from the parrels of the real world ..quote quote quote copy paste you are a joke guy and no it's not to funny it's pathetic atleast bring forth something fresh T-bag

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he was saying I was right about some stuff (gravity, initial velocities determining trajectory), and wrong about the influence of suspensions interaction with a jump face.

gravity, g, is a constant acceleration, 9.81 m/sec . the 'force of gravity', from F=ma, is F=mg.

so, with nothing underneath the mass to provide a reactive force, the mass would fall, changing velocity.

the person sitting in the chair has an added force. They still have F=mg acting, but in order to not move, they have an equal and opposite force acting on their body: the normal force from the chair. So if the force of gravity equaled mg, the chair force would equal -mg. sum the forces to total F=0, acceleration will equal zero. acceleration g is still acting on the body even when it isn't moving.

exactly! I guess not only are you good at google but u understand what you read too. Wow thats strange.

Cr

There he goes trying to belittle someone while saying he isn't throwing his dick around. Last resort attack someones grammar on a forum.. Man thats genius, why haven't i thought if this? So in the response where you say im clogging up servers and what not while talking about physics and how bikes react to it, where did you not clog up these servers with crap?

Edited by T-Doshi9

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exactly! I guess not only are you good at google but u understand what you read too. Wow thats strange.

Cr

There he goes trying to belittle someone while saying he isn't throwing his dick around. Last resort attack someones grammar on a forum.. Man thats genius, why haven't i thought if this? So in the response where you say im clogging up servers and what not while talking about physics and how bikes react to it, where did you not clog up these servers with crap?

You need to read these posts...you have your arguments confused..dee da dee

My sole purpose in life is to rid the world of bullshitt like well u...got some sand in your cooter? Needin some sil? Simply put the op is somewhat of a newby what would you have done with 47 pages of flawed logic and copy and paste...oh your an engineer you scrub everything first shot just cuz your a smart &%$#@! ..who over explains shit that was ...from what you said summed up on the first page...

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Based on the simplistic way the question was asked its safe to assume getting more distance in his mind did not entail two stones traveling the same velocity in a vacuum or any other physics related explanation other than a technique worldly known to most riders as loading up his suspension/ preload the linear spring equation with speed traveled degree of lip is not going through his head on approach. So it goes without sayn it didn't need four pages of Wikipedia copy and paste on physics maybe just a link to a YouTube video....probably woulda solved his question without being bogged down by quoted banter

That's just not how it works here. Let me cut and paste something from Wikipedia to demonstrate...

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You need to read these posts...you have your arguments confused..dee da dee

My sole purpose in life is to rid the world of bullshitt like well u...got some sand in your cooter? Needin some sil? Simply put the op is somewhat of a newby what would you have done with 47 pages of flawed logic and copy and paste...oh your an engineer you scrub everything first shot just cuz your a smart &%$#@! ..who over explains shit that was ...from what you said summed up on the first page...

did i? Please show me where i dis this! Ill be waiting. Also please show me where i said i was an engineer. Here is a plate of crow... Dont worry i have a great recipe. Only one looking like they are full of bullshit is u. Rid the world of bullshit... May want to start in ts or being a politician.

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did i? Please show me where i dis this! Ill be waiting. Also please show me where i said i was an engineer. Here is a plate of crow... Dont worry i have a great recipe. Only one looking like they are full of bullshit is u. Rid the world of bullshit... May want to start in ts or being a politician.

Too funny ...I know they have sarcasm in Colorado do I need to explain? We know you know how to wiki that s ...giv er a try

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Too funny ...I know they have sarcasm in Colorado do I need to explain? We know you know how to wiki that s ...giv er a try

wiki what? The recipe? Oh no this is a special recipe i made up, i have ate it many times, its good!

Great cover up with the sarcasm thing.

Edited by T-Doshi9

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