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Old 12-17-07, 03:56 PM   #51
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Well, I guess it comes down to your definition of "skilled". Personally, I practice braking at the limit all the time. Coming up to a stop-sign, I'll test how short I can stop from 20-30mph from 100ft out. Then let up the brakes and slowly approach @ 5mph the rest of the way. My hands are always close to the levers in case a car pulls out. When you're doing a panic-maximum-OMG-emergency stop, most of your braking-power will come from the front-brake. Test it out yourself, get up to 30mph and try practicing panic-stops with only the rear-brake, then only the front-brake, then try both. You'll find that there's minimal difference between front-only vs. both while rear-only will take forever.

Similar things happen in the motorcycle world. A lot of new riders are afraid of the front-brake due to endos form their bicycling days. However, the longer wheelbase and much lower COG of a motorcycle pretty much makes it impossible to lift the rear-end up very much (unless you're hopping up off the seat a little intentionally to do a stoppie). In a vast majority of the motorcycle vs. car crashes (66% are caused by cars turning in front of a bike they didn't see), there are long skid marks from the rear-tyre of the motorcycle. They're using their rear-brake only and are slidding into the wreck. If they had used front-brake only, they would've stopped in plenty of time before coming close to the wreck. Unfortunately, learning the "skill" of maximum-braking in an emergency situationhas much more severe repercussions on a motorcycle vs. a bicycle. Best to practice that "skill" and get it down to an automatic response intentionally in a safe and controlled environment before you'll actually need it.
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Old 12-17-07, 05:32 PM   #52
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I you ride at a regular speed 20-25 km/h yes. However, if the bike would be tested in the crash lab environment, and the speed will be increased at 120km/h, and the front brakes will be instantly deployed at 100% braking power, chances are, Slipstream too will flip over.
Even then, with limited friction between front wheel and ground, the front wheel can easily lock up before the rear wheel lifts.

Wheelbase doesn't make any difference in these calculations, except as it affects the position of your center of gravity.

What's this all for, anyway?
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Old 12-17-07, 05:34 PM   #53
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No, you are right also. I was just reading from the link. Since we have this issue taken care of, we can now move on to the real issue. Let's design some "Anti-Lock" front brakes and market them.
I have seen devices mounted on brake cables that absorb some of the pull on a brake cable to achieve this exact result.

Only on cheaper bikes, of course; got to save the people from themselves!
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Old 12-17-07, 05:43 PM   #54
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Even then, with limited friction between front wheel and ground, the front wheel can easily lock up before the rear wheel lifts.
I sure know what thats like, one moment you're in panic stop mode, the next you're wheels are perpendicular to the ground because you're front wheel has locked.

Front only braking there, didn't even think of grabbing the rear, the more balanced braking would have probably saved me from some scratches, or a little less panic braking.
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Old 12-17-07, 07:14 PM   #55
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Even then, with limited friction between front wheel and ground, the front wheel can easily lock up before the rear wheel lifts.

Wheelbase doesn't make any difference in these calculations, except as it affects the position of your center of gravity.

What's this all for, anyway?
Sure it does. Imagine a rotation around the front contact patch. The longer away the COG is away from this pivot-point, the more torque you'll need to rotate it up the same number of degrees. Imagine a bike with zero-wheelbase, a unicycle. Just about any quick deceleration will plant you on your face unless you initially start a rearward rotation before slowing down.
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Old 12-18-07, 03:30 AM   #56
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Please check your PM

[QUOTE=DannoXYZ;5825703]Well, I guess it comes down to your definition of "skilled". [QUOTE]Hey DannoXYZ,

Can you please check your PM?

Thank you!

SR
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Old 12-18-07, 05:40 AM   #57
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People most of you are off topic!!!! The questions of the topic are:

Q1): Does anyone know what is the name in physics of this generated force. ( the one that throws you over the handlebar)

Q2): Based on speed, bike/rider mass-height how can this force be calculated.


Thank you anticipated!
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Old 12-18-07, 05:52 AM   #58
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A1: Inertia
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Old 12-18-07, 11:31 AM   #59
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Sure it does. ... The longer away the COG is
So you're talking about COG position, not wheelbase. The two aren't necessarily directly related.

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People most of you are off topic!!!! The questions of the topic are:
First, it's not a force, just like centrifugal force. There is no force that throws you over the bars. Your speed creates momentum, your braking causes a moment of rotation, and at some point this moment overcomes the opposing moment created by gravity.

Second, it's not a force, but everything you could possibly need has been provided by DannoXYZ on page 2.
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Old 12-18-07, 01:49 PM   #60
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People most of you are off topic!!!! The questions of the topic are:

Q1): Does anyone know what is the name in physics of this generated force. ( the one that throws you over the handlebar)

Q2): Based on speed, bike/rider mass-height how can this force be calculated.


Thank you anticipated!
The force isn't generated isn't it? It's continues to be there in the person even though the bike has lost it's force.
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Old 12-18-07, 02:00 PM   #61
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People go over the bars when they dont brace their elbows for braking. They apply the front brake, tha bike stops and they fly forward because their arms are not holding them back with the bike. Their body then hits the bars and their momentum carries them over.
Depends on the force. I did a panic stop due to a car right hooking me a few years ago. I went over the bars and as a result of the force sheared off the heads of both my radius bones. Locking my elbows to brace for the stop resulted in six weeks of casts on both arms and another six weeks of rehab.
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Old 12-18-07, 03:27 PM   #62
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People most of you are off topic!!!! The questions of the topic are:

Q1): Does anyone know what is the name in physics of this generated force. ( the one that throws you over the handlebar)

Q2): Based on speed, bike/rider mass-height how can this force be calculated.


Thank you anticipated!
Anticipate this!
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Old 12-18-07, 08:33 PM   #63
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Anticipate this!
You're so funy, funy, funy... ... Or so you'd like to believe...
Ever tried Club Comedy 54?!?
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Old 12-18-07, 08:46 PM   #64
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You're so funy, funy, funy... ... Or so you'd like to believe...
Ever tried Club Comedy 54?!?
Is that like La Batts?
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Old 12-18-07, 10:35 PM   #65
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I do not know is you guys realized by now but I am not a physicist... Noooo... really, I am not!!!

When describe how things are moving, and when you want to be accurate about it, you need to pay attention of the terms in which you describe the motion. Most of the time scientists are paying a close attention in choosing the terms/words they want to describe something because they want to represent nature as accurately as possible.
Language can often be imprecise, especially when you are a scientist, aware being that statements can often be misinterpreted.
However, as I mentioned before, I am not a scientist nor I pretend to be, therefore there is no need for some of you to flame me and be cocky about my lack of better terms.
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Old 12-18-07, 10:38 PM   #66
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Is that like La Batts?
Could very well be ...hey!
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Old 12-19-07, 11:40 AM   #67
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I do not know is you guys realized by now but I am not a physicist... Noooo... really, I am not!!!

When describe how things are moving, and when you want to be accurate about it, you need to pay attention of the terms in which you describe the motion. Most of the time scientists are paying a close attention in choosing the terms/words they want to describe something because they want to represent nature as accurately as possible.
Language can often be imprecise, especially when you are a scientist, aware being that statements can often be misinterpreted.
However, as I mentioned before, I am not a scientist nor I pretend to be, therefore there is no need for some of you to flame me and be cocky about my lack of better terms.
Dude, I was tweaking you for: People most of you are off topic!!!!

This is a forum to exchange ideas and hopefully have some fun, not your private research facility.

If you want to pick our brains don't be fussy about the results.
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Old 12-19-07, 07:02 PM   #68
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This is a forum to exchange ideas and hopefully have some fun, not your private research facility.

If you want to pick our brains don't be fussy about the results.
Blah, blah, blah and yap, yap yap... Looks you are mastering this science better than bicycle physics and dynamics... (with all due respect!)


With best regards,

SR

P.S. Oh yeah...almost forgot... if you do not believe me read carefully forum's "


General Principles"

"expect our members will make a sincere effort to contribute their thoughts on interesting subjects in a meaningful and respectful manner" - where "MEANINGFULL" is the key word

At no point is says to make fun of someone or at someone's expense.


"Posting messages and otherwise interacting on BikeForums is completely optional"
Meaning if you read a post and you can meaningful contribute to the discussion" express your point of view, if not.. .. read on my friend... read on...


Being stupid ( like me) and asking questions does not contravene with those guides, on the contrary meets the means of this forum.

Being mean and disrespectful... .. does not.. .. so.. . read on my friend.. .. read on.. ..

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Old 12-20-07, 11:24 AM   #69
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I don't think you are stupid; perhaps a little ********.

"expect our members will make a sincere effort to contribute their thoughts on interesting subjects in a meaningful and respectful manner" - where "MEANINGFULL" is the key word

I think "expect" really is the key word; my participation on this forum is not an agreement to live up to your expectations.

Maybe a little less time in physics and a bit more (any?) at people skills?
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Old 12-20-07, 10:34 PM   #70
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I think it's time for people to go ride their bikes, seriously.
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Old 12-21-07, 03:08 PM   #71
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Hello to everyone.. ..

yeah... .. except very few people participating to this thread, most of you guys, do not know anything at all or too little about physics.. .. me including...
The only difference between me and others is that I do not pretend to be a "Super Rider" and I do not try to down play my ignorance... ..

Those being said, many, many, many thanks to DannoXYZ with some very informative posts, very knowledgeable and very modest in the same time, CaptainCool, StephenH,grolby and few others for their insightful contributions.

I believe that at this point in time, from this post and different other sources the answers to my questions would be (please correct me if I am wrong):

Q1) Not exactly a force. Angular momentum, a quantity that likes to be conserved and will take any opportunity that arises to lob you off the front. And I only have a back brake... Well, the force would be centripetal force. The rider has momentum (is what carries them over the handlebars, and this is no force). Newton's first law tells you that an object wants to keep going in a straight line until acted on by an external force.
In regards to the flipping part, that is simply a pivot point being introduced and the rider's arms or whatever providing the centripetal force required to introduce circular motion.
If the rider would completely let go when hitting a stationary object, most likely, he will just keep going in a straight line and not flip over.


Q2) Using the following equation: Fast speed + wheel lock = Faceplant. Assuming that the wheel locks up and does not slide whatsoever, or very little (as is the case in real life). Then, all your momentum is transferred into a rotational movement about the wheel, the center of the virtual circle would be the point where the wheel contacts the ground. If the cyclist is only thrown off and the bike is stationary and remains so, then mass (of combined bike & human) * velocity = mass of human * new velocity.

So... if a cyclist of mass 70kg at 15m/s, with a bike of mass 10kg, will have a momentum of [(70kg+10kg)*15ms], which means he'll be moving at 17m/s, and will have some 10kJ of energy to dissipate, which most likely is not going to be pretty.

Did I ever mentioned many thanks to DannoXYZ?!?
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Old 12-28-07, 08:48 PM   #72
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This is real easy to do. You get yourself a high-wheeler. Then you pedal as hard as you can going downhill. Then you are leaning far over the handlebars you stick your foot into the spokes. Over you go.

It is a bit harder to do on a conventional bicycle because the pedals are not on the front hub.

In other words what everybody knows is something out of the far distant past that pertains to equipment most of us have never even seen. Even before the internet old stories never died.

I personally have never seen a bike go head over heels unless something went into the spokes first.
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Old 12-28-07, 09:06 PM   #73
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Then again- Endo's are possible on all bikes but this is normally caused by the front wheel hitting an imovable object like a Dog- Car or tree. Not the usual situation on a normal bike ride.
Actually I think that most end overs are caused by twisting the wheel around sideways. I assume we are talking about riding on a level surface with the rider on the saddle. Since you can get bike up on its front wheel with body english, you certainly can get it to topple forward from that position. But normal braking with the bicycle under control?
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