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Re: Telix fork brace how too?
Posted: Wed Mar 23, 2011 5:10 am
by ME 109
[quote="Major Softie"]Yes, Rob, if that vertical axis force, which certainly does exist, is followed down through to where it leaves the bike, you will see that, in a corner, that axis must travel through the air to reach the ground.
I've traveled through the air a few times to reach the ground
That vertical axis force is being resisted by the contact patch, which is not aligned with the force axis, and that resistance is not perpendicular to the force axis. The torquing of the forks that vanzen is talking about is the result of your axis of force, and his contact patch, not being in alignment. Thus, the force is trying to bend the fork out of alignment.
I look forward to Vanzen aligning his contact patch with the Major's axis of evil force.
Wait a minute! No I don't
Sorry.
Re: Telix fork brace how too?
Posted: Wed Mar 23, 2011 6:51 pm
by Major Softie
Oops, doubled up
Re: Telix fork brace how too?
Posted: Wed Mar 23, 2011 6:55 pm
by Major Softie
ME 109 wrote:
I've traveled through the air a few times to reach the ground
I'm aware of very little such travel that does not end up reaching the ground.
ME 109 wrote:
I look forward to Vanzen aligning his contact patch with the Major's axis of evil force.
Wait a minute! No I don't
Wait a minute. I believe the "axis of
evil force" is Rob's, rather than mine. Thus, it will be Rob Frankham and Vanzen who will be aligning themselves. I will merely stand by and point out where they fail to reach the ground.

Re: Telix fork brace how too?
Posted: Wed Mar 23, 2011 7:25 pm
by vanzen
Major Softie wrote: I will merely stand by and point out where they fail to reach the ground.
... and I thank you for that, Major. Sometimes it just needs to be done.
Re: Telix fork brace how too?
Posted: Wed Mar 23, 2011 10:57 pm
by Chuey
Major Softie wrote:
On a banked turn, if the banking and speed are such that the axis you spoke of is perpendicular to the "ground" of the banking, then no such torquing of the fork would occur, as the contact patch would be perfectly centered on that axis.
So, in other woids, the Wall of Death rider needs no stinking fork brace?
Chuey
Re: Telix fork brace how too?
Posted: Thu Mar 24, 2011 1:33 am
by Steve in Golden
Hmm, I had no idea that fork dynamics was such a complicated topic. Does all this flexy perpindicularity vertically challenging stuff apply to the telelever front end, such as the one on my R1150R, too? Me likee the way my R1150R handles, and it has no fork brace. Not that I push it all that hard in corners or anything.
Re: Telix fork brace how too?
Posted: Thu Mar 24, 2011 2:07 am
by Major Softie
Steve in Golden wrote: Me likee the way my R1150R handles, and it has no fork brace. Not that I push it all that hard in corners or anything.
You are mistaken, sir.
What do you think the end of the A-arm is resting on? The "Fork Bridge" (part #31427654089). Your fork brace just isn't at the top of the sliders (like a telefix), it's 1/2 way up, behind your fender.
Plus, you have much larger diameter tubes and (I believe) a larger diameter axle held in stronger clamps (than an airhead), all of which helps combat those forces.
Re: Telix fork brace how too?
Posted: Thu Mar 24, 2011 6:46 am
by Ken in Oklahoma
Chuey wrote:
So, in other woids, the Wall of Death rider needs no stinking fork brace?
Very cute Chuey, seriously!
Seriously, for the wall of death rider, there is still that air gap between the centerline of the tires and the, ah, woood. The motorcycle is responding to two forces, gravity and centrifugal force, so the motorcycle is at an angle from the vertical wall. But you already knew that.
Not so seriously, I love the image of a devil may care wall of death rider actually caring about whether or not his forks have a brace.
Ken
Re: Telix fork brace how too?
Posted: Thu Mar 24, 2011 8:33 am
by Rob Frankham
Major Softie wrote:Yes, Rob, if that vertical axis force, which certainly does exist, is followed down through to where it leaves the bike, you will see that, in a corner, that axis must travel through the air to reach the ground. That vertical axis force is being resisted by the contact patch, which is not aligned with the force axis, and that resistance is not perpendicular to the force axis. The torquing of the forks that vanzen is talking about is the result of your axis of force, and his contact patch, not being in alignment. Thus, the force is trying to bend the fork out of alignment.
On a banked turn, if the banking and speed are such that the axis you spoke of is perpendicular to the "ground" of the banking, then no such torquing of the fork would occur, as the contact patch would be perfectly centered on that axis.
No sorry, I'm still not getting this...
If you resolve the forces acting on a bike in a curve using - say - a vector diagram there will be a number of differing forces. These will include gravity, precession from the rotation of the wheels, inertia from the movement through the bend and others. These can all be resolved into one overall 'force' known as the resultant. With emphasis on the assumption that we are talking about a balanced bike in a constant bend on a smooth surface, the point where that resultant intersects the ground must be within the contact patch of the tyre (if it isn't, the bike will fall into or out of the bend which means that our initial assumption is no longer true). It follows that, in these somewhat idealised circumstances, the resultant must be parallel to the vertical axis of the bike... or at least within a degree or two of that. This being the case, the pressure applied to each stanchion will be (more or less) the same and there is no reason for one stanchion to be compressed more than the other.
Rob
Re: Telix fork brace how too?
Posted: Thu Mar 24, 2011 10:30 am
by vanzen
Steve in Golden wrote:Hmm, I had no idea that fork dynamics was such a complicated topic. Does all this flexy perpindicularity vertically challenging stuff apply to the telelever front end, such as the one on my R1150R, too?...
Yes, an extremely complicated topic ...
Which serves to render a simple and succinct explanation difficult, if not impossible ...
BMW has not magically transgressed the immutable laws of physics, they still apply.
Rather BMW has chosen, wisely IMO, to pursue alternative forks systems which address and resolve
many of the inherent design inadequacies of the telescopic fork.