| Author |
Message |
    
Rocketman
| | Posted on Thursday, December 03, 2009 - 05:14 pm: | 
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Well you learn something everyday. However I now have a problem. If the braking load from an offset brake set-up is so marginal to steering input it takes a robot to detect it, then why is a single sided swing arm any different? I mean, if you look at a single sided swing arm it is only the arm that is single sided. Where the arm is cast into the structural hinged area the pivot point is spread evenly between frame or crankcase attachment. So why would the load point, contact patch to hub, along the arm, to the pivotal area be different in the way it loads to say that of a load applied to a centrally placed steering stem from an offset braking device?
It would seem to me that the laws of physics are not changed and both scenarios though totally different are subject to the same laws from similar loads be they different in their execution.
Rocket |
Aesquire
| | Posted on Thursday, December 03, 2009 - 07:08 pm: |
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I'm inclined to look at load paths in a graphical manner. ( bad habit from CAD work & those nifty finite element color readouts ) It seems in a front brake it's all about where the caliper hangs on the fork. The offset forces in the wheel proper should be pretty small I'd think. Its very stiff.
The forces that would affect steering seem to be the bending load on one vs. both fork legs. My old Suzuki 750B did deflect way more than your S1 does. You COULD feel it on that old bike. ( though tire technology limited how much force could be applied ) My GS1100E with twin discs didn't have that much better a front fork, and didn't try to steer with the front brakes.
Single sided swingarm flex? sure. An asymmetric swingarm would point the wheel like a spring. I'll bet the Ducatis flex too little to be felt by most people. Is your single sided? Grand Prix bikes? I bet they can feel it. |
Rockstarblast1
| | Posted on Thursday, December 03, 2009 - 09:03 pm: |
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what brand bike is that at the top? it keeps sayin benelli to me but i know that snot it! there is another motorcycle brand thatstarts with s b (no not being a smart @ss thinking buell) its an italian bike |
Rocketman
| | Posted on Thursday, December 03, 2009 - 09:06 pm: |
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I never felt flex on my 916 and I pushed that bike very hard often - to its limit.
Rocket |
Gregtonn
| | Posted on Thursday, December 03, 2009 - 09:42 pm: |
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"If Greg really is as unique as I, then surely he'll find some time to throw together a nice free body diagram to illustrate the whole situation.  "
Actually I'm much more unique than that.
My ego doesn't need the strokes so I guess you'll have to do your own FBD.
G  |
Eaton_corners
| | Posted on Thursday, December 03, 2009 - 11:11 pm: |
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IIRC, Ducati stopped using single-sided swingarms on their race bikes for a while. I think it had something to do with extreme race conditions. |
Rocketman
| | Posted on Friday, December 04, 2009 - 06:23 am: |
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Its initial use was racing where tyre changing was necessary. Its design and use had little to do with structural strength / handling advantage. It proved very popular with the public for streetbikes, thus it became a Ducati trademark on their production models, still is, and production is what's raced in SBK so it remains. Flex or not. Intentional or otherwise.
Rocket |
Kustomklassix
| | Posted on Friday, December 04, 2009 - 05:29 pm: |
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"what brand bike is that at the top? it keeps sayin benelli to me but i know that snot it! there is another motorcycle brand thatstarts with s b (no not being a smart @ss thinking buell) its an italian bike"
Rockstarblast - Are you thinking of Bimota? They are one company that make some honestly crazy, INSANE bikes.
http://www.bimotaamerica.com/
Kinda something like this --
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Blake
| | Posted on Monday, December 07, 2009 - 03:12 pm: |
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"If the braking load from an offset brake set-up is so marginal to steering input it takes a robot to detect it, then why is a single sided swing arm any different?"
If properly designed, it isn't.
There is a difference though as not all the braking load follows an asymmetric load-path in the forks, only that which is counteracting the caliper. Both forks are carrying equal shares of the overall deceleration loading. Not so with a SSSArm, where the entire load path and structure between wheel hub and swingarm pivot is wildly asymmetric.
A front brake rotor on one side of the front wheel is much more akin to a single drive chain or belt acting on only one side of the swingarm.
No one has a problem with that configuration, do they?
Note that Ducati and all SSSArm implementations put the drive chain on the same side as the swingarm structure, one reason it works. If you put the drive chain on the opposite side, you'd have a huge problem. |
Blake
| | Posted on Monday, December 07, 2009 - 03:14 pm: |
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It would give a whole new meaning to the idea of using the throttle to help steer the bike. LOL. |
Midknyte
| | Posted on Monday, December 07, 2009 - 03:20 pm: |
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A front brake rotor on one side of the front wheel is much more akin to a single drive chain or belt acting on only one side of the swingarm.
Dual drive purists - now that'd be entertaining |
Jstfrfun
| | Posted on Monday, December 07, 2009 - 04:05 pm: |
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The only part of this monstrosity that I see that can be compared with the Buell braking system is the rotor, the rest of it has a lot of holes in it as far as weight heat dispersion strength under hard use...to say nothing of looks. I guess I just don't get it  |
Rocketman
| | Posted on Monday, December 07, 2009 - 07:10 pm: |
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There is a difference though as not all the braking load follows an asymmetric load-path in the forks, only that which is counteracting the caliper. Both forks are carrying equal shares of the overall deceleration loading. Not so with a SSSArm, where the entire load path and structure between wheel hub and swingarm pivot is wildly asymmetric.
It's only asymmetric along the arm though. The pivotal area it's spread equally across the centre of the bike where the load is distributed presumably to left and right side pivot equally. Just the same as an offset calipers load in your intelligent explanation explains how the force is so marginal the central positioning of the steering head doesn't see it to any significance. So why would the same laws not apply to the ss arm? The ss arm is the offset caliper. The swing arm pivotal area is the steering head?
Rocket |
Blake
| | Posted on Monday, December 07, 2009 - 07:25 pm: |
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Sean,
"So why would the same laws not apply to the ss arm?"
If I understand you accurately, they do! I certainly never meant to imply otherwise.
The rear tire's thrust load vector originating at the rear tire contact patch typically bisects (as viewed in plan, from above) or nearly so the swingarm bearings. But actually that is not necessary for chassis stability. Most importantly, the thrust load vector must lie on the center-plane of the chassis.
Take note of the configuration of the Buell 1125R rear suspension? You'll likely be shocked; pun intended.  |
Rocketman
| | Posted on Monday, December 07, 2009 - 09:24 pm: |
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That doesn't answer my question Blake.
Are you saying the same law does apply to the swing arm pivot as that for the steering head as both loads in our scenarios are offset - ssarm / offset brake?
If that's so then why does the swing arm see flex? Are you saying it flexes not at and around the pivot area but along its length in the relevance we are talking?
Rocket |
Delta_one
| | Posted on Tuesday, December 08, 2009 - 11:09 am: |
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http://eurocomponentsusa.com/wheels_&_brakes/produ cts.php?id=08020&img=a |
Kustomklassix
| | Posted on Tuesday, December 08, 2009 - 12:44 pm: |
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Ok, the first front rim design can be forgiven because the disc is inside the rim and actually different, but come on, this one is Buellschidt. |
Swordsman
| | Posted on Tuesday, December 08, 2009 - 01:12 pm: |
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Wow, those guys took the worst of both, didn't they? Rotor is mounted on one side, spokes are mounted to the other side. That's messed up. Why did they need to move the spokes off to the side at all?
~SM |
Kustomklassix
| | Posted on Tuesday, December 08, 2009 - 05:22 pm: |
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To offset the weight cuz now its purfekt! |
