Swing Arm: Double vs. Single

Discussion in 'Road Warriors' started by urbaneccessity602, Apr 6, 2007.

  1. urbaneccessity602

    urbaneccessity602 Banned

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    I am sure this debate will echo in the halls of eternity and has been echoing for that long, especially among most of the older riders. The older riders that have seen locomotion go from horse and buggy to wheel devices with engines.

    To the riders that are from the "yester year" I am sure that a mono shock was something that only the imagination could conjure up. Sitting in a Diner and drawing on a napkin a design that has changed the motorcycle forever.

    Who would have thought that balancing the rear end on a motorcycle would only take tightening up the tolerances on a swing arm. Granted the mono shock design is leaps and bounds from the "dual shock" design, it almost seems to be experimental.

    From tightening the tolerances I mean designing a swing arm that on all the joints would have less play where the joints come together, I am hoping this, but it seems logical. The "mono shock" design must have been equivocated to a man walking on the moon to the generations before us. Can you imagine balancing the rider by placing a shock in the middle of the bike, designing it to counteract the forces of movement along and axis or arc.

    I don't know if it is just me but sometimes I do feel just the slight play in the rear wheel when I go around corners, it must be within the tolerances of the design.

    Now the single-sided swing arm is coming into play and I dont know if the Japanese are making fun of the Germans and others that are using the single-sided swing arms or not, but the new Versys and Ninjas have a rear shock design that is found on a single-sided swing arm and their bikes are dual arm, super reinforced.....


    [​IMG]
    (Versys)

    [​IMG]
    (Ninja 650)

    Well... they are baffling when compared to a single side swing arm:
    The Versys just looks to be a bigger more "beefed up" swing arm with the side mounted shock. But when you look at the new BMW F800ST and see the logic of the technology of the side mounted shock with a single side swing arm, it is only then do you start to wonder.

    (F800ST) Although I am not an engineer, this seems logical as to why the shock would be mounted on the side because the swing arm is "mono". So for Kawa to place a side mounted shock on different bikes with different dual arm swing arms is somewhat confusing, where to the BMW engineers it is the only place where they could put the shock.

    The rhetorical question as an engineerr put it to me, "everything from the past is over built for safety" this was regarding the bridges and tunnels of the old NYC. According to him they can support 30 times the weight of what a full traffic jam would weigh today. Maybe I am from the old school with the notion that "over building" is good and is not seen as waste.

    Let's just apply this to motorcycles.

    Are we as motorcycle enthusiasts about to be "eaten" by the technology we crave as a society.

    Input, commentaries are more than welcome!!! To those that have taken apart a bike, I might just be blowing wind....
    #1
  2. wannaklr

    wannaklr Long timer

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    Would a single sided swingarm cost more. If so putting one on a relative budget bike like the Ninja 650R would affect the final price. Many buyers are looking for a competent cheap do it all kind of bike. I'm sure the Japanese engineers are compensating for any side loads coming from a non-centered shock placement.

    Other than tire changes are there any real benefits to a single sided swingarm? Assuming weight is the same.

    They do look sweet though!!!
    #2
  3. urbaneccessity602

    urbaneccessity602 Banned

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    Do you think the weight limitations are different from double to single? Would a 300 lb pound rider feel the same as a 150 lb rider?
    #3
  4. BikePilot

    BikePilot Long timer

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    Single sided swingarms are at a disadvantage from a performance standpoint - for a given level of investment they will either be more flexy or heavier than a traditional swingarm, simple physics. Their advantage is in enabling super-quick tire changes for endurance racing, cosmetic appeal and packaging (i.e. providing more room for exhaust etc).
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  5. urbaneccessity602

    urbaneccessity602 Banned

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    That is interesting, I would have never made a connection from the professional racing level ley alone for quicker tire changes in the pit.

    I was starting to think maybe the fuel economy of the bike was at stake or something that had to do with the ride, I was just trying to find out some info.

    From a physics level we all know that if you lift something that is heavy with two arms it we bill even heavier with one arm, therefore the bracing has to have more stress which in turn will destroy the integrity of the link.

    From the advantage of just how they do it, I figured it would have to be shorter to adjust the pivot of the rear wheel and maybe the angle of intercept, where the end of the swing arm and the frame meet would have to be at a slight angle to get the wheel to move differently than a dual swing arm, consider the length of the swing arm also to get the physics of the wheel movement to line up with the side mounted shock, for there to be any benefit.

    Then I was thinking that there was a second piece under the intercept of the swing arm and the frame to make the rear wheel pivot to intercept the shock, of course I am talking about the full momentum of the moving rear wheel.

    They seem quite popular as a modification for the street bikes, a simple search yielded various companies that produce aftermarket single sided swing arms.

    By the way anyone have any pictures of a single swing arm disassembled with a frame?
    #5
  6. wannaklr

    wannaklr Long timer

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    Haven't found a pic with a frame, but here is a Goldwing swingarm.

    [​IMG]

    Pretty beefy, huh. I bet it could have been done lighter, but it sure makes the rear tire change easier!
    #6
  7. urbaneccessity602

    urbaneccessity602 Banned

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    huh...
    #7
  8. Terrytori

    Terrytori Namaste

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    Ha..ha...ha...ha...

    Mono shocks are so old dude that your great grandmother may well have ridden bitch on one.

    Enjoy:

    " In 1908, Merkel merged his company with the Light Motor Co. and the new Merkel-Light Motor Co. moved activities to Pottstown, Pennsylvania.

    Flying Merkels were known for having one of the finest rides in all of motorcycling and also as one of the most reliable motorcycles on the road. Merkels were more costly than many motorcycles of the time, but Merkel engines utilized the best German-made bearings and other high-quality materials, which led to excellent reliability.

    Merkel also helped design a unique front and rear suspension system on his motorcycles. The rear suspension was a mono-shock design that proved to be decades ahead of its time. Yamaha would later make a similar single rear shock design popular again on racing machines of the 1970s and beyond. Even more impressive than the rear suspension was the front fork of the Flying Merkels. The fork was so good (telescopic in principle, using dual coil springs, yet looking like an unsprung trussed fork) that many other manufacturers put Merkel forks on their factory racing machines even through the 1920s, years after Merkel had ceased production.


    Hey what goes around comes around... again and again and again.
    #8
  9. urbaneccessity602

    urbaneccessity602 Banned

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    Here she is... "The Flying Merkel"

    [​IMG] Back in 1913 the bike was the bomb. A converted bicycle frame...The Japensese must have been blown away with the idea, I just can't get over the purely aesthetics of the single-sided swing arm.
    #9
  10. chiefrider

    chiefrider Chrome won't get you home

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    If dual-sided swingarms were so superior, race cars would have them for each wheel. Cars have much greater weight & loads at the axles.

    Tom
    #10
  11. rbrsddn

    rbrsddn 3banger

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    Man, I knew the Onza Porcupine MTN bike tire was an old design, but I didn't know it went back to1913!:eek1 Here's a pic of my speed Triple SSA.
    [​IMG]
    #11
  12. AZbiker

    AZbiker Crunkin' with crackers

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    My HawkGT had a SSS, and it debuted in 1988...not so new.

    So did the Ducati 916.
    #12
  13. wannaklr

    wannaklr Long timer

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    You asked "By the way anyone have any pictures of a single swing arm disassembled with a frame?" I found a picture of a pretty beefy swingarm for a GL1800 Goldwing. Not quite what you were looking for but pretty damn neat engineering. Seems like Honda did it just because they wanted to. Would make a tire change easier though.
    #13
  14. Grainbelt

    Grainbelt marginal adventurer Super Moderator

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    The side mounted shock on the Ninja 650R and Versys is a packaging solution. Looking down from the top, imagining the rear subframe and seat aren't there, the battery sits on the left, the shock is on the right. This, combined with the design of the transmission, leaves room for the exhaust under the shock without an unnecessarily high seat height.

    Its nice that the preload adjustment is right there, and I think from a styling perspective it works well with the lines of the steel trellis frame, but as outlined above, I believe it was a packaging solution. A really sweet packaging solution.
    #14
  15. xlcr

    xlcr Stop being a dick, dick.

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    If single sided is better, why do all of the Dakar winning BMW cycles have rear forks?
    #15
  16. urbaneccessity602

    urbaneccessity602 Banned

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    Jumping to the term "forks", bikes have them in the front and rear. Let's suppose that a tuning fork, which is something that artisans use to tune instruments, which also resembles the front and rear forks of motorcycles.

    On tuning forks enrgy is conducted when the artisan strikes the tuning fork on one side and the vibration travels throughout the fork when the other side vibrates in opposition to the origin of the energy... a sound is produced and according to the size of the tuning forks the artisan makes the device he is tuning sound like the sound of the tuning fork.

    Well the rear swing arm resembles a tuning fork and a vibration on either side will produced enough energy to produce a vibration that resonates between the rear wheel, maybe the designers were able to reduce the vibration by removing one of the forks...also the sheer elegance of being able to change a tire more quickly just fell into place in the order of operational sequences. Same with the front, I think I have seen some motorcycles with one front fork also.

    In that case would the total motorcyle forks, front and rear, be of opposing sides, in other words the total motorcycle would make the structure of a dual sided arm. Front fork right is the right arm and the rear is the left.


    I'm just saying......

    http://www.freepatentsonline.com/5417305.pdf

    [​IMG] [​IMG]


    The Fly FZ750-http://www.insidebikes.co.uk/bikebible/reviews/misc/the_fly/750_main.htm

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]BMW is the inventor of this type of one sided swing arm called the monolever.

    [​IMG] BMW's paralever

    The article goes on to the front types of monolever shocks also....http://www.carbibles.com/suspension_bible_bikes.html
    #16
  17. gatling

    gatling Long timer

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    I think the single-sided swingarms look muey bueno...but my question is this:

    On all of my conventional swingarmed (i.e., dual-sided) bikes, if the rear wheel was slightly out of alignment, the bike would pull to one side or the other when I took my hands off the handlebars. This typically occurred when I used the scribe marks on the swingarm to align the rear wheel after a tire change and when adjusting chain tension. I would then mentally reason which way the rear wheel needed to go (i.e., if the bike pulled to the right, I would pull the right side adjustor back...think about it for a minute and you'll understand) until the moto was neutral with hands off.

    Do the single-sided swingarms get it that perfect that in a hands-off situation, the steering is neutral?
    #17
  18. Ranmar850

    Ranmar850 Been here awhile

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    Total rigidity, impeccable high speed handling on lousy roads

    but it won't clean the driveway

    [​IMG]
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  19. urbaneccessity602

    urbaneccessity602 Banned

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    To attempt to answer that question I would have to say in terms of "alignment" they would have to or else the bike would fall apart from the shaking regardless of how "beefy" the rear swingarms were.

    The point is the attachment of the rear wheel on single-sided swingarms, the wheel is virtually or appears to be virtually held on to the rotor by means of lug nuts. Albeit the lug nuts are reinforced they are still lug nuts.

    Whereas the dual-sided swingarms are held into place by a rod of a certain thickness, so in case the bearings break the bike would not go flying off the road. It looks racy, sexy and all of that but other than racing in some race with a rider who has to qualify to ride the bike by weighing in under a certain amount of weight, is it safe?

    On the alignment question I think it would have to be dead on center.
    #19
  20. hpsVFR

    hpsVFR Hoosier Daddy

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    One big difference between a motorcycle fork and a tuning fork is that the tuning fork is open at one end while in use. The vast majority of motorcycles have both ends of the fork securely bolted to each other (triple/SA bearing at one end, axle at the other). That will completely change the harmonic properties of the system. That's not to say that there's no vibrations, no harmonics, etc., but that the system isn't nearly as simple as that.
    #20