| Author | Message | ||
     Liquorbox |
"Spike,I have a 20 year old yamaha FZR that has the gas low between the frame rails.The XB holds the gas pretty high when there is a full tank,it's not like the XB holds all the fuel low." I have owned and ridden several bikes. Of the four I now ride, the Buell is the only one that feels “top heavy” to me, and wants to stand-up in corners. I don’t think it’s a matter of how much fuel is where, so much as overall balance. The Buell places that huge heavy motor pretty high in the frame compared to most other bikes. Especially IL-4’s! | ||
| Ft_bstrd |
Sat on the new GSXR 750 at IMS. THAT was top heavy! If felt like someone had poured an anvil into the tank. I couldn't even imagine what it would feel like with a full tank of fuel. I guess my bike would like to stand up in the corners, but it has a giant bastard hanging off of it keeping it planted!  | ||
| Court |
There are a host. . . a myriad if you will . . . hell, make it a plethora of GREAT motorcycle frames in the world. Hell. . . . Buell has bought tons of them and destroyed them just to find out how good, and rigid, they are. Many are incredible. The XB sits at the top of the list. Remind me to tell you the story of putting the Ducati and Honda frames in a jig and press years ago . . . in the days of the early tubers. By the way . . .if you have an 1996-1998 S-1 go look at how that single pipe in the front curves the heck all over the place. . we'll talk later.  | ||
| Cityxslicker |
Yes, gas in the frame is a big deal, after riding the Ninja 12 for a season, I can definitely tell you that I like the buell balance much better. NOW if they could just manage to put a real gas gauge on the insturement cluster... (the low fuel light doesn't count) | ||
| Xl1200r |
I have owned and ridden several bikes. Of the four I now ride, the Buell is the only one that feels top heavy to me, and wants to stand-up in corners. I don’t think it’s a matter of how much fuel is where, so much as overall balance. The Buell places that huge heavy motor pretty high in the frame compared to most other bikes. Especially IL-4’s! Don't confuse top-heavyness with suspension setup. The first XB I rode was awful about wanting to stand up in the corners. It really caught me off guard on the first turn I tried make and I found myself in a hairy situation. I have ridden 2 XB's since then and neither felt like they wanted to stand up on me. Anyways, a top-heavy bike would feel more likely to fall over than stand up. As for total balance, the lower fuel adds to the total. You can't get a low center of gravity by changing one thing, it's a combination. Your statement showed you know this, but it seems like your discounting the fuel location's contribution to it. I will agree about how high the engine seems to be mounted in an XB. I like the idea of the exhaust under the engine, but it seems you should be able to mount a muffler somewhere else and keep it low so you can mount the engine lower in the frame. Maybe the primary hanging off the left side dictates this for ground clearance reasons... | ||
| Court |
Be cautious with the "lower is better". That may be great if you are a tenor, but not for dynamic stability. Take it Blake. . . | ||
| Freezerburn |
Court, you talking about the tubers is just adding Rocket Fuell! | ||
| Ridrx |
If a bike had it's COG 4-6 inches of the ground, I bet you would redefine the term high-side. A higher COG(within reason) provides resistance to the centrifugal force that wants to see just how far it can throw you. Believe it or not... All else being equal, a "top-heavy" bike would actually require less lean angle to negotiate turn, however a lower COG will increase the speed at which you can make the turn. | ||
| Naustin |
I'll say it again, the Bikes aren't the problem. The Motors aren't the problem. The frames and the styling isn't the problem. The problem is the Dealers and improving or expanding the product won't fix it. Even if all "8 projects" are fantastic successes over the next 3 years, Buell will still suffer the step-child effect at most of the dealerships. I wanna hear how they are fixing this attitude problem! And I would really like to hear that Willie G. is going to beat it out of them with a bat. If the strategy boils down to "dirt bikes will create new demand and cause the dealers to suddenly love Buells because they are selling so many of them" - then frankly, I'm skeptical and I don't believe that new models are going to change anything when it boils down to it. Maybe I'm wrong, but I had better not have to wait 3-5 years to find out. And, what if I'm right and the new models don't cure the Hate? What then?? Stand Alone Dealers? - Not going to happen in my town. Sell Buells at Yawasuki shops? Great, now I have to put up with being abused and ripped-off by Jap-Bike zealots instead of the "Lifestylers". Big improvement there. I don't know what the solution is. Its probably going to be about as easy as peace in the middle east. I do know it has got to happen in every Harley shop with no exceptions, and it's BMC and HD's responsibility figure it out and get it done. (Message edited by naustin on March 02, 2007) | ||
| Old_man |
Liquorbox, I found the reason my bike stood up in corners was the stock Dunlop tires. I used the Metzler M1 and now the Pirelli Scorpion Syncs. The bike has no tendency to stand up with these tires. | ||
| Rocketman |
Why would Buell consider the ultimate strength of a frame in a test jig as such an important issue as to suggest the XB frame is superior to all others because it sits top of the list. Whoever's or whatever that list is? Frame strength and / or rigidity isn't the ultimate test of any frame. If it were you might as well through away all bikes that don't actually have a frame as such, and there are many. Ask a different question. What exactly constitutes a motorcycle frame? A flat alloy sheet at top of an engine? A round bar the motor hangs off? A single or twin down tube cradle frame? The list is endless when it comes to frames, and many don't frame anything.  Incidentally, in recent developments several manufacturers have redesigned frames to be more flexible, taking away strength and rigidity, in an effort to improve handling and give better rider feedback. Rocket | ||
| Court |
>>>>>Frame strength and / or rigidity isn't the ultimate test of any frame. You are absolutely right . . sounds to me like you are quoting Erik from his recent speech in Boston. Rigidity. . . like top speed and horsepower is ONE COMPONENT. You're learning. | ||
| Buellshyter |
I personally have enjoyed watching one manufacture try to figure out the ZTL braking system and underslung muffler. Honda wants that stuff so bad they can't stand it. The patents don't last forever. | ||
| Xl1200r |
All else being equal, a "top-heavy" bike would actually require less lean angle to negotiate turn, however a lower COG will increase the speed at which you can make the turn. This is not true. First off, your statements are in direct contradiction. If a top heavy bike could lean less, then it should be able to take the turn faster because it has more lean to give. In any case, lean angle of the bike is dictated by how far the center of gravity is from the centerline of the bike - as in side-to-side, NOT top to bottom. Look at any good street rider or a bike race. The riders are hanging off the side of their bikes in order to squeeze as much lean out of the total package (bike & rider) as they can. This is a simple experiment to do yourself if you want - Ride is a straight line and hang off the side of the bike. The bike itself will lean in the opposite direction you are in order to compensate. | ||
| Cupp42 |
Incidentally, in recent developments several manufacturers have redesigned frames to be more flexible, taking away strength and rigidity, in an effort to improve handling and give better rider feedback. THEY CALL IT "TUNEABLE FLEXABILITY" THAT IS JUST A FANCY WAY OF SAYING THEY CANT GET IT RIGHT, SO THIS IS THE WAY TO MAKE FRAMES. THEY ARE JUST PISSED THEY CANT CARBON COPY THE XB FRAME YET. | ||
| Xl1200r |
There are some frames that need to be flexible in order to survive. Like the frame in a Mack truck to keep the torque from the engine tearing it apart. But on a bike? I can't see why a flexible frame would be a good thing where handling is important. To me, the frame would just be doing something that the suspension should be taking care of. | ||
| Thepup |
Cupp,Why would they want to copy the XB frame?I would say the other manufacturers are doing fine with the frames they have now. | ||
| Spatten1 |
Actually, newer frames flex laterally because at high lean angles the forks don't soak up verticle forces anymore, so the frame has to. This was discovered as forks went upside down and THICK, losing too much ablility to flex. Chatter resulted at race speeds and had to be addressed. Something has to soak up bumps at high lean angles when the forks can't. There is less uncontrolled ossicilations using the flex of the frame rather than the flex of the forks. | ||
| M1combat |
Why not just use the flex in the engine mounting system (provided the engine is a stressed member)? heh heh... "I guess my bike would like to stand up in the corners, but it has a giant bastard hanging off of it keeping it planted! " XB's do respond well to proper form for sure . As has been stated... The XB will tend to stand up mid turn if the suspension isn't set somewhere close to the riders weight (they give you the setup in the book...). It doesn't need to be exactly like that setup, but it's a good start if you ask me. It's not a bad thing though . You can use it to your advantage on the brakes . It's there for a reason if you ask me. Come into a mid second or third gear turn on the brakes and as you really start the roll in and transition to gas it lets the bike fall in more smoothly. I wonder... If the brakes make it stand mid turn... Does the gas make it plant, dig in and go ? Try that once instead of complaining about it. It can show this tendency with the stock D207's as well, but a lot less when you hang off. Provided you do hang off those are actually some fun tires if you don't mind sliding around when they get too warm . They seemed to slide predictably, just too soon. The Metzelers IMO are much better (Or the Pirelli's). I haven't tried others. The XB works beautifully when you've got your knee hooked around the corner of the seat and your riding it with pretty much just the bottom side of your lower thigh. Talk about feedback... That said... It works quite well when you just hang off a little bit too . | ||
| Blake |
The real and effective (for improved handling) goal of the fuel in the frame is to consolidate mass nearest the center of mass, aka "mass centralization." A center of mass (more formally correct engineer-speak and same-same as "center of gravity") that is lower is not necessarily a good thing for a sport bike. As XL1200R stated, the center of mass' vertical location has no beneficial effect on steady state lean angle versus speed around a corner. Why? The tipping moment caused by gravity must always offset the opposite moment due to the angular acceleration of turning, commonly known as "centrifugal" forces. Both of those moments act through the center of mass, so moving the center of mass doesn't change their relation to each other. If you want to corner at a lateral acceleration of 1g, the center of mass of rider and bike had better end up being leaned over right about around 45o from horizontal. If you want to corner at 2 g's, you'll need a bike+rider CG lean of approximately 30o from horizontal. Actually considering the effect of tire profile, a lower CG would actually tend to require a more aggressive lean angle (for the same turn at the same speed) than that of a higher CG. Why? As a bike is leaned over and rolls onto the sides of the tires, the center of the tires' contact patches, the load bearing reaction points, move laterally (to the side) off-center in the direction of the lean/turn; they also move upwards towards the CG just a bit, but not nearly as much as they move laterally, at least not for sane lean angles on the street. We have a diagram around here somewhere...  What vertical location of the CG does effect and what Court is hinting at is ease of turn-in and how much of the road is required to get the bike leaned over and ready for turning and/or to get the bike stood back up exiting a turn. In this, a higher center of mass is actually advantageous as it provides more leverage, a longer moment arm for lateral forces acting on the front tire during counter-steering. There is an easy experiment we can do to illustrate this to ourselves. If anyone is interested, remind me to tell you. I gotta run. Too much fun, this is. | ||
| Blake |
Puppy, Where is the fuel tank located in the RC51, or the SV650, or the SV1000, or in the V-Strom, or in the Ducati Twins, or in the Aprilia twins? Fuel in the frame is a very elegant (engineering wise) solution for a V-Twin engined sport bike. The fuel in the frame is especially elegant for its exploitation of one part to perform extremely well two vital functions, those of frame and fuel tank. Even the IL4 sport bikes you mention, if they could incorporate fuel in the frame, would benefit significantly by reduced weight and fewer parts. They cannot. Buell owns the patent. Advantage Buell. Ditto for the Buell ZTL wheel and brake system. Less mass and less parts is always a good thing on a sport bike. Ever notice how high up the fuel tank is on a motocross bike? Hmmmm... | ||
| Buellfighter |
Can't remember which one it was, Suzuki or Honda, experimented with switching the gas tank and airbox in an effort to bring the weight lower to improve handling. The need for a fuel pump and an unbalanced bike (too much weight in back, not enough in front was the result) has kept them from going that direction, so far. Edit  ops, forgot to mention this is for the motocross bikes (Message edited by buellfighter on March 03, 2007) | ||
| Spatten1 |
The V-max and Voyager have gas under the seat. The "gas tank" is just air box and electronics. Done in the 1980's by Yamaha. Since they are not sportbikes, my guess is that moving the fuell cell was for styling, not handling. (Message edited by spatten1 on March 03, 2007) | ||
| Spatten1 |
Great CG writeup Blake.s | ||
| Xl1200r |
The real and effective (for improved handling) goal of the fuel in the frame is to consolidate mass nearest the center of mass, aka "mass centralization." A center of mass (more formally correct engineer-speak and same-same as "center of gravity") that is lower is not necessarily a good thing for a sport bike. As XL1200R stated, the center of mass' vertical location has no beneficial effect on steady state lean angle versus speed around a corner. Why? The tipping moment caused by gravity must always offset the opposite moment due to the angular acceleration of turning, commonly known as "centrifugal" forces. Both of those moments act through the center of mass, so moving the center of mass doesn't change their relation to each other. If you want to corner at a lateral acceleration of 1g, the center of mass of rider and bike had better end up being leaned over right about around 45o from horizontal. If you want to corner at 2 g's, you'll need a bike+rider CG lean of approximately 30o from horizontal. Wow. Would you believe I go to an engineering school? I guess this is why I'm a management student - I don't need nearly as many words | ||
| Court |
Who is that on the bike in the diagram? I think I recognize him. | ||
| Spatten1 |
People underestimate the value of weight placement. I used to watch a couple of guys that raced in a different class than me on their YSRs. One hung off the bike very well, and the other rode on the seat more. When they went the same speed around some corners the "hang off" guy's bike was far more upright than the guy on the seat, whose bike was leaned over much more. Eventually as they both went faster the guy that hung off less started crashing as his bike ran out of traction. It was cool to see the weight placement vs. CG theory work in real life. | ||
| Dbird29 |
That is LineRider! http://www.lineriderflash.com/line_flyer.html YouTube video http://www.youtube.com/watch?v=D5-VaA14O1E  (Message edited by dbird29 on March 03, 2007) | ||
| Ft_bstrd |
Someone has WAAAAAAAAY too much time on their hands. That's friggin' hypnotic! | ||
| Thepup |
Blake,the SV,Ducati,RC51 have a 90 degree V-Twin.The 45 degree twin of the Buell makes it harder to get the weight lower,so they came up with a frame that works very good for Buell.As for less parts being a good thing,I agree,so shouldn't Buell get a different engine so the can get rid of all those extra parts and weight for the engine mounting system,how about the extra weight and parts in the oiling system,or how about all the parts in the primary system. |
