| Author | Message | ||
     Jaimec |
This is probably something only "Anonymous" could answer but any engineering types are welcome to chime in. I noticed that the new engine spins THREE counter balancers. You may recall an earlier posting where I pointed out that energy being used to spin a counter balancer is energy NOT being used to spin the rear wheel (Law of Conservation of Energy). I can understand the need to spin the counter balancers to cancel out the primary imbalances of the two pistons, that makes sense. But I'm wondering WHY the engine was designed so that the third counter balancer (to cancel out rocking couple) would be necessary? In order to have rocking couple, the connecting rods must be side-by-side on the crank pin. This would make the power pulse from each piston slightly offset from the power pulse from the other piston, hence the "rocking" from side to side. The previous engine eliminates rocking couple altogether by using a "knife and fork" arrangement for the connecting rods. If that same arrangement were to be used on the new engine, then the third counter balancer (and the energy it is "stealing") wouldn't have been necessary. I'm just curious as to the design decisions that led to this "situation"? | ||
| Vagelis46 |
From what I have read so far, the 1125 engine is solid bolted to the chassis to increase the stifness. Also the swingarm is directly mounted to the engine. Any vibration is bad and puts load to the chassis to the rear shock and to the swing arm, and the handling/feeling is not as good. I think the handling of the 1125R is going to be phenomenal. I imagine my XB12R with no vibes to stress the chassis and the rear shock and comprimise the handling (XB12R handling is already GREAT, so imagine what the 1125R will be). For me 2-3Hp loss due to counter-balancers are no big deal. We are talking a 1125cc V2 monster engine with 12.3:1 compression and 146Hp. I am looking forward to the introduction of the bike to the press. | ||
| Jaimec |
I realize the power loss to the third counter balancer is miniscule... but on the racing grid (where you know this bike will end up), every little bit counts... | ||
| Davegess |
By mounting the rods offset as opposed to the "knife and fork" arrangement you do indeed get a rocking couple that is absent form the H-D engines. But it allows the use of plain bearings as opposed to rollers and this should allow higher RPM. Higher RPM means more power. This offsets the loss to the balancer. Also by making the engine smoother you reduce fatigue that occurs both in the motorcycle and the rider. By reducing vibration you can make many parts of the bike lighter which also compensates for the power loss to the balancer. Overall I would think you are ahead of the game with the balancer. | ||
| Jaimec |
Ah! I didn't realize the "Knife and Fork" arrangement required roller bearings. Okay, now it makes sense. Thanks! And yes, I've always pointed out that two things negatively affected longevity and reliability: Heat and Vibration, two things of which the air cooled lump had plenty. This new engine should create a new reputation of Buell reliability in the long run, I'd suspect. | ||
| Davegess |
Ah! I didn't realize the "Knife and Fork" arrangement required roller bearings Not sure that it does but all the H-D bikes have them. I would think it might be tough to package plain bearings in a knife and fork crank. | ||
| Blake |
Countebalancers are just lopsided flywheels, yes?  So it may well be the case that any inertia added via counterbalancer(s) is subtracted from the flywheel, resulting in an inertial wash, meaning no increase to overall drivetrain inertia. Note also that as speed increases, engine inertia becomes a less and less significant factor. When racing at high speeds, 100+ mph, the engine is not accelerating extremely rapidly, not like at normal street speeds. The counterbalancer(s) drive mechanism(s) will add some parasitic/frictional loss though, which becomes more and more significant with increasing engine speed. Anyone know what the ignition sequence is for the 72o 1125R engine? The sketches on www.Buell.com in the 1125R's mini-site show the engine in various see-through pseudo-cutaway views. It sure looks like the two connecting rods share a common crank pin. I wonder if they tried to get a knife and fork configuration to work. I don't see why it couldn't, even with plain ol' journal bearings. It might just have presented to many tradeoffs thus making it undesirable. It would have narrowed the engine and eliminated the need for the lateral counterbalancer. Would sure be interesting to hear all the history behind this engine's specification and engineering. If you haven't checked out the entire 1125R mini-site on www.Buell.com, you're missing out. For engine information, click on "Complete Power" then on "Features" and then on the various choices in the listing. The "Valve Train" and "Drive Train" pages each offer four tabs each with different graphic depiction of the engine internals. Cool stuff! A repeating animation of the whole thing running through the entire combustion cycle would be very cool. Hint. ![: ]](http://www.badweatherbikers.com/buell/clipart/proud.gif) (Message edited by blake on July 11, 2007) | ||
| Jaimec |
It's definitely on the same crankpin, but side-by-side, not knife-and-fork. Hence my original question. Blake, I think your animation suggestion should be turned into a Windows screen saver module...  (Message edited by Jaimec on July 11, 2007) | ||
| Ceejay |
I agree. That mini-site with valve and drive train info, working pics is cool. even better with a fluid in/out scenario... | ||
| Vagelis46 |
Firing sequence for a V2 72 degrees would be, in degrees of crank rotation : 432-288-432-288-432-288...... I think this engine would be more powerful than the Ducati's 1098. When the 1000cc engines of the Aprilias RSV (Rotax made) and the 999 were compared ,the Aprilia was making better max Hp value and midrange. The RSV has 2 counter balancers, as opposed to none for the 999. And still it was more powerful. I think the story of the lost Hp because of the balancers is overestimated. A better designed combustion chamber or intake ports is more important. The only point that the Ducati was better than the RSV was throttle response, since it was better injected. But this had nothing to do with the engine, but with the injection system. I think Ducati had MAGNETI-MARELI and the RSV a Sagem or a Siemens unit. SO the new 1125R will better the 1098 in performance, since there are extra 25cc and 72 degrees for better breathing compared to the 60 degrees of the Aprilia. Our new BUELL is going to be very HOT. |
