Kawi2strokes.com Forum

Interesting, I think Moo touched on this point as well...
I suppose vibration isn't as important as putting power to the ground in this case.

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http://kawatriple.com/wtf/

There will always be guys that "we" never hear of. There have been a bunch on the last few decades. And the motors work, just with things done that don't follow convention. But it never hurts to be "wary". They might be legit, but there are so many red flags. Seems they are "fudging" a bit, as some thing just don't make sense. Then there is the pricing, which seems almost astronomical, and everything has a cost. It costs to answer questions, a newletter (I think) that has a fee.

Another thing that is a red flag to me is if you read through the other motors, they are almost all, " it will be built" like this. Singles costing 7000.00 plus?

They do talk about a "winning" motor, but where? Was it a national? I have raced against guys on ZX10's and Gixxers and beat them, can I say my 500 is faster than a ZX10 on the track? Yes I can. Does it mean anything, NO, the riders were novices. And we all know many "hillclimbers" are nothing more than a Barn bike, with a long swinger slapped on.

The whole thing just looks to be a big (buck) sales pitch, without much to back it up.......... JMHO.........

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

Always with the negative waves, man.

Oddball

their crank stress argument makes a little bit of sense for their crank configuration. if you have 3 cylinders, spaced 180 apart, then the first cylinder to fire will be acceleratin the crank a lot. If that cylinder is far away from the clutch side of the motor, then the whole crank gets twisted until the middle cylinder fires, then the right cylinder. Now, if the cylinder closest to the clutch fires first, it still has to accelerate the crank. But, only the end wheel is being loaded, the rest of the crank is just being loaded by the pistons.

another way to think of it: the crank is like a torsion bar on a truck. the longer the bar the more you can twist it, but the less stiff it is

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ride hard, ride long, ride safe!
Jason
72 h2 in a 93 Katana
03 cbr600rr
80 kz750 ltd
94 pw50

t=Ia, where t=torque, I=moment of inertia, and a=angular acceleration
The torque (t) applied to the crankshaft equals the force from the piston times the offset of the crank (1/2 stroke). The force that each piston applies to the crankshaft is essentially equal to each of the other two, no matter which one fires first, so the torque applied to the crank is also. The moment of inertia of the crankshaft is fixed. This means the acceleration from a cylinder firing is the same for each of the three cylinders. So up until the torques from two consecutive firings overlap, it won't matter which is fired first. Once you overlap the torques, you are adding two torques, and really are applying extra stress to the crankshaft. If anything, bunching the firings together makes overlapping crankshaft torques more likely than the stock configuration.

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If it surges, that's normal, upshift.

I was going to post that, but didn't have the information until Jim posted it........

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

In the 80's I was talking to some speedway (dirt) sidecar guys, they were running a Two up One down 180 degree crank in a H2 engine with some success (and big vibes). Maybe Nev knows more with his background . I'm sure someone would have tried it on the street, if it was a success we would all know about it

jim
you are correct, that the torque is independant of the distance of the cylinder to the clutch. However, the stress the crank is seeing (at least in my explanation) is the stress due to the crank being twisted abou the centerline of the main journals. if you hold one end of the crank still and apply a torque close to that end, you cannot twist the crank very much. however, if you apply the same torque to the far end of the crank, you can twist the crank proportionately more.

As for the acceleration of the crank: the crank will slow between power strokes. So, if you have 180 degrees of crank rotation between power strokes, the crank will slow more than if you have power strokes every 120, and more so than if you have 90. So, if you have a 'big bang' motor, you want that first power pulse close to the clutch basket.
force = mass * acceleration The torque applied to the crank by any one cylinder will be equal to the others, the mass of the crank will always be the same, so the only variable that changes is acceleration. Acceleration is the change in velocity over time, so the cranks speed will change much more after the first power pulse. Less change in acceleration will equal less force being applied to the crank.

I know, I know, torque is a force, but I think you can see where I'm trying to get to. It all has to do with the amount of twist the crank is being subjected to.

Here's a link to polar moment of inertia, essentially what I'm talking about
http://en.wikipedia.org/wiki/Polar_moment_of_inertia

_________________
ride hard, ride long, ride safe!
Jason
72 h2 in a 93 Katana
03 cbr600rr
80 kz750 ltd
94 pw50

Nope, since t=Ia, If the torque applied by the pistons is equal among cylinders, and the moment of inertia of the crankshaft remains constant (you used the term "mass" which is used in the linear F=ma equation) then the angular acceleration, from this very equation, is also equal among firings, not variable. Taking the equation t=Ia and dividing both sides by I, you get t/I=a. As you said, t (torque from each of the pistons) and I (moment of inertia of the crank) are constant, so a (angular acceleration) is defined by the equation as constant, not more for the 1st one to fire.

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If it surges, that's normal, upshift.

The way I see it, there is no advantage to grouping the power pulses closer together other then to help with traction.... and I'm taking your word for that even, as I can't imagine it would be significant. Well certainly on the street, I can say that it would be a waste of time.

The power pulses have a duration and if you group them so there is an overlap then you are raising the stress in the crank regardless of which one fires first... Cool conversation though.

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http://kawatriple.com/wtf/