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Re: Gearing on zx 1200r

Posted: Tue Apr 17, 2012 9:23 pm
by Greg Watters
in my experiance C of G is in more than one plane , too low is as bad as too high , too far to the back and you have a pendulum , too far front and its no use
And have you ever tried to throw a dart backward ...
I took a very well mannered bike that was the fastest outright at Bubs 2010 and made it into a poor handling beast , moving the weight down and extending the 35mm swingarm more :evil: ,

And weight near the singarm pivot could be considered semi sprung

Re: Gearing on zx 1200r

Posted: Wed Apr 18, 2012 5:32 pm
by kermitracing
Hi Stayt'ie and Greg, Thanks for the tip on the balance thing between both front and back wheels. At the moment it handles like chopper with the 20 kg. in the swingarm so I will bring along some front forks straps to rachet them front down a tad. The 12,s in their natural unmolested state have an elevated back end so they tip easier into corners so when you muck a round with the geometry the handling charateristics go out the window. Don't know why, but they seem to be a much maglined bike, always seem to run bridesmaid to those ugly busa's (no disrespect to busa riders). I know the busa's are slipprer and that will be next years project to make the kwaka shaped like a banna so i can slid on past them.
Cheers Paul

Re: Gearing on zx 1200r

Posted: Thu Apr 19, 2012 1:50 am
by RGV
Dont know if you have seen this before. Why Bussas are quicker. Its not all HP.

http://www.sportrider.com/tech/146_0106 ... to_07.html

Re: Gearing on zx 1200r

Posted: Thu Apr 19, 2012 5:19 pm
by Stayt`ie
i have read that, and similar stuff before, and find it a little puzzleing, as on the dragstrip, a 12 (in standard form) will topend Busa`s of the same era, :?
despite what you read in the media, the 12 actually has a smaller frontal area than the Busa,, however the tail area is what restricts them aerodynamicaly :roll: ,, blind freddie can see how "enclosing" the Busa rear bodywork is,,,

Re: Gearing on zx 1200r

Posted: Sun Apr 22, 2012 12:04 pm
by momec3
Greg,

An interesting observation on C of G. Made me think about why? What came to me was the thing we used to do as kids when we had the front wheel off the pushie.

Hold each end of the axle and spin the sucker. Even at those slow speeds the gyroscopic effect was so strong.
Must be enormous on both ends of a bike at speed.

Is the axle centreline where the C of G needs to be aimed on a bike for high speed stability (straight line)??
Is the leverage effect of lowering your C of G like holding the pushie front wheel instead of the axle but say the headstem of a set of forks and trying the same exercise; much more dificult to control the motion.

I'm most likely stating the obvious to you bike guys but the charicteristics are so opposite to building a stable car it made me give it so thought.

Chris

Re: Gearing on zx 1200r

Posted: Sun Apr 22, 2012 1:28 pm
by RGV
It seems the C of G can be too low. Heres a pic of a Honda GP bike that didnt work, fuel tank at the bottom.

Image

Re: Gearing on zx 1200r

Posted: Sun Apr 22, 2012 8:14 pm
by Greg Watters
RGV Any details about the bike ,??

Chris , not sure why , but my handling turned bad and when i talked to a guy in the US , he had similar problems , to the point the track marshal had called rider down, but he did not quite crash, maybe the gyroscope saved him ;)
but his only change had been similar to mine , decided it would be better to make the weight sprung and low
put it back to previous positions and all was well again , mine is not realy sprung just tried to make use of some empty space
this is my new weight box , and will be getting some of the lower section removed
Image

Re: Gearing on zx 1200r

Posted: Tue Apr 24, 2012 6:37 pm
by momec3
RGV. Always think if it looks right it is right.

That thing looks all wrong but at least it would be good at roasting nuts. :lol: :lol: :lol:

Chris

Re: Gearing on zx 1200r

Posted: Wed Apr 25, 2012 8:04 am
by JonB
Honda ran that bike in 1984, ridden by Freddie Spencer.
Freddie hated it as the COG was too low with a full tank to get decent weight transfer under accelaration and braking.
Mechanics hated it as they had to pull the exhaust to do anything at all on the engine.

Cheers
jon

Re: Gearing on zx 1200r

Posted: Wed Apr 25, 2012 8:15 am
by Greg Watters
:D thanks Jon