Driveline gear ratios

[Natho]

Hi I a novice in this area, but I have read different posts and I notice that most teams only seem to use the 1st, 2nd and 3rd gears during an event. Would it not be better to increase your final drive ratio so your are using 4 & 5 gears and maximise the spread of torque under acceleration? The sae team i am joining currently has a purely mechanical shift system and the drivers prefer using only the 1st couple of ratios as it is difficult to shift. If a pneumatic system was implemented and shifting was made easier would it not be beneficial to use all the ratios available? I know there are other factors such as the torque curve of the motor, just wondering what the thoughts are on this?

[Pete M]

As the shifts get faster and faster, shifting more will be faster. The trade off between being in the right part of your power band and not losing time to shifts will be different for each package. Remember though, that if you're only changing the final drive ratio, you won't be changing the spacing of the gears in terms of engine rpm, only in terms of drivetrain speed. If you want to use more of your power band, you have to change the transmission ratios themselves.

[Brett Neale]

Another thing to think about it sprocket sizes too - We ran a 11 tooth front sprocket (as small as you can possibly go) and the rear had to be 48 teeth to give us our required ratio. This worked, but increasing the ratio would make the rear sprocket bigger and harder to package into the rear assembly.

[The AFX Master]

the compromise between shift times, gear usage and final drive is very important on the driveline design.

Charlie Ping wrote a paper taking into account the effect of the shift times on the final drive selection, do a search on the forum or PM him. A well done and useful lecture..

We also send our gearbox to the slaughterhouse to get rid of the 4th,5th,6th gears (CBR 600 f4i).. you'll impressed with the lot of weight you can shave off your engine. We had no reliability problems on almost 3 years with that

[Natho]

Cool thanks guys.
Is there anyway i can access the Charlie Ping article other than paying $14?

[Charlie]

It's recommended that you buy it (not that I get a cut), but if you dig a bit it's not hard to find. http://fsae.com/groupee_common/emoticons/icon_smile.gif http://fsae.com/groupee_common/emoticons/icon_wink.gif (http://www.cpmaverick.com/Misc/2004-01-3554.pdf)