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C3 (vuosimallit 1968-1982) Corvette C3 - "Shark Body"

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Old 28.07.2018, 16:15
barum's Avatar
barum barum is offline
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barum on oikealla tiellä
Toki, tyhmiähän ne vetteinssit tunnetusti on.

Tässä Tadgen kommentit kyseiseen reunaehdolliseen optimointitehtävään:

Good observation, Nosferatu. A true "gearhead" question.

Before I worked in car design, I assumed that transmission gearing would be a lot like gears on a bicycle - you could match a set of gear teeth and get most any torque multiplication you wanted. Automotive transmissions are a lot more constrained. For several generations we have used 6 and 7-speed boxes from Tremec. There are few manual transmission suppliers left in the world and Tremec's unit is the one that fits best in a Corvette and is durable behind our engines. If you study all the ratio sets we have ever used with that transmission, you will notice that 4th gear is always 1:1. That is a foundational aspect of the transmission's architecture, essentially a fixed gear that we have to work around.

Gear selection involves a balance of performance, fuel economy, driveability and other metrics. Typically the standard car is biased towards taller ratios, better fuel economy and easy driveability. On more serious performance models we get more aggressive with the ratios to get higher performance off the line, better 0-60 and 1/4 mile times and quicker lap times on auto cross and most race tracks. If we could change 4th gear and get more even drops, we would, but that is just not possible. In the end, we decided not to ignore the performance potential of aggressive gearing in 1st - 3rd just to avoid a larger than optimal drop on the 3-4. Fifth gear is rarely used on the track but the major considerations there are optimization for top speed and end-of-straight speed at the Nurburgring.

Another way to accomplish the same end is to change the final drive ratio in the differential. Here again there is no free lunch. We use a variety of final drive ratios from 2.41 - 3.42 with the manual at 3:42. We already spec at the aggressive end of the range for all manual transmission cars. Why no 4:11, or more aggressive gear set? Durability and packaging. The final drive ratio is set by the relative size of the ring and pinion gear. To get more ratio, we would have to go down in pinion gear size or up in ring gear size. Smaller pinion gears are just not durable enough to stand up to a life in a Corvette. Larger ring gears make the whole differential larger, adding mass and making the whole transaxle longer. Since the location of the transaxle in the rear is pushed as far forward as it can be already, the impact of a larger differential actually make the wheel base and whole car longer! That would add even more mass. So you see, as usual, what we have in production is a carefully selected balance of competing constraints.

The question also specifically refers to "overdrive" gears. From a technical standpoint all that means is that the ratio is less than 1:1. Architecturally our manual transmission must have all gears above 4th as overdrive gears, but that is not a bad thing. Theoretically you could have a transmission with all overdrive gears and still have a perfectly driveable car - you would just need an extremely short final drive ratio. Mechanically, that is not practical or efficient so you don't see it in production on any mainstream cars.
"The world has gotten it into its head that wind power is the solution to everything, and I just don't think it is. Wind is just annoying, internal combustion is good."
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Old 25.04.2019, 10:22
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Puman Puman is offline
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Puman on oikealla tiellä
Originally Posted by MrT
On, täydellinen yhdistelmä. Ykkönen riittää satkun vauhtiin ja vitosella (0,62) 2000rpm~120kmh

Olikso sulla TKO 500 vai TKO 600?
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