Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
If we are going to break the mold of how things have been done historically with the vette I think mid engine is not the way to go. Let's just put a supercharger or twin turbos(my preference, let GM buy STS ) on a rear wheel drive setup. I cringe at the maintenance difficulties generated by putting the engine in the middle surrounded by bodywork. While they are at it they need to make it simpler to change out the clutch, removing 2/3 of the drivetrain to replace the clutch is dumb.
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Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
No Doubt, I bow to your wisdom. You are truly knowledgable in the ways of automotive physics! Polar Moment. Of course. Same as a wheel. Same weight, different diameters, the larger diameter wheel will have greater inertia and take need more force to achieve a given acceleration.
If mid-engine gets all the mass closer to the spin-axis of the car, it'll turn faster. Du-uh.
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Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
Quote:
Originally Posted by RocketSled
If mid-engine gets all the mass closer to the spin-axis of the car, it'll turn faster. Du-uh.
Yes, but that was exactly my point: The car's center of gravity does not correspond to the rotation of the car when the front wheels are steering, so in this sense it is _not_ the same as a wheel... ...or so I thought?
Interestingly, a few years back Jeep had come up with this concept car which had all-wheel steering, and it had this mode where all 4 wheels would point their axis towards the center of the car, and would allow it to spin on itself. _That_ car would benefit from a 50/50 weight distribution
Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
Quote:
Yes, but that was exactly my point: The car's center of gravity does not correspond to the rotation of the car when the front wheels are steering, so in this sense it is _not_ the same as a wheel... ...or so I thought?
RocketSled was using a wheel as an example of how a rotating mass affects moment of inertia. The point was simply to explain polar moment of inertia and how moving a mass such as the engine either forward or backward affects it.
Remember, a cars CoG moves, both laterally as well as vertically. As the car accelerates, brakes or uses fuel the CoG shifts. Think of load transfer as an imaginary shift in weight, whereas weight transfer is an actual shift or relocation of a given mass in relation to the CoG and is what we are discussing in relation to a rear mid-engine car vs. a front mid-engine car.
The wheel example RocketSled gave is one whereby an actual weight is relocated toward or away from the center of a revolving wheel, not unlike the figure skater example I used.
Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
Quote:
Originally Posted by Jofu
Yes, but that was exactly my point: The car's center of gravity does not correspond to the rotation of the car when the front wheels are steering, so in this sense it is _not_ the same as a wheel... ...or so I thought?
Think of a big fly-wheel, mounted horizontally right in the middle of the passenger compartment (so it'd have to slice you and a passenger in half at the waist so you could fit in the car). That wheel has inertia, it requires force to get it to rotate. A mid engine car has all it's mass closer to the center of the fly-wheel, the fly-wheel is in essence smaller in diameter even though it still weighs the same. It's inertia is lower and it takes less force to get it to rotate.
Picture your car from above as it traverses a closed circle, say, like on a skid pad. As the car goes around and around, it is rotating on it's "Z" axis, the same axis as that big-ass horizontal fly-wheel example from above (the car's nose is always turning to point in the direction of travel. Viewed from above, the direction the car is facing rotates 360º for every loop. The car is in fact "spinning" at a constant rate as it goes around the circle at a constant rate!). The front wheels push the car in the direction of the turn, that is true, but the force they're exerting is battling the centrifugal force that's trying to push the car out of the turn.
So, when you change direction in your car, you need to rotate the car around it's Z-axis just like in the examples above. But unlike the situation above where the rate of rotation is constant, you must accelerate the car around that axis (first one way to initiate the turn, and then the other to cancel it out) to effect the change. It's the tires that generate the force to achieve that acceleration. So all other things being equal, the lower the car's inertia, the less force is required and the more quickly the car changes direction.
Last edited by RocketSled : 08-25-2007 at 01:03 PM.
Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
Both cars depicted above could have a 50/50 weight distribution. That is, both cars could have the same weight over the front and back wheels depending on mass locations and weights. However, a rear weight bias is often preferable to a 50/50 weight distribution for the reasons discussed above.
Even if the car with the lower polar moment of inertia had a 50/50 weight distribution, it would turn faster since it requires less force to cause an acceleration: F = ma.
Bonus question: Can anyone tell me what size the tires are by looking at the drawings above?
Note: The size of the black squares merely represent a mass and are not relative to size or exact location.
Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
Quote:
Originally Posted by RC45
Does the automotive world really need yet another "just like all the other" mid-rear non-allrounder supercars?
No, it doesn't. While I'm certain GM could make a mid-engined car that looks nice, it just doesn't sound Corvette-ish to me. One of the things I like most about vettes when I'm in them is looking out over that broad powerful and long hood. I suspect you'd give that up with a mid-engined design. A small thing perhaps, but important to me at least. It all sounds like change for the sake of change, not change for the sake of improving the blood line. I'd be happy to eat crow if GM proves me wrong.
Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
I agree with you in a way, Snakecharmer. As I've said before, I don't feel a rear mid-engine design would be of benefit to the Corvette demographic at this time.
The rear mid-engine design has benefits and it also has drawbacks, but aesthetics are not chief among them. However, aesthetics do play a role in how well a car sells, if it sells at all. A case in point was the Edsel. Although technically speaking it had features ahead of its time, it simply didn't go over well with buyers. Never mind the fact it was a POS and a Ford to boot.
I too may be eating crow but I just don't see GM totally changing gears, unless...
There may be some other motivation and/or outside force/s that compel them to change direction as far as Corvette design philosophy. I'm speaking of course about things such as future emissions and C.A.F.E. standards that may preclude the use of a larger, front engine, V8 design.
A smaller, lighter car with, dare I say it: something other than a V8 may eventually become a necessity. Then again, I was saying the same thing circa the mid to late 70's on the future of Corvette design. In fact, at one time I among others believed the Corvette would ultimately take the form of something akin to a (don't laugh) Pontiac Fiero or Sunbird.
Re: The Mid-Engined Corvette is not only back on the front burner - it looks to be a
I have had all variants, front, mid and rear engine sports cars. Each has it's issues and drive completely different. At then end of the day each car was fun to drive once I learned how to drive it. Front engine is the most familiar to everyone so the learning curve is easier. The rear engine car (911 Turbo) was the most difficult to learn how to drive since it is completely different from your normal reaction response. May current car a 1975 Pantera (Mid Engine) is great to drive but when it gets loose things happen very quickly. My favorite is the front engine, but it is not easy to go AWD with that configuration. If I had a choice of Mid engine AWD or Front not AWD I would choose Mid AWD. One last point right now the Pantera can carry luggage and a set of golf clubs with out any issues can't say that for any other current Mid engine car I've seen lately.
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) on a rear wheel drive setup. I cringe at the maintenance difficulties generated by putting the engine in the middle surrounded by bodywork. While they are at it they need to make it simpler to change out the clutch, removing 2/3 of the drivetrain to replace the clutch is dumb. 
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