Nissan takes a brave leap in Le Mans

[NeilBlanchard]

Three-Wheel Vehicle Handling Characteristics



The reverse trike is much better for aerodynamics and for high speed stability than the trike; all else being equal. Just look at the ideal template and see how to best put it on 3 wheels.

[tjts1]

Nope, sorry. A shorter wheel base would have required much wider front tires and as a result wider front end. If they reversed the configuration there wouldnt be enough traction in the back and they would be giving up all the aerodynamic benefits. Don't forget that this is a racecar which is either accelerating or braking at all times. The engineers got it right. Also this isnt a trike.

[Frank Lee]

Originally Posted by NeilBlanchard

The Cg on a trike projected as a 45 degree cone to the ground forms a circle, and that circle *must* be within the triangle formed by the tire contact patches. This DeltaWing is technically not a trike, but it might as well be. Under hard braking and hard cornering at the same time would really threaten the stability of this layout.

It is odd that *both* the stability and the aerodynamics would be better if the two (widely spaced) wheels were in the front. Then the wheelbase could be shorter because the weight shift under hard braking and hard cornering would move the Cg closer to the wide track wheels and this would be far more stable.

They want fast steering response so they did it correctly.

[niky]

Remember also that that COG isn't precisely centered in the vehicle, but very far back... supposedly on the rear axle itself... so the balance is not quite the way we expect it to be.

[womprat]

Originally Posted by NeilBlanchard

Three-Wheel Vehicle Handling Characteristics



The reverse trike is much better for aerodynamics and for high speed stability than the trike; all else being equal. Just look at the ideal template and see how to best put it on 3 wheels.

I'd gather that's the reasoning for the really long wheelbase. Those two front wheels being way out in front gives back the stability lost with the format. But the issues with getting power down in a reverse trike are harder to mitigate.

Now, this is a high power to weight ratio racer, I can imagine a reversed layout was considered, but a single (or narrow pair) driven rear wheel probably didn't meet the traction requirements for acceleration. Bare in mind this thing has one insane power to weight ratio. 631hp per ton.

I also imagine a clever differential will help this thing keep pointing in the right direction, something you lose the ability to have on a reverse delta.

Add to that your race driver doesn't need to re-learn car control skills, he still has two powered rear wheels to manage with his right foot that should work just the same.

So there's some reasoning why it is what it is, this is probably the only way to do a delta layout for racing at this level.

[tjts1]

A couple more shots for comparison.


Front and rear tires

[NeilBlanchard]

If you read the Riley article I linked to, the quick steering response is a characteristic of all trikes and reverse trikes. I think though that since this a rear engined race car, and that the rear wing is need to add down force on the rear wheels, are the reasons they went this way.

I realize there are two front wheels, but it is effectively a trike.

[tjts1]

Yeah, i dont think you can compare this to a 3 wheeler for many reasons.

[serialk11r]

I'm pretty sure the car is meant to steer primarily with torque vectoring at the back rather than using the front wheels (which have barely any weight over them). Should turn out to be interesting.

[botsapper]

Not exactly as a joke but a pointed analogy. The DeltaWing's two rear wheels will have the bulk & double responsibilities of forward traction as well as torque steering capabilities, relegating the tiny & vestigial two front wheels essentially as forward casters or bogies.

http://www.youtube.com/watch?v=rBKB1eQxEVQ