Care to relate as to how it isn't?

Safe to say we're now we're barking up the right tree.

Getting away from the "anti-everything-related-to-Zeta" mindset for a moment, there will be alot of the items learned from the Zeta (low cost to produce, very low cost to alter to other configurations, no set conventional "firewall" height or importance to structural rigidity, ability to alter wheelbases and wheel-to-"A" pillar relationship without reengineering an entirely new front structure, and so forth) is jumping off where Zeta left off, and will use many ideas from Zeta.

Is the Alpha a revised Zeta?
No

Is Alpha incorperating many of the innovations from Zeta?
Yes. And expanding them.

Also expect to see a bit of Kappa's jump off points on the Alpha (ie: front & rear IRS, and other bolt on components).

Technically, it is an all new chassis. But thinking it's an all new, clean sheet, based on nothing else design isn't actually true.

We also are extremely likely to even see quite a bit of Espilon in the Alpha via shared wiring routing and nondrivetrain and nonstructural related subsystems and assemblies, which will enable GM to use existing systems that customers don't see without having to invest money and time in developing these systems and a new OEM network to supply them (the thing that is now being admitted as being the key that sunk the North American Zeta program... the expense of setting up everything here).


Think of it as a Kappa to the Corvette, or the '83 F-body to the Monza.

New chassis... Plenty of improvements... But a lot carried over from the older platforms (both directly and new ideas based on them) as well.

And sorry... that includes Zeta.

 

This is train of thought I was trying to imply in saying that I wasn't sold on Zeta being completely turfed completely, but never really got there - Guy said it much better..... and more coherently.

 

Everybody has different ideas about what is meant when someone says "based on".

To me and, from what I understand, Z284ever "based on" means that you took an existing chassis and said how could I redesign this to meet the needs of _________ .

On the other hand if they say lets come up with a new chassis for _______ . If that chassis draws from past experience including lessons learned from Zeta its not the same thing to me.

1. Lets take Zeta and shrink it and improve it.
2. Lets build a new chassis to fit our needs.


2 is always going to draw on past experience that doesnt mean its a jumping off point. If that were the case then you could make the argument that any previous chassis was a jumping off point.

 

You've got my attention now!

 

Actually in this instance, it is. Here's what I mean.

When GM decided that the mid 70s Monza would not replace the Camaro, and they decided not to base the 3rd gen Camaro on the upcoming FWD X-body, they took a look at the best RWD option they had: The Chevrolet Monza-Vega. The rear suspension setup came directly from those cars, and the underbody setup is based on the Monza.

Another example.

When GM decided to downsize it's cars in the 1970s, the downsized full size cars used GM's then current intermediates as the starting point. The frame was altered somewhat, but the 1977 Impala still had alot of 1977 Chevelle under it's body.

Final example.

The Kappa. The Kappa isn't identical to the Y-body (Corvette). but you can see a whole lot of Corvette principles at play in the unskinned rolling chassis.


The reason for these types of jump-offs is cost, speed, and the ability to use as much existing tooling or systems as possible.



I think the problem here is that we're thinking too far in absolutes. Based on what you wrote, you seem to take the view that either something is a modified Zeta or it's an all new design.

Take the Zeta's quasi-frame up front. It's a tubular structure that carries the load and the forces of a head on or offset frontal collision. It also enables the front suspension assembly to be mounted anywhere along that frame with minimal investment. The traditional unibody method is to have an entire stamped side and firewall sections to the engine compartment that bear loads, take impact forces , but if you want to alter anything (wheel location, lowering or raising the beltline), you have to spend alot of money creating essentially a whole new front substructure.

The proportions of the new Camaro would have been impossible on a traditional unibody constructed chassis. Camaro has a higher beltline & front wheels farther from the passenger compartment than the Commodore/G8. It cost GM comparatively very little money to do that. If it had been done on (say) a Sigma, it would have been prohibitively expensive.



That Zeta type front substructure will no doubt be in the new Alpha (it's being planned for usage in a wide variety of types of car, so it's a necessity). GM might create a lighter version of it (since it doesn't have to withstand the impact of a 2 ton vehicle behind it). GM might decide it wants to engineer in more flexibility in configuring the front end. GM might decide that instead of Zeta's heavy tubular rear section where the IRS attaches to, they can go the route Ford did with the DEW, and simply fortify the section where the IRS assembly attaches to the underbody (since the Alpha won't have to have the capacity to becaome a pickup truck...a Ute... baked into the chassis).


I feel you're seeing it as the 2 extremes of either GM sitting a Zeta in the garage and figuring out how to cut some weight or else GM starting all new from scratch which isn't what's likely happening in this case.

In fact, GM is more likely looking at various aspects of Zeta and saying "OK, we need this front inner structure from Zeta... how do we make it more adaptable and lighter", or we need this IRS system from Kappa adapted to fit on a unibody instead of a rolling chassis.

I think this clears up my meaning of "Jump off point" in this instance.

 

Doesn't Kappa use the narrow Gen I Sigma's IRS? Also isn't the SLA setup very similar to the 4th gen F-body one?

 

Now we're making progress my friend.

You've gone from: Alpha is dead ----->Alpha is based on Zeta -------> to ----> Is Alpha a revised Zeta? No.

Bravo.

I'd LOVE to see that, especially Kappa's nifty front suspension. But we'll see. Using struts up front instead of a coilover SLA, like Kappa's, is the easiest way to save afew hundred bucks per car.

I think it's safe to say that, (like every other car company), GM shares parts, systems and techniques throughout it's lineup. I can look at a Cobalt and Corvette and see where they've shared parts or design. That however, is not the same as saying that the Corvette is based on the Cobalt.

 

Absolutely.

I can't imagine Cadillac reverting to the austere IRS used on the previous Commodore though. Alpha's IRS will certainly be top shelf if Cadillac gets it's way. And it won't be saddled with the requirement to withstand 700 hp in a 4200 pound car.

They may comparatively skimp on the front though. We'll see.

Oh yes I agree, it'll be very interesting to see what develops.

 

What are the odds that Alpha could accommodate both a simple (cheap) McPherson setup (Zeta) and the elegant (expensive) SLA (Sigma) setup? Should the chassis have a modular/flexible front end as Guy is suggesting with different axle: dash ratios and firewall heights would it be that expensive/difficult?

 

Just a hunch, but I'd doubt they'd do that.