21 replies to this topic

[Gerald Ryan]

I just finished an interesting conversation with a colleague about vehicle dynamics, handling, steering, driver feedback etc.

Two points.

First; some while ago it was reported that an engineer at GM (Cadillac?) proposed continuing to develop GM's front-wheel-drive chassis (for the large cars) on the premise they could be made competitive with the rear-wheel-drive offerings of the Eurozone luxury car manufacturers. It was thought that with careful development of vehicle stability systems and electronic traction controls etc., the front-wheel-drive chassis could be made to handle at least as well as the rear-drive competitors, while retaining significant advantages in low traction conditions and also being more economic (for the manufacturer as well as for the vehicle user). I remember something being reported about this project by McGuire (I think). Does anyone know more about it and what occurred? Who was the lead engineer on this? Are there any papers or information around that can be looked up?

Second; my colleague reports the stunning results that Lotus had with active rear-wheel-steering and how intervention at the rear wheels of the car could "rescue" it from events that would ordinarily result in loss of control situations ("departures" he called them). He also was most positive about how the system could significantly improve how the car behaved in normal driving and how much better it felt to the driver. That's interesting. Perhaps a combination of rear-wheel-steer and front-wheel-drive chassis really could offer something advantageous. Any coments?

[Greg Locock]

With regard to the GM comment, yes, I think that with the exception of steering feel, and acceleration out of corners, you could build a FWD car that sort of matched RWD for steering/handling. Would it be as cheap, quiet, etc etc? I don't know. The ultimate performance would have to be less, for a given weight and tire size.


Was the Lotus rear steer an active rack? If so, when?

Or was it vectored thrust (ie variable diff split) or a conventional brake based system?

Reason I ask is that I worked on the Lotus SID and it just had a donor driveline from a 6R4, and no rear rack, so an active rear wheel steer system must have been since 1990. I am occasionally in contact with the original engineer for that program, Richard Hurdwell.

[phantom II]

The Cadillac DTS and the big FWD Buicks will be discontinued this year announced this week. Tragic really. The smoothest riding, quietest and nicest luxury car on the road is the DTS. There is no intrusion into the passenger compartment by the mechanicals which calls for a lighter and more insulated structure than a RWD platform. My wife's FWD V8 Oldsmobile is a wonderful car. Except when you floor it and drive in mud, snow or slippery roads, you will never know the difference. For 99% of situations and 99% of drivers, FWD passenger cars are superior. Why, I even heard of a guy who wants to build a FWD Ferrari. :
Talking about Cadillacs, where is their S class or Bentley size luxury car in the fastest growing and most profitable automotive global segment? Where? American motor manufactures seem to have no will to survive. Maybe that applies to our whole nation anymore.

Originally posted by Gerald Ryan
I just finished an interesting conversation with a colleague about vehicle dynamics, handling, steering, driver feedback etc.

Two points.

First; some while ago it was reported that an engineer at GM (Cadillac?) proposed continuing to develop GM's front-wheel-drive chassis (for the large cars) on the premise they could be made competitive with the rear-wheel-drive offerings of the Eurozone luxury car manufacturers. It was thought that with careful development of vehicle stability systems and electronic traction controls etc., the front-wheel-drive chassis could be made to handle at least as well as the rear-drive competitors, while retaining significant advantages in low traction conditions and also being more economic (for the manufacturer as well as for the vehicle user). I remember something being reported about this project by McGuire (I think). Does anyone know more about it and what occurred? Who was the lead engineer on this? Are there any papers or information around that can be looked up?

Second; my colleague reports the stunning results that Lotus had with active rear-wheel-steering and how intervention at the rear wheels of the car could "rescue" it from events that would ordinarily result in loss of control situations ("departures" he called them). He also was most positive about how the system could significantly improve how the car behaved in normal driving and how much better it felt to the driver. That's interesting. Perhaps a combination of rear-wheel-steer and front-wheel-drive chassis really could offer something advantageous. Any coments?

[Greg Locock]

I've just been contacted by another ex Lotus engineer (presumably Gerald's colleague), he confirmed it was true 4ws with a second rack. Turns out I had been in that car and did some work on it!

Renault or Citreon have just brought out a 4ws FWD production car I think.

[phantom II]

This is a fully active suspension and steering on all 4 corners from Racecar Engineering a few years back.



There have been many mechanical rear wheel steering mechanisms, Honda Chevy truck and Renault to mention a few. I built a 3 trailing link roll understeer live axle in my roadster years ago and it worked better than the IRS I replaced it with. I remembered the axle from a Renault 12 which had roll oversteer which worked really well in their FWD car. They even had a Gordini sports car version that handled very well.
Cadillac was well underway with a new RWD platform for its $100 000 V8/12 Cadillac based on the 16 concept, but it was recently abandoned because of corporate average fuel economy standards which only apply to American car companies.. A bunch of communists telling me what I'm allowed to drive.
Mean time there is a $120 000 Lexus available on this market. Mercedes, BMW, Bentley and soon a small Roll Royce will be here also. Where is Cadillac? The FWD Cadillac platform is at the end of its build cycle after the FWD Northstar transaxle has been perfected, what a damned shame.
I would love a $100 000 FWD Cadillac. Caddy have made huge FWD cars since 67. The Bentley has a huge V12 Volkswagen engined front transaxle, and Cadillac could easily make a similar AWD layout. This is the way to go for a luxury car and Cadillac could showcase advanced technology that you descibe. I hope somebody throws some light on it.
The emerging markets would love such a vehicle and the active rear steering would cure any violent understeer that the Bentley has. Cadillac could and should be the standard of the world again. China already builds a stretched version of the Cadillac STS. We don't get it because of side impact laws.
I am totally ******* myself about the impending communist government due in November.
GM and me may leave these shores for friendlier pastures were $100 000 Cadillacs abound.

Originally posted by Gerald Ryan
I just finished an interesting conversation with a colleague about vehicle dynamics, handling, steering, driver feedback etc.

Two points.

First; some while ago it was reported that an engineer at GM (Cadillac?) proposed continuing to develop GM's front-wheel-drive chassis (for the large cars) on the premise they could be made competitive with the rear-wheel-drive offerings of the Eurozone luxury car manufacturers. It was thought that with careful development of vehicle stability systems and electronic traction controls etc., the front-wheel-drive chassis could be made to handle at least as well as the rear-drive competitors, while retaining significant advantages in low traction conditions and also being more economic (for the manufacturer as well as for the vehicle user). I remember something being reported about this project by McGuire (I think). Does anyone know more about it and what occurred? Who was the lead engineer on this? Are there any papers or information around that can be looked up?

Second; my colleague reports the stunning results that Lotus had with active rear-wheel-steering and how intervention at the rear wheels of the car could "rescue" it from events that would ordinarily result in loss of control situations ("departures" he called them). He also was most positive about how the system could significantly improve how the car behaved in normal driving and how much better it felt to the driver. That's interesting. Perhaps a combination of rear-wheel-steer and front-wheel-drive chassis really could offer something advantageous. Any coments?

[desmo]

I recommend the People's Rupublic of China comrade. They make stuff cheap and don't have laws that affect rich people much or any of that gay hippie environmental regulation. Don't forget to join the Party for full benefits

[Ben]

Originally posted by phantom II

I am totally ******* myself about the impending communist government due in November.

Communist! Are you mad. Please find a dictionary and a history book...

Ben

[Fat Boy]

Originally posted by phantom II

I am totally ******* myself about the impending communist government due in November.

It is getting pretty close to election time. Instead of spending time on cars don't you have to go cut eye holes in a bed sheet?

[McGuire]

Originally posted by phantom II
I am totally ******* myself about the impending communist government due in November.

That's why they make the special undergarments for people your age.

[phantom II]

I can always count on the usual suspects. Communists, the lot of you.
"You may not be interested in history, but histroy is interested in you." Trotsky

[phantom II]

I would buy this car tomorrow for $120Gs if GM wasn't so cowardly by capitulating to the commies.

[Fat Boy]

Yep, I'm such a lefty.

[Gerald Ryan]

Gentlemen

I was seeking comment about front-wheel-drive and rear-wheel-steer. Seriously, that was what I wanted to learn more about. That is why I asked you about it. How about we get stuck into that and not each other?

So, does anyone know where material relating to the GM FWD for large cars may be found? Who was the engineer?

Regards

Gerald

[phantom II]

The FWD Cadillac chassis will be discontinued this year. This means that any development along these lines have almost surely been abandoned. McGuire is probably the only one here that could address your query, and he aint talking. The DTS is faster in all areas of performance over the E class, and 5 series BMW including the slalom according to Road and Track. The question is, Are you a communist?

Originally posted by Gerald Ryan
Gentlemen

I was seeking comment about front-wheel-drive and rear-wheel-steer. Seriously, that was what I wanted to learn more about. That is why I asked you about it. How about we get stuck into that and not each other?

So, does anyone know where material relating to the GM FWD for large cars may be found? Who was the engineer?

Regards

Gerald

[Gerald Ryan]

Phantom II

I'm no communist; not a socialist either.

Gerald

[Gerald Ryan]

Greg ,

Seems we have some mutual associates. I correspond with a couple of Lotus alumni. On this occasion I was speaking with an ex-Bishop designer. BTW you're held in high regard.

The Lotus SIDS is supposed to have ended up with a rear r&p which was controlled actively. I understand there was an SAE paper that discussed some of the results of the test program. I'm sure I have a copy, but it's in a box (one of several) that I have yet to open (since the last big house move). If I locate it I'll post the SAE number.

I don't know much about asymmetric thrust across the differential. Seems a good idea worth exploiting; probably offers means to correct a lot of sins (avoiding some annoying compromises) in a chassis. It could be very useful in a FWD car. Did SIDS have it? I don't know the answer.

Regards

Gerald

[Greg Locock]

I wish we did more work with Bishops, one of 'my' best vendors.

Like I said SID's drivetrain was pure 6R4, I am 99+% sure the axle diffs were passive, in that timeframe. Unfortunately I left Lotus soon after they got SID running, so I was never involved in the test program.

[PirateTaco]

Originally posted by Greg Locock
I've just been contacted by another ex Lotus engineer (presumably Gerald's colleague), he confirmed it was true 4ws with a second rack. Turns out I had been in that car and did some work on it!

Renault or Citreon have just brought out a 4ws FWD production car I think.

The Renault Laguna GT has 4ws called Active Drive at the moment. unfortunately there isn't much on the internet about the system or how it works.

[Greg Locock]

There was a 2 page feature on it in one of the trade mags, with pictures, I'll see if I can find it.

We were just talking about this yesterday - apparently one of the problems Mazda found with using in phase steering at high speed is that if you do need opposite lock in a high speed lose, then the rear wheel steering is making things worse.

[cheapracer]

But you get to a higher speed before you lose it with the addition of RWS.
Rob Peter to pay Paul.

[cheapracer]

Originally posted by desmo
I recommend the People's Rupublic of China comrade. They make stuff cheap and don't have laws that affect rich people much or any of that gay hippie environmental regulation. Don't forget to join the Party for full benefits

Rich people here have laws the same as the poor people but Judges and Police get about $150 USD per month salary so when the rich folk poke a couple of thousand under their noses the judgements tend to go in your favour - suprise, suprise.

Most Judges and Police drive various levels of new cars here - on a $150 per month.

The Caddys are popular here P11 along with Chrysler 300C's and I'm starting to see more and more Buick Parkroyals around (Holden Caprice).

[pingu666]

think my dads old citroen xanti estate or whatever its called has fwd, and rear stearing, only 5 degrees or something small