Steering Problem?

[Mike O'D]

Hi Barry,

I agree, but think the chances of a shop doing that nowadays is fully none. I think that in the U.S. back in the day they probably never did it either. I also don't believe that a shop will put weights anywhere in the car before doing an alignment. So, I'm one of those design engineers (not cars, but the thinking is the same) - let me give you a different perspective. The only way to set accurate alignment specs is if every car is sitting at exactly the same ride height. Full tanks, nearly empty, junk in the trunk, etc. etc. will all effect that. It's not that they expect it to ride there, but if the spec is set at that point, then it will be good at whatever the load is. Setting the book spec at some other ride height - who knows what you actually have. I have no idea how much difference it will actually make, but the thinking is solid.

Mike

 

[Shannon Boal]

[Series Alpines don't come anywhere close to having the steering axis intersecting the center of the tire contact patch. Primarily because of a very low steering axis inclination, Series Alpines have more than 2" of positive scrub radius with factory wheels]
Barry, you have given us all a ton of stuff to think about......none of which I have figured out entirely.
Rootes used 5-1/2 degrees SAI, steering axis inclination.... SAI causes the outboard tire in a turn to be loaded heavier than the inboard, because it raises that side of the vehicle as the wheels are turned, lowering the other. This helps a car to enter a turn, to prevent understeer. USA small cars were using about 7 degrees. Was this effect needed less on the Alpine, than the American cars, because of the Alpine's low center of gravity, and low roll center?
The low SAI created positive scrub radius, as you pointed out.....the Alpines were refined by racing on gravel and dirt roads..... did the tire scrub only matter on paved roads?
The Alpine has a wider front track than rear track, was this also suited for dirt/gravel racing? And....is this all part of why they hunt about in the lane on asphalt highways? Debbie's Dodge Dually is much wider in the rear than the front, and it sure does like to hunt around the lane......At best, this is food for thought, but you got me thinking!
Shannon

 

[husky drvr]

[Series Alpines don't come anywhere close to having the steering axis intersecting the center of the tire contact patch. Primarily because of a very low steering axis inclination, Series Alpines have more than 2" of positive scrub radius with factory wheels]
Barry, you have given us all a ton of stuff to think about......none of which I have figured out entirely.
Rootes used 5-1/2 degrees SAI, steering axis inclination.... SAI causes the outboard tire in a turn to be loaded heavier than the inboard, because it raises that side of the vehicle as the wheels are turned, lowering the other. This helps a car to enter a turn, to prevent understeer. USA small cars were using about 7 degrees. Was this effect needed less on the Alpine, than the American cars, because of the Alpine's low center of gravity, and low roll center?
The low SAI created positive scrub radius, as you pointed out.....the Alpines were refined by racing on gravel and dirt roads..... did the tire scrub only matter on paved roads?
The Alpine has a wider front track than rear track, was this also suited for dirt/gravel racing? Shannon

Shannon,

I'll throw in a couple more things to think about for Rootes' suspension design.

First, is that the design was not developed specifically for Alpines. It dates back to at least the first Audax body design, the Rapier. Next the design was carried forward through the Minx and Husky iterations, leading to the parts bin used for Alpine development. So, do you think the large scrub radius might have been intentional to provide slightly "easier" steering effort because no power steering was available for a larger, heavier sedan body?

Second, the front control arm design is a "semi-trailing arm" design, where the motion of the upright and stub axle is not just vertical in response to a bump input. The upright actually moves upwards and backwards at the same time to travel over a bump. This was done to make the suspension feel more supple and compliant when encountering a bump by slowing down the accelerations imparted to the suspension and thence into the unibody. As you might imagine, this design can also influence road handling performance in some unexpected ways - mostly negative. As an example, consider that when the body is in roll in a turn, (the instant roll center - IRC), the left IRC and right IRC will not stay in the same position. Most designs wont, but will stay fairly close to each other on the same vertical axis. The Alpine's design also has the IRC's shifting away from each other in the fore and aft directions. If you've ever seen a picture of a stock Rootes car in a maximum cornering effort, then you've probably seen how the outside front corner appears to, not just want to roll down to the outside, but also seems to want to roll the car's outside front corner back and down under the rest of the car. This motion also wants to lift the inside rear tire off the ground because of the way the body's roll axis is skewed.

Just more to think about,

Don

 

[RootesRooter]

And yet, for all these supposed design faults, you can put a neutral-steering Alpine, with stock suspension, out on a track and it'll keep up with the best of its day - in the corners at least.

Shannon,

I'll throw in a couple more things to think about for Rootes' suspension design.

First, is that the design was not developed specifically for Alpines. It dates back to at least the first Audax body design, the Rapier. Next the design was carried forward through the Minx and Husky iterations, leading to the parts bin used for Alpine development. So, do you think the large scrub radius might have been intentional to provide slightly "easier" steering effort because no power steering was available for a larger, heavier sedan body?

Second, the front control arm design is a "semi-trailing arm" design, where the motion of the upright and stub axle is not just vertical in response to a bump input. The upright actually moves upwards and backwards at the same time to travel over a bump. This was done to make the suspension feel more supple and compliant when encountering a bump by slowing down the accelerations imparted to the suspension and thence into the unibody. As you might imagine, this design can also influence road handling performance in some unexpected ways - mostly negative. As an example, consider that when the body is in roll in a turn, (the instant roll center - IRC), the left IRC and right IRC will not stay in the same position. Most designs wont, but will stay fairly close to each other on the same vertical axis. The Alpine's design also has the IRC's shifting away from each other in the fore and aft directions. If you've ever seen a picture of a stock Rootes car in a maximum cornering effort, then you've probably seen how the outside front corner appears to, not just want to roll down to the outside, but also seems to want to roll the car's outside front corner back and down under the rest of the car. This motion also wants to lift the inside rear tire off the ground because of the way the body's roll axis is skewed.

Just more to think about,

Don

 

[husky drvr]

And yet, for all these supposed design faults, you can put a neutral-steering Alpine, with stock suspension, out on a track and it'll keep up with the best of its day - in the corners at least.

LOL ... In the context of "all suspension designs are a compromise in some manner", the Rootes design is optimized for other things than "best" performance handling. I didn't say it was a BAD or lacking design.

On the track? Is that a totally original setup? Or something that more closely follows C. Chapman's quote, "any suspension will work, if you don't let it."?

Either way, it's probably a better comment on the "state of the art" of suspension design, in general, for the Alpine's production time frame. Or maybe it's just that the Alpine's somewhat heavier, stiffer body allows the suspension to operate a bit closer to it's design parameters than its competitors?

 

[Jay Laifman]

FWIW, I recently communicated with a former Rootes factory driver. I don't have the specifics. But he said there was something about the front suspension for racing that needed modification on the early series, but was revised by the factory for the later series, and that lowering the rear end and the fuel tanks was necessary for best handling.

 

[husky drvr]

200 feet diameter skid pad - not quite level - pic is about where pad starts breaking down hill - white cloud might have some tire smoke from lifted inside rear but mostly marking chalk - driven by my dad.

I don't recall the numbers - this was done mid '70's, but it was the worst on the skid pad that day at "Test and Tune" event.

Transitional is not too bad but steady state is a challenge.

 

[Barry]

The information I have found / seen indicates that the Series Alpine front suspension dimensions and geometry are essentially identical to the post-WWII 1945 Hillman which was probably essentially identical to the pre-WWII 1939 Hillman. The bottom line is that the Series Alpine front suspension design dates from a 75+ year old English family sedan. It is neither a modern nor "sports car" front suspension and expecting either modern or sports car performance is unrealistic.

 

[RootesRooter]

The information I have found / seen indicates that the Series Alpine front suspension dimensions and geometry are essentially identical to the post-WWII 1945 Hillman which was probably essentially identical to the pre-WWII 1939 Hillman. The bottom line is that the Series Alpine front suspension design dates from a 75+ year old English family sedan. It is neither a modern nor "sports car" front suspension and expecting either modern or sports car performance is unrealistic.

Yet the Alpine displayed modern (for it time) sports car performance. At SUNI II, Don Sessler claimed that his class-winning Series IV had stock suspension, tho I think the back end was lowered.

 

[husky drvr]

Yet the Alpine displayed modern (for it time) sports car performance. At SUNI II, Don Sessler claimed that his class-winning Series IV had stock suspension, tho I think the back end was lowered.

Claiming something is "stock" doesn't always mean the assembled parts are what the factory assembled on the car originally.

 

[DAK]

Jay Laifman, Mike O'D, Shannon Boal, Barry, RootesRooter, Bill Blue, jumpinjan, Junkman, husky drvr, and anyone I missed:

Thanks for all the input regarding my "Steering Problem?". You've certainly given me a lot to consider and check out. I appreciate the time that all of you took to read my post and respond to it.

I apologize for taking so long to return to the forum. Family matters.

Thanks a lot to all

Don K