You sure you know what you're doing? Reveng of the Nerds...
02-20-2014, 05:36 AM
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Re: You sure you know what you're doing? Reveng of the Nerds...
:sigh:
Who can I trust if I can't trust Shine and the Soooper Genius?
FWIW, I forgot to update this thread but I did a test day with the reduced caster and didn't notice any difference in behavior at the autoX. Not sure what the deal was with the initial test drive but my guess is that it was influenced by the weather more than anything (cold weather, cold rear tires) whereas at the autoX they got some heat into them and the balance was back to normal.
Who can I trust if I can't trust Shine and the Soooper Genius?
FWIW, I forgot to update this thread but I did a test day with the reduced caster and didn't notice any difference in behavior at the autoX. Not sure what the deal was with the initial test drive but my guess is that it was influenced by the weather more than anything (cold weather, cold rear tires) whereas at the autoX they got some heat into them and the balance was back to normal.
03-01-2014, 02:47 PM
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Re: You sure you know what you're doing? Reveng of the Nerds...
You know how amongst the annoying things about nerds is that they keep coming back? And so it is with the inner nerd - it keeps coming back...with "What about This?!" And so I'm back.
Here's the thing - I don't know Dick...Shine...but the picture I've drawn of him is that he got results, was willing to tell what he knew/thought, but didn't/couldn't explain this one thing - his thing about caster on front wheel drive race cars. With not much to go on, and one failed attempt at solution already, I still want to believe him.
I was all hung up on what happens from the contact patch by way of the steering axis and up thru the steering wheel. And my belief in the hypothesis pulled me into unsustainable thoughts (Road Runner Physics). My inner nerd had to retreat into my brains silent workshop.
The other day I found myself drawn to read a thread on the F1 Technical board about driver styles, and found my conscious mind asking "Why am I reading this?". That I kept reading seems to have been due to a work order originating in the workshop. "What about this?"
If you read the chapter in RCVD on Tire Behavior, you find two images of particular interest here: a plot of Lateral Force (call it Fy) against Slip Angle, and a plot of Aligning Torque (call it Mz) against Slip Angle. You can (and have) to imagine the "sum" of those plots as they are expressed at the steering wheel.
As we add Mechanical Trail, the proportion of the Fy signal sensed at the steering wheel increases. The peak Fy still occurs at the same Slip Angle, and so it's easy enough to plot a set of cumulative curves for increasing amounts of Mechanical Trail. I did three of them at half, equal and double the amount of force from Mz.
At zero MT, the force at the steering wheel (AT only) peaks before Fy and tends toward zero as Fy is peaking. By an MT of double the AT the force at the steering wheel peaks at about the peak Fy.
All very fine and well...but So What?
My inner nerd is telling me to tell you to think about how we drive a front wheel drive race car thru a corner. What "style" does the stupid car force on its driver if only thru the narrow set of options it allows?
Do we actually drive a front wheel drive race car at peak Fy very much? Do we want, amongst the three driver inputs (eyes, ***, hands) to be reconciled, Peak Fy to be the one we're sensing thru the wheel?
I think I mentioned how Smith implanted for many of us the idea that we were driving to the "top" of a curve. But upon reflection, I'm asking myself if I am thinking and doing two different things? Sensing a soft curvy top isn't easy. Sensing a significant falling off is easier. An answer has to relate back to the drivers sensitivity and resolution. I've driven both types of curves and am pretty sure I prefer "falling off".
So think in terms of a falling off type curve from relatively low caster. There's a zone from peak Mz to peak Fy. How do I know where I am and what I'm doing? Those other two senses...AND a right foot.
Something should be bugging you about peak Fy. What can't you do at peak Fy? Apply any throttle. You got a problem with that? I got a problem with that.
See where I'm going? When you add caster, and push the feedback curve toward peak Fy, you are inviting a racing driver of average skill and sensitivity to operate the car at or beyond a point at which application of throttle can only result in push and add heat to the front tires.
This reinforces the idea that a key part of making a front wheel drive race car TURN, is that the rear of the car "let go" well before peak Fy at the front. From there we control the rear with the throttle, and the gap between where we are and peak Fy is the drive capacity we have available for the job.
I believe that this is what Dick Shine was on to and couldn't explain. The high caster front wheel drive car actually conveys Less information to the driver and biases that information such as to encourage overworking the front tires.
Scott, whose inner nerd is asking when he gets to drive again...
Here's the thing - I don't know Dick...Shine...but the picture I've drawn of him is that he got results, was willing to tell what he knew/thought, but didn't/couldn't explain this one thing - his thing about caster on front wheel drive race cars. With not much to go on, and one failed attempt at solution already, I still want to believe him.
I was all hung up on what happens from the contact patch by way of the steering axis and up thru the steering wheel. And my belief in the hypothesis pulled me into unsustainable thoughts (Road Runner Physics). My inner nerd had to retreat into my brains silent workshop.
The other day I found myself drawn to read a thread on the F1 Technical board about driver styles, and found my conscious mind asking "Why am I reading this?". That I kept reading seems to have been due to a work order originating in the workshop. "What about this?"
If you read the chapter in RCVD on Tire Behavior, you find two images of particular interest here: a plot of Lateral Force (call it Fy) against Slip Angle, and a plot of Aligning Torque (call it Mz) against Slip Angle. You can (and have) to imagine the "sum" of those plots as they are expressed at the steering wheel.
As we add Mechanical Trail, the proportion of the Fy signal sensed at the steering wheel increases. The peak Fy still occurs at the same Slip Angle, and so it's easy enough to plot a set of cumulative curves for increasing amounts of Mechanical Trail. I did three of them at half, equal and double the amount of force from Mz.
At zero MT, the force at the steering wheel (AT only) peaks before Fy and tends toward zero as Fy is peaking. By an MT of double the AT the force at the steering wheel peaks at about the peak Fy.
All very fine and well...but So What?
My inner nerd is telling me to tell you to think about how we drive a front wheel drive race car thru a corner. What "style" does the stupid car force on its driver if only thru the narrow set of options it allows?
Do we actually drive a front wheel drive race car at peak Fy very much? Do we want, amongst the three driver inputs (eyes, ***, hands) to be reconciled, Peak Fy to be the one we're sensing thru the wheel?
I think I mentioned how Smith implanted for many of us the idea that we were driving to the "top" of a curve. But upon reflection, I'm asking myself if I am thinking and doing two different things? Sensing a soft curvy top isn't easy. Sensing a significant falling off is easier. An answer has to relate back to the drivers sensitivity and resolution. I've driven both types of curves and am pretty sure I prefer "falling off".
So think in terms of a falling off type curve from relatively low caster. There's a zone from peak Mz to peak Fy. How do I know where I am and what I'm doing? Those other two senses...AND a right foot.
Something should be bugging you about peak Fy. What can't you do at peak Fy? Apply any throttle. You got a problem with that? I got a problem with that.
See where I'm going? When you add caster, and push the feedback curve toward peak Fy, you are inviting a racing driver of average skill and sensitivity to operate the car at or beyond a point at which application of throttle can only result in push and add heat to the front tires.
This reinforces the idea that a key part of making a front wheel drive race car TURN, is that the rear of the car "let go" well before peak Fy at the front. From there we control the rear with the throttle, and the gap between where we are and peak Fy is the drive capacity we have available for the job.
I believe that this is what Dick Shine was on to and couldn't explain. The high caster front wheel drive car actually conveys Less information to the driver and biases that information such as to encourage overworking the front tires.
Scott, whose inner nerd is asking when he gets to drive again...
Last edited by RR98ITR; 03-01-2014 at 03:17 PM.
03-01-2014, 03:35 PM
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Re: You sure you know what you're doing? Reveng of the Nerds...
See where I'm going? When you add caster, and push the feedback curve toward peak Fy, you are inviting a racing driver of average skill and sensitivity to operate the car at or beyond a point at which application of throttle can only result in push and add heat to the front tires.
This reinforces the idea that a key part of making a front wheel drive race car TURN, is that the rear of the car "let go" well before peak Fy at the front. From there we control the rear with the throttle, and the gap between where we are and peak Fy is the drive capacity we have available for the job.
I believe that this is what Dick Shine was on to and couldn't explain. The high caster front wheel drive car actually conveys Less information to the driver and biases that information such as to encourage overworking the front tires.
This reinforces the idea that a key part of making a front wheel drive race car TURN, is that the rear of the car "let go" well before peak Fy at the front. From there we control the rear with the throttle, and the gap between where we are and peak Fy is the drive capacity we have available for the job.
I believe that this is what Dick Shine was on to and couldn't explain. The high caster front wheel drive car actually conveys Less information to the driver and biases that information such as to encourage overworking the front tires.
Thank you Scott.
03-03-2014, 05:27 AM
#29
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Re: You sure you know what you're doing? Reveng of the Nerds...
+1. I can't say with any authority that the Coyote is "right" but it's certainly convincing and it aligns with some of my experience/perceptions.
My ITR was, IMO, the best handling Honda I've ever owned... now, that's not to say that it was without fault. And it's problem wasn't really a problem in my head until I read the description of steering feel. One thing that I was cognizant of (and tried to explain to my intermediate students), was to "drive the car off the outside rear wheel". Basically, that I was balancing the amount of throttle with the slip angle of the outside rear and trying to maintain enough slip that I could be flat(ish) from the apex all the way out and down the next straight. The side effect of this was that the steering feel wasn't exactly great and tended toward an overly light feel. I suspect that what I was feeling through the steering was what Scott's describing (though it didn't occur to me at the time) and how I was driving was off of my built-in posterior accelerometer.
I guess that leads to the question of "will it be faster" with less caster. I dunno... if you've learned to drive around the less than ideal feedback will you go slower and then faster as you learn the new feel? Or just as fast?
I guess that leads to the question of "will it be faster" with less caster. I dunno... if you've learned to drive around the less than ideal feedback will you go slower and then faster as you learn the new feel? Or just as fast?
03-05-2014, 06:53 AM
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Re: You sure you know what you're doing? Reveng of the Nerds...
I have come to notice over the years that the high-caster mobiles are
usually rear-drive vehicles. But, I once thought this would be a way to find
some more grip at the autocross, so I played with caster (swapping upper
control arms L/R->R/L) to dismal results...although, I felt it was mostly
the bump steer that made it unbearable. Nonetheless, I've always wondered
how much caster we could/should dial into the Civic.
It is pretty obvious that Honda's best suspension designs came out during
the development of the NSX and trickled down and was refined through most of
their lower tier products shortly after that. Time and time again I have
learned that the brains at Honda were good brains, they made good, rational
engineering choices.
So, in regards to caster, this lead me to ask....What did Honda do?
Here I have compiled all the factory specs for caster for all the models for
which I have the service manual information for:
Honda FF
________________
92-95 Civic: 1*10' +/-1*
94 Integra: 1*10' +/-1*
1993 Integra: 1*30'
2002-03 RSX: 1*30'
2002-03 EP3 Civic: 1*33' +/-1*
1996 Civic: 1*40'
92-96 Prelude: 2*40'
1994-95 Accord: 3*00'
1990-91 CRX: 3*00' +/-1*
1991 Legend: 3*45'
Honda MR
_____________________
1991 NSX: 8*00'
Honda FR
__________________________
2000-03 S2000: 6*00' +/-45'
Conclusions
________________
1.FF cars should generally stay below 3* of caster.
2.Lighter vehicles can get away with less caster, the only outlier is the CRX, but this was before the NSX, so maybe that design was not as well refined.
3.If you have an MR or FR vehicle, you can play with much more caster.
So Honda said, and so it shall be done!
Oh, too bad I don't have data for AWD, but I think the FF situation should apply.
usually rear-drive vehicles. But, I once thought this would be a way to find
some more grip at the autocross, so I played with caster (swapping upper
control arms L/R->R/L) to dismal results...although, I felt it was mostly
the bump steer that made it unbearable. Nonetheless, I've always wondered
how much caster we could/should dial into the Civic.
It is pretty obvious that Honda's best suspension designs came out during
the development of the NSX and trickled down and was refined through most of
their lower tier products shortly after that. Time and time again I have
learned that the brains at Honda were good brains, they made good, rational
engineering choices.
So, in regards to caster, this lead me to ask....What did Honda do?
Here I have compiled all the factory specs for caster for all the models for
which I have the service manual information for:
Honda FF
________________
92-95 Civic: 1*10' +/-1*
94 Integra: 1*10' +/-1*
1993 Integra: 1*30'
2002-03 RSX: 1*30'
2002-03 EP3 Civic: 1*33' +/-1*
1996 Civic: 1*40'
92-96 Prelude: 2*40'
1994-95 Accord: 3*00'
1990-91 CRX: 3*00' +/-1*
1991 Legend: 3*45'
Honda MR
_____________________
1991 NSX: 8*00'
Honda FR
__________________________
2000-03 S2000: 6*00' +/-45'
Conclusions
________________
1.FF cars should generally stay below 3* of caster.
2.Lighter vehicles can get away with less caster, the only outlier is the CRX, but this was before the NSX, so maybe that design was not as well refined.
3.If you have an MR or FR vehicle, you can play with much more caster.
So Honda said, and so it shall be done!
Oh, too bad I don't have data for AWD, but I think the FF situation should apply.
03-05-2014, 07:35 AM
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Re: You sure you know what you're doing? Reveng of the Nerds...
In case you're a MR or FR owner, I think there are some MAJOR benefits to be had in dialing in a ton of caster, and it would be interesting to see how far you could really go with this. As I see it as a poor man's dynamic camber system a la the Mercedes F400 Carving's 'Active Camber Control'.
"DaimlerChrysler is exhibiting a special concept study at the 35th Tokyo Motor Show: the F400 Carving is a research vehicle packed with dynamic systems designed to give the cars of tomorrow and beyond substantially enhanced active safety, dynamic handling control and driving pleasure.
The main attraction in the F 400 Carving is a new system that varies the camber angle on the outer wheels between 0 and 20 degrees, depending on the road situation. This considerably enhances active safety, since better lateral stability equals improved road adhesion and greater cornering stability.
The DaimlerChrysler engineers also charted new territory when it came to the suspension tuning, and introduced a first: an active hydropneumatic system that optimises the suspension and shock absorption in line with the changing situation on the road, all at lightning speed. Active camber control boosts the research vehicle's maximum lateral acceleration to 1.28 g, meaning that the concept study outperforms current sports cars by some 28 percent."
"DaimlerChrysler is exhibiting a special concept study at the 35th Tokyo Motor Show: the F400 Carving is a research vehicle packed with dynamic systems designed to give the cars of tomorrow and beyond substantially enhanced active safety, dynamic handling control and driving pleasure.
The main attraction in the F 400 Carving is a new system that varies the camber angle on the outer wheels between 0 and 20 degrees, depending on the road situation. This considerably enhances active safety, since better lateral stability equals improved road adhesion and greater cornering stability.
The DaimlerChrysler engineers also charted new territory when it came to the suspension tuning, and introduced a first: an active hydropneumatic system that optimises the suspension and shock absorption in line with the changing situation on the road, all at lightning speed. Active camber control boosts the research vehicle's maximum lateral acceleration to 1.28 g, meaning that the concept study outperforms current sports cars by some 28 percent."
03-05-2014, 04:42 PM
#33
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Re: You sure you know what you're doing? Reveng of the Nerds...
The headgear and eyewear are interesting...sort of priest/technician...
Meanwhile back in a deep tunnel near Nordhausen:
Meanwhile back in a deep tunnel near Nordhausen:
03-11-2014, 05:57 PM
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Re: You sure you know what you're doing? Reveng of the Nerds...
"We've been working on "perfecting" front wheel drive for a Really Long Time..."
03-14-2014, 03:15 PM
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Re: You sure you know what you're doing? Reveng of the Nerds...
Interesting...don't know why you would do an FF without a transaxle, as it seems to negate the benefits...and, does that first car (Artemis) have the wheels connected directly to the crank? if so, that's got be pretty efficient for an ICE! and it's got front dualies to boot! sweet!
03-14-2014, 05:45 PM
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Re: You sure you know what you're doing? Reveng of the Nerds...
Well, it was 1905...and there is a gearbox involved...on the Christie...
Here's about as much as can currently be known about Christie (who you might have heard of in connection with his more famous work on tank suspension as most prominently deployed on the Russian T34):
http://justacarguy.blogspot.com/2011...-car-1904.html
http://www.stohrdesign.com/christie-...09-a-blog.html
Go to 3:40 to see the Christie....what?...yeah...UNDERSTEER:
Scott, who is sad but glad that Lee Stohr had / was able to go back 100 years or more to find an opportunity to be creative beyond the shackles of racing inanity...
Here's about as much as can currently be known about Christie (who you might have heard of in connection with his more famous work on tank suspension as most prominently deployed on the Russian T34):
http://justacarguy.blogspot.com/2011...-car-1904.html
http://www.stohrdesign.com/christie-...09-a-blog.html
Go to 3:40 to see the Christie....what?...yeah...UNDERSTEER:
Scott, who is sad but glad that Lee Stohr had / was able to go back 100 years or more to find an opportunity to be creative beyond the shackles of racing inanity...
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