From observation, it seems that for a particular style of vehicle group (i.e. front-engine rear-drive sedan, rear engine sports car, etc.) there are suspension characteristics that have been proven to work very well. My question is: For a front-engine rear-drive sedan with a SLA front suspension and a standard live axle (watts link or panhard lateral control) what seems to be the optimal camber change curve for a road race setup. Currently my design utilizes an upper control arm length of about 8.5" and an effective lower control arm length of 14.5". The static RCH is approximately 0.85" above ground. This changes to about 1.75" above ground when one side is bumped 2" and the other is 2" in rebound. From my estimates this design requires about -2 degrees of static camber to keep the tires "flat" during max cornering. The front of my vehicle will utilize an anti-roll bar, but the back will not. The back will be controlled by changing the RCH with an adjustable watts link pivot point. Any thought on this, especially those related to the camber-change curve will be very much appreciated. Thanks..
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Camber Change Curve 1
- Thread starter Joest
- Start date
GregLocock
Automotive
The way I'd set it up is to give zero camber, or thereabouts, at design, and 2 degrees of inward lean on the outside tyre, relative to the road, at full steady state cornering roll.
The 2 degrees figure is tyre dependent.
What this means is that the body roll/g, and your steady state suspension travel, become a very important parameter in your initial design.
Good choice in suspensions by the way.
Cheers
Greg Locock
The 2 degrees figure is tyre dependent.
What this means is that the body roll/g, and your steady state suspension travel, become a very important parameter in your initial design.
Good choice in suspensions by the way.
Cheers
Greg Locock
-
1
- #3
If you design for a tire flat on the ground at maximum roll what will be the camber in bump at maximum straight line braking? What will the camber be as you ease up on braking and turn in? If you design for maximum roll, what percentage of an average lap will you be in that attitude? Where do you need maximum grip on the front tires as you go through an average lap to gain the largest advantage?
On some small sedans (small bore GT) that we have converted from strut front suspension to SLA front suspension we have set them up with verticaly adjustable upper inner pickup points to allow adjusting camber gain. If this is done it can be advantagious to also make lower inner or outer pickup points adjustable to allow more RC adjustability.
In one instance where we set up for ideal tire patch under maximum roll, under straight line braking we were eating the inside edges off the tires under straight line braking, this was on a course that had anumber of high speed straights ending in a tight corner which did require hard straightline braking. Just some thoughts on the subject . There is alot of room for discussion on the ideal setup, for various tracks.
On some small sedans (small bore GT) that we have converted from strut front suspension to SLA front suspension we have set them up with verticaly adjustable upper inner pickup points to allow adjusting camber gain. If this is done it can be advantagious to also make lower inner or outer pickup points adjustable to allow more RC adjustability.
In one instance where we set up for ideal tire patch under maximum roll, under straight line braking we were eating the inside edges off the tires under straight line braking, this was on a course that had anumber of high speed straights ending in a tight corner which did require hard straightline braking. Just some thoughts on the subject . There is alot of room for discussion on the ideal setup, for various tracks.
Hello, I'm new here and I have a question about camber change on unequal length wishbone suspension. I know the longer the lower wishbone (with an appropriate length upper wishbone) the less the camber change during suspension movement.
If one looks at F1 suspension the arms are very long, mazda mx5's are quite short (miatas?).
I am a little confused because I wonder how much camber will be absorbed(right word?) by the tyre wall, with the tyre remaining flat? I know aspect ratios are getting less so camber is becoming more important. (I mean tyres are getting wider)
Confused all round ( can u tell ?)
Can any-one answer my question? And what books would you say are good to find this out?
(If you could answer my question b4 the book list because my birthday is still a couple of months away
)
If one looks at F1 suspension the arms are very long, mazda mx5's are quite short (miatas?).
I am a little confused because I wonder how much camber will be absorbed(right word?) by the tyre wall, with the tyre remaining flat? I know aspect ratios are getting less so camber is becoming more important. (I mean tyres are getting wider)
Confused all round ( can u tell ?)
Can any-one answer my question? And what books would you say are good to find this out?
(If you could answer my question b4 the book list because my birthday is still a couple of months away
)- Thread starter
- #5
Greg,
So, if I understand you correctly, I should design for 0 degrees of camber (tire contact patch parallel to the road) with the car experiencing maximum cornering loads? This makes sense since from my understanding most tires perform best with -0.5 to 0.5 degrees of camber for maximum grip in a corner. Please confirm this is what you intended to say.
I plugged my proposed suspension pivot points into your slarck spreadsheet. Maybe you could take a look at it and comment. It looks like its going to be tough to get the tire contact patch flat with the road unless I set the static alignment to about -2 degrees of camber.
Maybe assuming 2" of suspension compression on the outside front tire during cornering is too much. This will obviously be a function of anti-sway bar stiffness and spring stiffness, but I'm looking for a baseline number before I attempt to calculate it out. My Koni 30 series coil overs will only have about 4 inches total travel (100mm), which means about 2" bump and 2" rebound. With that in mind, maybe a more reasonable number for outside tire movement is 1"-1.5".
When I finally do the calc, I will assume my CG is about 18-20" above ground and calculate weight-transfer based on a 57.8" front track width. The goal will be to have a car that can corner at 1.0-1.1 g's on sticky street tires (275/40/17 front and 315/35/17 rear) and possible higher with racing slicks.
Any further input will be a great asset to the project.
Cheers.
So, if I understand you correctly, I should design for 0 degrees of camber (tire contact patch parallel to the road) with the car experiencing maximum cornering loads? This makes sense since from my understanding most tires perform best with -0.5 to 0.5 degrees of camber for maximum grip in a corner. Please confirm this is what you intended to say.
I plugged my proposed suspension pivot points into your slarck spreadsheet. Maybe you could take a look at it and comment. It looks like its going to be tough to get the tire contact patch flat with the road unless I set the static alignment to about -2 degrees of camber.
Maybe assuming 2" of suspension compression on the outside front tire during cornering is too much. This will obviously be a function of anti-sway bar stiffness and spring stiffness, but I'm looking for a baseline number before I attempt to calculate it out. My Koni 30 series coil overs will only have about 4 inches total travel (100mm), which means about 2" bump and 2" rebound. With that in mind, maybe a more reasonable number for outside tire movement is 1"-1.5".
When I finally do the calc, I will assume my CG is about 18-20" above ground and calculate weight-transfer based on a 57.8" front track width. The goal will be to have a car that can corner at 1.0-1.1 g's on sticky street tires (275/40/17 front and 315/35/17 rear) and possible higher with racing slicks.
Any further input will be a great asset to the project.
Cheers.
GregLocock
Automotive
Can you give me the exact hardpoints?
I think we were talking at cross purposes - relative to the road you want the outside wheel leaning in (a little) at max steady state cornering.
Say you've got 40 mm spring travel at that condition, and the track is 1600 mm, then the body is at an angle of sin-1 (40+40/1600), or about 3 degrees. So, relative to the car you want at most -3 degrees of camber at 40 mm jounce on the outer wheel. Add in another (say ) 2 degrees for carcase deformation, that gives -5 degrees at 40 mm jounce.
As you can see the big fudge factor here is the amount of extra camber needed for the tyre - this depends on a whole lot of things, Milliken includes an example (Figure 2.30)where the optimum negative camber for lattac is 5 degrees, in which case you'd want to set the camber up at -8 degrees at 40 mm of jounce. The implication of this is that you would end up with a fair amount of neg camber at design height, as camber gain of 200 deg/m is too much, at least I don't remember seeing numbers that big. Typical production cars would be more like 20 deg/m, although they are much softer in roll so they use more of the suspension travel. As you can see, everything is interrelated!
Cheers
Greg Locock
I think we were talking at cross purposes - relative to the road you want the outside wheel leaning in (a little) at max steady state cornering.
Say you've got 40 mm spring travel at that condition, and the track is 1600 mm, then the body is at an angle of sin-1 (40+40/1600), or about 3 degrees. So, relative to the car you want at most -3 degrees of camber at 40 mm jounce on the outer wheel. Add in another (say ) 2 degrees for carcase deformation, that gives -5 degrees at 40 mm jounce.
As you can see the big fudge factor here is the amount of extra camber needed for the tyre - this depends on a whole lot of things, Milliken includes an example (Figure 2.30)where the optimum negative camber for lattac is 5 degrees, in which case you'd want to set the camber up at -8 degrees at 40 mm of jounce. The implication of this is that you would end up with a fair amount of neg camber at design height, as camber gain of 200 deg/m is too much, at least I don't remember seeing numbers that big. Typical production cars would be more like 20 deg/m, although they are much softer in roll so they use more of the suspension travel. As you can see, everything is interrelated!
Cheers
Greg Locock
You can also use positive caster to increase your camber gain in roll, while not affecting camber in pure bounce as under bracking. This has worked well on Mustangs and Camaros running in AS classes in SCCA. It can also help by moving camber in a positive direction on the inside tire.
The final word on camber will only be attained by doing tire temperatures at the track.
The final word on camber will only be attained by doing tire temperatures at the track.
- Thread starter
- #8
- Thread starter
- #9
Greg - I posted a follow-up to your comment about the thread I started regarding camber-change curves. My follow-up stated that I plugged my suspension pickup points into your Slarck spreadsheet and I was hoping you could comment on the results. Thanks in advance.
GregLocock
Automotive
Joest and I were diddling about in email for a bit - here's the guts of the correspondence. I've appended some questions at the bottom.
1
I posted a follow-up to your comment about the thread I started
regarding camber-change curves. My follow-up stated that I plugged my
suspension pickup points into your Slarck spreadsheet and I was hoping you
could comment on the results.
J
2
OK, got your file. That geometry is very gentle, I'd be far more
aggressive in the camber curve, for a road racer. As someone else
pointed out, in theory you want to use tire temps to set your camber
at design ride height, but if you are going to be using it much on the
road you'll be more worried about wear, so you'll want to keep static
camber at around 0, at design.
So I think I'd try and double the camber gain, and see where that
ends up. You might like to get some positive camber on the inside wheel as
well.
The bad news is that you'll get more bump steer, but that may be
acceptable. I don't suppose you have any info on the tires you'll be
using? They really are the most important thing, unfortunately.
G
3
Thanks for taking a look at it. The design you looked at uses a
upper control arm that is about 220mm. I plugged in parameters for a
shorter upper arm (190mm) and it give a little more camber gain, but nothing
like what you think I should have. A control arm length ratio of 0.6
seems like its about all I can get with a standard passenger car layout
front-engine-rear-drive. Using an upper arm shorter than about 190mm
in not practical because it leaves little room for coilover dampers. I have
measured a C5 corvette suspension in the past and remember that it
had an upper arm about 8 inches long and a lower arm of about 13 inches.
I'm not sure I can achieve the camber values you suggested at 40mm bump on
your latest posting at Eng-Tips without using an ungodly amount of static
camber. Any more thoughts on this?
J
4
Yes, try dropping the inner position of the upper arm. I always prefer
to leave the lower arm horizontal for production car designs, since
steering deteriorates if it isn't, but I don't know of any reason why
the upper arm should be horizontal (it will tend to jack, but you can
compensate for that in the spring rate). If you just let the solver run
eventually it will force you into a swing arm configuration, which has
too high a roll centre. Therefore I add a maximum height for the roll
centre. At RCH of 55 I got about 3 degrees of camber at 40 mm. Not
great, but at least it is 75 degres per metre, ie substantially more
than a production car.
You may need to design a bracket for the upper arm that brings the
mounting points out and down relative to the strut top. We do this on
our production car. I see other people have started using castings for
this, we'd like to.
G
So,
1) does anyone have a feeling for camber / metre of jounce travel for race cars?
2) Is an angled upper arm OK?
3) Is an angled upper arm going to jack the car?
4) If it jacks the car can you compensate by changing the anti roll bar?
Here's my geometry
Rolling radius of tyre 299.72 mm
static camber 0 deg
Y Z
centre of wheel -734.1 299.7 mm
hence contact patch -734.1 0.0
Lower control arm to body -275.6 108.1 mm
Lower control arm to spindle -678.7 260.7 mm
Upper control arm to body -358.4 334.0 mm
Upper control arm to spindle -528.8 523.0 mm
Cheers
Greg Locock
1
I posted a follow-up to your comment about the thread I started
regarding camber-change curves. My follow-up stated that I plugged my
suspension pickup points into your Slarck spreadsheet and I was hoping you
could comment on the results.
J
2
OK, got your file. That geometry is very gentle, I'd be far more
aggressive in the camber curve, for a road racer. As someone else
pointed out, in theory you want to use tire temps to set your camber
at design ride height, but if you are going to be using it much on the
road you'll be more worried about wear, so you'll want to keep static
camber at around 0, at design.
So I think I'd try and double the camber gain, and see where that
ends up. You might like to get some positive camber on the inside wheel as
well.
The bad news is that you'll get more bump steer, but that may be
acceptable. I don't suppose you have any info on the tires you'll be
using? They really are the most important thing, unfortunately.
G
3
Thanks for taking a look at it. The design you looked at uses a
upper control arm that is about 220mm. I plugged in parameters for a
shorter upper arm (190mm) and it give a little more camber gain, but nothing
like what you think I should have. A control arm length ratio of 0.6
seems like its about all I can get with a standard passenger car layout
front-engine-rear-drive. Using an upper arm shorter than about 190mm
in not practical because it leaves little room for coilover dampers. I have
measured a C5 corvette suspension in the past and remember that it
had an upper arm about 8 inches long and a lower arm of about 13 inches.
I'm not sure I can achieve the camber values you suggested at 40mm bump on
your latest posting at Eng-Tips without using an ungodly amount of static
camber. Any more thoughts on this?
J
4
Yes, try dropping the inner position of the upper arm. I always prefer
to leave the lower arm horizontal for production car designs, since
steering deteriorates if it isn't, but I don't know of any reason why
the upper arm should be horizontal (it will tend to jack, but you can
compensate for that in the spring rate). If you just let the solver run
eventually it will force you into a swing arm configuration, which has
too high a roll centre. Therefore I add a maximum height for the roll
centre. At RCH of 55 I got about 3 degrees of camber at 40 mm. Not
great, but at least it is 75 degres per metre, ie substantially more
than a production car.
You may need to design a bracket for the upper arm that brings the
mounting points out and down relative to the strut top. We do this on
our production car. I see other people have started using castings for
this, we'd like to.
G
So,
1) does anyone have a feeling for camber / metre of jounce travel for race cars?
2) Is an angled upper arm OK?
3) Is an angled upper arm going to jack the car?
4) If it jacks the car can you compensate by changing the anti roll bar?
Here's my geometry
Rolling radius of tyre 299.72 mm
static camber 0 deg
Y Z
centre of wheel -734.1 299.7 mm
hence contact patch -734.1 0.0
Lower control arm to body -275.6 108.1 mm
Lower control arm to spindle -678.7 260.7 mm
Upper control arm to body -358.4 334.0 mm
Upper control arm to spindle -528.8 523.0 mm
Cheers
Greg Locock
1) does anyone have a feeling for camber / metre of jounce travel for race cars?
Around 0.2deg/25mm - 16deg/m - for Formla cars like F3, F3000, LMP
2) Is an angled upper arm OK?
Yes - and normal, though it looks to me that some current F1 cars have the upper arm angled the other way - anhedral - see Williams
3) Is an angled upper arm going to jack the car?
In as far as it affects the roll centre height, yes
4) If it jacks the car can you compensate by changing the anti roll bar?
You tell me - I'd like to know!
Andy
Around 0.2deg/25mm - 16deg/m - for Formla cars like F3, F3000, LMP
2) Is an angled upper arm OK?
Yes - and normal, though it looks to me that some current F1 cars have the upper arm angled the other way - anhedral - see Williams
3) Is an angled upper arm going to jack the car?
In as far as it affects the roll centre height, yes
4) If it jacks the car can you compensate by changing the anti roll bar?
You tell me - I'd like to know!
Andy
Camber curves
For solo cars we have run from:
.8 to 1.2 deg. / inch of bump, with RC of 1.5 to 2.5 in.
Upper inner PU points are adjustable. they angle up towards the outer PU. Lower arm is 15.3in, upper is 7in. FV instant center is 60in.
This is with FWD VW Rabbit converted to SLA front suspension, with stock type rear twist axle. Car is very stable very quick turn in response, runs very flat tire temps. Car runs with front anti roll bar. Finished 2nd. at SCCA solo Nationals last year. The driver did have something to do with it.
Have done a CRX Honda very similar, that is a road race car, but have camber curves at .7in to 1in. at the higher gains on tracks with allot of high speed straight line bracking inside edge of tires go away, so requires lower gain. This again is a very competative car. But we are still workingn on tire life.
For solo cars we have run from:
.8 to 1.2 deg. / inch of bump, with RC of 1.5 to 2.5 in.
Upper inner PU points are adjustable. they angle up towards the outer PU. Lower arm is 15.3in, upper is 7in. FV instant center is 60in.
This is with FWD VW Rabbit converted to SLA front suspension, with stock type rear twist axle. Car is very stable very quick turn in response, runs very flat tire temps. Car runs with front anti roll bar. Finished 2nd. at SCCA solo Nationals last year. The driver did have something to do with it.
Have done a CRX Honda very similar, that is a road race car, but have camber curves at .7in to 1in. at the higher gains on tracks with allot of high speed straight line bracking inside edge of tires go away, so requires lower gain. This again is a very competative car. But we are still workingn on tire life.
- Thread starter
- #13
The last two posts have been really helpful, not to mention Greg's previous posts. I am really interested in vehicles that began life as production cars and are now being used for competition.
Formulas cars are different because of their low CGs, but I'm glad the LMP900 posted his info since I would also like to build a FSAE type vehicle for auto crossing in the future.
The numbers given by pmwltd are exactly what I am looking for. My car will be front-engine rear-drive instead of front-engine front-drive, but the camber change curves should still be in the ballpark. For your CRX, I assume you meant the camber change was 0.7 inch to 1 inch/ degree right? This seems like a reasonable number that I too can achieve. Greg was suggesting a lot more (75 degrees/meter), which is about 2 degrees/inch.
From my literature, a good setup is to limit the body roll to 2-3 degrees max (about 1-1.5" suspension movement during full cornering assuming a 58-60" track width), place the roll center 0” to 3" above ground, and setting the static camber such that during maximum cornering it is about -0.5 degrees on the outside tire (A little bit negative to compensate for tire carcass deformation).
I checked out Milliken & Milliken chapter 2 that Greg mentioned in an earlier post (figure 2-30) and it seemed insightful, although the numbers refer to a 225/70/15 tire who's carcass will deform significantly more than the 275/40/17 (BFG G-force T/A KD) that I intend to use. Milliken's graph showed that the 225/70/15 tire performed best with approximately -5 degrees of camber(wow!!!). I don't know about you, but that seems unrealistically high. To get that would require running about -6.5 degrees of static camber, which would destroy straight-line handling and be devastating to tire life.
If you have some thoughts about what camber should be during corner for low profile, stiff carcass tires such as 30-40 series please speak up. Also, keep the knowledge flowing about the other topics above because things are getting interesting.
Cheers
Formulas cars are different because of their low CGs, but I'm glad the LMP900 posted his info since I would also like to build a FSAE type vehicle for auto crossing in the future.
The numbers given by pmwltd are exactly what I am looking for. My car will be front-engine rear-drive instead of front-engine front-drive, but the camber change curves should still be in the ballpark. For your CRX, I assume you meant the camber change was 0.7 inch to 1 inch/ degree right? This seems like a reasonable number that I too can achieve. Greg was suggesting a lot more (75 degrees/meter), which is about 2 degrees/inch.
From my literature, a good setup is to limit the body roll to 2-3 degrees max (about 1-1.5" suspension movement during full cornering assuming a 58-60" track width), place the roll center 0” to 3" above ground, and setting the static camber such that during maximum cornering it is about -0.5 degrees on the outside tire (A little bit negative to compensate for tire carcass deformation).
I checked out Milliken & Milliken chapter 2 that Greg mentioned in an earlier post (figure 2-30) and it seemed insightful, although the numbers refer to a 225/70/15 tire who's carcass will deform significantly more than the 275/40/17 (BFG G-force T/A KD) that I intend to use. Milliken's graph showed that the 225/70/15 tire performed best with approximately -5 degrees of camber(wow!!!). I don't know about you, but that seems unrealistically high. To get that would require running about -6.5 degrees of static camber, which would destroy straight-line handling and be devastating to tire life.
If you have some thoughts about what camber should be during corner for low profile, stiff carcass tires such as 30-40 series please speak up. Also, keep the knowledge flowing about the other topics above because things are getting interesting.
Cheers
GregLocock
Automotive
I know that Avon, and some other manufacturers, do release some Pacejka type info on their racing tyres. Perhaps it is worth talking to your tyre supplier and pestering them, obviously this curve of latacc vs camber angle is crucial to your setup.
I'm glad everyone elses figures are back in the realms of what is seen on production cars, I was a bit worried by some of my numbers. Incidentally pmwltd's figure is about 40 deg/m.
Cheers
Greg Locock
I'm glad everyone elses figures are back in the realms of what is seen on production cars, I was a bit worried by some of my numbers. Incidentally pmwltd's figure is about 40 deg/m.
Cheers
Greg Locock
Sorry about the screw up. On the CRX the numbers should be .7 to 1.0 deg. of camber change per inch of bump travel from static ride height. We normaly run about -.5deg. of static camber.
We had tried to set this car up for flat tire contact at maximum roll, but found we were eating the inside edges of the tires, due to excessive negative camber under straight line braking. We have used +caster up to 6 deg. to try to improve camber curve in roll without excessive straight line braking change, and found that to help. Tthese are FWD cars and we run 0 to negative .125 in. of scrub radius, and a SAI of 12 deg. or less, to minumize corner jacking in steer. Tires are Goodyear cantilever slicks 13X9.5 on either 6in. or 7in. wheels depending on the class. We set spring and bar rates to keep roll in the range of 2deg. I can link you to pictures if you have an interest. Also if you are running a live rear axle, I do have a setup showing a Mumford link, which works much better then a Watts link.
I do all the suspension geometry layout on Mitchell's WinGeo3. It has been a very good tool, and Bill is an excellent person to work with. No question goes unanswered.
Hope some of this helps. Take what will help and leave the rest.
We had tried to set this car up for flat tire contact at maximum roll, but found we were eating the inside edges of the tires, due to excessive negative camber under straight line braking. We have used +caster up to 6 deg. to try to improve camber curve in roll without excessive straight line braking change, and found that to help. Tthese are FWD cars and we run 0 to negative .125 in. of scrub radius, and a SAI of 12 deg. or less, to minumize corner jacking in steer. Tires are Goodyear cantilever slicks 13X9.5 on either 6in. or 7in. wheels depending on the class. We set spring and bar rates to keep roll in the range of 2deg. I can link you to pictures if you have an interest. Also if you are running a live rear axle, I do have a setup showing a Mumford link, which works much better then a Watts link.
I do all the suspension geometry layout on Mitchell's WinGeo3. It has been a very good tool, and Bill is an excellent person to work with. No question goes unanswered.
Hope some of this helps. Take what will help and leave the rest.
- Thread starter
- #16
That is excellent information PMWLTD. I'm glad that you are providing specific number that seem to agree with my theories. Please send me the link to your pictures. The Mumford link sound interesting. The watts link that I am using allows me to adjust the RCH by 5 inches total. I'm using a mount with 4 different pivot locations each spaced 1.25" apart to achieve this. The watts link is used in conjuction with a relatively long torque arm to control axle rotation. It should be a good setup once I sort out the front geometry, but I am always open to something better.
The web site is Then go to the gallery pages.
I guess I am at times an overly enthusiastc proponent of the Mumford link. I spent too many hours in front of AutoCad trying to work out the geometry based on pictures in magazines. The main advantages of a Mumford link are the ability to run moderate to very low RC, all the way down to ground level and below if you want. They give you minimal and symmetrical lateral movement of RC, and the vertical movement of the RC matches the chassis movement very closely.
The Mumford was brought into its own by Arthur Mallock in England, who raced live axle sports racers there for many years. His development of 4 link live axles, with torque control geometry, was facinating. There is a very interesting article in a back issue of Racecar Engineering magazine that he wrote which is very worthwhile reading
I guess I am at times an overly enthusiastc proponent of the Mumford link. I spent too many hours in front of AutoCad trying to work out the geometry based on pictures in magazines. The main advantages of a Mumford link are the ability to run moderate to very low RC, all the way down to ground level and below if you want. They give you minimal and symmetrical lateral movement of RC, and the vertical movement of the RC matches the chassis movement very closely.
The Mumford was brought into its own by Arthur Mallock in England, who raced live axle sports racers there for many years. His development of 4 link live axles, with torque control geometry, was facinating. There is a very interesting article in a back issue of Racecar Engineering magazine that he wrote which is very worthwhile reading
- Thread starter
- #18
Pmwltd,
Thanks for adding your link. I like the concept of fitting SLA suspension to vehicles that originally were equipped with struts. It makes a lot of sense for racing. It seems that one of the main complications is modifying the upright such that it can accept the upper control arm ball joint. I did this for my application by making a bracket that bolted to the mount originally used by the strut (works for bolt in struts). It isn't as easy for the "clamp-in" strut style since there is nothing there to bolt to. For your jobs did you source controls arms from donor vehicles?
Also, I have a 240Z I have wanted to build for open track events. Your reference section shows you have a customer in the states with one of these vehicles. Did convert it to SLA in the front? If not, have you ever considered it?
Thanks for adding your link. I like the concept of fitting SLA suspension to vehicles that originally were equipped with struts. It makes a lot of sense for racing. It seems that one of the main complications is modifying the upright such that it can accept the upper control arm ball joint. I did this for my application by making a bracket that bolted to the mount originally used by the strut (works for bolt in struts). It isn't as easy for the "clamp-in" strut style since there is nothing there to bolt to. For your jobs did you source controls arms from donor vehicles?
Also, I have a 240Z I have wanted to build for open track events. Your reference section shows you have a customer in the states with one of these vehicles. Did convert it to SLA in the front? If not, have you ever considered it?
the VW rabbit is a much easier conversion as far as the upright is concerned. It has a verticle pinch clamp at the bottom which makes for much better geometry than those that have the stock lower PU point on the upright at an angle. The top of the strut can be easily modified to allow a bolt on PU point. The CRX required a welded on PU point on the top. there is always the exposure that the preheat and welding process is going to distort the bearing housing, but so far that has not been a problem. Modifying the steering arm on the uprights and extending the inner steering rack PU points, makes for some interesting fabrication.
As to the control arms they are all fabricated from scratch. On the front wheel drive cars the packaging inside the front wheel gets very interesting. So far for the lower coilover spring mount we have used mounting forks from a second generation CRX.
As to the 240 Z, it is the one p[ictured in the photo gallery with the Caster/Camber assemblies added. It runs modifyed struts that use VW rabbit cartridges, and 2.5 inch coilovers. It has adjustable camber plates on the rear struts. It runs in ITS SCCA on the east coast of the US.
Sorry this response took so long
Dave
As to the control arms they are all fabricated from scratch. On the front wheel drive cars the packaging inside the front wheel gets very interesting. So far for the lower coilover spring mount we have used mounting forks from a second generation CRX.
As to the 240 Z, it is the one p[ictured in the photo gallery with the Caster/Camber assemblies added. It runs modifyed struts that use VW rabbit cartridges, and 2.5 inch coilovers. It has adjustable camber plates on the rear struts. It runs in ITS SCCA on the east coast of the US.
Sorry this response took so long
Dave
Hello all,
I am a newcomer to both Eng-Tips and your thread. I am a mechatronic engineer but there does not seem to be a category for such a branch at Eng-Tips so Industrial will suffice.
I am currently involved in a garage project dubbed Dynamic Camber Control (DCC). The point of this project is as follows:
1 Improve tyre wear and life time
2 Increase lateral acceleration by optimising the camber for any instantaneous body roll.
3 Improve linear acceleration/braking by applying zero camber.
It is applied to the rear suspension of a small open wheeler I am making. It is rear wheel drive and simmilar to a Formula Ford.
This idea is not at all new since Torix Bennett used it in the sixties (Fairthorpe GT, rear end only), Dax Kit Cars are using a purely mechanical version (front end only) and Mercedes Benz have a concept car 'F400 Carving' that uses an hydraulic feed forward control system. The trouble is that the merc needs special tyres and requires an expensive setup in hardware. It is also requires a significant amount of power to maintain its operation.
I have a suspension mechanism that creates a virtual pivot at the shear centre (or close to) of the tyre-road surface contact patch. This is the unique and distinguishing feature of DCC and hopefully, will significantly reduce the power consumption of the system.
The rationale for this conclusion (please confirm or constructively criticise on this point) is that the virtual pivot does not move laterally with respect to the vehicles centre line (excluding deformation of linkages and tyre under load). Thus, there is no mechanical advantage to be added when cornering nor is there any in the verticle axis, as the downward weight of the vehicle also passes through the contact patch centriod and again, external moments are avoided.
I am currently researching the effects of roll centre and weight transfer on this mechanism and this is where I am coming unstuck - my area of expertise is in control systems. I am working on a Matlab program to simulate the effects of varying linkage lengths but with limited success.
A further point. Tyre temperature has been mentioned in earlier postings as a possible method of determining camber angles.
One of my input variables is to use the differential heat emminating from across the tyre and hence determine which way the camber should be rectified. In my research, I have found that tyre wear is a function of excessive tyre temperatures and by reducing the thermal stress on the outer or inner annulus of the tyre, longer life expectancy may be achievable (please comment).
Question: Does anyone know how much time delay is likely to occur between tyre temperature measured and the input shear stress applied to that same unit area of tyre (surface temperatures only)? Could you provide me with any reference sources or links to such information?
All feedback welcome,
Piers (Australia)
I am a newcomer to both Eng-Tips and your thread. I am a mechatronic engineer but there does not seem to be a category for such a branch at Eng-Tips so Industrial will suffice.
I am currently involved in a garage project dubbed Dynamic Camber Control (DCC). The point of this project is as follows:
1 Improve tyre wear and life time
2 Increase lateral acceleration by optimising the camber for any instantaneous body roll.
3 Improve linear acceleration/braking by applying zero camber.
It is applied to the rear suspension of a small open wheeler I am making. It is rear wheel drive and simmilar to a Formula Ford.
This idea is not at all new since Torix Bennett used it in the sixties (Fairthorpe GT, rear end only), Dax Kit Cars are using a purely mechanical version (front end only) and Mercedes Benz have a concept car 'F400 Carving' that uses an hydraulic feed forward control system. The trouble is that the merc needs special tyres and requires an expensive setup in hardware. It is also requires a significant amount of power to maintain its operation.
I have a suspension mechanism that creates a virtual pivot at the shear centre (or close to) of the tyre-road surface contact patch. This is the unique and distinguishing feature of DCC and hopefully, will significantly reduce the power consumption of the system.
The rationale for this conclusion (please confirm or constructively criticise on this point) is that the virtual pivot does not move laterally with respect to the vehicles centre line (excluding deformation of linkages and tyre under load). Thus, there is no mechanical advantage to be added when cornering nor is there any in the verticle axis, as the downward weight of the vehicle also passes through the contact patch centriod and again, external moments are avoided.
I am currently researching the effects of roll centre and weight transfer on this mechanism and this is where I am coming unstuck - my area of expertise is in control systems. I am working on a Matlab program to simulate the effects of varying linkage lengths but with limited success.
A further point. Tyre temperature has been mentioned in earlier postings as a possible method of determining camber angles.
One of my input variables is to use the differential heat emminating from across the tyre and hence determine which way the camber should be rectified. In my research, I have found that tyre wear is a function of excessive tyre temperatures and by reducing the thermal stress on the outer or inner annulus of the tyre, longer life expectancy may be achievable (please comment).
Question: Does anyone know how much time delay is likely to occur between tyre temperature measured and the input shear stress applied to that same unit area of tyre (surface temperatures only)? Could you provide me with any reference sources or links to such information?
All feedback welcome,
Piers (Australia)
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