Need help
- Thread starter just fish
- Start date
paulkish
old fart
The two sentences below are exaggerated to make it easy for me to try to explain the difference.
A little bit of turning of the steering wheel will give you a little bit of turning of the tire, with the tie rod at the end of the spindle farthest away from the kingpin.
A little bit of turning of the steering wheel will give you a LOT of turning of the tire, with the tie rod close to the kingpin.
________________________
And then think about how having one side close to the kingpin(the left side) and the other far away from the kingpin(the right side), would effect things.
A little bit of turning of the steering wheel will give you a little bit of turning of the tire, with the tie rod at the end of the spindle farthest away from the kingpin.
A little bit of turning of the steering wheel will give you a LOT of turning of the tire, with the tie rod close to the kingpin.
________________________
And then think about how having one side close to the kingpin(the left side) and the other far away from the kingpin(the right side), would effect things.
CarlsonMotorsports
Site Supporter
Called Ackerman. You can slow or speed up the turning rate of each corner. Generally, you will want the tie rods in the farthest hole from the kingpin. Check with your chassis manufacturer to be certain that's where they want you running. For small tracks with tight radius corners, I move the LF tie rod up one hole (closer to the king pin) than the RF. This helps turn the LF more than the RF.
--
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
--
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
alvin l nunley
Site Supporter
Wikipedia has a very good illustration of what true Ackerman looks like.
First off, (in my estimation) some features are added to karts simply because other karts have those features. A manufacturer doesn't want his kart to be derided because it lacks some feature that another kart has. It appears that, the more adjustability built into the kart, the more people like it. Adjustability is a very sought after feature. The practicality of all these features is debatable, some will like this feature others will like that feature. Finding a use for these extra holes, in the spindles, is up to the individual driver.
One thing I have noticed; looking at the Wikipedia illustration, if those extra holes are positioned along that line from the spindle to the center of the rear axle, then the steering stays, remotely, within the Ackerman specification, if not, it does not. Now very few karts adhere strictly to the Ackerman specification. The ones with extra holes, at least the ones that I have seen, do not adhere to the Ackerman specification. For that matter, only a kart with a drag link actually adheres strictly to the Ackerman specification.
Actually, I have seen spindles drilled with the holes in a straight line parallel to the centerline of the kart. The farther you place the tie rods from the kingpin, the farther you get away from the modified Ackerman specification. This also slows the steering and makes it easier to turn the kart. You have to turn the wheel farther for the same amount of steering input.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
First off, (in my estimation) some features are added to karts simply because other karts have those features. A manufacturer doesn't want his kart to be derided because it lacks some feature that another kart has. It appears that, the more adjustability built into the kart, the more people like it. Adjustability is a very sought after feature. The practicality of all these features is debatable, some will like this feature others will like that feature. Finding a use for these extra holes, in the spindles, is up to the individual driver.
One thing I have noticed; looking at the Wikipedia illustration, if those extra holes are positioned along that line from the spindle to the center of the rear axle, then the steering stays, remotely, within the Ackerman specification, if not, it does not. Now very few karts adhere strictly to the Ackerman specification. The ones with extra holes, at least the ones that I have seen, do not adhere to the Ackerman specification. For that matter, only a kart with a drag link actually adheres strictly to the Ackerman specification.
Actually, I have seen spindles drilled with the holes in a straight line parallel to the centerline of the kart. The farther you place the tie rods from the kingpin, the farther you get away from the modified Ackerman specification. This also slows the steering and makes it easier to turn the kart. You have to turn the wheel farther for the same amount of steering input.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
http://www.asos1.com/
Go down right side to Basic Go-Kart Mechanics and click on it, explains ackerman and you can get a visual of how it works.
alvin l nunley
Site Supporter
that is some real interesting programming. The person that did that is really clever. While the Ackerman illustration gives you somewhat of an idea of what Ackerman is, it doesn't tell you what real Ackerman is. It also doesn't show you the effect of the single point of attachment of the tie rods on the steering shaft. Looking at that illustration, and it is a really clever illustration, might give somebody the idea that they know what true Ackerman is, but it doesn't. Nonetheless, it does give you a very superficial understanding of why we have Ackerman. It could be titled, "Ackerman for dummies". lol
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
paulkish
old fart
just fish: There are only two reasons to adjust how much each front tire turns.
The first is to set how much the tire can be turned, before more turning will cause it to reduce grip. You only need either front tire to turn enough, so when working together they are able to make the front end, go where you want to go.
If your able to get all your front end turning from the RF(right front) tire, where the LF(left front) which is not gripping at all is pointing, makes no difference while turning. The same goes for the LF. If your able to get all your front end turning from the LF, then while turning it doesn't matter what the RF is doing.
It will matter after your done turning and want to go straighter, but while turning if either is doing all the turning you don't need the other.
In the paragraph above to have either the RF or the LF do all the turning, then all the front end weight, in the turn, also has to be totally on one tire or the other. Hope I'm doing ok so far explaining, don't be afraid to ask more questions.
If my explanation is so far so good, you will see if all the turning is being done by the RF, all the weight up front is also on the RF and we can move on.
I'll move on anyway now suggesting you think about what if weight was equally on each front tire.
If it were then each front tire would have to also be carrying half of the load or weight on the front end. OK, so what...
The so what is the LF tire because it's on the inside, will go around a smaller circle or in other words turn more. And the RF tire being farther away to the outside and because it's going around a on a larger circle, doesn't have to turn so much.
That's why the holes are in your spindles. There there so you can independently adjust how much each tire turns, depending on how much weight it is carrying or in other words, how much it's loaded. Because of that the amount of difference and any changes in which holes are used on each side is almost totally load dependent. Who ever made your kart designed it so the LF will automatically turn more then the left and it's done through building Ackerman into your front end.
Don't get caught up in the confusion of all the different ways there are to build Ackerman into a front end. The holes are there only because of how when load on the front end is changed, it helps compensate for the shifting of front end load side to side. The net of it is it's all about needing grip to make the front point and go where you want it to go. If it ain't, then it's something to try to make the front end work better out on the track.
There really is no second reason to adjust it except to see if one way works better then the other. Changing how much each front tire turns, changes a lot of other things too, but the only reason real reasons to need to turn one more then the other is because of the load each has to carry and the different curved line each travels.
ps... I don't think anyone has ever explained it on here that way before. No one until just now has made the connection between carrying load and changing how much each front tire is turned. Until just now writing I never made the connection either, but I think it's valid. The closest we've come on here before was to relate to slip angles, but slip angles given like tires are totally load dependent. One last thing to remember, when I throw bull out there like I just did, it is all IMHO and ain't necessarily right anyway. ...
The first is to set how much the tire can be turned, before more turning will cause it to reduce grip. You only need either front tire to turn enough, so when working together they are able to make the front end, go where you want to go.
If your able to get all your front end turning from the RF(right front) tire, where the LF(left front) which is not gripping at all is pointing, makes no difference while turning. The same goes for the LF. If your able to get all your front end turning from the LF, then while turning it doesn't matter what the RF is doing.
It will matter after your done turning and want to go straighter, but while turning if either is doing all the turning you don't need the other.
In the paragraph above to have either the RF or the LF do all the turning, then all the front end weight, in the turn, also has to be totally on one tire or the other. Hope I'm doing ok so far explaining, don't be afraid to ask more questions.
If my explanation is so far so good, you will see if all the turning is being done by the RF, all the weight up front is also on the RF and we can move on.
I'll move on anyway now suggesting you think about what if weight was equally on each front tire.
If it were then each front tire would have to also be carrying half of the load or weight on the front end. OK, so what...
The so what is the LF tire because it's on the inside, will go around a smaller circle or in other words turn more. And the RF tire being farther away to the outside and because it's going around a on a larger circle, doesn't have to turn so much.
That's why the holes are in your spindles. There there so you can independently adjust how much each tire turns, depending on how much weight it is carrying or in other words, how much it's loaded. Because of that the amount of difference and any changes in which holes are used on each side is almost totally load dependent. Who ever made your kart designed it so the LF will automatically turn more then the left and it's done through building Ackerman into your front end.
Don't get caught up in the confusion of all the different ways there are to build Ackerman into a front end. The holes are there only because of how when load on the front end is changed, it helps compensate for the shifting of front end load side to side. The net of it is it's all about needing grip to make the front point and go where you want it to go. If it ain't, then it's something to try to make the front end work better out on the track.
There really is no second reason to adjust it except to see if one way works better then the other. Changing how much each front tire turns, changes a lot of other things too, but the only reason real reasons to need to turn one more then the other is because of the load each has to carry and the different curved line each travels.
ps... I don't think anyone has ever explained it on here that way before. No one until just now has made the connection between carrying load and changing how much each front tire is turned. Until just now writing I never made the connection either, but I think it's valid. The closest we've come on here before was to relate to slip angles, but slip angles given like tires are totally load dependent. One last thing to remember, when I throw bull out there like I just did, it is all IMHO and ain't necessarily right anyway. ...
Someone ...
Member
The thing about Ackerman is that it was conceived to offset a perceived "problem" while turning a vehicle - that the wheel on the inside turns at a sharper arc than the wheel on the outside. Which is true, but exaggerated. If you map out how both front wheels travel you'll find that the physical difference between their angles is a small fraction of one degree. Most Ackerman designs allow adjustments much more than that. When we also consider the tire slipping on the track surface then those angle differences become even less important. In effect Ackerman causes additional toe-out while turning. Too much toe can scrub off speed.
However, Ackerman setting can have advantages. That scrubbing due to added toe can heat a tire, which in turn can cause it to grip better (assuming you don't overheat it). It also creates stronger feedback ("feel") for the driver, so you can use it to make your driver more comfortable.
What's the best setting? As usual it depends on many things, with track conditions and front stagger / toe / caster / camber settings and driver experience probably the main factors. If your track changes (and most do) then any setting may only be "perfect" for a short time.
I suggest you experiment. Start with the tie rods in the center holes and run some laps (maybe several races if the driver is inexperienced). Then move a tie rod into a different hole and run more laps, and ask the driver how it feels as well as measure lap times with a stopwatch. Because of changing track conditions you'll get more realistic results if you can do this during a test session where you can run a few laps at one setting then make a change and immediately run some more laps and then change again etc. etc.
As a driver I've found that I do not have enough talent to "feel" any significant difference in which spindle holes I connect my tie rods to, so I keep them in the center holes to reduce scrub. I've had much more talented drivers on my karts who also couldn't "feel" a difference. But that could just be us or my karts. If you have testing time go for it because then you might find something that works for you. But overall I agree with Al that this is a "me too" setting more than a significant advantage.
However, Ackerman setting can have advantages. That scrubbing due to added toe can heat a tire, which in turn can cause it to grip better (assuming you don't overheat it). It also creates stronger feedback ("feel") for the driver, so you can use it to make your driver more comfortable.
What's the best setting? As usual it depends on many things, with track conditions and front stagger / toe / caster / camber settings and driver experience probably the main factors. If your track changes (and most do) then any setting may only be "perfect" for a short time.
I suggest you experiment. Start with the tie rods in the center holes and run some laps (maybe several races if the driver is inexperienced). Then move a tie rod into a different hole and run more laps, and ask the driver how it feels as well as measure lap times with a stopwatch. Because of changing track conditions you'll get more realistic results if you can do this during a test session where you can run a few laps at one setting then make a change and immediately run some more laps and then change again etc. etc.
As a driver I've found that I do not have enough talent to "feel" any significant difference in which spindle holes I connect my tie rods to, so I keep them in the center holes to reduce scrub. I've had much more talented drivers on my karts who also couldn't "feel" a difference. But that could just be us or my karts. If you have testing time go for it because then you might find something that works for you. But overall I agree with Al that this is a "me too" setting more than a significant advantage.
alvin l nunley
Site Supporter
"Someone" wrote; The thing about Ackerman is that it was conceived to offset a perceived "problem" while turning a vehicle - that the wheel on the inside turns at a sharper arc than the wheel on the outside. Which is true, but exaggerated. If you map out how both front wheels travel you'll find that the physical difference between their angles is a small fraction of one degree.
a "perceived problem"? I don't think so. If you've got some horses dragging a wagon, with wooden wheels, around some tight corners, I think you would change your mind about this, "perceived problem"! I will agree that, with a kart, the chance of breaking wheels is not a problem, but the rolling resistance is still there.
I laid "this" out in my CAD/CAM program; 50 foot radius turn, 28 inches between kingpin centers, four inches between tie rod bolt centers and kingpin centers, 40 inch wheelbase. The outside wheel turns 1.07 degrees while the inside wheel turns 1.15 degrees. Not much difference, this is true. Of course "small fraction of a degree" is subject to interpretation. I also didn't figure in all the forces acting on the tire. What I did find was, the tie rod bolt centers, from straight ahead, to the turn angle to make the 50 foot radius turn, where the same out to two decimal places.
I haven't done the lay up for a typical kart steering geometry yet, but I will, soon. I'm sure that I will find that the, "Ackerman" steering geometry used on karts will not come even close to matching the true Ackerman steering results.
Most Ackerman designs allow adjustments much more than that. When we also consider the tire slipping on the track surface then those angle differences become even less important. In effect Ackerman causes additional toe-out while turning. Too much toe can scrub off speed.
and that's the point, "Ackerman" in the current configuration for most karts, is most likely scrubbing off speed.
However, Ackerman setting can have advantages. That scrubbing due to added toe can heat a tire, which in turn can cause it to grip better (assuming you don't overheat it). It also creates stronger feedback ("feel") for the driver, so you can use it to make your driver more comfortable.
I see a problem there; if it's scrubbing off speed, wouldn't the amount of scrubbing increase as a tire got hotter?
What's the best setting? As usual it depends on many things, with track conditions and front stagger / toe / caster / camber settings and driver experience probably the main factors. If your track changes (and most do) then any setting may only be "perfect" for a short time.
I think I would change, "perfect" with, "optimal". Small point.
Other than these small points where I disagree with you, I think you really understand this stuff.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
a "perceived problem"? I don't think so. If you've got some horses dragging a wagon, with wooden wheels, around some tight corners, I think you would change your mind about this, "perceived problem"! I will agree that, with a kart, the chance of breaking wheels is not a problem, but the rolling resistance is still there.
I laid "this" out in my CAD/CAM program; 50 foot radius turn, 28 inches between kingpin centers, four inches between tie rod bolt centers and kingpin centers, 40 inch wheelbase. The outside wheel turns 1.07 degrees while the inside wheel turns 1.15 degrees. Not much difference, this is true. Of course "small fraction of a degree" is subject to interpretation. I also didn't figure in all the forces acting on the tire. What I did find was, the tie rod bolt centers, from straight ahead, to the turn angle to make the 50 foot radius turn, where the same out to two decimal places.
I haven't done the lay up for a typical kart steering geometry yet, but I will, soon. I'm sure that I will find that the, "Ackerman" steering geometry used on karts will not come even close to matching the true Ackerman steering results.
Most Ackerman designs allow adjustments much more than that. When we also consider the tire slipping on the track surface then those angle differences become even less important. In effect Ackerman causes additional toe-out while turning. Too much toe can scrub off speed.
and that's the point, "Ackerman" in the current configuration for most karts, is most likely scrubbing off speed.
However, Ackerman setting can have advantages. That scrubbing due to added toe can heat a tire, which in turn can cause it to grip better (assuming you don't overheat it). It also creates stronger feedback ("feel") for the driver, so you can use it to make your driver more comfortable.
I see a problem there; if it's scrubbing off speed, wouldn't the amount of scrubbing increase as a tire got hotter?
What's the best setting? As usual it depends on many things, with track conditions and front stagger / toe / caster / camber settings and driver experience probably the main factors. If your track changes (and most do) then any setting may only be "perfect" for a short time.
I think I would change, "perfect" with, "optimal". Small point.
Other than these small points where I disagree with you, I think you really understand this stuff.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
Someone ...
Member
Al, we're on the same page. You're correct that I could have stated the difference in wheel angles more precisely. You're also correct about Ackerman effecting wooden buggy wheels more than modern metal wheels with rubber tires, but I didn't remember that since I don't drive horse buggies. I also have no problem with your choices of better words.
As far as tire scrubbing increasing as tires get hotter... generally true - until you overheat the tire. At that point the tire loses grip and may just wear away quickly.
As far as tire scrubbing increasing as tires get hotter... generally true - until you overheat the tire. At that point the tire loses grip and may just wear away quickly.
paulkish
old fart
Hi Al. I want to offer you a mental exercise. Would you try considering what ackerman does, without including the need to unload the inside rear?
I'm not offering this as an argument, only as a fun exercise which I think if you involve yourself with it, it will bring fun and enjoyment to you and your thought process. Al, I really do have a lot of fun thinking about how stuff works and I know you enjoy it too.
I'm not offering this as an argument, only as a fun exercise which I think if you involve yourself with it, it will bring fun and enjoyment to you and your thought process. Al, I really do have a lot of fun thinking about how stuff works and I know you enjoy it too.
paulkish
old fart
just fish, ... How are we doing bs'in and arguing back and forth about ackerman?
Did all our normal bantering help you gain an understanding of the three holes?
If it did that's what this place is all about. If not, I'm sorry and I have to ask what we can do to fix it. I think what we all really want to do is to help you enough and throw all our bickering aside, to help in anyway we can.
Did all our normal bantering help you gain an understanding of the three holes?
If it did that's what this place is all about. If not, I'm sorry and I have to ask what we can do to fix it. I think what we all really want to do is to help you enough and throw all our bickering aside, to help in anyway we can.
alvin l nunley
Site Supporter
Paul, I don't remember every connecting the two? I'm sure you're aware that horse drawn wagons never unload the inside rear. lol.
I would be happy to consider your proposal, but quite frankly, I've never connected the two in the same thought. I'm at a loss?
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
paulkish
old fart
I think you(not your personally, everyone) must connect the two. The results racing because of changing ackerman is in both tire presentation and load changes.
The end result is totally about slip angle and the release and engagement of each front tire with the track.
_______________________________
"I'm sure you're aware that horse drawn wagons never unload the inside rear. lol."
Yep and wagons don't have stagger, nor is each rear wheel connected solidly to the axle. I agree with you, the end result of ackerman on a wagon is solely about the front wheels, to make them turn more easily.
To try to make a point, I'm going to say the sole purpose of ackerman on a wagon is to reduce friction when the wheels are turned. I think i'll get a yes from you on it, but ????
Racing using rubber were not interested in reducing grip.
Were only interested in increasing grip or using the grip we have more efficiently. The use of ackerman in a wagon and the use of ackerman racing, are at the opposite ends of the spectrum and only relate to each other as a tool for measurement. They do not in any way relate to each other in function.
The end result is totally about slip angle and the release and engagement of each front tire with the track.
_______________________________
"I'm sure you're aware that horse drawn wagons never unload the inside rear. lol."
Yep and wagons don't have stagger, nor is each rear wheel connected solidly to the axle. I agree with you, the end result of ackerman on a wagon is solely about the front wheels, to make them turn more easily.
To try to make a point, I'm going to say the sole purpose of ackerman on a wagon is to reduce friction when the wheels are turned. I think i'll get a yes from you on it, but ????
Racing using rubber were not interested in reducing grip.
Were only interested in increasing grip or using the grip we have more efficiently. The use of ackerman in a wagon and the use of ackerman racing, are at the opposite ends of the spectrum and only relate to each other as a tool for measurement. They do not in any way relate to each other in function.
alvin l nunley
Site Supporter
I think, more precisely, it's so both wheels will be rolling along the paths of different diameter arcs. Without Ackerman, the inside wheel would be pulled, dragging along the inside arc, not rolling. In most karts today, the inside wheel is being pushed, (sideways, to a certain degree) along that path. The more the deviation from the proper angle, the more pushing, the more drag.
I did a layout of a typical kart front end geometry. (I have no formal engineering training) Fairly easy to do if you have CAD/CAM. With the RF wheel turned, (1.07 degrees) to follow a 50 foot radius path, the inside wheel, with Ackerman, turns measurably less, (1.15 degrees) than it does with a typical kart steering arrangement, (1.25 degrees) even with the same Ackerman geometry on the spindles. In other words the same spindles with both, separate tie rods, or a drag link.
Few Karts have real Ackerman steering! They have steering that mimics, (somewhat) the Ackerman effect. The effect being, the inside wheel, in a turn, turns a greater number of degrees, (or fraction there of) than the outside wheel.
The thing about all this is; front end geometries are all over the place. Few karts, if any, have spindles that strictly follow the Ackerman specification. Further compounding this is the fact that the number of karts built today, with a drag link steering arrangement, can be counted on the fingers of one hand. And that last statement is vague because; I haven't seen all the karts being built in the world today.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
paulkish
old fart
No kart or car must have ackerman set to true ackerman.
A wagon does but a kart or car to include over the road cars, do not.
I did a search on does a car need ackerman and below is the first thing which came up after Wikipedia's explanation of ackerman:
http://www.me.ua.edu/me364/PDF/Steering_Ackerman.pdf
Please note figure 5 on page 6: The car on the right is fast, the car on the left is not so fast.
A wagon does but a kart or car to include over the road cars, do not.
I did a search on does a car need ackerman and below is the first thing which came up after Wikipedia's explanation of ackerman:
http://www.me.ua.edu/me364/PDF/Steering_Ackerman.pdf
Please note figure 5 on page 6: The car on the right is fast, the car on the left is not so fast.