Steering Geometry [Archive]

InsaneSpeed

December 19th, 2005, 07:41 PM

I hope you can see the picture I attached. Ackerman angles are referenced from the non-steering axle centerline. In this case the rear axle. What I do to set this up on my karts is:
1. Mark the center line of the rear axle. As long as you plan on having the rear tires evenly spaced from the frame, you can mark the center of the axle using the axle mounts, or bearings as measuring points.
2. Take a piece of string, or rope and tie one end to either side spindle nut or bolt. The spindle does need to be mounted on the frame. Run this around the centerline of the axle that you marked and back to the opposite side spindle nut or bolt. This will make a triangle shape, and is shown in red on the picture.
3. You will have a hole, or holes on the pitman arms for the tie rods. This hole needs to be directly under this string or rope. I usually put a long bolt throught the hole to better align it with the rope.
4. You will have to hold the pitman arm pretty steady to get a good tack on it. After its tacked, you can take everything apart and fully weld the arms on.

Josh

RUBICON

December 19th, 2005, 10:12 PM

THANKS for the detailed information...I asked ( before this forum ) for months and no one would help me...i finally found a sithe that explained this but not real good data on caster and its effect on handling...lessons from experienced kart guys is a real help....

sweav

December 19th, 2005, 10:26 PM

That's the same thing I'm running into. There's not alot of info floating around about how to set up the geometry of the frame and steering to work properly. I did alot of searching and reading when I built my sons go kart but it was still trial and error. Any helpful info is always greatly appreciated.

InsaneSpeed

December 20th, 2005, 02:58 AM

Okay. I will try to help a little bit on caster, and camber.
Caster is the verticle relation of the spindle centerline to an imaginary line drawn perpindicular to the ground. In the picture, the dotted line is the caster angle. 8-10* positive caster is good. This does a few things. It allows greater stability at speed by naturally keeping the front wheels pointed forward. On a car, when you let go of the wheel, and the car still goes straight, thats the caster at work. On karts, or BSR, it also allows, in a turn, the inside rear wheel to come off the ground. To get a picture- you turn left, the left rear wheel would lift off the ground. If you run a live axle, this helps eliminate a pushing condition by only letting the outside wheel move the kart/BSR. This can be built into the front axle just by using an adjustable protractor of some kind. For 10* positive caster, the protractor will read 80* if placed on the rear of the spindle and 100* if placed on the front.
Camber is the relation of the tire to a line drawn perpindicular to the ground as viewed from the front or back of the tire. Now, normally the tire itself is angled. In the case of Karts/BSR, I have always angled the spindle instead and got the same results. Now for some imagination b/c I don't have a picture. A BSR- all 4 tires on the ground and pointing straight. You turn to the left, and don't move forward, or back. The right side-front tire will come off the ground. If you were driving this, the forward momentum would cause the BSR to lean to the right. This would put both front tires back on the ground, and lift the left side-rear off the ground. What you need to think about is, without camber the right front will be touching the ground on the outside edge of the tire. When you want maximum traction with the front, this is bad. Camber lets the wheel turn, and with the momentum tilting the BSR to the right, places the full footprint of the tire in contact with the ground. It will also let the left front do the same thing.
When I built my Radio Flyer, I was a little excessive on the angles, and used 20* caster, and 12* camber. I built a jig to make my own spindles to this angle as most anything bought, with the exception of race kart parts, had no geometry built into them. No Ackerman, no Camber, and most of the time the spindle bracket had the 5/8" bolt holes all out of wack. An easy way I have found to make an axle for something like this is to use round tubing. Cut the camber angle on the ends. If you want 10*, cut both ends but make sure you cut them to like a triangle shape, not a trapaziod shape. Its easier than you might think to do. I have done it a few times. Yeah I got a picture for that too!! Once the spindle brackets are welded on, rotate the tube back (toward the rear of the frame) until you get the desired caster. If anyone needs further help, please let me know.
I appologize for the picture quality. I have'nt got Photoshop installed on our new computer yet. I had to use Paint.

Josh

sweav

December 20th, 2005, 08:34 AM

Thanks Josh, great info! I'm using square tube and was planning on cutting my camber angle into the end then where it welds up to the frame cut my caster angle there (basically what you said about the round tube and rotating it) I was going off of how the front ends are set up off of cars and it sounds like there isn't much difference. A couple of us from work worked on the caster and camber on my sons go kart for about 2 weeks until we felt it was right. Man that thing turns on a dime and my son can take that thing and slide it around corners and take off straight comeing out of it. Advice from someone that has done all of this is great. Again THANKS, I hate going back to redo things and it's a pain in the ass to grind welds off to move something.

moto1fast

December 20th, 2005, 11:14 AM

Hello, Thanks Insane that cleared up a lot on steering set up,Caster/Camber. One Question what about Toe in? What would you recommend? I will be running dual wheels on back with a Rear width of about 60" (5 foot). I was going to use a rear diffy, but I am getting to much in this thing and am trying to cut down on costs. This is going to be more of a show Bsr than a racing one. Any help to improve handling with this setup would be appriciated. Would you use a live axle or not? What would this do in a wheelie, pull to one side? Thanks Friends!! Also please keep me in your thoughts or Prayers, I just Had my Fifth Heart Attack last Monday and just got out of Hospital. I would like to finish this thing before I Kick the Bucket!:wave:

RUBICON

December 20th, 2005, 02:41 PM

LET"S SEE????.......Nitrous barstool or a heart attack.....what would be my choice???.....CRASH AND BURN...OR just fade away....just kidding.....thought sick humor would lighten your heart....you just need an overhaul....come to think of it ...a pacemaker.....or MSD box....all the same....good rest....busy hands....hope you heal fast....your heart that is....bones take a while...

Differentials will not affect a wheelie...and for me i need info on toe-in...I started with toe in and the steering was too quick and sensitive.....I went with toe-out and it was much better.....now with 15 degrees of new caster...I may need to revisit my experimenting on toe settings...any advice will help....My goal is to finalize my braided brake line upgrade and get ready for a one time experience @ a real drag strip.....just want a few great pics...a video for sharing and a "time slip" to frame with the pics....and get-er-done safely......

InsaneSpeed

December 20th, 2005, 09:06 PM

Toe in, or out, on a kart/BSR depends mostly on the driver. This is nice because it is adjustable within the range on the tie rods, and tie rod ends. Rubicon is correct. Toe in will allow the BSR to turn more aggressively. Go back to making a left turn, and the momentum transfering weight to the right front tire. If you have toe in, the right tire is at a sharper angle in relation to the left tire, than would be present if toe was zero. Because of the extra weight, it will turn faster, or slightly sharper. This is what Rubicon was experiencing. Toe in will also increase drag on the front tires. They will "scuff" instead of rolling true. If total max speed is not of main concern, toe in won't really be a problem. Toe out is a little dangerous. If you can picture this: Both front tires are trying to turn away from each other. If you hit a bump, or get one tire to lose grip while going straight, the BSR will turn in the direction of the still gripping tire. I would stay away from toe out. Either set it at zero, or slightly toe in. To start with, set to zero. This is a pretty good starting point. B/c everyone is different, there is no majic number to use. And b/c toe is adjustable through the tie rods, this really isn't a problem.

Toe In -- Quick turns -- More stability -- Slight scuffing
Neutral
Toe Out -- Slower turns -- Less stable -- Slight scuffing -- Not recommended.

sweav,
It sounds like you may have more experience setting these up than I. I have never really set up a kart for racing. And yes it sucks reding things. I made 2 different front axles for the wagon before I fully understood what the angles did for the steering.

moto1,
You need to keep those heart attacks away. After 5 of them, just make sure your doing things right. A live axle for that type of deal would be fine. The diff just lets you turn easier. As far as the toe, start at zero. The caster, camber angles will help more in turning something like that than the toe settings.

Rubicon,
If your going for strip time, I would set the toe to zero. Is that 15* of caster added to what you already have, or it is 15* total? That should help keep those tires straight on the strip.

Josh

sweav

December 20th, 2005, 09:49 PM

the go kart I built my son isn't for racing. I had some old lawnmower tires off of a craftsman. Big huge back tires and not small front tires. Had an old power washer with a 5.5 honda. Built the frame and put in a 1.8:1 jack shaft. Built it with a 52 tooth drive sprocket but it was too fast. My daughter (19) would even run full speed, so I geared up to a 66 and seems to do better. Have the throttle turned down on it for him b/c he tends to get carried away with the throttle (but who doesn't) Turned out really good, have to go back and change a few things but all in all it's killer. He is going to turn 6 this year and he drives it better then alot of people.

InsaneSpeed

December 20th, 2005, 11:04 PM

My mistake. I was in the "racing" mind set! I have 5 childen and the oldest 2 are the main ones wanting to make a go on karts. The oldest, 9, loves riding the wagon. Jeremiah, 6, still has some growing to do. His legs can't reach over the engine yet. When the Anglia is done, he should be able to ride that.

sweav

December 20th, 2005, 11:17 PM

With my son, with have a set of pedals set up a closer for him. He loves it but mom bought a power wheels for him about a year ago and I just couldn't stand watching him putt around on that thing. It ended up being an 18 volt 4 wheel drive that can get air born. I think it's great, my dad always had either a go kart, mini bike or motorcycle for me to mess around with. I miss my daughter being younger, she would get greasy with me, but hten she turned 13. Now she's out on her own but now she wants to get greasy with me again, so it all worked out. Have you figured out an easy way to set up a jig to get the soindle brakets squared up?

InsaneSpeed

December 21st, 2005, 01:31 AM

We have 1 girl out of 5 children and at 3, she has no intention of getting dirty. Outside of the garage, she is all daddys girl though. I am going to assume you are talking about the U shaped bracket. I will take some .25" x 1.25" flat stock, cut 2 pcs. that are 1.75" long. (Part A) Then drill a 5/8 hole that is centered 5/8" from the edge on the 1.75" length. It is easier to do both at the same time using a drill press if available. Cut another pc. of .25"x1.25" that is 3" long. (Part B) I will already have made the spindle 2 7/8" long also. Run a bolt through one pc. of part A, then the spindle, then the other part A. Put a nut on it and tighten it loosely. Put this in a vice so the bolt is running horizontal. The vice will clamp on the 2 part A's. Lay part B on top so 1/16" is resting on each part A. This doesn't have to be exact. While holding part B down with hand, clamp, whatever, tack part B to both part A's. Once this is done, run a weld across each end of part B to part A. Let this cool off. Take the bolt, and spindle off the bracket and weld on the inside of part B. This will be a 90* corner. As long as you get a good weld, these should hold up with no problem. I have yet to break any of the ones I have made this way. Knock..Knock The picture may help more.

moto1fast

December 21st, 2005, 10:14 AM

Hello, Lots of good info. Thanks to all who post things to help! Friends helping Friends thats what is about!!! Let me see if I understand camber! It is the vertical line of the angle of axle or spindle mount bracket. With positive camber the upper spindle bracket will be angled in at the top 10 to 12 degrees. Ok, is the axle going to be angled also or is it going to be Horizontal with the ground? If so I may have bought the wrong spindle assy's because they have no angle built into them! Do you build your own spindles also and degree them at 10 to 12 degress negative camber? Thanks Bsr Bros!!!:dizzy: :cheers:

Bustedup

December 21st, 2005, 10:40 AM

Has anyone thought of using heim joint spindle mounts? My first BSR had the standard weld-on mounts, but once it's welded it is very hard to adjust. So, me and my buddy copied a design on the web and can now adjust castor, camber and ride height. Just a thought.

If I can figure out how I'll post some pic's.

InsaneSpeed

December 21st, 2005, 07:19 PM

moto1,
Negative camber is when the tops of the wheels are closer to each other than the bottom of the wheels. ---OR--- In the case of our BSR, the wheels will be straight, but the spindle will be angled in at the top. The picture I made a few posts back is of negative camber. The axle will be straight, but the spindle will be angled. I've made a picture of this. I do make my own spindles. I don't like the ones that I have found at various places to buy for the reason that no geometry is built in. I have a jig to set the angle at 12*, and 0*.
Bustedup,
I have seen what you are talking about. Here are some pictures. I thought about this, but the Heim joints are expensive if your on a budget, and making all the mounting brackets would take time. Wait, I've been doing that anyway. Okay, the time part wouldn't be a problem, but the expense might be to some.

http://www.barstoolracing.net/Nitro%20Mike's%20Page.htm

sweav

December 21st, 2005, 08:32 PM

What I did was I bought a set of spindles. Then cut the bolt off and re-welded a grade 8 bolt back on so it was parralel to the ground. Haven't had any problems with it yet. I did have to re-weld the mount for the tie rod also. I have found a few kits that are not welded that I will probably get when I build the front end on my bsr. Thanks Josh for all the info.

Terry Skinner

December 22nd, 2005, 12:10 AM

Also please keep me in your thoughts or Prayers, I just Had my Fifth Heart Attack last Monday and just got out of Hospital. I would like to finish this thing before I Kick the Bucket!:wave:

Done.. My first one was at 45, then another at 55, now at 65 (pushing 66) and still going strong. The 4 way was hard to go thru but well worth it. The chemicals are making things better too. Just don't plan your life around being sick. And pick your cardiologist. If you like each other he will work hard for you and you will do what he says. And one last thing before I get off this soap box.... God put you here for a reason. If you are still here you have not accomplished it. So keep going!!...........Terry

Mike Bean

December 27th, 2005, 09:44 AM

Hey Moto,

If you have the spindle kits with the weld on brackets, you can always position the brackets with the alignment you need and tack weld into place. After the tack cools check again and tack a few more places and then finish weld. (You can tap the bracket with a hammer after you place a couple of tack welds if anything moves.)

I think when they designed the spindle kits that are weld on they were mainly intended for fun karts, not high performance racing karts which can take advantage of camber.

Honestly, I just square up my steering assembly to the frame and weld. Never had any problems and I am usually running wide open throttle.

I did find out that welding the swivel on my barstool (because the bearings were wearing out from vibration), improved my ability to handle the BSR quite a bit. I never noticed how much the seat swiveled when I was riding making it more difficult to drive.

Mike Bean

Hello, Lots of good info. Thanks to all who post things to help! Friends helping Friends thats what is about!!! Let me see if I understand camber! It is the vertical line of the angle of axle or spindle mount bracket. With positive camber the upper spindle bracket will be angled in at the top 10 to 12 degrees. Ok, is the axle going to be angled also or is it going to be Horizontal with the ground? If so I may have bought the wrong spindle assy's because they have no angle built into them! Do you build your own spindles also and degree them at 10 to 12 degress negative camber? Thanks Bsr Bros!!!:dizzy: :cheers:

monkey-1

December 27th, 2005, 05:31 PM

I have been playing with castor on my Radio Flyer and it makes a huge difference when you get it right. I originally built it with about 5 degrees of castor and had some ackerman built into the front end:

http://www.studmonkeyracing.com/v2/radioflyer/radioflyer2/dsc02016.jpg
http://www.studmonkeyracing.com/v2/radioflyer/radioflyer2/dsc02027.jpg
http://www.studmonkeyracing.com/v2/radioflyer/radioflyer4/DSC02336.JPG

It drove ok in a straight line, but it took ALOT of 'body english' to turn it. I took it to a friends house and a bunch of people rode it and thats the only complaint they had, that it was hard to turn around. The front tires just seemed to scoot along and not grip to turn. I decided that I wanted a better handling wagon, so I redid it all the w/e. First I took the plasma to the front end and cut off (or unbolted) everthing. I went from using 12.5 inch front end plates to 8 inch plates (to shorten the wheelbase some). Then I cut them out and drilled the hole for the front axle. I put zero camber in it, and no ackerman. I then used my laser to line up the front spindle mounts and tacked them on the front axle. Then with the front end at ride height, I tilted the front axle (with the spindles mounted square to each other) back to 20 degrees of castor. I know it sounds like alot, but that was the ticket!! The wagon steers on a dime now. Here is how it looks now:

http://www.studmonkeyracing.com/v2/radioflyer/radioflyer5/122605a.jpg
http://www.studmonkeyracing.com/v2/radioflyer/radioflyer5/122605b.jpg
http://www.studmonkeyracing.com/v2/radioflyer/radioflyer5/122605c.jpg

It drives so much better now its like a different machine.

sweav

December 27th, 2005, 10:45 PM

Hey monkey it's funny you bring this up. I was talking to a friend today and we got to talking about the bsr and the steering. He said the same thing, that I would want caster but not really any camber. He also said that I would want the ackeramn angle set on the front spindles. I've been doing alot more reading and have found out alot. Here is a site I found that really gets in depth on it (a little too much ZZZZZZ) but it gives some ways to fix problems in the steering http://www.karting.co.uk/KandK/Tech/KartSetup.html I think I'm gonig to set mine up with around 12-15 caster and ackerman angle w/ no camber and see what happens. Hey sniffles in another thread you asked when I was going to cut my first pice of steel, this friday. I've already told my wife that I'm living in the garage this weekend. Oh to let everyone know, I go the motor back together and fired it, didn't run it for long since it was clamped in a vise but the main thing is it fired!

Redrooster

February 1st, 2006, 06:46 PM

Hey Monkey-1 do you have any real close up pictures of your front end of your radio flyer wagon?

monkey-1

February 2nd, 2006, 03:01 PM

Hey Monkey-1 do you have any real close up pictures of your front end of your radio flyer wagon?

I can get you some, what do you need exactly??

Redrooster

February 2nd, 2006, 03:21 PM

Hi monkey-1.... Mabey some close up shots of your spindle set with the with the angle that you set them at.... and your new brackets that holds the front axle.... thanks Roger.........

1100kaw

February 2nd, 2006, 09:28 PM

I have read everthing in this forum about steering, I think.
Alot of info, Good info. Beleive it or not, I still have some questions.
Lets chew on some of these.
#1 InsaneSpeed had a very good picture on setting up the Ackerman,
If a chassis is set up like this is Ackerman automatically correct?
#2 If ACkerman is not correct, how is it corrected? how is it measured?
I have seen on chassis sites that the inside wheel should turn about 3* more than outside.
#3 Is there a magic measurement for the steering arm length on the spindles?
#4 Is there a measurement for the length of the steering arms on the steering shaft?
#5 for all around handling, what are the best Camber and Caster numbers?
#6 When I turn, the bars are in my chest and the other end is a stretch.
Is there a way to make the wheels turn quicker than the handlebars,
without screwing up all this hard to get right, Geometry?
Thanks Darrell

RUBICON

February 3rd, 2006, 01:58 PM

My 2cents on a couple of questions:
#3 steering arm length on the spindle is not critical...but is in a range near equal to the length of the arm on the steering shaft. If both are equal the angular movement for both are the same...
#4 Steering arm length on the shaft should be near the length of the spindle arm...however...if it is longer your steering will be "quicker" ( more movement of the spindle for th esame movement of the shaft )..if your steering arm is shorter the opposite is true.....now...if the steering arm is too short you will not get the maximum angle on the wheels...look at regular kart spindles and make them close to that...
# 5 I think most would agree that camber can be @ zero...I think that comes int play mostly in high cornering loads.....I have 15 degrees of caster....
#6 This relates to what I said above...if you increase the length of your steering shaft arm and leave the spindle arm alone you will increase the steering ratio....I did 4 or 5 different setups to get where I am now...

Terry Skinner

February 3rd, 2006, 09:38 PM

#2 If ACkerman is not correct how is it measured?
Darrell

O.K. Here goes. I will try to explain my understanding of Ackerman. Draw a straight line on the shop floor. Park the barstool with the rear axle on that line. Now turn the front wheels all the way to the left. Now draw a straight line on the floor thru the left spindle. This line will cross the line thru the rear axle. Now do the same for the right spindle. Draw a straight line on the floor thru the right spindle. This line will cross the line thru the rear axle. If both of the lines cross the rear axle at the same point the Ackerman is correct. Now do the same on the other (right) side. We are looking for the same results. All three lines should intersect at the same point. This is an 8th grade education speaking so I am hoping I am saying it right..........Terry

Terry Skinner

February 3rd, 2006, 10:12 PM

#2 If ACkerman is not correct, how is it corrected? Thanks Darrell

Most of the spindles I have looked at have the arm welded on exactly 90 degrees to the spindle. Considering how short the wheel base is on a barstool I would guess that it should be closer to 100 degrees. Using the lines on the floor method previously described cut almost thru the arm and bend it inward untill the lines intersect. Be sure to shorten the tie rod to compensate. Then do the same for the other side. Granted this is a crude method but with a little fiddling around it will work. At least it did on a '55 Ford that we took 3 feet out of the frame. An easier method would to be corner an automotive engineer and promise him a ride in exchange for running the calculations for you. HTH..........Terry

monkey-1

February 5th, 2006, 05:56 PM

Hi monkey-1.... Mabey some close up shots of your spindle set with the with the angle that you set them at.... and your new brackets that holds the front axle.... thanks Roger.........

Here you go man:
http://www.studmonkeyracing.com/forums/fe1.jpg
http://www.studmonkeyracing.com/forums/fe2.jpg
http://www.studmonkeyracing.com/forums/fe3.jpg
http://www.studmonkeyracing.com/forums/fe4.jpg
http://www.studmonkeyracing.com/forums/fe5.jpg
http://www.studmonkeyracing.com/forums/fe6.jpg
http://www.studmonkeyracing.com/forums/fe7.jpg

If you need andy measurements or questions, let me know.

Redrooster

February 5th, 2006, 06:46 PM

monkey-1

February 5th, 2006, 09:00 PM

Thanks Monkey-1 .... that helps alot to see up close how you set up your spindles and front axel .... you say that by changing the angle it made all the difference in turning the wagon .... now you dont have to lean when you turn .... and the back wheels dont bind when you turn .... Thanks for the help....
Rerooster

Before I redid the front end, it was hard to steer. It would steer, but you needed to use alot of body english. I decided to shorten the front end 4 inches and put more castor in the spindles (20 degrees). I figured it woud take the combination to make a difference. It now steers so good that I wish I hadnt shortened the front end, but I klike how it looks and it steers so much better.

sweav

February 12th, 2006, 02:05 PM

On my front end I sat it 15 deg + castor, o deg camber and set up the ackerman angle correctly and set a little tow in. Going straight I can let go of the bars and it goes perfectly straight and when turning it takes the wheight off of one the rear wheels just enough to turn it on a dime. Thanks to everyone that had an input on the front end set up. Wouldn't have gotten the first try with out it.

tqm3

August 11th, 2006, 07:36 AM

Talking about caster, I'm going to set mine up with around 8-10 deg. and set the tie rods apart on the pitman instead of one single mount with them ontop of each other. Any thoughts from anyone.

I set mine up with 0 degrees caster when I first built it. I did not know any better. It was a handfull at speed. After reading this and the other thread on steering geometry I cut the spindles off and welded new ones on with 15 degrees caster. It handles much better at speed and it will turn now at slow speed on asphalt....:cheers:

BlownT

May 30th, 2007, 04:15 PM

Ackerman is the angle of the steering arms to the center of the rear axle. I know in a T bucket you can play with it all ya want but there won't be that much difference. It mainly comes into play at high speed and on a road course. Whick I doubt you won't be seeing many BSR doing, or T buckets. What really affects my bucket is tire pressure, toe-in and alignment, and I have a pretty good feeling that will be the same once I get my BSR done and running.

BT

reg440

May 31st, 2007, 12:43 AM

Wish I would have had all this info when I first built my BSR. I put 5* of camber in my BSR. The problem I have is when getting on the gas in a corner it will slide the front tires and I keep going straight. Next BSR I will make sure to put caster in instead. Thanks everyone for setting me straight.

garleness

May 31st, 2007, 08:21 AM

Here is the set i used front axle is cut to 12 deg and spindle are 12 degree fully adjustable more expensive but any adjustments will be real easy.

BlownT

May 31st, 2007, 08:56 AM

that is a real nice setup. Think its a little overkill for a BSR but it does show off your abilities and uniqueness. Nuttin wrong witdat. That is very impressive and TOO KEWL. I remember back in the 70's when I raced my Bug/Mac90 kart. There was NUTTIN to adjust. Just air pressure and gearing, dats about it. Now my son's Birel/KT100 kart is SO adjustable. Even adjusting da bumpers and nerf bars can affect grip. Getting ready to step up to a better kart soon.

Have many T bucket buddies and have seen all sorts of steering arm angles. Some of them are angled out (away from the centerline) and some have forward steering arms. They all do not affect steering or turning that much. Most turning is done at speeds under 20 mph. Like I said, I think the Akerman only comes into play in high speed turning like a road course or rallye.