High School Shop Kart- Steering Geometry Issues

gijoe985

New member
Hello all,

Well, I'm a high school shop teacher. I've got lots of automotive background, but almost nothing kart related. That said, I picked up a kart for my shop students to work on and learn on. The long term goal would be for the auto and metals classes to replicate a few of these. Anyway, as you can see from the pictures, we've got an odd steering geometry issue. Note that the outer wheel begins to turn inward once you pass 10 (or 2) o'clock.

Now, seeing that this isn't really an issue you'd see on a car, I'm trying to figure out if we need to 1- setup a steering stop that doesn't let you turn too far or 2- if there is another fix that will prevent this from happening and hopefully even improve our turning radius.

The turning radius is horrible right now. Perhaps if we attached the tie rod higher up on the arm and then limit the steering radius?

I've got lots of other questions coming up I'm sure. But this is #1 for now.

Steering at 12 o'clock

Steering at 10 o'clock

Steering at 8 o'clock
 

XXX#40

TRUMP 2020
That's a racing kart, they are designed that way.
Take the tie rods off, drill a new hole in the center and stack them on top of each other.
You'll have to drill new holes in the spindle arms to get the tie rods in line from one tire to the other
They weren't designed to be turned that far in either direction
 

JPMKarting

Premium User
What you are seeing is whats called "ackermann".

https://en.wikipedia.org/wiki/Ackermann_steering_geometry

This is a common style in sprint/roadrace karts. If you used on single hole to attach the tie rods to the steering shaft plate (not two seperate as pictured), you would find a much more even turn radius between both wheels.

Also, the further you move the tie rod ends up the spindle arm towards the kingpin, the more "direct" steering input you will have.
 
It's ackerman. The steering geometry in cars does this too.
There are things you can do to "limit" or change the amount of ackerman in the steering, but is that something that you wish to do? The reason that the turning radius is so long, is a relation of the wheelbase (40") with the fixed rear axle (both rear tires driving at the same rate (ie no limited slip)) having a rear tracking about the same width (probably wider on your chassis) than the wheel base.


-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 

Ted Hamilton

Design Drafter / Racer
That Emmick chassis, having a non-adjustable front end, is now semi-collectible for the vintage racers. It will also potentially be harder to find OEM parts for, although there's a healthy kart aftermarket. I'd consider preserving it (don't chop it up) and sell it after the high school year to a collector, then find another adjustable front-end kart. There's a TON of good HS projects available -- converting motorcycle calipers to rear brakes.... converting motorcycle master cylinders to kart brakes... Machining adjustable front end parts... Welding tubing for nerf bars / bumpers... making adjustable seat struts, bushings, etc. etc. Karts are a great project for HS because they're complicated enough to require work, simple enough to see the results. Look up Mark Bergfelt on facebook or here. He was a HS shop teach in Beaver, PA who did this thing his whole career...and runs the Unlimited All-Star kart series. Good luck! What's your address? Post here and people may ship you some free parts...including myself! :)
 

Jimbo

A trial w/o witnesses is like racin w/o tech
The reason the inner wheel turns more than the outer wheel is because the inner wheel has to negotiate a smaller radius.


In 1878, a Frenchman, Charles Jentaud, applied the Ackerman principle to his mechanical propelled vehicle, and found that best results are obtained when a projection of the edges of the trapezium intersect over the rear axle.
 

XXX#40

TRUMP 2020
Lol, guy hasn't been back since he made the post..
I didn't mention Ackerman because he said he had extensive auto experience
 

flattop1

Dawg 89
helpful post Jimbo .
I wondering how it could not have a small turning radius?
may need to add engine for the full effect!
 

gijoe985

New member
That Emmick chassis, having a non-adjustable front end, is now semi-collectible for the vintage racers. It will also potentially be harder to find OEM parts for, although there's a healthy kart aftermarket. I'd consider preserving it (don't chop it up) and sell it after the high school year to a collector, then find another adjustable front-end kart. There's a TON of good HS projects available -- converting motorcycle calipers to rear brakes.... converting motorcycle master cylinders to kart brakes... Machining adjustable front end parts... Welding tubing for nerf bars / bumpers... making adjustable seat struts, bushings, etc. etc. Karts are a great project for HS because they're complicated enough to require work, simple enough to see the results. Look up Mark Bergfelt on facebook or here. He was a HS shop teach in Beaver, PA who did this thing his whole career...and runs the Unlimited All-Star kart series. Good luck! What's your address? Post here and people may ship you some free parts...including myself! :)

Ok, so to start, we had a snow day yesterday, and I only check these when I'm at work. I have enough other projects to keep me busy in my personal life. I'm sorry you missed me XXX#40! ;)

As far as Ackerman goes, I'm very familiar with it. What I was trying to show you from between the the two last pictures. Notice that the outer wheel straightens out when you turn beyond 90 degrees. So that's not really an Ackerman thing. And since cars use steering boxes/racks, you don't really run into this on a full sized racecar.

That said, I did notice that the pitman arm does have a central hole in it, so I can relocate the tie rod arms to that central hole.

And I do agree that moving mounting point further up the spindle arm would help increase turn radius some. Fixing the initial problem will be step 1. We can reassess the turning after that.

The Grandiew High School address is
1601 W 5th St
Grandview WA 98930

I'm Joe Edwards-Hoff. We'd happily take any donations. That said, I feel more lead to keep this Kart and go from there. I don't think we will be hacking at it much, but the previous owner has already modified it some to relocate the engine to make more room for him. He was 6'2" @ 270lbs.
 

flattop1

Dawg 89
Your free to do as you wish , that style chassis is designed to work in that manner.
My old Dino kart was the same way , the steering almost locked when turned full in either direction.
Its definitely a funny effect when the outside wheel starts moving in the opposite direction.
It would be a teaching aid having the ability to demonstrate the effect of relocating the tie rods on the pitman arm.
As someone posted if your turned full lock you have got other trouble.
 
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Bob Evans

Grumpy Old Admin
Staff member
What I was trying to show you from between the the two last pictures. Notice that the outer wheel straightens out when you turn beyond 90 degrees.
Doesn't seem that complicated.
If you draw an imaginary line from the center of the steering shaft and the tie rod mounting point on the spindle, the center attaching point of the right tie rod is overcenter in the 8 o'clock position. The only thing stopping it from further reverse travel is the left tie rod coming into contact with the steering shaft.
 

gijoe985

New member
You never turn the wheel that far when you're driving.

I think with it having a limited turning radius, it's natural to turn a steering wheel as far as it will turn. Though it is counter intuitive that by turning more, you turn less.

That said, that's why I mentioned possibly installing a steering stop.

What would you all say the turning radius of a kart should be at slow speeds? I can compare that to our kart. I just assumed it would be able to pull a u turn in a 20ft wide space.
 

flattop1

Dawg 89
Question do you have an engine on it?
I'm pretty sure none of mine would turn a u turn In a 24' double garage.
The 20' space would be a ten foot radius .
I think your expectation is off.
 

gijoe985

New member
I'm away from the kart now, but I can check tomorrow. And if my expectations are off, then that's ok. At least I'll know what to expect. I was hoping to put together a short course that went through our shop and then back outside. That said, I figured that it'd need to be able to do some tight turns.
 

Gab507

Member
Karts turn because of inside rear wheel lift. The geometry (caster, camber, and ackerman) contributes to this lift so at very slow speeds it will be very difficult to turn but at higher speeds will turn quite easily with very little steering input. That is what Walt meant when he said you don't need to turn it that far. Our most difficult turn is the one coming onto the track LOL
 

gijoe985

New member
Yeah, if we build these karts, they won't be for a real racetrack. But I'd love to make a little, 20-30 second laptime, course. We have an 8,000 sqft shop with 3 bay doors and some gravel and pavement outside. It'd be like ralleycross... ;)
 

flattop1

Dawg 89
The kids are lucky to have shop class.
They've pretty much disappeared around home and that's farm country.
 
gijoe985,

There is a local high school near us that just purchased 10 Margay karts and LO206 engine packages that will be running them on a designated course on school property as part of their tech class.
This has been part of a state (Indiana) effort to get kids interested in techs & trades again.
You might want to lobby your state to do something similar.

I wish we had something like these programs when I was in school.
We did have wood shop class -- I learned little that applies today unfortunately.
Teach your kids well, with something they can apply in a trade 5-10-25 years from now.
 
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