OT: Custom Built "Shifter Kart"- Frame in the Works

[70shortwide]

A shifter kart doesn't need as much motor as you might think. We had a Kawasaki 80 2 stroke and a Yamaha 125 4 stroke. The little Kawi was very fast.

I had one a couple yrs back that had an OLD 125 2 stroke motor on it. easy 80+mph kart. lots of fun to check the mail on!

[Ranchero50]

Add some sort of suspension, your back will appreciate it. Also make sure your rear isn't locked. I rebuilt a 5hp one for the kids, solid axle tears front tires up, they are gone after about 10 hours of running.

[evan_flatt69]

Add some sort of suspension, your back will appreciate it. Also make sure your rear isn't locked. I rebuilt a 5hp one for the kids, solid axle tears front tires up, they are gone after about 10 hours of running.

We're going to be using it for rode use only, but we're going to try to get some type of basic front suspension with camber so maybe it will take a turn a little better. And how would we rig up some type of rear differential?

[evan_flatt69]

Any ideas on the color of this thing? I'm thinking a glossy orange frame with most of the other parts black.

[Ranchero50]

Mine is orange, used the Rustoleum industrial saftey orange.

We use our on the road but you feel every crack and peice of gravel. The most fun we had with it was tooling around the neigborhood in a couple inches of snow.

[DuckRyder]

I mean this in the nicest possible way, but putting a 600 or 1000CC "ninja" motor on a shifter cart is just plain crazy...

I'm betting the guy in the "donuts" video isn't the one paying for tires and parts...

Orange and black would look good...

[PhantomoftheBumpside]

It's not camber that you need to keep from tearing off your fronts, or flipping out of a turn... it's Akermann angle. The inside front has to turn at a tighter angle than the outside front (bigger arc).

This means that as you steer the front tires (or all 4 in case of 4WS) are changing TOE at DIFFERENT RATES.

Basically you want to aim for having all the tires turning in their own concentric circle around the turn center... which at rest and at low speed is found on the extended imaginary center line of the rear axle... speed changes this... the turn center actually moves forward as speed increases... (this is why you have to steer less at higher speeds)...

It's fairly easy to comprehend if you draw it out with a compass, but complex to engineer properly.

The Ackermann arm on your steering knuckle is the key. Roughly, if your tie rods are going to be behind the front axle, then, when the front wheels are straight, you want the Akermann arms (where you tie rods attach to the knuckle)to be pointing at the center of the rear axle. (and should probably be about 5" long (my rough est) from the CL of your knuckle pivot to the CL of your hole for the tie rod) If your tie rods are going in front of the front axle, then you are really getting complicated.

As for the rear end, a solid rear end will mess up the rear tires the same way. The differential allows for the difference in distance around the arcs of the rear tires.

The caster actually affects camber during turning. Much like counter steer on a bike, the camber can be improved through the turn to better match your rubber patch to the road. Caster 'leans' your tires into, or out of, the turn (by causing an effective change camber). This is also why too much negative caster makes your front end feel "light" and you loose a lot of control.

Getting this close to right is way more important on pavement than dirt.

Hope that helps.

[evan_flatt69]

How much of a degree would you recommend on the caster? And should it have any toe-in or be as close to straight as possible?

[evan_flatt69]

I couldn't edit my post so I have to make a new one:

Thanks for the tips Phantom. Your comments will improve our go-kart greatly

But I have a few questions that will probably make me seem uneducated when it comes to steering and suspension..

We originally planned to have our Ackermann arms aimed in front of the spindle to allow for the steering wheel. How would keeping them aimed forward change the steering properties?

And what kind of caster angle should I be going for? And should I have any camber at all?

Thanks

[BobbyFord]

GSXR 1100 kart...
http://www.youtube.com/watch?v=2Xv76qiJFJg

[evan_flatt69]

GSXR 1100 kart...
http://www.youtube.com/watch?v=2Xv76qiJFJg

Seen that video before and I am in love with it..

[PhantomoftheBumpside]

I couldn't edit my post so I have to make a new one:

Thanks for the tips Phantom. Your comments will improve our go-kart greatly

But I have a few questions that will probably make me seem uneducated when it comes to steering and suspension..

We originally planned to have our Ackermann arms aimed in front of the spindle to allow for the steering wheel. How would keeping them aimed forward change the steering properties?

And what kind of caster angle should I be going for? And should I have any camber at all?

Thanks

Basically, assuming some type of light sprung suspension which means the vehicle will settle a little when the driver sits...

About +1º of Caster (top toward rear) to create a bit of trailing force in the front wheels to help the cart track straight (good range 1/2º to 1 1/2º, more will cause hard steering, oversteer and shimmy at low speed)

About +1/2º of Camber (top leans out) to allow for driver weight to settle the cart to 0º (normal vehicles will have about 1/4º curbside and 3/4º driverside to even stuff out, here you are in the middle.) May take a little more Camber if the suspension is light and/or the driver is heavy.

About 1/4º - 1/2º of Toe-In (front in) to allow for the wheels to pull to 0º at speed. This will depend on how tight the rest of your steering setup is. Wheels have a tendency to toe-out at speed, and the looser your front the more they can.

As far as locating the Ackermann arms to the front, the geometry will be different, and figuring what works will be a little more complicated... but you can build a model of it to test it on the computer, right?

[evan_flatt69]

One last question: What if we opt for no suspension at all?

And as far as the computer model goes- Yes, in theory..

[PhantomoftheBumpside]

Then Camber should be close to 0º. There will still be a little chassis flex, so a smidge + wouldn't hurt.

[Ranchero50]

I'd kick both camber and cast a bit, camber helps seat the tread when you are turning and the caster helps it feel more stable. Mine had a good bit of both, thinking 3-5`. I would still build something with some sotr of suspension. The kids just sits in the shed because it's hard on everyones back.