1/2 Scale Cycle Kar(t)

sav0r

Coast to Coast
Replace those steering yokes with a plate, then put a heim joint above and below your karting spindle. You can either run two bolts in single shear or one long bolt with a spacer between the spindle. That will let you get the camber in check down to half a turn on each heim. I'd imagine that running large tires that are also round means you are looking at some serious camber thrust if the front end is off even a smidgen. You're probably going to want to run some castor and decent scrub radius, because with the differential and the rack and pinion, the steering isn't going to self center very well. Also, to get the camber right the thing should be on the scales, with the cross weights minimized, then the cambers set, then the cross weight adjusted again, then cambers reset. It will be a process with that swing axle arrangement. It always is with my F-Vee. Once complete I bet it drivers rather well though.
 

Jimbonaut

Over 1,000 Posts
DTT SUPPORTER
*Me* - finds lamp, rubs it.
*Genie* - you know the drill, three wishes mate.
*Me* - 1, Catherine Zeta Jones circa Entrapment era. 2, my wife being totally cool with that and 3, probably world peace yadda yadda yadda.

If I had a fourth it would be to be a kid in this class. Or being able to fly. A coin flip for sure.
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Replace those steering yokes with a plate, then put a heim joint above and below your karting spindle. You can either run two bolts in single shear or one long bolt with a spacer between the spindle. That will let you get the camber in check down to half a turn on each heim. I'd imagine that running large tires that are also round means you are looking at some serious camber thrust if the front end is off even a smidgen. You're probably going to want to run some castor and decent scrub radius, because with the differential and the rack and pinion, the steering isn't going to self center very well. Also, to get the camber right the thing should be on the scales, with the cross weights minimized, then the cambers set, then the cross weight adjusted again, then cambers reset. It will be a process with that swing axle arrangement. It always is with my F-Vee. Once complete I bet it drivers rather well though.
I'm having a hard time visualizing this plan. I understand steering yokes to be the fittings that attach the rack and pinion to the steering wheel via the steering shaft. Are you talking about the arms on the spindle that the tie rod is attached to via the tie rod end? Or are we attaching a plate to the tie rod that has two helm joints (one above and one below the spindle)? My understand to how we would adjust camber would be to move the shock towers in or out to move the angle of the wheel.
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
I'm having a hard time visualizing this plan. I understand steering yokes to be the fittings that attach the rack and pinion to the steering wheel via the steering shaft. Are you talking about the arms on the spindle that the tie rod is attached to via the tie rod end? Or are we attaching a plate to the tie rod that has two helm joints (one above and one below the spindle)? My understand to how we would adjust camber would be to move the shock towers in or out to move the angle of the wheel.
I think I know what you mean. You mean the ends of the swing axles where the bolt runs through to mount the spindles. Correct? Cut the ends off, add a plate. Mount helm joints top and bottom, so the spindle rotates by a bolt through the helm joints, but the spindle/helm joint assembly is mounted by the threaded ends of the helm joints to a plate at the end of the swing arm. Is that making sense and do I understand that?
 

sav0r

Coast to Coast
Yes, I think you go it.

Something like this, but instead of a spherical bearing at the bottom just use two heim joints. I assume they are using the swaged bearing on the lower in this photo, but it's probably way overkill.

 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Chain on and motor de-governored with a Mikuni TM24 upgrade. Now we’re figuring out braking. First try will be a mechanical caliper.
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We’re now looking for someone to machine a left steering arm to match our right steering arm. Since karts use a wagon style steering system, these are made with different lengths, so our wheels steer at different angles. This will cause the kart to push. Our rack and pinion steering needs arms that match.
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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Got a good lesson on steering geometry. These spindles are made for 1/4 midgets, so they go on oval track cars and they're designed to get the steering into the wheels and only go left. I'm looking at a bad angle on the steering no matter what with these arms, because it's putting my pin at 2 o'clock and 10 o'clock. I need to go straight out to 12 o'clock. This is a good opportunity to cut up sheet metal into steering arms and test the angle of the turn with several configurations. Yay for learning.
 

Texasstar

Can't is a four letter dirty word
Got a good lesson on steering geometry. These spindles are made for 1/4 midgets, so they go on oval track cars and they're designed to get the steering into the wheels and only go left. I'm looking at a bad angle on the steering no matter what with these arms, because it's putting my pin at 2 o'clock and 10 o'clock. I need to go straight out to 12 o'clock. This is a good opportunity to cut up sheet metal into steering arms and test the angle of the turn with several configurations. Yay for learning.
Another left turn?


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Hurco550

Keep er' Between the Ditches
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Got a good lesson on steering geometry. These spindles are made for 1/4 midgets, so they go on oval track cars and they're designed to get the steering into the wheels and only go left. I'm looking at a bad angle on the steering no matter what with these arms, because it's putting my pin at 2 o'clock and 10 o'clock. I need to go straight out to 12 o'clock. This is a good opportunity to cut up sheet metal into steering arms and test the angle of the turn with several configurations. Yay for learning.
Maybe you don't need to go as extreme as they are, but you don't want them at 12 o clock. We learned that lesson on our horseless carriage. Ackermann steering geometry. Basically if you draw a straight line from the center of your rear axle to the center of your spindle pivot, your steering arm pivot should fall along that line. It doesn't matter if the arms are in front or rear of the spindle.

Ackermann-steering-principle.jpg


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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Maybe you don't need to go as extreme as they are, but you don't want them at 12 o clock. We learned that lesson on our horseless carriage. Ackermann steering geometry. Basically if you draw a straight line from the center of your rear axle to the center of your spindle pivot, your steering arm pivot should fall along that line. It doesn't matter if the arms are in front or rear of the spindle.

View attachment 228323

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Good stuff. I’m using that pic in class. I’m assuming we’ll be at 12 o’clock on the arms, but I have another set of spindles we may opt for that gives several angles to test. The plan in class today is to cut arms out of sheet metal at different angles to test steer. We’ll also string our line from axle to kingpin.
 

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