What thickness should my steel be for making the frame for a go kart that’s going to be carrying me plus a roll cage

[Sleepingturtle]

Caster, camber and Ackerman are only important if you want to go straight or turn while moving. If you want it to just sit in the garage only then can they be ignored.
I’ll let you in on a little secret but you got to promise not to tell anyone else. The taller or wider or both the tire is the more critical they are. SSHhhhh! Now don’t tell anyone.
It’ll be our little secret!

Ok interesting, my kart is going to have pretty large tires so I should focus on making this work well

 

[Sleepingturtle]

You do need caster for sure if you plan to drive faster than you can run. Not having any caster will cause kart to wander and twitch while you try to keep it straight at speed. Caster let's it straighten its own self out at speed if you let go of the steering.
Confession: I built my current monster without caster accidentally due to experimenting with some really innovative A-arm connections. Would be way too much destruction to fix it now. Can tell you that on last test run I felt the lack of caster dramatically.
Spindle note: My spindles were ordered from BMI (3/4" x 4.5" axles) without my realizing they come at 90 degrees, no Ackermann at all, you have to make your own for that. Hugely important for a live axle (no differential) kart, so I found a way to get perfect Ackermann into it without relocating axles.

Do you think These plans would be fine for going decently fast and taking corners? It looks like they don’t have any caster like you were saying but I’m not sure

 

[madprofessor]

The finish picture does show zero caster (vertical kingpin bolt), but you just weld the spindle brackets on differently than they did for caster. They held the brackets vertical so the kingpin bolts through them were also vertical, then welded them to frame.
All you have to do is weld the brackets to the frame with them tilted back (top tilted toward rear of kart) a little for caster, to make it go in a straight line without a nonstop fight making you crazy. Straight line or straitjacket, your choice.
Here's my briefest Ackermann school: Have your spindle brackets welded on already (with caster), spindles in the brackets, kingpin bolts dropped into them, and wheels mounted. Line your front wheels up perfectly straight. Tie a string to the exact center of your rear axle. Stretch it tight towards either spindle, and on further on with the head of the kingpin bolt passing directly beneath your string. Whether your spindle arm (where tierod attaches to it) is leading ahead of or trailing behind the kingpin doesn't matter, wherever the bolthole in the spindle arm is to be positioned and welded is in the same straight string line as the kingpin is.
One straight string line should, from the rear axle's center, pass dead center over the head of the kingpin and dead center over the bolthole for the (leading) tierod in the spindle arm. Or vice versa for a trailing arm. Repeat on other side.
Note: You'll see how spindles like mine with the spindle arms and spindle axles being welded on 90 degrees from each other at the factory cannot have any Ackermann angle. I had to remake my tierod attachment points to put them inline with the string.

 

[Denny]

Grant was a member here (Kartfab). Whe put his plans out there to give people an idea of how to build a kart and about what to get to do it. He in no way meant it to be a bible. He encourages people to modify and build it to their specs. He knows a kart for a 4’ person and a 6.5’ person are going to have different needs size wise, or if you use bigger tires or engine. See the variables? Not to mention the differing road or trail surfaces. Have fun! I hope I blew your mind some more!

 

[Sleepingturtle]

Grant was a member here (Kartfab). Whe put his plans out there to give people an idea of how to build a kart and about what to get to do it. He in no way meant it to be a bible. He encourages people to modify and build it to their specs. He knows a kart for a 4’ person and a 6.5’ person are going to have different needs size wise, or if you use bigger tires or engine. See the variables? Not to mention the differing road or trail surfaces. Have fun! I hope I blew your mind some more!

Haha you definitely did blow my mind!