Off Road Kart Square Tubing Wall Thickness?

[SquidBonez]

My plan is to use 1"x1" square tubing for an off road go kart/mini buggy. I want it to be as light as possible while also (obviously) being strong. My question is just about tubing thickness. How thick should I go? I've been basing a lot of my inspiration for this buggy off of this kart I found on a Google image search binge:

This kart was built entirely from 1"x1" 16 gauge tubing. But from what I hear, 16 gauge is a little thin for something like this (although don't quote me on that). KartFab recommends 11 gauge for their DIY go kart plans (which are much simpler than the kart above, just a solid frame. Spidercarts uses 14 gauge 1-1/4" square tubing for their Arachnid/Granddaddy karts. That being said, what's a good balance of strength vs weight for 1" square tubing? Keep in mind I will also have suspension arms/swingarm to worry about, so should I go thicker, thinner, or same as the main frame tubing on them?

For reference, here is a basic rough model of the frame I plan to build. Subject to change, but just to give an idea.

 

[OPmini]

I would use at least 10 gauge or thicker and reinforce all welds with flat iron or rebar

 

[SquidBonez]

I would use at least 10 gauge or thicker and reinforce all welds with flat iron or rebar

Is 10 gauge going to be very heavy?

 

[OPmini]

it will be moderatly heavy

 

[SquidBonez]

it will be moderatly heavy

That's something I'm trying to mitigate as much as possible. Would it be better to do like 10 gauge on the main frame and smaller gauge for the cage and suspension arms?

 

[chimmike]

Going with round tubing will allow for it to be not as heavy...

 

[itsid]

For reference, here is a basic rough model of the frame I plan to build. Subject to change, but just to give an idea.

yeah well that should change
When designing a kart, it's best to know what forces are involved and in what direction they apply to a frame,

that front end will never be a good design with it being buttwelded to the seat frame
continuous tubes front to back to make a strong ladder frame (adding sidepods if you want the seat-portion to be wider)
corner reinforcement need to be way bigger and tubes are to be preferred over plates...
perfectly vertical uprights are just stupid in 99.9% of all cases especially for a roll-cage like structure...

when fixing these things you can easily reduce the tube gauge w/o any issues from the 10ga OPmini recommended
since that and bigger is needed only because of your initial design

spiderkarts 1.25" 14ga recommendation is actually a good idea for round tube
KartFab's 1.25" 11ga a very good recommendation for square tube..
while being on the heavy side, it allows to reduce the total parts count and thus makes easier plans.

thicker isn't actually necessary I'd say.. if you just fix the major flaws of the design you'll have plenty strength in 11ga
you can get away with 14ga if you add clever bracing...
round tube makes it easier since it doesn't have a preferred direction. so it's worth to consider IMHO.
Unfortunately perfect bracing is non trivial if you're aiming to reduce weight that way..
tough for us home gamers.. and a lack of experience isn't helping any either.
Some good bracing however is surely enough to get away with 11ga (maybe even 12ga)
and still having a solid kart in the end

'sid

 

[Hybridracers]

Based on your design and the rudimentary form you're using as a model I'll assume a couple things....

My opinion is consider the safety factor first. Who is the user assuming risk? What is the environment it's being used in? This looks like a low power kart being built with the typical generator engine (predator 212 ect) and will have low suspension travel amounts as well as not being very large itself. Take those ideas into consideration.

10 gauge is you building a boat anchor for that.

You can easily build this with 1/8th for the main frame and main hoops and design your bracing with triangulation out of 16g or 14g.

The majority of the people building carts aren't engineers with solid works stress analysis plug ins and I look at what I'm building as a end use design. If it's not going to see massive loads from jumping, have potential fire high speed impacts or a powerful engine, why over build it?

I routinely use 14g instead of 1/8 on lots of things I'm building needing structural strength without the weight penalty. It's more about the build than it is the tubing. The fact that you're asking says that your welding is probably hobby skill at best and your weld is more than likely going to be a fail point. This said, could indicate using heavier tube because its easier to weld for those not really versed in that skill.

Your mileage might vary but it's the internet, we're all opinions at the ends of the day or you'd be buying plans from us.

 

[SquidBonez]

yeah well that should change
When designing a kart, it's best to know what forces are involved and in what direction they apply to a frame,

that front end will never be a good design with it being buttwelded to the seat frame
continuous tubes front to back to make a strong ladder frame (adding sidepods if you want the seat-portion to be wider)
corner reinforcement need to be way bigger and tubes are to be preferred over plates...
perfectly vertical uprights are just stupid in 99.9% of all cases especially for a roll-cage like structure...

when fixing these things you can easily reduce the tube gauge w/o any issues from the 10ga OPmini recommended
since that and bigger is needed only because of your initial design

spiderkarts 1.25" 14ga recommendation is actually a good idea for round tube
KartFab's 1.25" 11ga a very good recommendation for square tube..
while being on the heavy side, it allows to reduce the total parts count and thus makes easier plans.

thicker isn't actually necessary I'd say.. if you just fix the major flaws of the design you'll have plenty strength in 11ga
you can get away with 14ga if you add clever bracing...
round tube makes it easier since it doesn't have a preferred direction. so it's worth to consider IMHO.
Unfortunately perfect bracing is non trivial if you're aiming to reduce weight that way..
tough for us home gamers.. and a lack of experience isn't helping any either.
Some good bracing however is surely enough to get away with 11ga (maybe even 12ga)
and still having a solid kart in the end

'sid

The front end is easy enough to change. I can always make it one singular ladder frame rather than a square with a rectangle buttwelded to it. In fact, that would probably be easier. One question: is it stronger to have 3 continuous tubes with two outside frame rails and one rail running down the middle (like in my model) or is it stronger to have 2 outer frame rails with a few inner frame rails running perpendicular to the outer frame rails (like your standard ladder frame)?

Based on your design and the rudimentary form you're using as a model I'll assume a couple things....

My opinion is consider the safety factor first. Who is the user assuming risk? What is the environment it's being used in? This looks like a low power kart being built with the typical generator engine (predator 212 ect) and will have low suspension travel amounts as well as not being very large itself. Take those ideas into consideration.

10 gauge is you building a boat anchor for that.

You can easily build this with 1/8th for the main frame and main hoops and design your bracing with triangulation out of 16g or 14g.

The majority of the people building carts aren't engineers with solid works stress analysis plug ins and I look at what I'm building as a end use design. If it's not going to see massive loads from jumping, have potential fire high speed impacts or a powerful engine, why over build it?

I routinely use 14g instead of 1/8 on lots of things I'm building needing structural strength without the weight penalty. It's more about the build than it is the tubing. The fact that you're asking says that your welding is probably hobby skill at best and your weld is more than likely going to be a fail point. This said, could indicate using heavier tube because its easier to weld for those not really versed in that skill.

Your mileage might vary but it's the internet, we're all opinions at the ends of the day or you'd be buying plans from us.

I will be the user of it, it will be driven in grass fields, forest trails, and dirt roads (small jumps and hops would be the most abuse it will ever see). It will be using a built Predator 212 engine (stage 2) with Juggernaut torque converter. Speeds will be comparable to entry level ATVs like the Yamaha Blaster or the old Honda Odyssey FL250. Probably around 5" of suspension travel all around or somewhere close to that. Really just enough to provide some cushioning (I'm used to rigid frame karts, so any suspension at all will be a massive improvement). And yes, I'm building it to be as compact as possible. It will be about 50" wide so it can fit on ATV trails.

 

[madprofessor]

Just so you can see what it looks like to do it, here's some pics of what you get when building absolutely bulletproof with 1.5" square tube 11-gauge steel for the main frame, swingarm, motor rack, and a dashboard, and 16-gauge sheetmetal for the floorpans and dash. It's roughly 9' long (8' wheelbase), just under 4' wide, and 3' - 4' tall. What you get is 520 lbs. of fun that can use almost every bit of the 15+ hp. hotroddded up into its Predator 212.

 

[SquidBonez]

Just so you can see what it looks like to do it, here's some pics of what you get when building absolutely bulletproof with 1.5" square tube 11-gauge steel for the main frame, swingarm, motor rack, and a dashboard, and 16-gauge sheetmetal for the floorpans and dash. It's roughly 9' long (8' wheelbase), just under 4' wide, and 3' - 4' tall. What you get is 520 lbs. of fun that can use almost every bit of the 15+ hp. hotroddded up into its Predator 212.

I think I'm going to go with 11 gauge 1" square for the main frame/roll bar/suspension arms/swingarm and go with 14 gauge 1" square for the rest of the cage/any other chassis bracing. Trying to keep this thing as light as possible (ideally around or under 350 pounds). While your kart is no doubt strong, 520 pounds is way more than I would want. Then again, mine will be a single seater while yours is a 2 seater.

 

[madprofessor]

Actually mine is both a 2-seater and a single-seater. The steering shaft going through a tube in the dash moves from left-drive as a 2-seater to a center tube for center-single. The inside straps of the 2 racing harnesses flip in to be a center-single harness. There's dual gas and brake pedals to fit both ways comfortably, the wheel telescopes for fit, and it pops off with a quick-release.
Pointing out the 520 lbs. was to show how it adds up when using heavier gauge steel, and keeps adding up when you toss in a separate motor rack, a pair of cantilevers for the rear suspension, a dashboard, a massive front end to support the air shocks, and accidentally make it way longer than was necessary.
You don't need all those extras and their weight, and if my needlessly long wheelbase is bulletproof with 11 gauge 1.5" steel tube, then a smaller build could certainly benefit from a lesser gauge steel. I love to preach bracing to people, even though you don't see it in my big stuff.
The triangle is the most rigid form in construction. OPPOSED ANGULAR bracing (slanted, tilted, diagonal, whatever you want to call it) between 2 main struts can lock some quite thin struts into a very rigid structure that can weigh a good bit less than using pure gauge thickness to get strength over distance.
Looking at some kart plans I've seen struts they label as footrests, grab rails, bumpers, etc., and they're all missing a great opportunity. Just aligning some of those struts directly over the main frame struts, and welding in a few little short pieces of steel at opposing angles between them, would massively rigid that frame up. Enough that a much lighter gauge steel could be used on the main frame.
Some people refer to a similar setup as "ladder construction", and I've seen things that look like just that, a ladder. 2 straight struts with little pieces welded between them at 90 degree angles. Like a ladder. I could do that same thing but using opposing angles and make a rail structure out of merely 1/2" angle iron that you couldn't bend if you did jumping jacks on it.
Just some physics for you, something to think about. You could also just use all chrome-moly and aircraft aluminum tubing and have a kart you could carry on your shoulder. If you have an extra $10K laying around.

 

[SquidBonez]

Actually mine is both a 2-seater and a single-seater. The steering shaft going through a tube in the dash moves from left-drive as a 2-seater to a center tube for center-single. The inside straps of the 2 racing harnesses flip in to be a center-single harness. There's dual gas and brake pedals to fit both ways comfortably, the wheel telescopes for fit, and it pops off with a quick-release.
Pointing out the 520 lbs. was to show how it adds up when using heavier gauge steel, and keeps adding up when you toss in a separate motor rack, a pair of cantilevers for the rear suspension, a dashboard, a massive front end to support the air shocks, and accidentally make it way longer than was necessary.
You don't need all those extras and their weight, and if my needlessly long wheelbase is bulletproof with 11 gauge 1.5" steel tube, then a smaller build could certainly benefit from a lesser gauge steel. I love to preach bracing to people, even though you don't see it in my big stuff.
The triangle is the most rigid form in construction. OPPOSED ANGULAR bracing (slanted, tilted, diagonal, whatever you want to call it) between 2 main struts can lock some quite thin struts into a very rigid structure that can weigh a good bit less than using pure gauge thickness to get strength over distance.
Looking at some kart plans I've seen struts they label as footrests, grab rails, bumpers, etc., and they're all missing a great opportunity. Just aligning some of those struts directly over the main frame struts, and welding in a few little short pieces of steel at opposing angles between them, would massively rigid that frame up. Enough that a much lighter gauge steel could be used on the main frame.
Some people refer to a similar setup as "ladder construction", and I've seen things that look like just that, a ladder. 2 straight struts with little pieces welded between them at 90 degree angles. Like a ladder. I could do that same thing but using opposing angles and make a rail structure out of merely 1/2" angle iron that you couldn't bend if you did jumping jacks on it.
Just some physics for you, something to think about. You could also just use all chrome-moly and aircraft aluminum tubing and have a kart you could carry on your shoulder. If you have an extra $10K laying around.

I think for simplicity's sake I'm going with all 11 gauge tubing now. Been doing more looking around and a lot of people use it for go karts/off road minibikes. Even if I used over 150 feet of 1x1 11 gauge tubing, the frame itself would only weigh about 215 pounds (1x1 11 gauge tubing weighs 1.44lbs per foot according to what I've read).

 

[madprofessor]

Kudos 2 times, for research on weight per foot, and 150' guess for a kart. I regretted only using 6 sticks 12' long of 11 gauge 1.5" square tube. Wished I had a couple more. Since you're only using 1x1, 150' sounds good in that you need a little buffer so you're not scratching how to make a section out of scraps.

 

[SquidBonez]

Kudos 2 times, for research on weight per foot, and 150' guess for a kart. I regretted only using 6 sticks 12' long of 11 gauge 1.5" square tube. Wished I had a couple more. Since you're only using 1x1, 150' sounds good in that you need a little buffer so you're not scratching how to make a section out of scraps.

150 feet is just a completely random guess. Have no idea if that's actually what I'll use.