chassis design and material

[itsid]

i have tig welding available.. my question still stands
1) HOW TO CALCULATE OD FOR KART FRAME
2)HOW TO CALCULATE GAUGE for FRAME
i need formulaes so that i can verify that a given material with given specification can take the load of the kart

Simply: you don't!
You need to consider both, diameter and thickness at the very same time to find the tubings you need.
What exact tubing you need is based on the geometry, weight and weight distribution along the frame geometry.

Let's just stick with Fabroman's values for a second:
OD 25mm (~1") round tube, thickness 1.6mm (1/16", 0.0625", 16 ga)
that's a perfect tube for almost any kart.
But if you have your seat mounted on ONE of those tubes, and that tube is say 2m long and just attached to the rest of the kart at the very ends of said tube, this will not be sufficient at all!
On the other hand,
if you have a dual rail frame and every cross section of a single tube is connected to the other rail tube every 10" (~25cm) you can even use 16mm OD tubing with a wall thickness of just 1.2mm.

James just posted a pdf plan, that comes with a value of what tubing you should use for that layout.

If in doubt use the values Fabroman already mentioned.
If at one point you feel it won't carry the load, you can just beef that section up, we can show you where and how when that occurs.

'sid

 

[rish]

here is the basic design of my chassis..

 

[mckutzy]

Ok good, does/will the motor/battery/controler fit with you seated?
Based on your rough drawing pic. Id say add another bar to the rear most end to tie the rear end together.
Depending where you will put the motor, I could see the frame torquing about with little structure in the rear.

 

[itsid]

So a ’97 Tony Kart Extreme...

Tonys are made of 30mm tubes 2mm wall thickness AFAIK (chrome moly steel)
It'd be easier to simply BUY a tony chassis though

'sid

 

[firemanjim]

Ok good, does/will the motor/battery/controler fit with you seated?
Based on your rough drawing pic. Id say add another bar to the rear most end to tie the rear end together.
Depending where you will put the motor, I could see the frame torquing about with little structure in the rear.

IIRC you're gonna use an electric motor? Those have a lot of torqu, and IINSTANTLY! You are gonna want to tie the rear end together,and beef it up with some triangulation. You're gonna need to keep the frame from twisting under acceleration. Maybe even a torque arm set up..... jmo

 

[itsid]

It's open to save some weight,
the Bumper closes the gap and ties the rear end.

Just slide the plugs in and screw them tight, done!

'sid

 

[OzFab]

So a ’97 Tony Kart Extreme...

Tonys are made of 30mm tubes 2mm wall thickness AFAIK (chrome moly steel)

'sid

That sounds about right...

 

[mckutzy]

I still dont think that bumper is going to do it. I reckon it'll shortly wrench the rear portion. If the batteries are put there that might mitigate the torquing, but if it does fail, I hope he is using a sealed battery.

 

[itsid]

I still dont think that bumper is going to do it. I reckon it'll shortly wrench the rear portion. If the batteries are put there that might mitigate the torquing, but if it does fail, I hope he is using a sealed battery.

Well on a commercially produced frame it does!
I doubt an 800W e motor can bend that frame by just turning the rear axle.
On a home made replica.. depends!
Still unlikely, but not impossible.
There are better frames for an electric motor than that I assume
(I'd go for a symmetric set up for example)

'sid

 

[rish]

You mean to say that when motor is switched on then rear axle can bend the frame? A bumper is surely gonna be added.. Do i need 30mm od and 2 mm wall thicknesa or as said earlier 25mm and 1.2 mm wall thickness enough for me? how to add some triangulation at the end? Yeah i am using sealed battery.. I am taking tony as the basic chassis but some changes will b done according to our needs

 

[mckutzy]

I think material selection comes back to what can you afford, can easily acquire and weld successfully, Then work on design with the desired components in mind(weight/physical size and specs).

Triangulation is a brace like the one in the left rear portion near the rear bearing hanger.

Also have you accounted for axle diameter for part sourcing. 1", 40mm ect. Each have there issues on availability for this and in your area of the world. Shipping could be really expensive for you.

 

[OzFab]

25mm and 1.2 mm wall thickness enough for me?

No one suggested you use 1.2mm WT material for the frame, only for extra bracing; you should use no less than 1.6mm WT for the frame

 

[itsid]

Again: I suggest a symmetric kart frame for a good weight distribution.

The one khalil labaki made seems to be a good starting point for me:
http://grabcad.com/library/go-kart-frame-1
You can even find a complete electric kart there
http://grabcad.com/library/electric-go-kart
I didn't checked on what's included, but I think this can give you an idea how and where you could mount your batteries and the motor at least to have a good weight distribution
(free downloads, if you still do not want to register there, drop me a PM!)

if you think about using lead-gel batteries, I'd say use 30mm OD tubing instead of 25mm.


'sid

 

[rish]

Again: I suggest a symmetric kart frame for a good weight distribution.

The one khalil labaki made seems to be a good starting point for me:
http://grabcad.com/library/go-kart-frame-1
You can even find a complete electric kart there
http://grabcad.com/library/electric-go-kart
I didn't checked on what's included, but I think this can give you an idea how and where you could mount your batteries and the motor at least to have a good weight distribution
(free downloads, if you still do not want to register there, drop me a PM!)

if you think about using lead-gel batteries, I'd say use 30mm OD tubing instead of 25mm.


'sid

yeah i saw that link.. i was wondering how i would mount my motor and battery.. seems a nice idea to me the way they did it in that link.. but i think motor of 800w should be supported more heavily than this.. moreover the weight of motor is around 8-9 kgs...

 

[OzFab]

So you make the mount strong enough to hold it...

 

[itsid]

yeah i saw that link.. i was wondering how i would mount my motor and battery.. seems a nice idea to me the way they did it in that link.. but i think motor of 800w should be supported more heavily than this.. moreover the weight of motor is around 8-9 kgs...

Nope that mount is perfectly safe for almost any electric motor (based on the material being used).
All torque is applied to the face plate;
the "holder" is just a support for the weight of the motor.

similar mounts are used on motors well beyond 10,000 W;
so I think it's safe to assume that 800W will be fine with it
(check yt for electric go karts and see some of them)
stanford university for example:
http://www.youtube.com/watch?v=9vrmspERACw
(same tony frame )
And face-plate mount motor.
this I think

(5kW)

'sid

 

[mckutzy]

Ya, that it is called a C-face motor.
Rish- What motor and other parts do you have on hand at the moment? post pics.

 

[rish]

see right now i have to clear the virtual round of my competition where i will have to show them virtually what all i am using and why.. then in synamic round i will have to make my kart.. hope you get my point