[Kartbuilding] frame material

[Stephen Burke]

Hi Oscar,

I will answer your questions as outlined below.
Firstly: Yes - you can use Square Tubing for the chassis of the kart. It
does indeed make things much easier for welding and cutting. Make sure
however that you resist the temptation to drill holes in the square
tubing to bolt on the floor pan etc. Any holes (even from welding etc.)
can severely weaken a chassis, and cause it to bend with the driver and
load. Square tubing will still allow the same flexibility in designing
and making a kart chassis. A wall thickness of 0.120 (inches) on 1"
square tube will do fine.

As you mentioned, most commercial karts do not extend the front axle
across the frame. This can be seen here:
http://www.kartbuilding.net/chassis_design_book_1.jpg
http://www.kartbuilding.net/chassis_design_book_2.jpg
Yes - this is to provide more flexibility for the chassis which is
required for the live rear axle with both rear wheels been powered. The
roll cage will also help to strengthen the chassis while it should still
allow the chassis to twist and flex when required, i.e on cornering.

Apart from that - you seem to be well up on kart chassis's. It should
work out ok. I suggest you draw out the chassis to get an idea of the
scale and sizing. You could also draw the chassis on the ground using
chalk to see if the dimensions suit yourself and your engine.

If you get a chance to take any photos, feel free to forward them on,
and I can put an article on the www.kartbuilding.net website.

Best of Luck,
-steve

Oscar Forand wrote:
> Stephen,
>
>        I have been reviewing you racing kart chassis Dwg # 3 dated
> 12/16/05.  I know you call for 25MM tubing with a 2-3MM wall.    I
> also noticed to avoid the bending problems, you cut the tubing, fitted
> in the correct angles and rewelded the tubing to make the frame
> flexable.  My question is could SQUARE tubing also be used for the
> frame and would it provide the same flexability as the round tubing?
> What I was thinking of using is 1 inch square with a 0.120 inch wall
> (although I can get it with a .075, .085, and .095 inch wall).  (A 2MM
> wall is .079 inches and a 3MM wall is a .118 inch).  The square tubing
> also makes it much easier to fabricate the frame since notching is
> eliminated and  square tubing can be clamped and held in place more
> easily than round tubing when welding. I have also noticed that most
> of the high buck commercial karts do not extend the front axle across
> the frame, but weld the king pin mounting piece directly to the ends
> of the shaped tubing.  Is this another method of providing more
> flexibility?  I also have to run a full roll cage where I race. It
> appears that if I run the 2 front over head bars to the kicked up
> center section in front of the axle, I should still have flexabitily
> in the frame @ the front wheels. Any thoughts and comments on the
> above would be appreciated.
>
> Thank you,
>
> Oscar Forand
>