[Kartbuilding] frame material

[Stephen Burke]

Hi Oscar,

Sorry for the delay in replying to your email. I hope the knee is ok and 
you are back moving around.
The photos you sent on are very interesting. I like the idea of been able 
to quickly change the gear ratio of the sprockets. I take it you have a 
range of sprockets you have to hand and that you can swap in and out.

You also mentioned that you have it setup so only the left wheel is 
powered. How do you find that? Does it still corner good and provide 
stable handling going down the straight?

Anyways, best of luck. If you have any more photos etc. feel free to email 
them on.

-steve

On Wed, 23 Apr 2008, Oscar Forand wrote:

> Stephen,
>     I finally got started on the kart chassis and I'm sending you some
> pics. Jpg 25,26.27 are of the new chassis about 50% done.  I still have to
> do engine, gas tank, seat belt, seat, floor pan, rack & pinion steering,
> hydraulic disk brake and knerf bar mounts along with a roll cage. The silver
> gear drive you see on the back of the frame is how I set the engine RPM for
> the track I'm racing @. (We don't allow transmissions and are limited to 5.5
> to 6.5 HP 4 stroke engines)  I can change the gearing from the engine to the
> drive and from the drive to the axle.  This way I can set my Honda engine
> RPM to 6000 @ the end of the longest straight!  JPG 28,29 and 30 shows one
> of my older karts (way to stiff chassis!) with the double chain drive set up
> and left wheel drive only.  Will send other pics as I go along.  Having
> major knee surgery the end of this month so it'll be a little while before
> I'm working on this again.
>
> Oscar Forand
>
> On Tue, Oct 30, 2007 at 2:40 PM, Stephen Burke wrote:
>
>> 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
>>>
>>
>>
>