[Kartbuilding] Fwd: Chassis Tubing Size

Stephen Burke sburke at burkesys.com
Mon Feb 5 00:09:12 GMT 2007

Hi Alrin,

I recieved your email and JPEG of your SolidWorks Kart model fine. It 
looks good!
As for suspension - its a lot of hassle in my opinion. To get suspension 
working "correctly" it take a LOT of extra work. I had often though that I 
could easily modify my karts afterwards to include suspension - however I 
never got the time to trying it. My suggestion - is to get some nice sized 
wheels and let them take some of the bumps.
I have used a Honda GX160 5.5hp - its an ok engine - but on its own - its 
limited to 30mph for a on-road/tarmac kart with a simple centrifical 
clutch. The Honda GX240 sounds like a better engine with more power. I 
still think you may need a "torque converter" (google for it) or a gearbox 
to give you a high & low gear ratio which is essential for an off-road 
As for the diameter of tubing to use. First off - as I mentioned if you 
are running the kart off-road, and with no suspension, letting a little 
air out of the tyres will help soak up some of the bumps and punishment. 
If I was going doing some serious off-roading in the kart - I would go 
with 30mm diameter tubing. It all depends also on the weight of the kart, 
and whether the engine will take it. The 8hp engine of your should. The 
roll cage you have modelled up in SolidWorks will also help to transfer 
the load into the chassis better. I would add further members to the roll 
cage also - firstly to better support the ladder type chassis, and 
secondly to offer more protection if the kart did roll onto its side.
So - go with the 30mm tubing for the main members. You can use 25mm for 
the cross members. Also - look into getting some sort of a gearbox or 
Torque Converter.
Best of Luck,

  On Sun, 4 Feb 2007, Alrin Christians wrote:
> Hi Stephen
> My name is Alrin.(Cape Town-South Africa)In am busy building a semi off road
> cart based on the free plans I found on you website.This is my first project
> of this type so there is a lot of things I am not 100% sure of.I dont want
> to use suspension in my design because as I said before,this is my project
> of this kind and I dont want to make it too complicated.
> Originally I was going to use a Honda GX160 5.5hp motor but I ended up
> getting a Honda GX240 8hp motor.This motor weighs 60Kg.What worries me is
> the tubing size for the chassis.In my design I used 25mm mildsteel tubing
> (as sugested on you site).I also made the chassis a 150mm longer to place
> the engine behind the seat.The overall dimensions of the chassis is 1650mm X
> 700mm.What ads to this worry of mine is the fact that I wont use a
> suspension.Will the chassis be able to take the punishment or should I use
> maybe 30mm tubing or maybe even more?
> Attached is a Solidworks JPEG of my design so far.I bought the engine this
> weekend and I want to buy the tubing next,so I just wanted to make sure
> about the tubing size before I buy the material.
> You advice will be greatly appreciated.
> Regards
> Alrin

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