# “Poor man's” off-road kart



## Woodsmith (Jun 5, 2008)

Nice little project.

What I will say about the steering is firstly that the kingpin being upright will mean that the steering will kick a lot as it hits bumps.

Really the kingpin should be angled so that it points towards the contact point of the tyre with the road. That will give near centre point steering.
It means the tyre will turn almost on the spot rather then prescribing a circle on the ground.

Also as the tyre is turned it will lift the front axle a little. That will help add weight and feel and allow the steering to self centre a little more easily.

Secondly you want to the tilt the whole axle so that the kingpins point ahead of the tyre contact point.
That will add castor to the wheels, a little like the castors on your office chair.
It will help the kart stay in a straight line more easily. Too much castor will make steering heavy, too little will make it skittish.

Are you going to add any suspension or just rely on chassis flex to keep wheels on the ground?
There are simple ways to add a little movement, a centre pivot on the axle would do that. Or you can spring the axles with simple coil or leaf setups.


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## zwmaster (Nov 23, 2009)

Thnx Woodsmith.

I hope to understand now.








Front assembly should be angled like on this picture and lean forward like on the next one. How far would you sugest to go forward?








The whole castor thing I don't understand. Must be my translation problem.

For suspension I look for some shock’s from small motor bike or similar. What would you suggest from that? Could be suspension like on this picture work out?








Red dotted line would be shock absorber with coil spring.


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## Woodsmith (Jun 5, 2008)

zwmaster said:


> Thnx Woodsmith.
> 
> I hope to understand now.
> 
> ...


Yep, that looks right. Something around 3-5deg, maybe a touch more should do it.
If you look at teh front forks of a bycycle and follow a line down the steering tube until it hits the road, it is ahead of the tyre contact point. As the bike moves forward the forks 'lead' the front wheel dragging it along. The drag will cause the wheel to follow in a straight line.



zwmaster said:


> For suspension I look for some shock’s from small motor bike or similar. What would you suggest from that? Could be suspension like on this picture work out?
> 
> View attachment 6787
> 
> Red dotted line would be shock absorber with coil spring.


If you fit the spring between those two points you will get a reducing spring rate, the more load you put on it the softer the spring feels.
It would be better to move the top of the spring further out to make it more upright. That will give a correct increasing spring rate.

There is also a benefit from having a shorter top wishbone and longer lower wishbone. Get the relative lengths right and the track (the distance between the contact points of the front wheels) will stay mostly the same over the range of movement.

You could look at spring damper units from mountain bikes. Proper ones that have dampers would be a lot beter then cheap ones which only have pretend dampers.

I have even thought about making two transverse leaf springs from laminated wood. That would work too.


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