Force To Move 4 wheel Cart

1. Apr 10, 2013

andryuxa1985

Hello Guys
i'm constructing some cart with conveyor on it
weight of cart with conveyor is 300kg
cart has 4 wheels

i need to know if one person could move it, or i need to make it lighter
how can i to calculate the force than person needs to move this cart?
does radius of the wheels influences on required force?

thank you

2. Apr 10, 2013

andryuxa1985

this is the conctruction

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3. Apr 10, 2013

telecomguy

Yes, radius is the key to rolling. The force you have to overcome is the static friction at the axle of the wheels. This static friction is proportional to the mass of the cart. The radius is what gives you mechanical advantage. When you push, you are applying a latteral force to the center of mass of the cart. A reaction force is exerted by the floor at the perimeter of the wheel. As well as a reaction torque at the axle. Because the wheel is not completely constrained, it is able to roll. Rolling begins when the reaction force at the perimeter times the radius of the wheel exceeds the reaction torque at the axle.

4. Apr 10, 2013

Bandit127

A couple of observations on the design.

The centre of gravity is very high. That looks like a shelf or runner on top of it - any weight placed on that will make it even more unstable.

If it is a shelf or runner, any weight placed on the right hand side may move the CoG outside the right hand legs.

The wheels are small and may catch small objects or ridges in flooring.

To your original question - we use hydraulic lift trolleys at work with a safe working load of 300 kg. They weigh about that, so with a 200 kg load they come up about 500 kg. The wheels are about 200 mm in diameter. They are hard to steer and need a good push to get started but they can be moved by pretty much anyone.