Calculating Electric Motor Requirements for Golf Buggy

[bertie991]

I am designing a golf buggy with an electric motor drive. How do i determine what torque and power output i need from my motor if i know the weight of the buggy, my desired acceleration and the gradients i wish it to go up. Any advice will be gratefully appreciated.
If possible please use metric formula

Cheers

 

[berkeman]

I am designing a golf buggy with an electric motor drive. How do i determine what torque and power output i need from my motor if i know the weight of the buggy, my desired acceleration and the gradients i wish it to go up. Any advice will be gratefully appreciated.
If possible please use metric formula

Cheers

Welcome to the PF. What are typical power outputs of existing golf carts? I would start with the specs of existing units, and then try to see if they match my calculations...

 

[bertie991]

Thanks berkeman.

I have got specs for existing units however this task is part of a project and i have to show my calculations, however i have no idea of where to start.

 

[berkeman]

Thanks berkeman.

I have got specs for existing units however this task is part of a project and i have to show my calculations, however i have no idea of where to start.

Are you familiar with the formula for calculating the gravitational potential energy (PE) of an object, based on its mass and the change in height?

And are you aware of the equation relating power to energy and time?

Those two equations will get you started in calculating the power required to drive up an incline in some amount of time. However, since the golfcart has soft tires and is moving across soft ground, quite a bit of power will also go into that rolling resistance...

 

[jloram]

Assume direct drive; diameter of the wheel will tell you the torque you need. If not direct drive divide wheel torque by gear ratio.

HP is tricker: on the level you'll have to determine (assume?) the drag (rolling friction + aerodynamic). For uphill add hp required to lift weight at vertical speed required (do the trig).

 

[xxChrisxx]

There are two approaches to solving this problem.

The first uses a power method. It assumes very little about the buggy, it's basically tells you how powerful a motor you need to move the buggy from A to B in a set time. You define where it has to move and how fast it has to do it. From that you can specify gearing and wheel sizes to suit. This is the method Berkeman is talking about.




The second uses torque. You have to know some things about the cart to use this method. Wheel size, gearing (if any) weight and passengers. What you do is assume the worst case. For a golf buggy you don't really care about acceleration, so that's irrelevant it's also geared to a fast walking speed ususally.

The worst case for a golf buggy is hauling two/four people + cllubs up a hill. You torque requirements are to make the maximum weight of the vehichle go up the maximum gradient.

This method can be boiled down to a block on a slope equation, finding a force at the wheel contact patch. Which can then be turned into a wheel torque, which can then be urned into a motor torque.


I suppose the first method is a little more scientific, but I'd probably use the second method, and play with the inputs till I got a number I liked.