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Choosing the right electric motor?

harlanlw

Hi Everyone!,

 

I'm in need of some help in how to choose the right electric motor for my project.  I'm making an R/C vehicle with tank treads to act as a mover for equipment over 500 lbs.  I would like the system to be 24V.  The speed I'm trying to achieve isn't really important since it's mainly for moving electronics and I don't need anything to slide off, maybe something like 4 or 5 MPH.  As far as what torque and horse power, I don't know, this is all part of my question.  The chassis with all circuitry installed weighs roughly 100 to 150 lbs and will be of steel / aluminum construction.  To envision the design think of a USMC LAV (Assault Amphibious Vehicle - Wikipedia, the free encyclopedia) and make it flat on top and lower to the ground.  I hope that description kind of helps.  I would like to try and avoid a gearbox since my speed controls are all set in the receiver / main-board.  Any and all help is appreciated!  Thanks!     

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    Hi Lance,

    Trying to remember some old methods...

    If the total weight is 700 pounds and it has to go up an incline of 30 degrees the vertical lift is 350 pounds. (sin 30 x 700)

    If the speed is 5 mph (7 feet/s) vertical speed is 3.7 '/s.

    Horsepower = 350 x 3.7 / 550 = 2.33 HP

    If you are not going up steep inclines this will be significantly lower.

    Tracks probably cost 10-20% in friction losses so this increases the power required to 2.8 HP.

    The motor will need to be geared down.

    If it runs at 4000 rpm ( 67 rps) and the output wheel is 1 foot in circumference, the gear ratio will need to be about 20:1 to go 3.3 '/s

    You may want to plug in more realistic numbers, but this is the kind of rough calculation you can do to figure out your motor requirements.

    You also need to check the motor torque with similar logic.

    Doug

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  • 0

    Hi Lance,

    Trying to remember some old methods...

    If the total weight is 700 pounds and it has to go up an incline of 30 degrees the vertical lift is 350 pounds. (sin 30 x 700)

    If the speed is 5 mph (7 feet/s) vertical speed is 3.7 '/s.

    Horsepower = 350 x 3.7 / 550 = 2.33 HP

    If you are not going up steep inclines this will be significantly lower.

    Tracks probably cost 10-20% in friction losses so this increases the power required to 2.8 HP.

    The motor will need to be geared down.

    If it runs at 4000 rpm ( 67 rps) and the output wheel is 1 foot in circumference, the gear ratio will need to be about 20:1 to go 3.3 '/s

    You may want to plug in more realistic numbers, but this is the kind of rough calculation you can do to figure out your motor requirements.

    You also need to check the motor torque with similar logic.

    Doug

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