Confused about motors:

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Andrew Skinner (Skinnersplace)
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Username: Skinnersplace

Post Number: 1
Registered: 1-2009
Posted on Monday, February 9, 2009 - 5:46 pm:    Edit Post    Move Post (Moderator/Admin Only)

I have been looking at the specs of one of the Technobots motors: 

part 1471-103 24V 200W Geared 203rpm motor. 

The problem I am having is in my calcuations of how much weight the motor can move. 

I base my calculations on the torque of the motor. 

Torque = D * F 

Where Distance D = Radius of wheel 
Force F = Mass (combined vehical weight and load in KG) * Acceleration 

T = 9.36 nm for second motor (According to the web page) 

So Torque = ? * 0.3m * A 

where 

Acceleration = 1.04^2 m/s 
(as acceleration in m/s is usualy arround 1/3 of the top speed in mph) 

so (9.36/0.3)/1.04^2 = 28.8 Kg 

The website says the motor is suitible for golf carts ? how can that be if it can only move 30Kg ?
Admin (Admin)
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Post Number: 975
Registered: 10-2004
Posted on Monday, February 9, 2009 - 6:08 pm:    Edit Post    Move Post (Moderator/Admin Only)

Andrew, 

Are you saying you have 600mm diameter wheels!
Andrew Skinner (Skinnersplace)
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Username: Skinnersplace

Post Number: 2
Registered: 1-2009
Posted on Friday, March 6, 2009 - 8:48 pm:    Edit Post    Move Post (Moderator/Admin Only)

oops I had intended to calculate for a 30 cm wheel (0.15m raidius). 
but even with this correction it can only pull 60KG ?
Admin (Admin)
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Posted on Wednesday, March 11, 2009 - 8:23 pm:    Edit Post    Move Post (Moderator/Admin Only)

Andrew, 

Firstly, the motor to which you refer has been discontinued. Also, the website department description described a range of applications, the 1471-103 was the smallest motor in the range and of course is intended for the "smaller electric vehicle". 300mm wheels are rather large (as will be the speed) and thus the available torque to move loads is reduced. Golf trolleys and carts frequently use 200 to 250mm diameter wheels. Carts can and frequently do use more than 1 motor, 2 being the norm. 

It's a long time since doing these calcs but my calcs suggest the torque will carry even less load than you describe. I think you will find your force numbers should be in Newtons rather than kg.
Andrew Skinner (Skinnersplace)
Member
Username: Skinnersplace

Post Number: 3
Registered: 1-2009
Posted on Friday, March 13, 2009 - 3:42 pm:    Edit Post    Move Post (Moderator/Admin Only)

Many thanks for the help, I was using the motor as a point of reference to understand the calculations. 
From what you are saying, using a smaller wheel would increase the moveable weight to 86.5 kg but reduce the speed form to 4.8 mph. 

If this is not the case, I would be grateful if you could walk me through the calculations, so I can understand where I when wrong ? 


If the motor is now out of availability, can you recommend one suitable for an > 80kg load ?