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### Topic: Torque Calculation and Suggestion needed for finding the right motor (Read 404 times)previous topic - next topic

#### tk1221

##### Mar 19, 2018, 12:30 pmLast Edit: Mar 20, 2018, 12:29 pm by tk1221
Hi!
I just made an account to seek help for the project I'm planning on.
I've been spending quite a time on finding the right motor with right torque and dimensions.

So I'm planning on a project with spherical wheels, each wheel controlled with one stepper motor and a dc motor.

The wheel I'm using

Basically, I'll have 4 dc motors and 4 stepper motors controlling each wheels individually.
But here's the problem. Just like the images I've attached, I have limited room for dc motors, so I was first finding for right angle gear(or worm gear) motors. However, most of them were too big and heavy for my project.

Wheel weight = 100g
Wheel axis radius = 2"
Wheel diameter = 6"
Vehicle weight = Approx 30lbs.
Speed/Acceleration wanted = 15mph in 5 seconds.

I've looked for all different kind of motors but couldn't find the right one since I can't calculate the right torque needed.
I want the vehicle to be at least 70rpm(or 15mph in speed), so that's another factor I need to consider.

Can anybody help me calculate the torque for me?
Sorry if the question is too confusing, I'm a terrible writer as English is not my primary language.

Additionally, it would be great if you can let me know how to calculate the torque needed for each stepper motors too!

#### Paul_KD7HB

#1
##### Mar 19, 2018, 09:28 pm
You are starting from the wrong end of the design. You are building a moving vehicle. You gave the weight as 30 lbs. Now how fast do you want it to go? And how fast will it accelerate? From that you can compute the torque required to bring the vehicle from stop to maximum speed in the time you have given.

Google "vehicle acceleration power" and see if the results give you the formulas you need.

Since you have 4 motors, divide the needed torque by 4 and you have the required motor torque. This assumes no loss in bearings, joints, etc.

Paul

#### vinceherman

#2
##### Mar 19, 2018, 10:24 pmLast Edit: Mar 19, 2018, 10:26 pm by vinceherman
This assumes no loss in bearings, joints, etc.
Or rolling resistance.  What surface will this be moving over?
Hardwood floor has less rolling resistance than carpet which in turn has (much) less than a lawn

Additionally, it would be great if you can let me know how to calculate the torque needed for each stepper motors too!
I am not sure where the stepper motors are defined in your configuration.  You appear to be using the DC motors to drive the wheels for propulsion.
What do the stepper motors do?

#### slipstick

#3
##### Mar 19, 2018, 11:01 pm
I think we need the images that you didn't attach. I'm trying to work out how you control one wheel using a DC motor plus a stepper motor. I can't visualise your obviously unconventional vehicle.

Steve

#### tk1221

#4
##### Mar 20, 2018, 12:24 pm
You are starting from the wrong end of the design. You are building a moving vehicle. You gave the weight as 30 lbs. Now how fast do you want it to go? And how fast will it accelerate? From that you can compute the torque required to bring the vehicle from stop to maximum speed in the time you have given.

Google "vehicle acceleration power" and see if the results give you the formulas you need.

Since you have 4 motors, divide the needed torque by 4 and you have the required motor torque. This assumes no loss in bearings, joints, etc.

Paul

For speed, I want the vehicle to travel at least 15mph in 5 seconds.

#### MarkT

#5
##### Mar 20, 2018, 12:31 pm
First draw a diagram of your drive mechanism, it is not clear at all from just words.

Second its much easier if all your values are SI, then the standard Newtonian mechanics formulae
apply without any arbitrary constants - metres, seconds, newtons, watts...
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### tk1221

#6
##### Mar 20, 2018, 12:32 pm
Or rolling resistance.  What surface will this be moving over?
Hardwood floor has less rolling resistance than carpet which in turn has (much) less than a lawn

I am not sure where the stepper motors are defined in your configuration.  You appear to be using the DC motors to drive the wheels for propulsion.
What do the stepper motors do?

I edited my post and added the link for the wheel I'm using and the surface I'll be rolling over.
The wheels is made of EVA Foam(Stronger foam commonly used in gym) and will usually roll over a carpet floor or on hard wood floor.

Here's the image link:
https://imgur.com/a/6F7mK

Basically, DC Motor will roll the sphere, and the stepper motor(a box on the first image) will rotate the whole rotating sphere part to make turns.

#### tk1221

#7
##### Mar 22, 2018, 03:32 pm

Hi!
I just made an account to seek help for the project I'm planning on.
I have asked the same question a few days ago, but I found many people were being confused with not enough information for calculation. Therefore, I added more details to get help.

So I'm planning on a project with spherical wheels, each wheel controlled with one stepper motor and a dc motor.

The wheel I'm using

Basically, I'll have 4 dc motors and 4 stepper motors controlling each wheels individually.
But here's the problem. Just like the images I've attached, I have limited room for dc motors, so I was first finding for right angle gear(or worm gear) motors. However, most of them were too big and heavy for my project.

Wheel weight = 100g
Wheel axis radius = 50mm
(*Basically, I'll modify the axle so it creates an effect that the axis radius is 50mm, so it requires less torque to turn the wheel)

Wheel diameter = 150mm
Vehicle weight = Approx 30lbs.
Speed/Acceleration wanted = 15mph in 5 seconds.

I've looked for all different kind of motors but couldn't find the right one since I can't calculate the right torque needed.
I want the vehicle to reach 70rpm(or 15mph in speed) in 5 or less seconds, so that's another factor I need to consider.

Can anybody help me calculate the torque for me?
Sorry if the question is too confusing, I'm a terrible writer as English is not my primary language.

#### jremington

#8
##### Mar 22, 2018, 04:01 pmLast Edit: Mar 22, 2018, 04:01 pm by jremington
Study the torque calculation and other types of tutorial at http://www.societyofrobots.com/mechanics_dynamics.shtml.

How will you turn that ball into a motor-driven wheel?

#### vinceherman

#9
##### Mar 22, 2018, 04:48 pmLast Edit: Mar 22, 2018, 04:48 pm by vinceherman
Isn't this a duplicate of the thread you started 3 days ago?

#### robtillaart

#10
##### Mar 22, 2018, 05:02 pm
Moderator merged crosspost.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

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