@tahir ahmed You still need to input the actual radius of the wheel. The reduction would factor into the torque needed.
Mr. Benson, I assume you have run across the tentacle combat robot calculator and I wonder why they have radically higher numbers than your application. I assume that is because they assume a āpeddle to the metalā mode of driving and assign .9 friction coefficient by default. Do does your application use friction coefficient?
Thank you much.
@ernest seemann You can see the equations used here: https://www.robotshop.com/blog/en/drive-motor-sizing-tutorial-3661
They do not factor in a torque constant, voltage constant, gear ratio etc. It would be nice to compare equations.
Hi Coleman!
I was a little concerned about my design specs for a Electric cart I was building whose specās is as follows
Total mass - 140 kg
Velocity - 2.25m/s
Acceleration - 1m/s2
4 motors driving it on four wheels
On a Max inclination of 15 degrees
All terrain capable
And the wheel radius - 0.101 m
According to the calculation in the website, it showās we need 300 w motors .
But what we have noticed that an ebike needs only one 500w motor.
Have we gone wrong somewhere?
@Biswajit Roy Very good question! The electric bike uses one motor which is almost directly driven without many additional gear ratios. Increasing the efficiency of the system decreases the power required since there are fewer losses. A 300 pound robot is quite heavy, so one 300W motor operating at 24V would consume only 12.5A, which seems low. From what we can see, a common e-bike motor power rating is 36V at 15A = 540W. The bike itself weighs a lot less than the rider, and such bikes also have a maximum weight allowance. Secondly, a 300W e-Bike likely cannot work well on an incline and would struggle, or even not work at all. We have seen many reviewers and authors indicating 1000W is preferable. Last, the calculations used here are simplified (you can see the equations used in the tutorial) in order to provide ballpark estimates of the torque and RPM needed.
Helo sir i need your help little sir i am going trough a project in which i had to built a lifting system that is capable of lifting a weight of 15 kg upto a height of 10 meter so can u suggest me a sutiable gearmotor for that thanks.
@hussain The torque depends on the radius of the pulley you will use. Once you know the radius, you can calculate the torque (Force x radius), then knowing the RPM and nominal voltage, you can choose a gear motor.
Hi There 
I have the following values :
acceleration a required = 0.05ms-2
g (acceleration due to gravity) = 9.81ms-2
Theta = 20degrees
M = 5kg
r = 0.03m
N = 2
When I plug this into the above, I obtain the value 0.392 for torque required per wheel. However, when I use the equation explained in the tutorial, plugging in the same values, I get 0.0294Nm per wheel - I donāt get anywhere close using the 65% efficiency rule either. However, what Iāve noticed is for the Equation T = (a + gsinTheta)Mr/N, if I put these values in, I get 0.392 as the value inside the bracket (that is the a + gsintheta part of the equation in the tutorial). Why is this? Iāve tried both degrees and radians, and itās just not making sense to me - can you see where Iāve gone wrong?
Best wishes
Audrey
@Audrey We do appreciate that youāre taking a look at the equations. If there is an error, we will most certainly fix it, though it will be some time before we can look into the details. For now, we can give you a bit of insight if you are prepared to do a bit of digging - the calculations used are all in HTML: view the page source and youāll see the equations and exactly what is done. Start with the section āInputā in the HTML. Below that, again in the HTML you will see a section āfunction DTMotorCalculate()ā which is the start of the calculations. Just above it are the inputs and outputs.
Hi Coleman.
Thank you so much for this awesome tool, Iāve spend hours investigating on net for something similar since I do not want to learn whole stuff behind it and just want to build the RC lawn mower.
On the internet Iāve found that everybody uses wheelchair motors whit currents around 20A and 300W or more and Iām surprised to see that in your tool I need a lot less current and power for the 100kg mass. So I have only one question did I do this right http://prntscr.com/cinipp http://prntscr.com/cinisy ?
Thanks in advance.
Regards,
Magda.
@Magda We would need to know the input values. Wheelchair motors are a good and inexpensive option for medium sized robots, but keep in mind that you will most likely need to replace the controller. 8.5Nm is 1200 oz-in, which is quite powerful.
Hi Coleman.
Let me rephrase the question. Iāve input this http://prntscr.com/cj1lm0 and got this http://prntscr.com/cj1lqr and now my question is. What motor should I use? Do I look for the motor ( or motor with gear box ) who has RPM close to 191 and stall torque larger then 105 so that Iām sure that it will handle 20deg slope and thatās it?
Value for the current to use only for controller selection?
Regards,
Magda.
@Magda The tool is intended to give you ballpark figures for torque and RPM. Based on your inputs, you would need a 24V DC gear motor in the 100Kg-cm (continuous output as opposed to stall) range and ~200rpm. 70Kg is a heavy robot indeed and it needs quite a bit of torque to move up a 20 degree incline. The current is an estimate based on power divided by voltage.
Hello Coleman,
I am building a miniature Goliath tank and its track is made of ninja flex. I am thinking about buying a very small metal gearbox motor, but I am having problems selecting the best motor that will provide enough torque to move my rover. Because it is a tracked vehicle, the only drive wheels I have are the two in the back which will move the track. All of the other wheels I have are idle wheels. What would be the best way to calculate the torque needed for my motor?
Kindest Regards,
Sou
Thank you so much but i still have a question that needs a direct answer, am building a robot of about 5-10kg weight and i would like to know the true specifications of motors i should use and the rating of the battery
@Bruce The Drive Motor Sizing Tool is there to provide an initial ballpark figure given the data you enter. If you need something more exact, there is quite a lot more to factor in, which is beyond the scope of this tool. The battery relates to the nominal voltage you chose, and how long you need the robot to operate between charges.
Hi, I have a question, I am trying to build a drone of almost 3 kgs, letās say 2.9. It must have a speed of at least 1m/s, and the radius of the wheel is 0.04 m. which motor should I choose to avoid of using a gearbox? I would like the efficency to be at 80% at least. Can you help me please? Regards Giovanni
@Giovanni Motors without gearboxes are rarely able to provide sufficient torque (they spin very fast, but with almost no torque). To get a high efficiency, you need efficient gearing - try maxonmotors or faulhaber (they come at a price).
hiā¦nice to see this tutorialā¦is this still valid for stair climbingā¦??