Let's Make Robots!

Remote Controlled combat robot

Hello everyone and thanks for the help. I would like to know what kind of motors I would need for a rc vehicle to move around 5-10 pounds at max, If you could tell me how this torque thing and rpm applies to wieght and pulling ability I would extremely appreciate it. Also it needs to be able to handle tough terrains- mud, hills, debri, etc. - An outdoor fighter.

It will have a paintball or airsoft gun mounted on it and that i am thinking will be moved up and down by a servo and shot (the trigger pulled) by a servo also. 

I am thinking the base will be made out of plywood or thin steel. I have included a video of the robot i am trying to somewhat "clone" or make it off that design. 

Also if you could tell me if tracks are better or wheels. For the wheels/tracks and motors I would like it to be around $40 or less prefferably less haha!

Thanks for helping me and my tight budget! 


Radio system-http://www.robotmarketplace.com/products/0-GWS-GWT4A.html

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the wonders of modern technology.

Spend countless thousands of hours of personal working time, thousands of dollars, develop hi-tech..

all just so we can blow somone's brains out.


anyhow, to answer your question - try here:


check your work - I'm not convinced that this actually gives the right answer...



ok thanks, but when i type my stuff in it says i need 91.857 torque per ozf-in? is that stall or peak efficentcy? well i guess what im trying to say is would my one motor work?


that means that unless you have a motor that can supply a torque of 91.857 ozf-in (outrageous units...), then your motor will stall because it can't drive the load.

The "efficiency" that you enter in the bottom of that page is the efficiency of the whole system - the motor, bearings, the coupling of the wheels to the ground, etc, etc. The default value is something like 60%? If your terrain is complex and bumpy, I can imagine that the wheel-ground coupling won't be very good (i.e. skidding etc) so you might choose to use a more conservative 30% or so - anyhow, both of those numbers are pretty arbitrary but it's prudent to have some hefty over-engineering... as much as you can afford and be bothered to implement.

sorry ya i mean 12 for the torque sorry. and i entered 65 percent sorry i messed up.



alright so my torque is about 12-20, so if i press that motor to the stall torque it would break right if i understand that right. so i guess i would need a motor that the stall is what like 25?


12-20 is a pretty big range, almost double. but if your estimates are correct, then a motor that can deliver in excess should work without stalling and damaging the motor.

Those are pretty medicore demands -either your robot is VERY small and light, or you don't need it to negotiate very complex terrain?

ok thanks im glad i asked you guys first. i underestamated the situation. if you could answer my questions on the other reply i would appreciate it and i know ive took alot of your time. thanks again.

for a 7lb robot, with a 20cm diametre wheel, to move up a 60 degree incline, with two drive motors and a 30% efficiency, that calculator shows you'll need two motors that can supply 652 ozf-in. I think that's a pretty beefy motor and might cost you about $100 for the two. I'm thinking that unless you've done this before, you might wind up making some expensive mistakes. maybe a smaller, scale simulation of your robot would help?

Can you check your input parameters, or clarify mine?

thank you so much i have never done this scale before and really appreciate it. I agree i might get myself in a heap of trouble and loss of money. I will size it down and im guessing use some geared motors. The one motors i think i will go with are rated at a torque of like 100? and i think my incline would be like 35? tell me if im doing it wrong but i hope this will work. The last thing i would like to ask is how voltage works, it goes through the receiver battery and receiver right? So what kind of battery do i need? would a 700 mah work? thanks again, and sorry for being a pain.



okay, there's too much here for us to be able to tell you in a couple of posts. we need smaller steps I think.I'm a fan of following grandiose plans, but not drowning. so..

why not build a starthere robot first? - that video is really just a starthere robot, with guns, cameras...and.. okay.. not REALLY a starthere robot, but the principals are similar.

Or you could purchase pre-prepared chassis and mount your gizmos on that. Something like the 6wd all-terrain buggy

http://www.robotshop.com/dagu-wild-thumper-6wd-all-terrain-chassis-black-34-1-2.html looks fun - it has plenty of power and you just plug your uC into it.


There are lots of other issues that I'm not sure you've considered - what uC are you using?