I am in high school and we are trying to convert our gas go kart to electric for my engineering class but we cant figure out how to find out how much torque it will take to get our cart moving with an acceleration of about 8 ft/s^2 any and all help would be greatly appreciated. Our kart weighs about 90 kg and our motors have 4.5 hp at 4900 rpms and a stall torque of 3720 oz-in. We currently have a 6:1 gear ratio and a 15 inch wheel diameter
Last edited by Kelly_Bramble; 11-09-2012 at 03:39 PM.
We don't help with homework here, but.... here's a tip -
Get a spring scale, hook it to the go cart (with the weight of the driver in there) and pull on the scale, reading it carefully, until the cart starts moving.
Hint 1: Then you will know how much FORCE it takes to accelerate it AT THAT RATE.
Hint 2: FORCE is not TORQUE, but they are related.
Last edited by Kelly_Bramble; 11-09-2012 at 03:39 PM.
Thanks a lot
Please do not multiple post. It makes a sequence of answers impossible to follow and is just plain poor forum etiquette.
This is a fairly difficult problem for a high school student.
I would suggest you take iit up with your teacher, since given all the extraneous data you provided,
I don't think you have enough knowledge to get this alone.
This forum cannot provide answers, since it would violate to integrity of the educational system
But, we probably could give you hints if you could provide a sketch of the mechanism.
I am currently working with three other students and my teacher used to be an electrical engineer but i was mainly hoping to get some help on the formulas since google hasnt been getting us very far
Attachment 474
this is a picture of our go kart but for some reason i cant upload our inventor drawings of the gearing we were hoping to use
What kind of searches are you doing? We have a tight policy on homework help, but if you can show us some of the things you have been searching with, we may be able to prod you into a direction.Originally Posted by surfnskate
Get together and think of terms that would describe the basic movements or processes you need to understand. Looking for something like "gas to electric" will not get even close to what you are trying to learn about. It is the basic underlying mechanics and physics that you need to start with.
We are much more amenable to helping you refine your efforts than telling you what to do.
Did you check the allowable file types and sizes for uploading?
we have been searching with things like "calculations for starting torque" and "torque required to get a vehicle moving"
by the way this is not home work it is our chosen all school year, in class project and if we can make it run then we will quickly and easily make it radio controlled
Do you understand how to calculate force and torque?
Step one in learning to think like an engineer: break every problem into its smallest pieces.
Large problem: how to move cart.
Small problem #1: how much force is needed to accelerate 90 kg at 8 ft/s^2?
Small problem #2: how much torque is needed on the tire to create that force?
Small problem #3: how much force is needed on the drive chain driving the axle to create that torque on the tire?
small problem #4: how much torque is needed at the driving sprocket to create that chain force?
So on and so on all the way back to your motor.
And, that's why I suggested getting together to discuss the basic physics and "starting torque" does not even come close to what you need to start with. That term is a nonsense as is "torque to get a vehicle moving." They are way to generalized to be of any real basic Physics use.
If you are to be Engineers, you need to think about things in abstract mode. Something that would apply to many disparate situations. To get you started, search on "Rolling Resistance." That is what you are **first** trying to overcome.
Once you apply those fundamentals to your project, you will learn more about other "things" required to get your project moving. (pun intended)
Your project still falls within our homework interpretation and we can only prod you in a direction, or get you back on track should you falter.
we used the spring scale method in the first reply and added 3 extra pounds to ensure plenty of power and we needed to overcome 22 pounds of force (97.856 N) to get the cart rolling.
using F=MA we got 86.94746 Kg*1.5m/s^2=130.421 and using T=wheel radius*F we got .1905*130.421=24.845 Nm (18.325 ft-lbs) which tells me how much torque it would required to move the drive wheel with that amount of force . is this correct?
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