The need of mechanical engineering's genius

Hi Dingo:

We'll also have to know how fast you want to accelerate; that's where the power gets used.

I suppose we also need the friction of the wheel bearings and due to the [rubber?] tires on the floor, but the acceleration is the big one. In other words, how much time do you want it to require to get up to 7 mph?

Don

There are so many unknowns here that you would need to know first. For instance, is the robot to go up an incline? Are the wheels rubber tired? What is the nature of the surface the wheels are on? Very rough - like gravel - or smooth like asphalt or concrete?

If the wheels were smooth steel and the surface was smooth, level concrete, the force needed to move the robot would be relatively small - just to overcome the friction between the wheels and the ground. The force needed to accelerate the robot to 7 mph must be added to the to get the minimum needed. If you want to get it up to

7 mph in a very few seconds, the force will be large. If you can wait a minute to reach speed, it will be a lot less.

Lots of questions. No answers.

Building on Don's note: another variable of interest is the max slope you would like it to be able to make max speed while climbing...

Brian W

per Rusty "There are so many unknowns here that you would need to know first."

my comments......

not really, "the equation" doesn't exist.

you (or someone) needs to develop a mathematical model (equation) that describes the operating environment & behavior that you desire or your robot.

without any of the details "fleshed out" its pretty difficult to determine the robot's power requirment. the other posters have asked very valid questions.

My answer.....a couple or a few hp :)

regards Bob

There are many factors involved. You first need to learn the basics. See

and perhaps you will be able to work this out for yourself.

Good Luck,

David

Hey, thank you very much for pointing some important info out.

Accelerate from 0 to 7mph = 2 seconds Friction = rubber tire on concrete/asphalt Max Slope = 30 degree with max speed of 3mph

I need some clarify in the formula i found through some engineering books.

To get enough horsepower to make this possible: (on flat surface)

800lbs, from 0 to 7mph in 2 seconds

to find feet per second for the speed:

7mph * 5280ft / 3600 seconds = 10.26 feet per second

m = 800lb v= 10.26 ft/s t = 2 s g= gravity= (32.2 lb * ft) / (s^2 * lbf) = 32.2

given formulas:

P= 1/2 (m * v^2) / (g * t) = 1/2 (800 * 10.26^2) / (32.2 * 550) = 1/2 (800 * 105.2676) / (17710) = 1/2 (84214.08) / (17710) = 1/2 (4.76) = 2.38 HP

Does this make sense?

And now that I will have two motors, will HP split into 1/2? (1.19 HP each)

One more formula for getting up the slope m=mass g=gravity (32.2ft/s^2)

0 = degree of slope u = coefficient of friction

Fapp=mgsin0 + umgcos0

here what I have done: Fapp=12880 + 16061.875 Fapp=28941.875 (of what?)

is this correct and did i miss anything?

Hope you can help, Dingo-San