The discussion revolves around determining the minimum radius required for a loop in an experiment involving a 2.4GHz remote control car that reaches speeds of 45 mph. Participants explore various calculations and considerations for the loop's size, taking into account the car's dimensions and performance characteristics.
Participants express a mix of agreement on the need to consider practical dimensions and performance factors, but there is no consensus on a specific minimum radius or diameter for the loop. Multiple competing views and calculations are presented without resolution.
Limitations include the lack of specific measurements for the car's wheels and bumper clearance, as well as the assumptions made in the calculations regarding speed and forces acting on the car.
This discussion may be useful for students and hobbyists interested in physics experiments involving motion, energy, and the design of physical models, particularly in the context of remote control vehicles.
Simon Bridge said:Welcome to PF;
You mean you want the max radius of the loop that the car will get all the way around?
Rule of thumb - try: d<v^2/20 where v is the max speed on the horizontal and d is the diameter of the loop.
This guarantees that there is enough KE at the bottom of the loop to make it to the top ... this size is smaller than the maximum you can get away with because it does not account for the car being under power all the way around.
45mph is about 20m/s
so a diameter less than 10m? ...
There are better calculations you can do.
I agree.It might be better to decide what is a practical size loop you can build and see if we can predict the minimum speed required to make it around the loop.
Liamj said:It's not related to anything in school right now, just that I'm really into cars and the teacher wants us to pick something that interests us...
Wheel base is 12 1/2" center to center and overall with bumpers is 22".
That is a good idea, let me think about this...Thanks againSimon Bridge said:The usual one is to gravity feed cars into the loop - you can see how the initial ramp height compares with the loop height.
If you can control the speed of your car, you can just run it slower.
If it takes a bit to reach top speed you can find minimum run-up distance to loop the loop.
The main issue is just that the car has to be able to fit on the loop. A 3' diameter may be a bit tight.
How about building a ramp and working out the farthest you can get the car to jump?
Thank you, at least I have some options...yuiop said:There is a lot of overhang on that car! To make sure it will fit on a 3' loop without catching the bumpers, scratch out an arc on the ground using an 18" piece of string, lay the car on its side with the wheels touching the arc and check the bumpers do not touch the arc. We could of course do it mathematically, but we would need the diameter of the wheels and the clearance height of the bumpers together with the measurements you have already given us.
For the physics, there is potential energy, kinetic energy, centrifugal/centripetal force, rolling and air resistance, etc.
That is a little more than I can handle, but thank you.rcgldr said:If the car has a suspension, then suspension compression needs to be taken into account in order to make sure everything clears while experiencing maximum force, which will occur at the bottom of a circular loop. You could try making something like a clothoid loop or constant g loop, but that would be difficult.