- #1

zacharoni16

- 19

- 0

## Homework Statement

This is not a homework question, I am working on a project to get it data from how rough the road is, mostly road bumps/pot holes. My project is for a capstone project, I want to use an accelerometer to measure the upward G's on the car frame when goes over bumps, or into a pot hole. I imagine I will have to filter out the high frequency noise from the engine and drive train.

I'm calculating the upward G force that a car frame would move up/down to going over like 3 inch high bump at 40mph, I'm getting like 22G's but I believe the suspension will will dampen the the G's experienced because the final velocity won't be much over horizontal so it should be less than half this value. do you think I would be safe with a 6G accelerometer to order for testing?

## Homework Equations

I basically used constant speed, and that the bump would only redirect a few degrees above horizontal. This will be a sudden large acceleration, a brief jolt but with great force

I'm getting like 5.5 G's now lol... more sensible

basically I used F = dP/dt

Calculated initial momentum let's say the car weighs liek 2000 pounds

The initial momentum is mass * velocity = 2000 lb / (32 ft/s2) * 200 MPH * (1.46 ft/s /1MPH) = 911.8 pounds

did some collision calculations

Time of collision is very brief

found the magnitude of the collision force

Found the horizontal / vertical forces

The force was like 11000 pounds

Then the G force was like 11k/2000 =5.5 G's

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I questions are, can I estimate the total damping of the cars suspension? I was thinking of measuring the fender height with the car sitting there, and then adding in weight (barbell weights) in 50 pound increments in the backseat and calculate the change in displacement? I'm not really sure if this is a way to do it, anybody have any ideas? Also, how would the damping coefficient of the suspension affect my above calculation for the G force? Not sure how to apply it.

I'm planning on starting small scale with a remote control car with a simple spring suspension, I assume I would have to take the Accelerometer data and do an FFT on it? do to all the noise, would putting the accelerator on the frame of the car in the back be the best position? The real car in the large scale is a 1994 Nissan pathfinder SUV has a ridgid frame not unibody and shocks in the rear with no springs.

The ultimate goal of this project is to be mounted on the car, detect rough road conditions and use GPS positions to record and log their locations on the road. Then I will have to come up with a way to average the roughness of the road and have it draw on say Google Maps different colors where the rough and smooth parts of the road are.

I know there is the International Rough Road Index, would this be useful here? Anybody have any idea or suggestions of the best way to approach this?