Engineering a sway bar

[MattAvino]

Are you actually selling the bar?

[TwoJ's]

There is a few things I would do differently if I were to do it again.

[Massimo]

late to the party but why you no make blade style bar

[giantkeeper]

Just read the bumped thread, very cool!

[TwoJ's]

Anyone want to buy the sway bar? I'll sell it cheap.

[ThatOtherGuy]

dude...

You are fucking awesome

[fiftytakedowns]

Those are the kind of numbers that sell products

[TwoJ's]

go seahawks!

yes!

[enigmaticdream]

Dude, that's an awesome senior engineering project. Congrats on the 10.6% increase. Also, Go Seahawks!

[TwoJ's]

Okay, so I have finally gotten some workable data. I have abandoned the gyroscope. For starters, the roll angle of the car with my sway bar is so low that the roll rate is within the noise level of the circuit. On top of that, I came to the realization that I was not placing the gyro directly on the roll axis of the vehicle. I won't go in to that too much, I'm sure you can visualize that scenario and realize the effect it would have on a gyro.

So I decided that maximum lateral cornering acceleration would be my primary test data. Through a friend, I was able to go down to Renegade Raceway in Yakima and do some "skidpad" testing. I did 5 runs going left and 5 going right with my sway bar installed and the stock sway bar installed. I was able to get some good data and will proceed with my analysis and testing report.

Here is a plot of lateral acceleration vs. time. It is negative because this was a right turn. You can clearly see the point of maximum cornering force, and then loss of traction. This particular run induced oversteer.



I ended up with a 10.6% increase in cornering acceleration with my bar vs. OEM.

[TwoJ's]

Yes, I was getting about 500 mV of ignition noise, not the 100 I originally thought (had it on a different scale than I thought). I fixed that issue with the battery, but I am still getting the mechanical noise.

http://www.twojsengineering.com/files/test1.xlsx

That is the excel file from a run I did. A sharp left followed by a long bender and then a sharp right turn. Channel A was the accelerometer and B was the gyro. Notice the Gyro is basically giving me nothing. Play around with it if you would like. I quickly made a chart with a 5 period moving average (which is much higher than I would like to use).

I have no time to play with this tonight. I'll have to deal with it more tomorrow.

I've got some work to do. There is a 4.5x scaled output on the circuit board for the gyro that I am likely going to have to use.

[george graves]

So you had ignition noise *and* physical/mechanical vibration noise?

[TwoJ's]

George, you hit the nail square on the head! I went and did three test runs and I had a ton of noise -- enough to make it absolute garbage data. I put it in excel and it appears there was a 100 mV spike for each ignition pulse. I just went and got a 9V battery, and surprise, radio shack doesn't have the proper connector for it. I am really starting to hate RS.

I'll report back later, hopefully with some real world data.

[McGyver]

wow, im just finishing up my sophomore year of ME at vcu in richmond. its nice to see the applications of what im learning! good lock with your job and i hope the bar comes out great!

[TwoJ's]

Thanks george for the input. I'm not too confused at all by that. I'm going to go in to the lab and find someone to ride with me and be my data logger. I'll do a few test runs, and I'll host the excel files so you can take a look at them if you want to give me some input.