Lift Light

[TD]

As Ron pointed out, I'm pretty sure linear and rotary potentiometers have been regularly used to measure various displacements (steering angle, suspension loading, throttle position) on race cars.

Great stuff here, thanks!  I'll go back to lurking now

Tim

[ggl205]

Tim:

You are correct. I use an LVDT to measure throttle position and originally thought about using them to measure axle movement. But LVDT?s are expensive and you need four of them. Chuck?s idea to use LIDAR tech to measure lift and compression could also be used to measure axle movement. We talked about that but once again, I did not want to overdrive my headlights here. If the lift sensor works, it will be applied elsewhere on the car.

John

[POPS]

We recommend using string or linear pots.  They work great.  We had linears on the front end and a string pot on the rear end.  Both wired to the Racepak.   We also had a rod that was mounted to the front axle and extend thru the body so the driver could see any lift.        New car will have them as we wouldn't consider running without them.  Racepak also sells a laser ride height sensor for cars without suspension.
POPS
7800 A/BFS

[datadoc]

A few more thoughts on suspension travel sensors: I read one posting talking about the cost of the linear sensors. Of course cost is relative but one can build with a little work travel sensors from throttle position sensors (TPS) TPS sensors sell in the 30-50 dollar range and then with a little machining can be made to work. Reading the data and interpreting the data will give some insight on what is happening. At Racepak we setup the suspension travel channels to record at 1,000 Hz. At that rate one can see the front suspension move and then followed by the appropriate time delay based on velocity and wheel base the rear senors will tell you if the car has gone over a bump. Looking at the front suspension data signature after a bump I believe one could tell by the suspension "hang time" if you were getting close to the edge. I must say after looking at hundreds of graphs this is something that I have never seen but then I've never seen a car with suspension travel sensors blow over. I'm basing this on driving hydroplanes and what the feeling is before your in trouble. The ride gets eerily smooth. So I'm quite sure the data from a car that was close to the edge would look different on how it responded to bumps than one that wasn't.

[John Burk]

Couldn't resist this . With the front bias of front wheel drive lift isn't a concern .

[wobblywalrus]

Us bike guys are using those little go pro cameras to do things like watch how the suspension works.  It is far less mental than sensors.

[n49racer]

Hi all
We use GM TPS sensors re purposed as suspension sensors, they work great and are cheap. We also use EFI with a MegaSquirt MS3 Pro Ultimate controller/data system. It has the ability to give an output when the readings go outside a preset range which will turn on a light.

ted

[ggl205]

Datadoc/n49racer:

Aside from the lift light, plans are to gather axle data next. I like your idea for using TPS?s for this purpose. I assume you have data from your car that has been treated for analysis. Would it be possible to see a portion of it to get an idea if it will serve my purpose? Anything would be greatly appreciated.

John

[datadoc]

Hi GGL205,
  I'm trying to attached a screen print showing shock travel at both the front and rear. Not sure if this was what you where looking for or not. For some reason when I scanned in the screen print it was upside down and I couldn't seem to save it right side up. I'm not even sure that the file will attach to this reply. On top of that I can't seem to get the Preview function to work. I'll hit post and hope for the best.

[Elmo Rodge]

I can see it and yes, it's upside down. As advertised. 
Wayno

[ggl205]

Datadoc, it came through loud and clear. Thank you

[4-barrel Mike]

How about?

Mike

[n49racer]

I?ll try post a screen shot of our front and rear data

Ted

[ggl205]

Thanks, guys. This has really been helpful.

John

[ggl205]

Mike:

Looking at your graph, am I seeing damper motion for a beam axle? Right shock moves opposite to left shock.

John