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30 minute steering angle sensor install

celesco sm1 string potentiometer

Note – since this post we’ve released a new , better String Potentiometer – check it out here: https://www.autosportlabs.com/new-product-string-potentiometer-sensor

Unlock the secrets of your fast drivers

In the mad scramble during the last minutes before our 24 hours of Lemons race we remembered wanting to install a steering angle sensor so we could get the magical full driver data profile: throttle position, brake pressure and the elusive steering angle.¬†Yes, we need all three of these data channels so we can unlock the secrets of our fastest drivers! ūüôā

String potentiometer to the rescue!

celesco sm1 string potentiometer

For a long time we’ve¬†imagined a quick way to install a steering angle sensor using a precision Celesco String Potentiometer¬†. So we set to work on the installation: I measured the diameter of the steering shaft and determined¬†it was 1″. ¬†On¬†our Merkur XR4Ti the steering ratio is 2.75 turns lock to lock – a pretty fast ratio for twisty tracks – but I¬†digress. If I¬†used¬†the rotation of the steering shaft to pull and retract the string potentiometer, I would¬†need a total throw of:

ŌÄ X steering shaft diameter X number of turns lock-lock

or

3.14 X 1 X 2.75 ¬†= about 8.6″

So the 12″ version of the Celesco string potentiometer would work nicely.

Quick, Dirty and Awesome

To finish the installation I mounted the potentiometer to the roll cage using a hose clamp more-or-less closely aligned with the steering shaft. Note, alignment isn’t critical at all but OCD¬†dictated I get it¬†as close as possible. Then, I¬†took a length of 24 gauge stranded copper wire, wrapped the tail¬†around the steering shaft and anchored it with aluminum tape. ¬†The steering wheel was set to center point and the string potentiometer was extended 1/2 way. ¬†Keeping the steering wheel straight I connected the¬†copper wire to the loop at the end of the cable. Once the full travel was verified I moved to wiring¬†the sensor- which took the bulk of the remaining time.

Calibration

RaceCapture/Pro calibration was a matter of measuring the voltage going into the sensor input under varying steering wheel positions: At full 360 degree left, center and 360 degree right. These voltages mapped to -360, 0, 360 degrees in the Sensor calibration view so a meaningful value can show up in analysis with no post-processing needed.

Conclusion

How would we improve the design? While quick, dirty and actually quite reliable, we’d probably improve this design by using¬†monofilament line with a small anchor tapped and mounted into the steering shaft- mostly a cosmetic improvement. Not much beyond that!steering angle sensor install steering angle sensor install

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