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Sep 25, 2009, 09:50 AM
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#1
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How to measure suspension travel to gauge downforce?
I have seen references made to being able to mention suspension compression to estimate downforce. How would I go about doing this? What kind of device/gauge/etc. do I need? Obviously the cheaper the better. 
l8r)
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Sep 25, 2009, 10:47 AM
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#2
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Did some digging...
Any thoughts on Linear Variable Differential Transformer (LVDT) vs. slide potentiometer and how to hook them up?
l8r)
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Sep 25, 2009, 02:48 PM
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#3
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I've done this... none of the displacement sensors really have enough resolution to give you what you want - especially with high spring rates.
I installed mine on my stock suspension hoping the low rates would be OK - but it's still no good. A stock EVO creates lift, the Cyber EVO creates about 60 lbs of downforce at freeway speed. You need to be able to clearly see changes of 20lbs and that's hard with displacement based sensors.
You need to measure strain in load members.
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Sep 25, 2009, 03:30 PM
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#4
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Hmm, so thinking about it, let me know if I'm on the right track here:
I run progressive rate springs, with a final spring rate of ~358 lbs/in in the front and I'm going to assume a final spring rate of ~ 300 lbs/in in the rear. Ignoring the progressive nature of the spring, in order to measure a 1" change in ride height due to downforce, I'd have to generate ~ 1300 lbs of total downforce, correct? 
Now, if I had a sensor that can measure a 2.5mm change, then that would correspond to to being able to measure a change of ~35 lbs on each front spring and ~30lbs on each rear spring, giving me a resolution of 130 lbs.  I see what you mean. I'd have to get sensors that can measure .25mm change, but still have a wide enough max range to accommodate suspension movement across bumps and in turns. Either that, or amplify the motion by a factor of 10...
l8r)
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"Learning is the beginning of knowledge ...
knowledge is the beginning of understanding ...
understanding is the beginning of wisdom."
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Quote:
Any society that would give up a little bit of liberty to gain a little bit of security will deserve neither and lose both.
- Ben Franklin, Thomas Jefferson -
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Sep 25, 2009, 04:06 PM
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#5
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Evolved Member
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Drives: 03 Evo VIII, 04 A8L, 00 A4 1.8T, 08 R32, 82 YF750
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What about using something like a laser distance gauge? Not sure how that would work at speed, though, and all I'm finding are the Home Depot style laser distance finders.
Does anyone make a strain gauge that I could temporarily install into a strut?
l8r)
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"Learning is the beginning of knowledge ...
knowledge is the beginning of understanding ...
understanding is the beginning of wisdom."
Suspension book for sale, NEW
Quote:
Any society that would give up a little bit of liberty to gain a little bit of security will deserve neither and lose both.
- Ben Franklin, Thomas Jefferson -
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bit, cyber, downforce, evo, gauges, lb, liberty, measure, measuring, rate, rates, security, sensor, spring, springs, suspension, travel  |
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