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Measuring suspension stroke in real time.

Posted by grisezd 
grisezd
Dennis from Ohio
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Measuring suspension stroke in real time.
October 22, 2015 06:09PM
Hello all. I'm a car test engineer and I need advice. I use linear pots to measure suspension travel often but this winter I need to use them in northern MN, snow, ice, and -20F. I'm hoping rally folks will have some ideas.

Does anyone have experience keeping linear pots working in those conditions? Photos of what big teams do?

Thanks,
Dennis
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Re: Measuring suspension stroke in real time.
October 22, 2015 06:43PM
Quote
grisezd
Hello all. I'm a car test engineer and I need advice. I use linear pots to measure suspension travel often but this winter I need to use them in northern MN, snow, ice, and -20F. I'm hoping rally folks will have some ideas.

Does anyone have experience keeping linear pots working in those conditions? Photos of what big teams do?

Thanks,
Dennis

The "big teams" where? Most shops know how to open cartons and bolt stuff on.. Some can even twist a know when the Pricepessa behind the wheel says they "need 2 clicks moar" whatever---in order to drive so slow its ridiculous..anywhere else in the world anyway.

Even the Dubya Arsey teams have historically farmed out their full suspension packages to whoever charges the most--it seems---all excpt in recent years Citroen has supposedly done some in-house designs then farmed the machining out.

Hate to say but I suspect there is a lot more "feel" than science in gravel suspension but what da fuq do I know---only been making/modding suspension stuff since 1975..



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SteveL
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Re: Measuring suspension stroke in real time.
October 22, 2015 09:58PM
Got a picture of your linear pot? I'd think adding a 10 or 15 watt resistor would keep it warm,
You need to find an electric forklift mechanic who works on freezer lift trucks...



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Paul Buck
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Re: Measuring suspension stroke in real time.
October 22, 2015 10:44PM
Try, http://www.p3america.com/linear_motion_potentiometers_oil_filled.htm

Seems that's what they're made for. Or any other oil filled linear pot you can find.



Edited 1 time(s). Last edit at 10/22/2015 10:45PM by Paul Buck.
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Robert Culbertson
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Re: Measuring suspension stroke in real time.
October 23, 2015 10:02AM
We use a few string potentiometers in hazardous and harsh environments. You can mount the pot in a nice safe spot and then run the string to the part that moves.
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Perry
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Re: Measuring suspension stroke in real time.
October 23, 2015 10:21AM
I have very little experience with this, but..
The formula car guys who want to hide this stuff sometimes run a rotary pot on the suspension arm with a little link. Or I've been told that you can order shocks with it built into the shock shaft internals.



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Re: Measuring suspension stroke in real time.
October 23, 2015 04:43PM
Go to the junkyard, get ride height sensors off of practically anything luxurious enough to have automatic suspension and/or auto-leveling headlights. Escalades/Suburbans are a good place to get 'em because they never fail and the people who tend to own these also tend to maintain them poorly/wreck them so lots in junkyards. Pre-engineered to definitely work under those conditions.



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Thomas Kimsey
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Re: Measuring suspension stroke in real time.
October 28, 2015 03:01PM
Honeywell makes stuff that should work. How much travel do you need to measure? MLT series should have you covered for what you spec'd out.


Function Level 1 Presence/Absence Speed and Positioning
Function Level 2 Contacting
Technology Level 1 Thick Film
Supply Voltage 30 Vdc max.
Measurement Type Linear
Housing Size 157,48 mm [6.2 in]
Total Mechanical Travel 128,27 mm [5.05 in]
Electrical Travel 127,0 mm [5.0 in]
Starting Force (max.) 28,35 g max. [1.0 oz max.]
Linearity ± 1.0 %
Backlash 0,0127 mm max. [0.0005 in max.]
Bearing Type Sleeve
Shaft Material Stainless Steel
Shaft Diameter 1/8 in - #4-40 UNC-2A thread
Element Type MystR® conductive plastic film
Housing Type Anodized Aluminum
Termination 26 awg, 3 cond. - 305,0 mm [12.0 in] cable
Wiper Current <1 µA
Resolution Infinite
Operating Temperature -40 °C to 80 °C [-40 °F to 176 °F]
Vibration 20 g / 0,75 mm (rms) 5 hz to 2 khz
Shock 50 g 11 ms half sine
Operating Life one billion dither operations
Resistance 7,500 Ohms
Resistance Tolerance ± 20 %
Insulation Resistance 500 MOhm @ 500 Vdc
Dielectric Strength 1000 V rms
Weight 30 g [1.06 oz]
Sealing NEMA 4
UNSPSC Code 41111945
UNSPSC Commodity 41111945 Linear position sensors
Availability Global
Comments Options; Electrical Travel, Total Resistance, Rod End Bearing, Metric Shaft Adapter
Series Name MLT


http://sensing.honeywell.com/product-page?pr_id=30705

Im sure there are other brands that would work as well.

Also you could always look at using a LVDT.
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grisezd
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Re: Measuring suspension stroke in real time.
November 03, 2015 05:54AM
Thanks everybody. Lots of options here. Most of the cold weather testing I've done involved measuring accelerations and rates, steer angle, brake and gas apply, wheel speeds, all things I can install inside the warm car or read from CAN bus. This time I'm looking at wheel forces and wheel motion, Vehicle slip angles. All using stuff ill suited to cold temps, moisture, and stuffing into snow banks. I have a feeling that it's going to be an expensive and frustrating couple of weeks!
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