Which strain gages to choose?

[James Montupet]

Hey guys/very few girls,

For those of you out there that run strain gages on pushrods or pullrods, what type do you recommend?

Department is under budget for the fiscal year and is like "hey, what do you guys need?" Has never happened, and will never happen again...

In the absence of better info, here's what I was thinking:
http://www.omega.com/ppt/pptsc.asp?ref=SG1-KIT&Nav=pree05

Nice in that it's a complete kit, with "everything" we'd need. But I'd guess there's something better suited to this application.

Thanks,

James Montupet
Chief Engineer
Duke University Motorsports

[James Montupet]

Hey guys/very few girls,

For those of you out there that run strain gages on pushrods or pullrods, what type do you recommend?

Department is under budget for the fiscal year and is like "hey, what do you guys need?" Has never happened, and will never happen again...

In the absence of better info, here's what I was thinking:
http://www.omega.com/ppt/pptsc.asp?ref=SG1-KIT&Nav=pree05

Nice in that it's a complete kit, with "everything" we'd need. But I'd guess there's something better suited to this application.

Thanks,

James Montupet
Chief Engineer
Duke University Motorsports

[The AFX Master]

Anyone had sucess sticking strain gages to their driveshafts?

[BStoney]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by The AFX Master:
Anyone had sucess sticking strain gages to their driveshafts? </div></BLOCKQUOTE>

I am fairly certain the boys from UWA were running wireless gages on their half shafts. Shoot them an email...I am sure they'd clue ya in.

[BStoney]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by James Montupet:
Hey guys/very few girls,

For those of you out there that run strain gages on pushrods or pullrods, what type do you recommend?

Department is under budget for the fiscal year and is like "hey, what do you guys need?" Has never happened, and will never happen again...

In the absence of better info, here's what I was thinking:
http://www.omega.com/ppt/pptsc.asp?ref=SG1-KIT&Nav=pree05

Nice in that it's a complete kit, with "everything" we'd need. But I'd guess there's something better suited to this application.

Thanks,

James Montupet
Chief Engineer
Duke University Motorsports </div></BLOCKQUOTE>

James:

I am partial to MicroMeasurements stuff from Vishay. They are top of the line and essentially an industry standard from my experience in the aircraft engine world. They offer educational discounts as well...

http://www.vishay.com/brands/measurements_group/strain_gages/mm.htm

[js10coastr]

...if these are going on the pushrods. For this application I'm a fan of load cells. They are a lot easier to install and you can move them from car to car.

Also, if you look around (I think Pi offers it) you can find a strain gauge that works on drive shafts.

[Drew Price]

For final project for a class I just took last quarter we put strain gauges on some of our steel suspension components, and we also used gauges from Vishay, we used p/n EA-06-250BG-120, which are temperature compensated for steel, and measures up to 5% strain in one axis.

Courtesy of Prof. James W. Phillips of UIUC, there is a writeup here Strain Gauges (http://www.mechse.uiuc.edu/portals/courses/TAM456/Lectures/04_strain_gages.pdf) on mounting gauges, some theory, and some things to watch out for.

Best,
Drew

[James Montupet]

Thanks for the good info.

js10coastr, by load cell, do you mean something like this:
http://www.b-tek.com/Original%20Images/images/digitalLoadCell.jpg

So make a shorter push/pull rod and attach this on there? If that's right, what's the advantage that outweighs the disadvantage of having to run different push/pull rods then you'd normally run?

James Montupet
Chief Engineer
Duke University Motorsports.

[js10coastr]

Similar to that... The current Champ cars have load cells at the top (the silver thing).

http://www.champcarworldseries.com/Content/Wallpaper/20...2007_Portland_08.jpg (http://www.champcarworldseries.com/Content/Wallpaper/2007/1280x1024/ccws2007_Portland_08.jpg)

I like them because they are less fragile than strain gauges and you can move them from car to car (cheaper and easier to make a new set of pusrods than to install new strain gauges). And if you want to be "F" accurate, you have account for or measure the bending in the pushrod when using strain gauges.

If there is anyone out there with differing opinions please chime in... I'm interested to hear reasons why strain gauges are used so often.

[Peter]

push rod Load cell (http://fp.beruf1systems.plus.com/products/measurement/strain_dallara_pull_rod.html)

You can move them from car to car, but the load cell has an integrated amplifier, making it more complex and probably more expensive compared to using strain gauges and a standalone amplifier.

The bending loads you can account for by using a full wheatstone bridge and with your own amplifier you can adjust the gain/offset per car/application. Tuning your gain will make it "F²" accurate, as you use the full voltage range and the loads will differ from car to car.

I think the load cells are the easier, more expensive solution. I am not sure if the load cells ever fail during crashes in Champ Cars or other series? If so, strain gauging should be cheaper. Also most universities should have the knowledge to do strain gauging.

Peter

Delft 04UK 06FSG

[B Hise]

the rod end load cells are very nice parts and have an accompanying high price. I think you'll learn more and spend less money making your own push/pull rod load measurement system.

Bryan