are these strain gauges

Post 23 Jun 2006, 22:05

Link

looking at massas crash at monaco looks like they are monitoring stress in the suspension

Guest · Post 23 Jun 2006, 22:21

usually strain gauges are logged in data aq, so i doubt those are. however, we run some temp stickers that look kind of like those. stick them whereever you want and then when you are done running it tells you the hottest it got. not sure why they would be using htem on the pushrod and wishbone linkage though, those shouldn't get all that hot

Tom · Post 23 Jun 2006, 22:23

I would have thought so at first but in tech studs we were told that when the gauge is parrallel with the strut it would measure the stresses and strains which the object was under. They look to be mounted perpendicular which appaently means they measure expansion/contraction due to heat and such like.

Ciro Pabón · Post 23 Jun 2006, 23:32

There is another possibility. I am not sure about cars, but in beam and pavement deflection, we use a perpendicular strain gauge, called the "zero gauge" or the "dummy gauge". Strain has little effect on it and, of course, any changes in temperature will affect both gauges in the same way. When you use a Wheatestone bridge, the relation of both gauges resistance does not change, but the Vo does. For example:

Dummy gauge:

Quarter bridge circuit:

Of course, I do not see the parallel gauges, so I am guessing they could be mounted under the element (that would be funny). Probably Tom is right, but why would they wish to measure temperature strains? This is a well ventilated part of the strut as neils observes.

There is a third possibility: those members could be heated by the repeated flexing and neils could be right about them being temperature sensors.

Tom · Post 23 Jun 2006, 23:39

not always through temperature but anything that would adjust the width of the arm.

Ciro Pabón · Post 23 Jun 2006, 23:46

Well, you are right. It occurs to me that those arms are subjected to really big torsional forces at braking, but then, I would put the gauges at the front and rear surfaces, not on top. Guess I would have to ask Felipinho...

Another question: it is just my browser, or this thread is like two miles wide? It does not happens to me at the other threads: the lines do not wrap around... If you do not understand me, please, do not care to answer... it is probably a hiccup of my PC.

Tom · Post 23 Jun 2006, 23:52

Nope, mine too. I'm pretty sure its due to the huge long link up top.

Before i knew how to insert pics I used to always be putting up these huge wide links.

zac510 · Post 24 Jun 2006, 00:17

They are temperature stickers and they put them tehre because the exhaust gas passes nearby (and possibly over). Schuey broke a suspension arm at Monaco one year caused by this.

The link at the top has stuffed up the width of the page.

Monstrobolaxa · Post 24 Jun 2006, 00:41

Correct...they r temp stickers...I have 1 on each caliper of my road car!

DaveKillens · Post 25 Jun 2006, 04:21

I don't even think they are guages, but just heat sensitive stickers.

Lukin · Post 25 Jun 2006, 04:52

AP do them in a range of temps and they are great for sticking anywhere you wondered what the temp was but were to afraid to ask (bodywork, calipers, chassis members etc).

I don't think the teams use strain gauges as such, most of the pics I have seen have been the little load cells at the end of the pushrod arms

From a champ car:

RH1300S · Post 25 Jun 2006, 11:28

Yup heat stickers - I have them dotted around the engine bay for when I was curious about temps around the turbo (thinking of putting an automatic fire extinguisher in there).

You can buy them at almost any place that caters for racing cars. They are often seen on brake parts (like calipers), along with heat sensitive paint.........

Post 26 Jun 2006, 03:22

thanks guy sorry about the link

i never thought about a load cell like that on a push rod thats a damn good idea

Ciro Pabón · Post 26 Jun 2006, 13:21

flynfrog wrote:thanks guy sorry about the link

i never thought about a load cell like that on a push rod thats a damn good idea

Another example: here you have a cell at the end of the "slightly bigger pushrods" we use on bridges. This photo is from the 80's. Cell has 3 million pound capacity.

You can see the designer has done all possible, at this bigger scale, to distribute materials in a way similar to the pushrod depicted before...

At this scale, termal differences are really important, the reason why sometimes dummy cells are used to compensate, as I posted.