Measurement of normal force (squeezing force) on a cylinder

[JasonNicholson]

I am working on a research project at Harvard. I have to measure the normal force created by a vine around a cylinder. It is interest problem posing many complications. See this video for a better understanding (requires divx and take a little while to load):
[link ftp://ftp.jashale:ftp@isua.iastate.edu/chmbrVine2.avi]Vine Video[/url]
If the link does not work copy and past this:
[ignore]ftp://ftp.jashale:ftp@isua.iastate.edu/chmbrVine2.avi[/ignore]

The forces are on the order of .01 to 1 newton. ANY SUGGESTIONS?

 

[itsmoked]

Hope this is a graduate project since there's not supposed to be any help dished out to students. Note below the submit button.

Think about the pressure in a balloon if you start squeezing it.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[JasonNicholson]

I am getting paid to do summer research project.

A problem that arises with a balloon is temperature effects. Also small forces spread out over a large area cause the change in pressure to the vine to be very small.

The balloon alone has already been tried. The vine does not like to grow on the balloon.

 

[IRstuff]

How about something like this:

http://www.tekscan.com/industrial/bpms_research_system.html

TTFN

 

[itsmoked]

Personally I would not use a balloon. I would use a thin sheetmetal cylinder with a temperature sensor and a pressure sensor. I would calibrate the cylinder in an oven (could be a cardboard box with a resistor and several small fans). Then your micro can compensate for the temperature.

Otherwise you take a cylinder, machine or cut a slot down its entire length. You then compress it slightly and affix a strain gauge across the gap. (epoxy is standard) Then uncompress it. You will get a tension. Now as the vine wraps it you will see a loss of this tension. You may still need to compensate for temperature but the same method will suffice.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[EdDanzer]

Try Pressurex.

http://www.sensorprod.com/pressurex.html