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Doug LaRock · Posted: Sat Sep 04, 2004 10:58 pm Post subject: Testing machine

Does anyone have experience with load cells and readouts. I would like to build a tension tester for testing Ripstop , sewing seams, line ,knots,and what ever else could be tested by pulling on it. I can build the mechanical part but I have no experiance with the electronic parts.

Doug

CJQ · Posted: Sun Sep 05, 2004 7:33 am Post subject: Load Cells

Hi Doug, Came from a company in the electrical power plug and switch mfg. business. Our R-D lab used cells to test torque , elongation, compression and many other forces. Cells produce an electrical potential. That signal must be harnessed. Since the signals are so minute ,sensitive electronics are required to provide force to read-out. Bottom line , the cost of equipment is sky-high . Even in the used equipment market the cost would be a lot. Some time ago I was equiping an engine dyno , for our race car engines to measure foot pounds up torque. I did a bunch of research and found that I was facing a big buck expense. To over come that problem I ended up fabricating a mechanical system with hydrolics and pressure gauges. I envision that for the things you wish to acomplish it could be done with levers and digital scales ,thus at a very reasonable expense. Go on line and punch in Load Cell , several companys will come up . Take notice the hi-tech stuff at high dollars. Now if you have the bucks , we can provide you with lots of testing projects .( just joking )Your endevor is quite intresting, in fact so vast that you'll never have time to make kites. Keep us posted on your search.

CLIFF

Doug LaRock · Posted: Sun Sep 05, 2004 4:20 pm Post subject:

Thanks for your input Cliff. A few years ago I wanted to measure pull on a Kite Line so I built a hydraulic device to do that . I built a cylinder with an area of 1 sq inch on the rod side then filled it with oil and attached a pressure gauge. This makes the gauge read directly in pounds. However I didn't use a high dollar gauge so the readout is kind of coarse. I was hoping to find some low cost electronics but if that doesn't happen I will have to look at buying a large diameter, finely calabrated gauge for this project. I remember a thread about strength of 1.5 oz and .75 oz Ripstop and it would be interesting to generate some real numbers.

Doug

Stan · Joined: 18 Nov 2003 Posts: 592 Location: San Diego

Let us know how this works out, Doug.
I've used a postal scale for testing fighter line and deflection of spars with spotty results.

Jimbo64 · Joined: 01 Sep 2004 Posts: 10

I would say the easiest way to do this in a pull type situation would be with a fish scale if its under 50 pounds, and an archery bow scale for higher readings.

These are both mass produced, so the prices are low, with a quality digital fish scale costing less than 40 bucks that reads to 50 lbs.

And bow scales are under 100 bucks that read up to 300 lbs, and around 50 bucks for 100 lb models. These are non digital units though.

Hope this helps a little.

C-ya Jimbo.

KiteSquid · Posted: Fri Sep 10, 2004 7:38 am Post subject:

I would have to point you to Bill Bigge.

He is a Physicist and is retired from The National Institute of Standards and Technology.

He is a kite builder and flyer.

He is a little hard to understand sometimes as he thinks at eight decimal places while I only think at two.

He is GREAT at cobbling up test equipment that is highly accurate.

Look him up in the AKA’s electronic directory.
_________________
VR/
KiteSquid
AKA TakoIka
AKA Harold
King George VA

P.S. Yet another post by the Squid..... Shocked

Doesent he ever shut up???

P.P.S. The wind is like the air, only pushier.

wdrwilson · Posted: Fri Sep 10, 2004 11:54 am Post subject:

I know this isn't exactly the topic that Doug started but do you think a Big Game hanging scale would work for measureing line load? i.e. like this one on ebay?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3697763110

Cheers,
Bill

Jimbo64 · Joined: 01 Sep 2004 Posts: 10

seem logical to me that it would work fine, as long as you brace the scale well. You wouldnt want your arm or body to work as a damper against the scale.

C-ya, Jimbo.

KiteSquid · Posted: Fri Sep 10, 2004 1:02 pm Post subject:

wdrwilson · Posted: Fri Sep 10, 2004 3:34 pm Post subject:

Even if it's within 5-10 lbs or even a little more it's not that big of a deal, is it?

For me I would like to know how much my kites pull to get a feel for it.. sort of like using a wind meter when you first start kite flying. You eventually know what 10 mph feels like. I hope to accomplish the same thing with a scale, I will eventually be able (I hope) to feel what 80 lbs or 20lbs feels like, etc. It will also help to identify the right line strength for my kites. I have a feeling that I over estimate the line strength required for my kites.

--Bill