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Hello
I am designing product that is similar to a clothespin /cloths-peg. i.e. It involves some jaws that need to be opened by a user with one hand.
I need to know:
a) What is the maximum ergonomic span between thumb and 1st (or 2nd) fingers?
b) What is the maximum acceptable for between thumb and 1st (or 2nd) fingers?
For use by male and female adults (aged at least late teens on wards).
Many thanks
J
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Hand-Tools.pdf
Last edited by Kelly_Bramble; 12-08-2015 at 06:43 PM. Reason: Attach file directy
Thank you.Originally Posted by JAlberts
Yes, under: 'Ergonomic Design: Grip span' It says '2.5”-3.5” is optimal' so it sounds like I can safely go up to a span of 3.5inches (8.9cm).
However I cannot find anything about suitable grip strength / acceptable limits of force/ squeezing Newtons. Any suggestions?
Once again, web to the rescue. See: http://www.topendsports.com/testing/norms/handgrip.htm
You really should be taking more advantage of web searches to find the information you need. It took me less than 10 seconds to find this info site by simply searching for "grip strength testing"
With respect, before having a go at my post you need to read the question more carefully because your link is not helpful.
Perhaps my question could have been better worded but to get clear:
a. I need to know how wide a span between thumb and first finger is likely to be ergonomically acceptable.
However your link does not tell us a single thing about maximum spans.
b. I am NOT interested in the strength of the overall grip (i.e. using all fingers at once) which appears to be what your web search found.
Instead, I am specifically interested in the strength of pinching between just the thumb and 1st finger.
Given that women tend to have smaller, weaker hands than men, the question is really more about women's hands than men's hands.
OP
If you want specific information, you need to supply a specific design brief; otherwise you are essentially saying "I want to re-invent the bull dog clip, will you do all of the work for me?"
You could even answer your own questions with a minimal amount of kit and, say, 10 average (mixed gender) friends with a bit of time to kill.
If you can't find the finger force data published, design a simple force test device go to a crowded area and ask women and girls to perform a simple test. Record the data.
A simple spring vs deflection device should be cheap and easy to design and build.
Sometimes you just have to to field research if you not happy with the internet..
Tell me and I forget. Teach me and I remember. Involve me and I learn.
The good news is that (with a little help from a another forum) I have finally located some force ergonomic data for maximum forces.
What I have failed to locate is data about maximum finger-thumb reach/grasp/stretch for women. Moreover part of the problem is that maximum forces start to diminish very quickly towards maximum reaches.
Yes, obviously I could do testing myself, however I am keen not to "re-invent the wheel" more than necessary. It would be extremely surprising if this work hand not been done somewhere in published literature before.
Hello
Getting there...
With a little help from the Chartered Institute of Ergonomics, I have finally discovered that for pinching between first and index finger (which is what will be required by our new product):
1). 95% of women should be able to pinch with 62+ Newtons
2). 95% of women should be able to grasp to a width of 94+mm
What I now need to know is how much to scale back to allow for:
A) Being at near maximum width of stretch (say 94mm) ==> reduce force by 25%?
B) For say 25 repeat pinches within 5 minutes ==> reduce force by a further 30%?
C) Reasonable comfort (as opposed to maximums) ==> ?
Are there any broad ergonomic principles or rules of thumb (!) that I might apply?
Many thanks
