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| how can i make a spring |
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| picclock:
My apologies for revisiting this, its just that I am having some trouble with maths. I'm using a spring program http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm#calc which should make everything easy but I'm struggling with the concept of a spring constant which is expressed in Newton Metres. I remember from my schooling days Hookes law about the force on a spring being a function of the length. So I want my spring to have a force of 13gms per mm (2mm=26gms etc). I just can't seem to get my head around how to convert that to Newton Metres - its the wrong type of unit (at least my head says it is) :Doh: I'm clearly missing something here - perhaps an expert could point (simply) to the path of enlightenment ? Best Regards picclock |
| Lew_Merrick_PE:
--- Quote from: picclock on March 05, 2013, 11:50:25 AM ---My apologies for revisiting this, its just that I am having some trouble with maths. I'm using a spring program http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm#calc which should make everything easy but I'm struggling with the concept of a spring constant which is expressed in Newton Metres. I remember from my schooling days Hookes law about the force on a spring being a function of the length. So I want my spring to have a force of 13gms per mm (2mm=26gms etc). I just can't seem to get my head around how to convert that to Newton Metres - its the wrong type of unit (at least my head says it is) I'm clearly missing something here - perhaps an expert could point (simply) to the path of enlightenment ? --- End quote --- Pic -- Be very careful with the stuff posted at efunda. It is not that well vetted! I have seen a couple of major disasters when people depend on equations coming from efunda. Their units are often screwed up. A spring constant is the force/deflection the spring supplies. It would be given in N/m or lb/in, not N-m (that is either energy or torque). In conventional engineering terms, the spring constant is designated by the letter k and the deflection of the spring (from its free length) is designated by the letter x. Thus, the force applied by a (linear force) spring is F = kx. The energy supplied by a (linear force) spring is E = 0.5k(x²). Does this help? |
| picclock:
@ Lew Yes, that makes perfect sense, or at least lines up with my world view. The reason for using that site was that plugging in the numbers is likely to get me to a closer result more quickly, but from the look of it its just not that useable. I really wanted a program where I could enter the wire type/diameter, spring diameter, number of turns, length etc which would then tell me the spring constant (in a form I could understand). Thanks for the swift reply picclock |
| mklotz:
When I look at the page in the original URL, it lists the units for spring constant properly as N/m or lbf/in. |
| picclock:
Hah - was just trying it with lb/inch and the site blocked me and wants membership and payment. Oh well it was an interesting visit while it lasted. Many thanks for your assistance Best Regards picclock |
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