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Mcmaster springs cheat sheet!

Using computer programming to get useful data

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#1 T da B

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Posted 29 September 2012 - 03:35 AM

Hi everyone! I recently quit video games and decided to pick up a new hobby. I settled on Nerf modding! This is my first post ever, and I wanted to provide some useful information for the NIC. I have a background in electrical engineering and computer science, so I decided to put my skills to use! I hope you guys find this guide enlightening--it certainly was for me!

People can feel a little overwhelmed by the number of springs on mcmaster.com--I sure was when I first started out! Eventually, I stumbled upon this post, which clearly explained how to obtain all spring properties given the weird Mcmaster constant (now changed to a rate constant) and other spring attributes. I decided to write a computer program (in Python) incorporating all the variables from Ozymandias's spreadsheet in the post I just linked.

The math was very simple--most of the time was spent making the output look pretty. My program creates spring objects that are initialized with their Mcmaster constants. I then wrote functions to print out various properties for various springs of various lengths with various compression. Say, for example, you want to find out how much power a 5 inch [k26] puts out with 3 inches of draw. You could write out a bunch of equations on paper and figure it out, or you could plug the [k26] values into my program, create the [k26] spring object, and print out all the useful data. Here is an example of my program's output for the [k26] spring:

[ [k26] ]
========================================
Deflection rate = 0.7528
Max load = 32.13 lbs (14.58 kg)
--------------------
length = 1 in
spring constant = 42.69 lbs/in
max draw = 0.75 in
--------------------
length = 2 in
spring constant = 21.34 lbs/in
max draw = 1.51 in
1 inch draw produces 21.34 lbs (9.68 kg) of force
--------------------
length = 3 in
spring constant = 14.23 lbs/in
max draw = 2.26 in
1 inch draw produces 14.23 lbs (6.45 kg) of force
2 inch draw produces 28.46 lbs (12.91 kg) of force
--------------------
length = 4 in
spring constant = 10.67 lbs/in
max draw = 3.01 in
1 inch draw produces 10.67 lbs (4.84 kg) of force
2 inch draw produces 21.34 lbs (9.68 kg) of force
3 inch draw produces 32.01 lbs (14.52 kg) of force
--------------------
length = 5 in
spring constant = 8.54 lbs/in
max draw = 3.76 in
1 inch draw produces 8.54 lbs (3.87 kg) of force
2 inch draw produces 17.07 lbs (7.74 kg) of force
3 inch draw produces 25.61 lbs (11.62 kg) of force
--------------------
length = 6 in
spring constant = 7.11 lbs/in
max draw = 4.52 in
1 inch draw produces 7.11 lbs (3.23 kg) of force
2 inch draw produces 14.23 lbs (6.45 kg) of force
3 inch draw produces 21.34 lbs (9.68 kg) of force
4 inch draw produces 28.46 lbs (12.91 kg) of force
--------------------
length = 7 in
spring constant = 6.10 lbs/in
max draw = 5.27 in
1 inch draw produces 6.10 lbs (2.77 kg) of force
2 inch draw produces 12.20 lbs (5.53 kg) of force
3 inch draw produces 18.29 lbs (8.30 kg) of force
4 inch draw produces 24.39 lbs (11.06 kg) of force
5 inch draw produces 30.49 lbs (13.83 kg) of force
--------------------
length = 8 in
spring constant = 5.34 lbs/in
max draw = 6.02 in
1 inch draw produces 5.34 lbs (2.42 kg) of force
2 inch draw produces 10.67 lbs (4.84 kg) of force
3 inch draw produces 16.01 lbs (7.26 kg) of force
4 inch draw produces 21.34 lbs (9.68 kg) of force
5 inch draw produces 26.68 lbs (12.10 kg) of force
6 inch draw produces 32.01 lbs (14.52 kg) of force
--------------------
length = 9 in
spring constant = 4.74 lbs/in
max draw = 6.78 in
1 inch draw produces 4.74 lbs (2.15 kg) of force
2 inch draw produces 9.49 lbs (4.30 kg) of force
3 inch draw produces 14.23 lbs (6.45 kg) of force
4 inch draw produces 18.97 lbs (8.61 kg) of force
5 inch draw produces 23.71 lbs (10.76 kg) of force
6 inch draw produces 28.46 lbs (12.91 kg) of force
--------------------
length = 10 in
spring constant = 4.27 lbs/in
max draw = 7.53 in
1 inch draw produces 4.27 lbs (1.94 kg) of force
2 inch draw produces 8.54 lbs (3.87 kg) of force
3 inch draw produces 12.81 lbs (5.81 kg) of force
4 inch draw produces 17.07 lbs (7.74 kg) of force
5 inch draw produces 21.34 lbs (9.68 kg) of force
6 inch draw produces 25.61 lbs (11.62 kg) of force
7 inch draw produces 29.88 lbs (13.55 kg) of force
--------------------
length = 11 in
spring constant = 3.88 lbs/in
max draw = 8.28 in
1 inch draw produces 3.88 lbs (1.76 kg) of force
2 inch draw produces 7.76 lbs (3.52 kg) of force
3 inch draw produces 11.64 lbs (5.28 kg) of force
4 inch draw produces 15.52 lbs (7.04 kg) of force
5 inch draw produces 19.40 lbs (8.80 kg) of force
6 inch draw produces 23.28 lbs (10.56 kg) of force
7 inch draw produces 27.16 lbs (12.32 kg) of force
8 inch draw produces 31.04 lbs (14.08 kg) of force
--------------------
30.00 lbs of force with a 3.00 inch draw requires a 4.27 inch spring

As you can see, you get pretty much everything you've ever wanted to know about the [k26]. My code is very simple, and it's very easy to plug in values for any cut-to-length compression spring in the McMaster catalog using Ozymandias's spreadsheet. I will now post the actual code. To run it, download Python off python.org and install it. It should already come with the IDLE editor. Just open up IDLE, paste the code in, and hit F5 to run it. Of course, you can add any springs you want. Here is the code:

#!/usr/bin/env python
"""
spring.py

A simple spring class that shines light on the properties of
Mcmaster cut-to-length compression springs.
"""

__author__ = "Thomas Megantz a.k.a. T da B"

class Spring(object):
    def __init__(self, name, rate_constant, coils_per_inch,
                 max_length, wire_diameter):
        self.name = name
        self.rate_constant = rate_constant
        self.coils_per_inch = coils_per_inch
        self.max_length = max_length
        self.wire_diameter = wire_diameter
        self.deflection_rate = 1 - (self.coils_per_inch * self.wire_diameter)
        self.k = self.rate_constant / self.max_length
        self.max_load = self.deflection_rate * self.rate_constant

    def print_stats(self):
        print '[ {0} ]'.format(self.name)
        print '='*40
        print 'Deflection rate = ' + str(self.deflection_rate)
        print 'Max load = {0:.2f} lbs ({1:.2f} kg)'.format(self.max_load, self.max_load/2.20462)
        print '-'*20
        for length in range(self.max_length):
            print 'length = ' + str(length+1) + ' in'
            spring_constant = self.rate_constant/(length+1)
            print 'spring constant = {0:.2f} lbs/in'.format(spring_constant)
            max_draw = (length+1)*self.deflection_rate
            print 'max draw = {0:.2f} in'.format(max_draw)
            for draw in range(1, int(max_draw)+2):
                if draw <= max_draw:
                    print ('{0} inch draw produces {1:.2f} lbs ({2:.2f} kg) of '
                           'force').format(draw, draw*spring_constant, draw*spring_constant/2.20462)
            print "-" * 20

    def get_length_for_load(self, draw, desired_load):
        spring_constant = desired_load / draw
        length = self.rate_constant / spring_constant
        print ("{0:.2f} lbs of force with a {1:.2f} inch draw requires a "
               "{2:.2f} inch spring").format(desired_load, draw, length)

def print_spring_data():
    # Add any springs here
    [k26] = Spring(name='[k26]', rate_constant=42.69, coils_per_inch=3.09, max_length=11, wire_diameter=.08)
    [k25] = Spring(name='[k25]', rate_constant=38.53, coils_per_inch=2.18, max_length=11, wire_diameter=.08)
    k18 = Spring(name='K18', rate_constant=32.92, coils_per_inch=2.09, max_length=11, wire_diameter=.091)
    k15 = Spring(name='K15', rate_constant=67.98, coils_per_inch=4, max_length=11, wire_diameter=.105)
    k14 = Spring(name='K14', rate_constant=73.96, coils_per_inch=2.45, max_length=11, wire_diameter=.105)

    # Make sure to add any new springs into the list below
    springs = [[k26], [k25], k18, k15, k14]

    for spring in springs:
        spring.print_stats()
        spring.get_length_for_load(3, 30)
        print "=" * 40

if __name__ == '__main__':
    print_spring_data()


Let me know what you guys think! I hope this helps the NIC as much as it helps me in selecting my springs and cutting them appropriately. For anyone who can't handle downloading Python and copy/pasting, let me know if you want me to paste output for other springs in Ozymandias's spreadsheet. Happy nerfing!

~T da B

Edited by T da B, 22 January 2013 - 03:43 PM.

  • 0
Make it funky.

#2 CaliforniaPants

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Posted 29 September 2012 - 04:46 AM

This is really neat, especially the max compression compared to length. I wonder if you could make a simple site with a drop down menu for the commonly used springs. Either way, great first post
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trans as shit because fuck you


#3 Coop

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Posted 29 September 2012 - 07:35 AM

This is really cool, bro. The display is super clean and easy to read.

I agree with CaliforniaPants, displaying all of the data on a page would be very beneficial for users that don't want to hassle with extra programs. Especially since many of the people on this site only use a few different springs from McMaster.
  • 0

On the other hand, the guy who posted before me used the word 'fuck' a lot so he probably knows what he's talking about.


#4 T da B

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Posted 29 September 2012 - 11:23 AM

Thanks for the feedback, guys! Unfortunately, I don't have a site or blog, so I guess I just post the data for 4 other popular springs ([k26], K18, K15, and K14) here. Enjoy!

[ [k25] ]
========================================
Deflection rate = 0.8256
Max load = 31.81 lbs (14.43 kg)
--------------------
length = 1 in
spring constant = 38.53 lbs/in
max draw = 0.83 in
--------------------
length = 2 in
spring constant = 19.27 lbs/in
max draw = 1.65 in
1 inch draw produces 19.27 lbs (8.74 kg) of force
--------------------
length = 3 in
spring constant = 12.84 lbs/in
max draw = 2.48 in
1 inch draw produces 12.84 lbs (5.83 kg) of force
2 inch draw produces 25.69 lbs (11.65 kg) of force
--------------------
length = 4 in
spring constant = 9.63 lbs/in
max draw = 3.30 in
1 inch draw produces 9.63 lbs (4.37 kg) of force
2 inch draw produces 19.27 lbs (8.74 kg) of force
3 inch draw produces 28.90 lbs (13.11 kg) of force
--------------------
length = 5 in
spring constant = 7.71 lbs/in
max draw = 4.13 in
1 inch draw produces 7.71 lbs (3.50 kg) of force
2 inch draw produces 15.41 lbs (6.99 kg) of force
3 inch draw produces 23.12 lbs (10.49 kg) of force
4 inch draw produces 30.83 lbs (13.98 kg) of force
--------------------
length = 6 in
spring constant = 6.42 lbs/in
max draw = 4.95 in
1 inch draw produces 6.42 lbs (2.91 kg) of force
2 inch draw produces 12.84 lbs (5.83 kg) of force
3 inch draw produces 19.27 lbs (8.74 kg) of force
4 inch draw produces 25.69 lbs (11.65 kg) of force
--------------------
length = 7 in
spring constant = 5.50 lbs/in
max draw = 5.78 in
1 inch draw produces 5.50 lbs (2.50 kg) of force
2 inch draw produces 11.01 lbs (4.99 kg) of force
3 inch draw produces 16.51 lbs (7.49 kg) of force
4 inch draw produces 22.02 lbs (9.99 kg) of force
5 inch draw produces 27.52 lbs (12.48 kg) of force
--------------------
length = 8 in
spring constant = 4.82 lbs/in
max draw = 6.60 in
1 inch draw produces 4.82 lbs (2.18 kg) of force
2 inch draw produces 9.63 lbs (4.37 kg) of force
3 inch draw produces 14.45 lbs (6.55 kg) of force
4 inch draw produces 19.27 lbs (8.74 kg) of force
5 inch draw produces 24.08 lbs (10.92 kg) of force
6 inch draw produces 28.90 lbs (13.11 kg) of force
--------------------
length = 9 in
spring constant = 4.28 lbs/in
max draw = 7.43 in
1 inch draw produces 4.28 lbs (1.94 kg) of force
2 inch draw produces 8.56 lbs (3.88 kg) of force
3 inch draw produces 12.84 lbs (5.83 kg) of force
4 inch draw produces 17.13 lbs (7.77 kg) of force
5 inch draw produces 21.41 lbs (9.71 kg) of force
6 inch draw produces 25.69 lbs (11.65 kg) of force
7 inch draw produces 29.97 lbs (13.59 kg) of force
--------------------
length = 10 in
spring constant = 3.85 lbs/in
max draw = 8.26 in
1 inch draw produces 3.85 lbs (1.75 kg) of force
2 inch draw produces 7.71 lbs (3.50 kg) of force
3 inch draw produces 11.56 lbs (5.24 kg) of force
4 inch draw produces 15.41 lbs (6.99 kg) of force
5 inch draw produces 19.27 lbs (8.74 kg) of force
6 inch draw produces 23.12 lbs (10.49 kg) of force
7 inch draw produces 26.97 lbs (12.23 kg) of force
8 inch draw produces 30.83 lbs (13.98 kg) of force
--------------------
length = 11 in
spring constant = 3.50 lbs/in
max draw = 9.08 in
1 inch draw produces 3.50 lbs (1.59 kg) of force
2 inch draw produces 7.01 lbs (3.18 kg) of force
3 inch draw produces 10.51 lbs (4.77 kg) of force
4 inch draw produces 14.01 lbs (6.36 kg) of force
5 inch draw produces 17.51 lbs (7.94 kg) of force
6 inch draw produces 21.02 lbs (9.53 kg) of force
7 inch draw produces 24.52 lbs (11.12 kg) of force
8 inch draw produces 28.02 lbs (12.71 kg) of force
9 inch draw produces 31.53 lbs (14.30 kg) of force
--------------------
30.00 lbs of force with a 3.00 inch draw requires a 3.85 inch spring
========================================
[ K18 ]
========================================
Deflection rate = 0.80981
Max load = 26.66 lbs (12.09 kg)
--------------------
length = 1 in
spring constant = 32.92 lbs/in
max draw = 0.81 in
--------------------
length = 2 in
spring constant = 16.46 lbs/in
max draw = 1.62 in
1 inch draw produces 16.46 lbs (7.47 kg) of force
--------------------
length = 3 in
spring constant = 10.97 lbs/in
max draw = 2.43 in
1 inch draw produces 10.97 lbs (4.98 kg) of force
2 inch draw produces 21.95 lbs (9.95 kg) of force
--------------------
length = 4 in
spring constant = 8.23 lbs/in
max draw = 3.24 in
1 inch draw produces 8.23 lbs (3.73 kg) of force
2 inch draw produces 16.46 lbs (7.47 kg) of force
3 inch draw produces 24.69 lbs (11.20 kg) of force
--------------------
length = 5 in
spring constant = 6.58 lbs/in
max draw = 4.05 in
1 inch draw produces 6.58 lbs (2.99 kg) of force
2 inch draw produces 13.17 lbs (5.97 kg) of force
3 inch draw produces 19.75 lbs (8.96 kg) of force
4 inch draw produces 26.33 lbs (11.95 kg) of force
--------------------
length = 6 in
spring constant = 5.49 lbs/in
max draw = 4.86 in
1 inch draw produces 5.49 lbs (2.49 kg) of force
2 inch draw produces 10.97 lbs (4.98 kg) of force
3 inch draw produces 16.46 lbs (7.47 kg) of force
4 inch draw produces 21.95 lbs (9.95 kg) of force
--------------------
length = 7 in
spring constant = 4.70 lbs/in
max draw = 5.67 in
1 inch draw produces 4.70 lbs (2.13 kg) of force
2 inch draw produces 9.41 lbs (4.27 kg) of force
3 inch draw produces 14.11 lbs (6.40 kg) of force
4 inch draw produces 18.81 lbs (8.53 kg) of force
5 inch draw produces 23.51 lbs (10.67 kg) of force
--------------------
length = 8 in
spring constant = 4.11 lbs/in
max draw = 6.48 in
1 inch draw produces 4.11 lbs (1.87 kg) of force
2 inch draw produces 8.23 lbs (3.73 kg) of force
3 inch draw produces 12.34 lbs (5.60 kg) of force
4 inch draw produces 16.46 lbs (7.47 kg) of force
5 inch draw produces 20.57 lbs (9.33 kg) of force
6 inch draw produces 24.69 lbs (11.20 kg) of force
--------------------
length = 9 in
spring constant = 3.66 lbs/in
max draw = 7.29 in
1 inch draw produces 3.66 lbs (1.66 kg) of force
2 inch draw produces 7.32 lbs (3.32 kg) of force
3 inch draw produces 10.97 lbs (4.98 kg) of force
4 inch draw produces 14.63 lbs (6.64 kg) of force
5 inch draw produces 18.29 lbs (8.30 kg) of force
6 inch draw produces 21.95 lbs (9.95 kg) of force
7 inch draw produces 25.60 lbs (11.61 kg) of force
--------------------
length = 10 in
spring constant = 3.29 lbs/in
max draw = 8.10 in
1 inch draw produces 3.29 lbs (1.49 kg) of force
2 inch draw produces 6.58 lbs (2.99 kg) of force
3 inch draw produces 9.88 lbs (4.48 kg) of force
4 inch draw produces 13.17 lbs (5.97 kg) of force
5 inch draw produces 16.46 lbs (7.47 kg) of force
6 inch draw produces 19.75 lbs (8.96 kg) of force
7 inch draw produces 23.04 lbs (10.45 kg) of force
8 inch draw produces 26.33 lbs (11.95 kg) of force
--------------------
length = 11 in
spring constant = 2.99 lbs/in
max draw = 8.91 in
1 inch draw produces 2.99 lbs (1.36 kg) of force
2 inch draw produces 5.99 lbs (2.71 kg) of force
3 inch draw produces 8.98 lbs (4.07 kg) of force
4 inch draw produces 11.97 lbs (5.43 kg) of force
5 inch draw produces 14.96 lbs (6.79 kg) of force
6 inch draw produces 17.96 lbs (8.14 kg) of force
7 inch draw produces 20.95 lbs (9.50 kg) of force
8 inch draw produces 23.94 lbs (10.86 kg) of force
--------------------
30.00 lbs of force with a 3.00 inch draw requires a 3.29 inch spring
========================================
[ K15 ]
========================================
Deflection rate = 0.58
Max load = 39.43 lbs (17.88 kg)
--------------------
length = 1 in
spring constant = 67.97 lbs/in
max draw = 0.58 in
--------------------
length = 2 in
spring constant = 33.99 lbs/in
max draw = 1.16 in
1 inch draw produces 33.99 lbs (15.42 kg) of force
--------------------
length = 3 in
spring constant = 22.66 lbs/in
max draw = 1.74 in
1 inch draw produces 22.66 lbs (10.28 kg) of force
--------------------
length = 4 in
spring constant = 16.99 lbs/in
max draw = 2.32 in
1 inch draw produces 16.99 lbs (7.71 kg) of force
2 inch draw produces 33.99 lbs (15.42 kg) of force
--------------------
length = 5 in
spring constant = 13.59 lbs/in
max draw = 2.90 in
1 inch draw produces 13.59 lbs (6.17 kg) of force
2 inch draw produces 27.19 lbs (12.33 kg) of force
--------------------
length = 6 in
spring constant = 11.33 lbs/in
max draw = 3.48 in
1 inch draw produces 11.33 lbs (5.14 kg) of force
2 inch draw produces 22.66 lbs (10.28 kg) of force
3 inch draw produces 33.99 lbs (15.42 kg) of force
--------------------
length = 7 in
spring constant = 9.71 lbs/in
max draw = 4.06 in
1 inch draw produces 9.71 lbs (4.40 kg) of force
2 inch draw produces 19.42 lbs (8.81 kg) of force
3 inch draw produces 29.13 lbs (13.21 kg) of force
4 inch draw produces 38.84 lbs (17.62 kg) of force
--------------------
length = 8 in
spring constant = 8.50 lbs/in
max draw = 4.64 in
1 inch draw produces 8.50 lbs (3.85 kg) of force
2 inch draw produces 16.99 lbs (7.71 kg) of force
3 inch draw produces 25.49 lbs (11.56 kg) of force
4 inch draw produces 33.99 lbs (15.42 kg) of force
--------------------
length = 9 in
spring constant = 7.55 lbs/in
max draw = 5.22 in
1 inch draw produces 7.55 lbs (3.43 kg) of force
2 inch draw produces 15.11 lbs (6.85 kg) of force
3 inch draw produces 22.66 lbs (10.28 kg) of force
4 inch draw produces 30.21 lbs (13.70 kg) of force
5 inch draw produces 37.76 lbs (17.13 kg) of force
--------------------
length = 10 in
spring constant = 6.80 lbs/in
max draw = 5.80 in
1 inch draw produces 6.80 lbs (3.08 kg) of force
2 inch draw produces 13.59 lbs (6.17 kg) of force
3 inch draw produces 20.39 lbs (9.25 kg) of force
4 inch draw produces 27.19 lbs (12.33 kg) of force
5 inch draw produces 33.99 lbs (15.42 kg) of force
--------------------
length = 11 in
spring constant = 6.18 lbs/in
max draw = 6.38 in
1 inch draw produces 6.18 lbs (2.80 kg) of force
2 inch draw produces 12.36 lbs (5.61 kg) of force
3 inch draw produces 18.54 lbs (8.41 kg) of force
4 inch draw produces 24.72 lbs (11.21 kg) of force
5 inch draw produces 30.90 lbs (14.01 kg) of force
6 inch draw produces 37.08 lbs (16.82 kg) of force
--------------------
30.00 lbs of force with a 3.00 inch draw requires a 6.80 inch spring
========================================
[ K14 ]
========================================
Deflection rate = 0.74275
Max load = 54.93 lbs (24.92 kg)
--------------------
length = 1 in
spring constant = 73.96 lbs/in
max draw = 0.74 in
--------------------
length = 2 in
spring constant = 36.98 lbs/in
max draw = 1.49 in
1 inch draw produces 36.98 lbs (16.77 kg) of force
--------------------
length = 3 in
spring constant = 24.65 lbs/in
max draw = 2.23 in
1 inch draw produces 24.65 lbs (11.18 kg) of force
2 inch draw produces 49.31 lbs (22.36 kg) of force
--------------------
length = 4 in
spring constant = 18.49 lbs/in
max draw = 2.97 in
1 inch draw produces 18.49 lbs (8.39 kg) of force
2 inch draw produces 36.98 lbs (16.77 kg) of force
--------------------
length = 5 in
spring constant = 14.79 lbs/in
max draw = 3.71 in
1 inch draw produces 14.79 lbs (6.71 kg) of force
2 inch draw produces 29.58 lbs (13.42 kg) of force
3 inch draw produces 44.38 lbs (20.13 kg) of force
--------------------
length = 6 in
spring constant = 12.33 lbs/in
max draw = 4.46 in
1 inch draw produces 12.33 lbs (5.59 kg) of force
2 inch draw produces 24.65 lbs (11.18 kg) of force
3 inch draw produces 36.98 lbs (16.77 kg) of force
4 inch draw produces 49.31 lbs (22.36 kg) of force
--------------------
length = 7 in
spring constant = 10.57 lbs/in
max draw = 5.20 in
1 inch draw produces 10.57 lbs (4.79 kg) of force
2 inch draw produces 21.13 lbs (9.58 kg) of force
3 inch draw produces 31.70 lbs (14.38 kg) of force
4 inch draw produces 42.26 lbs (19.17 kg) of force
5 inch draw produces 52.83 lbs (23.96 kg) of force
--------------------
length = 8 in
spring constant = 9.24 lbs/in
max draw = 5.94 in
1 inch draw produces 9.24 lbs (4.19 kg) of force
2 inch draw produces 18.49 lbs (8.39 kg) of force
3 inch draw produces 27.73 lbs (12.58 kg) of force
4 inch draw produces 36.98 lbs (16.77 kg) of force
5 inch draw produces 46.22 lbs (20.97 kg) of force
--------------------
length = 9 in
spring constant = 8.22 lbs/in
max draw = 6.68 in
1 inch draw produces 8.22 lbs (3.73 kg) of force
2 inch draw produces 16.44 lbs (7.45 kg) of force
3 inch draw produces 24.65 lbs (11.18 kg) of force
4 inch draw produces 32.87 lbs (14.91 kg) of force
5 inch draw produces 41.09 lbs (18.64 kg) of force
6 inch draw produces 49.31 lbs (22.36 kg) of force
--------------------
length = 10 in
spring constant = 7.40 lbs/in
max draw = 7.43 in
1 inch draw produces 7.40 lbs (3.35 kg) of force
2 inch draw produces 14.79 lbs (6.71 kg) of force
3 inch draw produces 22.19 lbs (10.06 kg) of force
4 inch draw produces 29.58 lbs (13.42 kg) of force
5 inch draw produces 36.98 lbs (16.77 kg) of force
6 inch draw produces 44.38 lbs (20.13 kg) of force
7 inch draw produces 51.77 lbs (23.48 kg) of force
--------------------
length = 11 in
spring constant = 6.72 lbs/in
max draw = 8.17 in
1 inch draw produces 6.72 lbs (3.05 kg) of force
2 inch draw produces 13.45 lbs (6.10 kg) of force
3 inch draw produces 20.17 lbs (9.15 kg) of force
4 inch draw produces 26.89 lbs (12.20 kg) of force
5 inch draw produces 33.62 lbs (15.25 kg) of force
6 inch draw produces 40.34 lbs (18.30 kg) of force
7 inch draw produces 47.06 lbs (21.35 kg) of force
8 inch draw produces 53.79 lbs (24.40 kg) of force
--------------------
30.00 lbs of force with a 3.00 inch draw requires a 7.40 inch spring
========================================
  • 0
Make it funky.

#5 therealnerfjunkies

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Posted 29 September 2012 - 02:15 PM

This is really neat. If you made a blog solely for the purpose of showing us these springs and stuff, then I would follow it. This is awesome! :)
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"You forgot the one rule of making a remake. Don't fuck with the original."

#6 Mully

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Posted 29 September 2012 - 06:11 PM

Truly awesome, this will be extremely useful in the foreseeable future.
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S.C.U.N.

#7 T da B

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Posted 02 October 2012 - 01:36 AM

Here's a little something to wrap your mind around: no matter what length of spring you have, if you compress it all the way you will ALWAYS get the same max load value! Pretty crazy, eh?
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#8 Zorns Lemma

Zorns Lemma

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Posted 02 October 2012 - 09:38 AM

Here's a little something to wrap your mind around: no matter what length of spring you have, if you compress it all the way you will ALWAYS get the same max load value! Pretty crazy, eh?

Assuming all else equal, the force at full compression of the spring is directly proportional to the ratio between the free length and the active coils. Since cutting a spring doesn't change that ratio, it doesn't change the force.

Read about it here: https://secure.wikim...(device)#Theory

Also spring calculators already exist: http://www.planetspr...-calculator.php
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#9 T da B

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Posted 04 January 2013 - 07:09 PM

Updated code to use Mcmaster's new "Rate Constant," which is just the free length * spring constant. Thankfully they got rid of their old constant which was much less intuitive.
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