A new idea to compare strengths 

By Tom Black   

    We’ve had some recent questions on the GripBoard and observations regarding the latest models of both the Ironmind and Beef Builder grippers.  People have noticed the relative strengths of the double stamped number 2 and the older number 2’s and others have noted that the beef builder grippers seem to have become easier due to smaller handle widths and different mounting of the spring.  Previous to calibration we all measured the width of handles on our grippers.  People were warned that spring mount makes a big difference too, and it is possible to have a wide handle width caused by a shallow mounting of the handles.  This can make the gripper easier than normal.  We never really tried to measure and compare spring mount, probably because it is a small measurement and if it varies by a millimeter can make a huge difference in the strength of a gripper.  I’ve been thinking about this a lot lately, especially since now it seems the beef builder grippers have changed dramatically, and that the Ironmind grippers have also once again changed.

     I now realize there is a measurement that encompasses both the handle width and mounting of the spring together in one number.  All the grippers I’ve checked fall exactly were I expect them too relative to each other! 

    I simply measure the gripper in the following manner (I recommend in millimeters):

 -Place the gripper with the handle tips on a flat surface, with the spring up.  The gripper is perpendicular to the surface and forms a triangle with the surface.

-Measure the distance from the surface to the top of the spring, along a line through the center of the handles, perpendicular to the surface (See photo below).

-Measure the diameter of the spring and divide by two (This is the radius of the spring).

-Subtract the radius from the top of spring measurement.

      I call the final number the “Width Adjusted Moment Arm” or WAMA.

     If you want to just compare your own grippers you can also place them side-by-side, and the lower one with the same spring should be the harder gripper (if they are both seasoned).  I’ve yet to find a gripper with the same spring that was stronger than another that also was higher.  Of course, many people wonder how their grippers compare to other peoples grippers and the “average” gripper.  This is why I have developed this measurement technique.   You may wonder why I subtract the radius from the total length number to the top of the spring.  I wanted to be able to compare the measurements from different sizes of springs.  Otherwise, the larger springs would yield higher numbers than the smaller springs due to this width.  Also, this number is similar to the total moment arm of the gripper, which is spring center to end of handle.  I realized, however, that knowing the moment arm is not enough to measure the total strength of a gripper because it does not take into account the handle spread which can also make a gripper harder.  If you want to compare grippers of the same sized spring you don’t need to subtract the radius. 

     You will find that when you do these measurements on grippers of the same sized springs that the smaller the number the harder the gripper.  Think about this for a moment.  As the handle width spreads wider the gripper is more “squat” to the flat surface.  Likewise with the spring mount; as they are mounted deeper the measured number would get smaller.

     Here are the measurements of some of my grippers; luckily the spring width is identical on all grippers of the same size.  If not, this could also explain some differences in the grippers due to tighter winding.  For grippers of the same size you can see that you really don’t need to subtract the radius, unless you want to compare between different sized springs.  I’ve also approximately identified when I purchased these grippers so that changes over time can be seen (see the Excel Spreadsheet attached below for even more information):

34mm diameter on Trainer springs, 17mm radius:

Vintage 2000 trainer- 127mm total height, WAMA=110

35mm diameter on #1 springs, 17.5mm radius:

Vintage 1999 #1- 126mm total height, WAMA=108.5mm

Vintage  2001 #1- 129mm total height, WAMA=111.5mm

Vintage 2001 #1- 131 total height, WAMA=113.5 (This was from the same batch as above, but with the handles mounted far from the spring.  This gripper is the most “out of spec” I’ve seen.  It is no surprise too me that it has the highest WAMA that I measured.  This also illustrates why I am subtracting half the radius from the number, comparing the full spring height to the #3’s below it doesn’t look like an unusual gripper (It’s the same height) until you take into account that the spring is not as thick as a #3.  This gripper is compared to “normal” in the grip gallery on Cyberpump.

36mm Diameter on #2 springs, 18mm radius:

Vintage 1999 Master- 126mm total height, WAMA=108

Vintage 2002 Double Stamped #2- 126mm total height, WAMA=108

Vintage 2002 Double Stamped #2- 128mm total height, WAMA=110

Vintage 1998 #2- Total height- 129mm total height, WAMA=111

37mm Diameter on all #3 springs, 18.5mm radius:

Silver Elite, Vintage 1999- 126mm total height, WAMA= 107.5 (the lowest WAMA number I measured, and an awesomely difficult gripper).

Vintage 2000 #3 - 129mm total height, WAMA=110.5

Vintage 2001 #3- 131mm total height, WAMA=112.5

Vintage 2001 #3- 131mm total height, WAMA=112.5 (same batch as previous).

PDA361-131mm total height, Radius= 18.25, Diameter was slightly smaller than #3 springs, spring is .003" thinner as measured with a micrometer.  WAMA=112.75

38mm Diameter on #4 spring, 19mm radius:

Vintage 2001 #4- 132 mm total height, WAMA=113

     Another reason I took into account spring diameter is to compare and find the average WAMA, regardless of gripper size.  Currently, among the 18 Ironmind grippers I’ve measured the average WAMA is 110.7 mm.   Interestingly, the older Ironmind grippers bring the average WAMA down because of spring width, but the new double stamped have low WAMA's due to spring mount.  There is a new double stamped #2 with the same WAMA as my Beef Builder Master.  This gripper is an interesting example because it is not as wide as the Master, but has a really deep mount into the spring (less than 1/8" from coil to handle top).  The two factors balance out in the WAMA number, and I believe with seasoning it will be identical to the Master in perceived closing strength.

    Since my other Ironmind grippers are significantly different from those made today it might be better to not average them into the final number since I think Ironmind probably has sold more in the last few years compared to before that.   Thus, the average WAMA might be 111 millimeters for grippers from 1999-2001.  If this is the case after many more grippers are measured we could conclude that any gripper above that is “easier” than average or “normal” and any gripper below would be “harder” than average or “normal”.   Also, for the grippers

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 that I have there was not one that upon closing was inconsistent with the WAMA number.  Hence, when I measured the double stamped number 2 that is the hardest I’ve ever tried the WAMA measurement of 108 was identical to my beef builder Master, and I was not surprised.  The only way for these numbers to not be consistent would be to compare a seasoned gripper to a non-seasoned one, or if the spring steel varies.  Invariably, all used grippers become seasoned so once seasoned they can be compared.

     I would be very curious as to other people’s measurements of their grippers, especially ones that have been compared hand-to-hand with others, and ones that have been calibrated.  I would like to know if anyone has a gripper that “feels” harder than a gripper of the same spring but with a lower WAMA.  This should not be the case, note the very low WAMA on the Master above, it is the hardest gripper of that sized spring that I own.  There is no question about it.  The calibrated grippers should have lower WAMA’s for harder grippers.  If they do not then either this measurement idea is wrong, or some other unknown factor is creating the discrepancies.   One unknown factor could be that different materials used in the springs could also have an effect of the strength of the grippers.   I think there is a possibility that my grippers made before 1999 have harder springs.  The material actually looks different.  These grippers are all harder and have consistent WAMA numbers, but they feel even harder than the numbers suggest.

     I have attached a spreadsheet written in Excel that contains all the measurements for my grippers, and  a few more from my training partners.  I have also measured the width between the handles for a specific reason.  Having both the height and the width of a gripper one can calculate the length of the tip of the handle to the center of the spring using Pythagorean's Theorem.  This is the moment arm of the gripper.  If you study the chart you will see some significant reasons why knowing only the moment arm is not enough to characterize the strength of the gripper.  The best example of this is gripper 13 compared to gripper 17.  Gripper 13 is my oldest #3 gripper from 1998 with a 135.1 mm moment arm and gripper 17 is a #3 from 2001 with a 135.7 mm moment arm.  The moment arms are only .6 mm apart, but the WAMA measurement varies by 2 mm.  Believe me, the old #3 is considerably harder than the new #3, consistent with the WAMA number more than merely the moment arm number used alone.  Nevertheless, I have decided to document handle widths and moment arms for the purpose of possible future calculations in which I weight the various factors of gripper characteristics.  That is, width may be more of a factor than spring mount per millimeter and hence a more refined number could be calculated by weighting the width 60% and the spring mount 40% (used only for example now).    

     Finally, when all is settled it might be possible to calculate an estimated torque from the measurements.  This may present itself as some of the numbers of calibrated grippers demonstrate that the calibration does not take properly into account the width of the handles.  The human closing a gripper must deal with this "sweep" torque, the calibration machine does not.  Even without a inch-pound number associated with a particular WAMA measurement I believe that we can discuss relative strength of grippers using the WAMA numbers and hence do not really need to know the inch-pound number in this context.

Here is the Excel Spreadsheet with the all the grippers measured:  WAMA.