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RGC Rating vs. IronMind-Numbers


Bodom

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*UPDATE: I was not happy with some numbers and I calculated the whole process again... now it should be correct*

This one is for the number guys and nerdy freaks:

Until now the calculation for the IronMind-Number from a rated gripper has been made with this formula:

((Meassured weight - standard weight) / difference) + standard number = rating

But this formula got one problem: depending on the standard gripper you got heavy variations. As a simple example shall be any gripper with a rated weight of 65kg / 143,298lbs. We can insert this weight into the formula and we use as reference a CoC #2, CoC#3 and a CoC #4:

CoC #2: ((143,298 - 110) / 27) + 2 = 3,23
CoC #3: ((143,298 - 150) / 40) + 3 = 2,83
CoC #4: ((143,298 - 209) / 59) + 4 = 2,88

All 3 values are not correct. Why? A little picture will show:

Beispiel_65.thumb.png.aa98f120d702b4a160095d73d6990660.png

This are the "correct" values for the Captains of Crush-Grippers. Beginning with a #2.5 and ending with a #3.0 - devided by 0.01. Now we can see: the 143,298lbs (65kg) is a 2.84 - not a 3.23 or any of the other calculated values.

Even for the IronMind-Standard-Grippers the formula can not offer correct results. We use a #4 as standard:

Captains of Crush #1: ((83 - 209) / 59) + 4 = 1,86

Captains of Crush #1: ((110 - 209) / 59) + 4 = 2,32
Captains of Crush #1: ((150 - 209) / 59) + 4 = 3,00

Captains of Crush #1: ((209 - 209) / 59) + 4 = 4,00

But why can't we get any correct results? The formula just provides approximated values based on a standard gripper. That means that the meassured gripper just behaves like a 3.23, 2.83 or 2.88 compared to a standard gripper. Now how can we get around this problem?

The solution is quite simple: we use the actual values from the intermediate stages. Those are not provided by IronMind but we can calculate them quite simple. For this we use another picture:

Beispiel_Normgripper_LBS.thumb.png.3d16b81f8fed5e8104b3ac63616d278d.png

You can seet that the CoC #1.5, #2.5 and #3.5 placed just in between the standard grippers #1, #2, #3 and #4. A standard #1 is rated at 83lbs, a #2 at 110. The average is exactly the strength of a #1.5: 96.5. We can use this for every other intermediate stage. The course of the Captain of Crush just differs at the #1, #2, #3 and #4. You can see that in the picture above.

Now I calculated the ratings for every intermediate stage - graded by 0.01 (if we use more decimal places it's just getting more difficult, annoying and the athlete does not feel the difference by closing the gripper):

Spreadsheet: RGC Rating vs. IronMind Numbers

Now comes the fun part: How did I calculate the values for the #5 and #6?

Well for this I take the standard values of the current #1, #2, #3 and #4 and create coordinates: A(83|1), B(110|2), C(150|3) and D(209|4). Now follows a simple math function for creating the graph:

f(x) = ax³ + bx² + cx + d

We can now insert our 4 points and create 4 formulas:

  1. 83 = a1³ + b1² + c1 + d = a + b + c + d
  2. 110 = a2³ + b2² + c2 + d = 8a + 4b + 2c + d
  3. 150 = a3³ + b3² + c3 + d = 27a + 9b + 3c + d
  4. 209 = a4³ + b3² + c4 + d = 64a + 16b + 4c + d

Now we have to find the correct values for a, b, c and d. For creating a standard formula we have to convert those variables into constants.

Step 1:
formula 5 = formula 2 - formula 1:
27 = 7a + 3b + c
 
formula 6 = formula 3 - formula 2:
40 = 19a + 5b + c
 
formula 7 = formula 4 - formula 3:
59 = 37a + 7b + c
 
Step 2:
formula 8 = formula 6 - formula 5:
13 = 12a + 2b
 
formula 9 = formula 7 - formula 6:
19 = 18a + 2b
 
Step 3:
formula 10 = formula 9 - formula 7:
6 = 6a
 
This is now the first constant we can calculate: a = 1. We can roll up the hole process from behind to get our values by inserting a = 1 into formula 8:
13 = 12 * 1 + 2b => 13 = 12 + 2b => 2b = 1 => b = 0,5
a and b are inserted into formula 5:
27 = 7 * 1 + 3 * 0,5 + c => 27 = 7 + 1,5 + c => c = 18,5
And finally we calculate d by inserting a, b and c into formula 1:
83 = 1 + 0,5 + 18,5 + d => d = 83 - 1 - 0,5 - 18,5 => d = 63
 
We have to check if we made any errors:
83 = 1 + 0,5 + 18,5 + 63
110 = 8*1 + 4*0,5 + 2*18,5 + 63
150 = 27*1 + 9*0,5 + 3*18,5 + 63
209 = 64*1 + 16*0,5 + 4*18,5 + 63
 
Every equation is correct and we got the formula we were looking for:
f(x) = 1x³ + 0,5x² + 18,5x + 63
With this we can calculate the values for a theoretically #5 and #6 by setting x = 5 and x = 6:
f(x) = 1*5³ + 0,5*5² + 18,5*5 + 63 = 293
f(x) = 1*6³ + 0,5*6² + 18,5*6 + 63 = 408
 
The chart for Ironmind standard grippers is shown in the following picture:
Beispiel_IronMind-Verlauf.thumb.png.43d11979bc7fb56c6f075493468915dc.png
Please be adviced that this only is correct for the CoC #1, CoC #2, CoC #3, CoC #4, CoC #5, CoC #6 etc. The intermediate stages have to be calculated by the values in the first part.
Edited by Bodom
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