Gripper Rankings

[amaury]

The only limits we have are in our head.

I can fly, yeah baby i can flyyyyyy !!!!

flabbergastenpoopy##g junkies...

[HAMMERHEAD]

Why can't this thread stay on track. This could actually be an extremly helpful thread for those looking for a specific strength. There are 2 pages of wether or not a WC can be closed. If you think it can be done just train for it for the rest of your life and stop bring up this old argument.

Hope I haven't offended anybody, but...

This is the FAQ section. Not the "I've now wasted 10 min of my time digging through a regurgitated (did I spell that right?) argument on the WC."

-HH

[HAMMERHEAD]

Fellas!

I just got a new gripper from Warren Tetting. I had him customize a Super Elite by lowering the handles a bit. It is way harder than my SOS 295 and considerably easier than my #4 or Grand Elite. Great in-between gripper that I will only be using for negatives right now.

This new gripper reminds me of when I first got the #3. Very hard to set. Till I get stronger.

-HH

[Rick Browne]

I got one of those back in the spring... called it a "Heavy Elite"

Spring wire of .306 Nice!

[HAMMERHEAD]

The SE is a beast, like I said mine is a custom so it is easier and more managable. I can barely force my GE/#4 shut, so my custom SE is a great addition.

-HH

[3djim]

There has been much discussion about gripper ranking and whether there is any math to estimate the "closing pressures" across all models. A couple people actually wanted to see possible equations behind gripper statics.

Here's my 2 bits worth. Clearly, what follows might need correction. I claim no originality, just curiosity. We are all in a learning process with this stuff.

I found an interesting Mechanical Design equation for torsion springs and haven't seen it published on the GripBoard. I t essentially states that closing torsion, T, can be estimated from:

T = E * (Theta)*( d^4 ) / [128 *(D + d)]

where,

E ~ 3*10^7 psi (modulus of elasticity for music wire as I can best obtain from Internet search; E relates to material properties)

Theta = closing angle (angle in radians between gripper handles when gripper is in untensed position)

d = wire diam (inches)

D = coil INSIDE diameter (inches)

(Note: This equation is directly related to established engineering dogma and WAS NOT derived by fitting short range data that might be contaminated by errors. The equation also allows the theoretical case of T=0 when d=0, which any representation must do to consistently simulate the physics.)

Given T, if one wants to generate a value related to "force to close" ,F, then that might be interpreted as force to close at a "point" on the handle. Assume that point is at handle mid point and assume the moment arm, R, is measured (along handle) from coil center to handle mid point. This is in the spirit of handle placement ("depth") on the spring legs such as standardized by some manufacturers, as I best understand.

Then F = T/R, from the relationship between 'Force at a point" and Torsion. (Torsion, i.e. FR, is a constant for a given spring in a closed position. So, if you have a standard R in mind, then the F-values associated with R can be meaningfully compared across a set of similar grippers. )

For example (not atypical of current grippers), let a hypothetical geometry be characterized by:

Theta = 30 degrees

d = .300"

D = .875"

R = 2.625

Then, (you need to convert 30 degrees to radians before using the eqn; i.e. multiply by 3.1415926/180)

F ~= 322lbs force or about 60lbs force stronger than a CoC#3.

But, one should regard such equations with flexibility when applied to specific grippers. This is since gripper manufacture has inherent errors as you people have often mentioned in your posts. To see just how much variability might arise, consider our hypothetical gripper above. Assume the manufacturing errors are:

Theta Error = +- 2 degrees

D Error = +- .002"

d error = +- .002"

R error = +- 1/16"

These values, as I best understand, are not unreasonable expectations.

Running the calculations over the intervals associated with the error bounds yields F values that can be off by 11% or 12% !! That is,,, over 30lbs of force deviation between grippers of the same model with the same design spec.

Hope these "old issue" ramblings help,,, if only to generate more thinking about the necessity of pushing on manufacturers for tolerances used to build grippers, as well as how far off an advertised "force" might be or what the advertised "force" really means. Afterall, grip athletes apparently want to have some tool to help cross-product comparison in order to minimize the costs of purchasing grippers blind and en masse. Filling "gripper gap" within your gripper arsenal can be expensive!

Additionally, it would be great if as a group we can produce the needed geometric parameters for all the grippers we own. We can measure ourselves or simply ask the manufacturers. Some of this has already been published on the GripBoard, especially wire diameters.

[3djim]

Sorry, ~40lbs stronger than a CoC #3.

[burkhardmacht]

Hello Bernie Hunt1

That's a great ranking list - but could you add the RB-crushers. I wonder in wich position the RB 300/330 are (and the RB130-180)?

Would be great if you or someone else could complete the list!

Thanks, B.

[JustinH]

Some of the strongest men in the world haven't been able to close even the #3 let alone the #4. Someone may someday be able to close the one that is just above the #4 but I doubt anyone will ever get higher than that. Maybe someday they will allow mechanical parts in the body then you will see all the impossible. Did anyone ever see that movie where the fighters had mechanical parts?

[kingkull]

I have two RB grippers, one 160IP and one 240IP. The RB 240 is somewhat in the middle between a CoC #2 and #3. The RB160 is close to the middle between a CoC #1 and #2. This is only based on the feeling of how hard it is to close them. There is a slight difference in handle diameter on the RB and CoC grippers, the RB grippers have a bit larger handle diameter. I have not measured the wire diameter or the handle diameter but I will do it and post the figures later. As 3djim wrote it is not only wire diameter that determines the closing force for a torsion spring but also the inner coil diameter.

[gotenmyoou]

I own a rb300 and it seems to fall between Elite & Super elite.

[kingkull]

Here are wire diameters of my RB grippers: RB160 6,55mm (.2559), RB240 7mm (.2756). Compared with my #2 6,65mm (.2618) and my #3 7,15mm (.2815). Inner coil diameter for the grippers are: RB160 24,3mm (.9567), RB240 20,8mm (.8189), #2 22,85MM (.8996) and #3 22,85mm (.8996). I guess the inner coil diameter will vary from gripper to gripper of same rating. The k factor of the spring will also wary and then these two parameters will give deviation in gripper strength as they are hard to get equal for every single gripper of a specifyed rating.

[Finnegann]

Excerpt from an email from Robert Baraban:

The wire diameter says nothing because i regulate the strength with how narrow

or how wide i wound the springs ,anyway here they are:

70ip 5,8mm

100ip 5,8mm

130ip 6,0mm

160ip 6,5mm

180ip 6,5mm

210ip 7,0mm

240ip 7,0mm

260ip 7,0mm

300ip 7,5mm

330ip 8,0mm

WT Gripper 10,00mm

[tusenkonstnar]

There has been much discussion about gripper ranking and whether there is any math to estimate the "closing pressures" across all models. A couple people actually wanted to see possible equations behind gripper statics.

Here's my 2 bits worth. Clearly, what follows might need correction. I claim no originality, just curiosity. We are all in a learning process with this stuff.

I found an interesting Mechanical Design equation for torsion springs and haven't seen it published on the GripBoard. I t essentially states that closing torsion, T, can be estimated from:

T = E * (Theta)*( d^4 ) / [128 *(D + d)]

where,

E ~ 3*10^7 psi (modulus of elasticity for music wire as I can best obtain from Internet search; E relates to material properties)

Theta = closing angle (angle in radians between gripper handles when gripper is in untensed position)

d = wire diam (inches)

D = coil INSIDE diameter (inches)

(Note: This equation is directly related to established engineering dogma and WAS NOT derived by fitting  short range data that might be contaminated by errors. The equation also allows the theoretical case of T=0 when d=0, which any representation must do to consistently simulate the physics.)

Given T, if one wants to generate a value related to "force to close" ,F, then that might be interpreted as force to close at a "point" on the handle. Assume that point is at handle mid point and assume the moment arm, R, is measured (along handle) from coil center to handle mid point. This is in the spirit of handle placement ("depth") on the spring legs such as standardized by some manufacturers, as I best understand.

Then F = T/R, from the relationship between 'Force at a point" and Torsion. (Torsion, i.e. FR, is a constant for a given spring in a closed position. So, if you have a standard R in mind, then the F-values associated with R can be meaningfully compared across a set of similar grippers. )

For example (not atypical of current grippers), let a hypothetical geometry be characterized by:

Theta = 30 degrees

d = .300"

D = .875"

R = 2.625

Then, (you need to convert 30 degrees to radians before using the eqn; i.e. multiply by 3.1415926/180)

F ~= 322lbs force or about 60lbs force stronger than a CoC#3.

But, one should regard such equations with flexibility when applied to specific grippers. This is since gripper manufacture has inherent errors as you people have often mentioned in your posts. To see just how much variability might arise, consider our hypothetical gripper above. Assume the manufacturing errors are:

Theta Error = +- 2 degrees

D Error = +- .002"

d error = +- .002"

R error = +- 1/16"

These values, as I best understand, are not unreasonable expectations.

Running the calculations over the intervals associated with the error bounds yields F values that can be off by 11% or 12% !! That is,,, over 30lbs of force deviation between grippers of the same model with the same design spec.

Hope these "old issue" ramblings help,,, if only to generate more thinking about the necessity of pushing on manufacturers for tolerances used to build grippers, as well as how far off an advertised "force" might be or what the advertised "force" really means. Afterall, grip athletes apparently want to have some tool to help cross-product comparison in order to minimize the costs of purchasing grippers blind and en masse. Filling "gripper gap" within your gripper arsenal can be expensive!

Additionally, it would be great if as a group we can produce the needed geometric parameters for all the grippers we own. We can measure ourselves or simply ask the manufacturers. Some of this has already been published on the GripBoard, especially wire diameters.

←

Interesting, I guess this formula is intended to only give relative comparisions? (like for grippers with coils of 3 wounds), otherwise it is very unphysical wit a formula that doesn't take the number of wounds in the coil into consideration.

It seems