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My rating device


Raymond

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I knocked this up today using stuff I had laying around in the shed. I don't know how it would compare to a device using a calibrated scale or weights but it gives me bit of a guide as to what I'm putting in my hand. The scales came from a local agricultural supplier and the guy who sold it to me said they are "pretty accurate" and they use them to weigh bags of feed etc, so I hope it's reasonably accurate.

This piece slides into a block I screwed to a post on my porch and it has a poly tube lining the hole where the gripper handle slides in so it doesn't damage the knurling.

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It's a fairly simple contraption and rather than hanging weights off the scale (because I don't have many) I just rigged it up with a lever that has roughly a 2:1 mechanical advantage (the last pic) and I just step on it with my foot until the handles just touch and then take the reading on the scale.

I bought a few grippers from ebay and I wanted to test them to ensure they are legit and not some cheap knockoff. So I rated the new grippers that I tried closing for the first time today and got these readings.

CoC #1 - 80lbs

CoC #1.5 -91lbs

CoC #2 -108lbs

I also got two grippers from a local grip store and measured them at.

CoC #1.5 - 88lbs

GHP #4 - 95lbs

So the ebay CoC tested 3lbs heavier than the one I'm sure is legit. I'm not sure why it's that much heavier but it feels about the same to close. There was only 4lbs difference between the heavy CoC #1.5 and the GHP #4 but the GHP felt much harder to close. It's pretty close to my limit right now so I suppose every pound counts when you get close to your max.

Feel free to criticize my setup, I'm new to all this so if I've done anything wrong with this test rig chime in and let me know 

 

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Those ratings do seem about right for the range I've seen in those models of grippers.  I have never rated grippers myself, but it seems to be a somewhat imprecise endeavor, which would be affected by the thickness of the strap, the precision of the human placing the strap on the gripper, the judgment of when to stop applying weight, and of course the fact that grippers themselves are not precisely calibrated so even precise measurement will result in a range of ratings for the same model.

I'd say that if you do it consistently, your setup will rate your grippers well relative to each other, and maybe will run a little higher or lower than someone else's ratings for the same grippers, but not enough to matter unless you are charging a fee for it and want to modify to please customers.

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Yeah I've got to agree @Vinnie it's not a high precision device by anyone's standards, I imagine there would be a degree of error if I sent the grippers to someone else to test. For training purposes at least it should give me a fairly good idea of how each gripper compares to others I have and I can plan a training regimen around my numbers.  I couldn't call them RGC ratings, more of my own benchmark.

I closed each gripper (in the rig) 5 times with a ten second hold in the closed position and then tested them 3 times each to get the numbers and they did some funny things. Some of them seemed to regain a pound or so of tension after resting before the 3 tests. I can't really explain that, the scale was still zeroed after the tests. It could be some weird thing with the spring dynamics of the spring scales opposing the gripper spring or maybe they do they do have some variance in tension from close to close. A digital crane scale could help to eliminate any weird stuff going on between two opposing springs. 

Edited by Raymond
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  • 2 years later...

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