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MalachiMcMullen

Rgc Ratings

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Cannon

Well, thanks Luke. I'm not trying be too defensive because I think the RGC is kind of a crude measurement in general. I think there are too many variables to plan on getting the same number every time. This is why I totally agree with averaging and rounding. I do think it's a good way to "ballpark" a gripper more accurately than in the hand. I really liked Bob's thread about things to watch for because I've come across many of the same issues--Is the spring oiled? Is the gripper pulling straight down? Is the strap exactly the right size? Is the strap in exactly the same spot? Is the gripper in the right spot in the RGC? Is the weight swinging? And so on... I believe it's possible for the same gripper to calibrate differently on the same setup if tested multiple times.

One thing I would enjoy is a video of someone calibrating a gripper from start to finish. There may be something I'm doing improper and I'm willing to learn whatever I can. But from what I've learned so far, I think my setup is as good as can be.

Cross-calibration helped me a lot to fine-tune but I think it has shortcomings too. What if the person you sent the gripper was off 2.5lbs? Or 5lbs? What are you really shooting for when you get it back? I sent two grippers to Acorn so I had more than one to work with. I think this is necessary when doing a cross-calibration. It really should be more---maybe along the lines of 5 grippers at different strengths. It should also be blind so you're not "trying" to hit anything specific. I would love to do more cross-calibration because it can only make my setup better.

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Bob Lipinski

Yeah, videos would be great. My camera sucks and my setup is in the basement, but I might still try to get a video done.

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Cannon

Another thought I had about cross-calibration is that it would be interesting for all of us doing calibrations to test the same few grippers. Maybe three grippers like IM 2.5, 3.0, and 3.5. We could mail them around as a set, test them a few times blindly, then send them to the next person. It wouldn't even take that long.

We could each report the final result to a neutral party who could ultimately post the complete results. Then we can all decide what number is the "target" for those three grippers. Hopefully it would be obvious. Then going forward they could be shipped out as necessary as a set for people trying to test their new setup.

I would be willing to buy 3 new grippers from Ironmind to be the set and start the process if there is interest in this. Everyone just pays their own shipping to send them on again.

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Bob Lipinski

Hell, if you are willing to start, I would be game.

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MalachiMcMullen
Another thought I had about cross-calibration is that it would be interesting for all of us doing calibrations to test the same few grippers. Maybe three grippers like IM 2.5, 3.0, and 3.5. We could mail them around as a set, test them a few times blindly, then send them to the next person. It wouldn't even take that long.

We could each report the final result to a neutral party who could ultimately post the complete results. Then we can all decide what number is the "target" for those three grippers. Hopefully it would be obvious. Then going forward they could be shipped out as necessary as a set for people trying to test their new setup.

I would be willing to buy 3 new grippers from Ironmind to be the set and start the process if there is interest in this. Everyone just pays their own shipping to send them on again.

Hell, if you are willing to start, I would be game.

Would my little plan no longer be needed then?

Edited by MalachiMcMullen

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Bob Lipinski

Zach, the more the merrier. Really.

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MalachiMcMullen
Zach, the more the merrier. Really.

Cool then :cool

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Paul Knight
Well alright then, we'll go with them. But I still say a 139 RB240N is pretty crazy. As far as I had heard, they were around 120ish. The only few that really seemed OUT THERE to me were the 240N, 05' #3 and the BBE. That makes all of them CRAZY hard compared to their brethren. I can't say they aren't out there though, so why not yours :)

I tend to sell my grippers once I close them and keep the hard ones. I have calibrations for others that I've sold but didn't post those because I don't have them now (133lb BBSM, 149lb #3, 152lb #3, 203lb #4 are some examples). That #4 was also calibrated by Eric Milfeld and Matti (Teemu has it now). I think Eric got 204lb and Matti got 206lbs.

Yep! Eric and I cal'ed it when we got it in the mail and were only 1 pound off - Matt got 203 and we got 204 - I'm a little suprised by the 206 result, I thought it would be closer to what we got - which leads to a whole other discussion - this may have been discussed before, but lets say Matt lives somewhere on the Equator and Matti lives at the north pole: is it possible that the same gripper could cal differently if the temps where the gripper is being cal'ed at are way different? like 95 degrees compared to 45 degrees. May be a silly question. :blush

some of my grippers

#2 - 112 - by Eric

#3 - 150 - "

#3.5 - 177 - "

#3.5 - 174 - by Eric and same gripper was cal'ed at 168 by Matti (6lb difference :blink )

still need to cal the rest of my grippers :rolleyes its kinda a pain in the rump to cal :dry

Edited by Paul Knight
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Martin_Arildsson

What do you guys think about grippers that feels much harder then what the RGC numbers say? I have a pretty good example, an MM2 replica that feels harder then an average #3. Mikael rated it to 3.14, while the RGC says 140,9xx pounds. This gripper has been used on several contests and no one has said that it's easier then the #3 which is used on the same contest.

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Paul Knight
What do you guys think about grippers that feels much harder then what the RGC numbers say? I have a pretty good example, an MM2 replica that feels harder then an average #3. Mikael rated it to 3.14, while the RGC says 140,9xx pounds. This gripper has been used on several contests and no one has said that it's easier then the #3 which is used on the same contest.

Very interesting that you are mentioning this! I've been having this discussion with Eric and Teemu. It seems that some grippers may close with a certain amount of weight on them while in the RGC, but not right away! Lets use 150lbs as an example. Take a #3 gripper, place it in the RGC and drop 150 on it, say its almost closed but not quite - then, you force it shut and let go - and it stays shut - is this a 150 gripper?!?!?!?! The RGC says it is - I bet it feels tougher ........... Good question! ;)

I defenitly want some conversation about this cause its been buggin me :erm

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Autolupus

Just using the power output graph as an example: http://www.gripboard.com/index.php?autocom...si&img=7687 It maybe that the spring strength peaks just before the close, with the graph as an example, the springs true strength would be 120, whereas the RGC would cal. it at around 117.

:)

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tja
What do you guys think about grippers that feels much harder then what the RGC numbers say? I have a pretty good example, an MM2 replica that feels harder then an average #3. Mikael rated it to 3.14, while the RGC says 140,9xx pounds. This gripper has been used on several contests and no one has said that it's easier then the #3 which is used on the same contest.

Very interesting that you are mentioning this! I've been having this discussion with Eric and Teemu. It seems that some grippers may close with a certain amount of weight on them while in the RGC, but not right away! Lets use 150lbs as an example. Take a #3 gripper, place it in the RGC and drop 150 on it, say its almost closed but not quite - then, you force it shut and let go - and it stays shut - is this a 150 gripper?!?!?!?! The RGC says it is - I bet it feels tougher ........... Good question! ;)

I defenitly want some conversation about this cause its been buggin me :erm

I think what's bugging you is friction. The when you put 150 pounds hanging, handles start closing, and while they move, friction works against the direction of movement. When you force it closed, with the same 150 pounds there, the spring tries to push the handles apart, and now friction is working against handles opening. A friction force of a pound or so may make the difference. You could measure some of the effect by doing the same experiment with spring oiled/cleaned from oil.

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jad
What do you guys think about grippers that feels much harder then what the RGC numbers say? I have a pretty good example, an MM2 replica that feels harder then an average #3. Mikael rated it to 3.14, while the RGC says 140,9xx pounds. This gripper has been used on several contests and no one has said that it's easier then the #3 which is used on the same contest.

Very interesting that you are mentioning this! I've been having this discussion with Eric and Teemu. It seems that some grippers may close with a certain amount of weight on them while in the RGC, but not right away! Lets use 150lbs as an example. Take a #3 gripper, place it in the RGC and drop 150 on it, say its almost closed but not quite - then, you force it shut and let go - and it stays shut - is this a 150 gripper?!?!?!?! The RGC says it is - I bet it feels tougher ........... Good question! ;)

I defenitly want some conversation about this cause its been buggin me :erm

I say NO. You should record whatever weight it takes to make the handles touch because you will have to deal with that sweep while closing it so it should be reflected in the calibration. Removing weight after the handles touch doesn't give an accurate calibration IMO. Either way though, we should decide on a standard.

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Bob Lipinski

Josh-

I think you are wrong on that account. I think whoever put it out above is right, it is friction that is keeping the handles from touching. Friction that won't be the same with oiling, humidity, or even slight variations in the force in which the weight is set down.

The original RGC protocol has you remove the weight after the handles touch, and maybe push them together again to make them touch. Check Greg+Dave's documents.

The problem in ignoring this is that you will add another random variable to a process that already has several innate factors for inaccuracy. Making the gripper touch will give you the most accurate measure in the long run, from what I have seen. The other way would require you to lower the weighstack as gently as humanly possible (or as fast as possible) to get a consistent reading. Also, you would need to add the entire weight necessary to close the gripper at once, because the friction makes it harder to start up a gripper that is paused halfway than it would be to have one continuous close.

How quickly you introduced the weightload onto the gripper would be the big variable here, and make things much more inaccurate than they already are.

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jad
Josh-

I think you are wrong on that account. I think whoever put it out above is right, it is friction that is keeping the handles from touching. Friction that won't be the same with oiling, humidity, or even slight variations in the force in which the weight is set down.

The original RGC protocol has you remove the weight after the handles touch, and maybe push them together again to make them touch. Check Greg+Dave's documents.

The problem in ignoring this is that you will add another random variable to a process that already has several innate factors for inaccuracy. Making the gripper touch will give you the most accurate measure in the long run, from what I have seen. The other way would require you to lower the weighstack as gently as humanly possible (or as fast as possible) to get a consistent reading. Also, you would need to add the entire weight necessary to close the gripper at once, because the friction makes it harder to start up a gripper that is paused halfway than it would be to have one continuous close.

How quickly you introduced the weightload onto the gripper would be the big variable here, and make things much more inaccurate than they already are.

Bob, thank you for your input. I think we might have a little miscommunication going on and if not then I guess we'll have to agree to disagree regarding the friction. To clarify: if you put 200# on and it shuts the gripper pretty easily and you start removing weight until the handles open, that is fine. What I have an issue with is taking say 195# and it won't make the handles touch so you add 2.5# to make it touch; then you drop it back down to 195 and it stays shut. I'm all for oiling it but if after oiling it, it still takes more to close it than it does to hold it shut then I think you should count the higher poundage. I don't think humidity should be considered because if it's humid at a contest, the competitor won't be able to force the gripper shut with two hands and hold it shut.

That said; if Greg and Dave were doing it your way from the beginning then we should stick with that method to keep everything consistent.

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Bob Lipinski

Sounds good Josh.

One thing- Usually it just take one push after a weight jump to make things okay. I typically put on some weight, make the handles touch, let them open, then repeat after every weight jump. If they stay down, I take off weight till the handles open a hair (usually 2.5-5 pounds does this), then add weight till they touch. By this point any pushing down doesn't seem to affect things much.

So typically, lets say I think a gripper will go 165ish-

Usually I start with 145, adjust the setup, then push the handles till they touch. I'll put on 20, then if there is still a little distance I'll make them touch again. Let's say they touch, I'll take off maybe 5 pounds, then add till they touch again. Then I would remove maybe 2.5, push the handles gently together, then add weight till they touch.

So I guess I do count the weight it takes to make them touch and not hold, but I have the handles touch a few times first just so I don't get a false reading. Maybe we have more common ground than we thought.

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jad
Sounds good Josh.

One thing- Usually it just take one push after a weight jump to make things okay. I typically put on some weight, make the handles touch, let them open, then repeat after every weight jump. If they stay down, I take off weight till the handles open a hair (usually 2.5-5 pounds does this), then add weight till they touch. By this point any pushing down doesn't seem to affect things much.

So typically, lets say I think a gripper will go 165ish-

Usually I start with 145, adjust the setup, then push the handles till they touch. I'll put on 20, then if there is still a little distance I'll make them touch again. Let's say they touch, I'll take off maybe 5 pounds, then add till they touch again. Then I would remove maybe 2.5, push the handles gently together, then add weight till they touch.

So I guess I do count the weight it takes to make them touch and not hold, but I have the handles touch a few times first just so I don't get a false reading. Maybe we have more common ground than we thought.

That seems like a very good method to me.

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MalachiMcMullen
Sounds good Josh.

One thing- Usually it just take one push after a weight jump to make things okay. I typically put on some weight, make the handles touch, let them open, then repeat after every weight jump. If they stay down, I take off weight till the handles open a hair (usually 2.5-5 pounds does this), then add weight till they touch. By this point any pushing down doesn't seem to affect things much.

So typically, lets say I think a gripper will go 165ish-

Usually I start with 145, adjust the setup, then push the handles till they touch. I'll put on 20, then if there is still a little distance I'll make them touch again. Let's say they touch, I'll take off maybe 5 pounds, then add till they touch again. Then I would remove maybe 2.5, push the handles gently together, then add weight till they touch.

So I guess I do count the weight it takes to make them touch and not hold, but I have the handles touch a few times first just so I don't get a false reading. Maybe we have more common ground than we thought.

That seems like a very good method to me.

Indubitably :)

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twig
Indubitably :)
Word of the day toilet paper? :dry

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Paul Knight

Ok - what about this: I'll use 150 as an example again (Bob, assuming the weight is slowly lowered onto the handle and not dropped). Put your 150 on the handle and its ~ 1/4inch from closing - then, DON'T force it shut, just let the weight sit there for 15 seconds or so and the gripper has slowly closed! Has anyone else expierienced this scenario? :erm

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MalachiMcMullen
Indubitably :)
Word of the day toilet paper? :dry

Indubitably :)

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Martin_Arildsson
Ok - what about this: I'll use 150 as an example again (Bob, assuming the weight is slowly lowered onto the handle and not dropped). Put your 150 on the handle and its ~ 1/4inch from closing - then, DON'T force it shut, just let the weight sit there for 15 seconds or so and the gripper has slowly closed! Has anyone else expierienced this scenario? :erm

Nope! Not even if it has been just a couple of mm from being closed.

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Paul Knight
Ok - what about this: I'll use 150 as an example again (Bob, assuming the weight is slowly lowered onto the handle and not dropped). Put your 150 on the handle and its ~ 1/4inch from closing - then, DON'T force it shut, just let the weight sit there for 15 seconds or so and the gripper has slowly closed! Has anyone else expierienced this scenario? :erm

Nope! Not even if it has been just a couple of mm from being closed.

That doesn't apply to all grippers, in fact, prolly most won't be like that, but I have seen it happen ;)

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Bob Lipinski

I've never seen it happen, probably because I have never really bothered to look.

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Cannon

I do the deloading slightly different, I think. I never actually push the gripper shut. Did Dave and Greg say to push it shut?

If I think a gripper will go 165-ish pounds, I'll start with 150 on the stack and hang that on the gripper. Then I'll add 10s, 5s, or 2.5s, or whatever it takes to close the gripper. Let's say I've added a 10 and 5 and the gripper is now shut at 165lbs. Then I will remove the 5, lift on the stack slightly to deload, then try a 2.5 instead to see if that closes the gripper. If it does close, I'll take the 2.5 off and try one more time. Go back to 160, deload, and add the 2.5 to make sure it closes again. In this case the calibration would be 162.5lbs. If the 2.5 didn't shut the gripper when I took of the 5, then I will go back to the 5 to make sure it closes the gripper. In that case, the calibration would be 5lbs.

Paul, I've never had a gripper slowly get pulled shut if I leave weight there, but I've never left it there for long with a gap. Maybe I will try this sometime.

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