An Idea For Improving How We Use Rgc To Compare Grippers

[bdckr]

If you're one of those guys who thinks we spend too much time thinking about grippers and not enough time squeezing them ... this post probably isn't for you

For those of you who RGC a lot of grippers, what would you think about doing a second measurement? Load the gripper with half the RGC rating, and use calipers to measure the distance between the handles.

Here's my reasoning:

Up to now, RGC ratings have been the best way to objectively compare different grippers, especially different brands. One common complaint has been that even though the RGC number gives us an idea of how difficult the gripper is at the close, we don't get any information about the difficulty of the sweep. Some have used surrogates to make guesses -- gripper spread, spring mount, etc -- but there hasn't been an objective way to describe the sweep, or how one gripper with the same (or even lower) RGC rating as another can be harder to close .

One previous suggestion was to pick some intermediate distances (between spread and close) and see how much weight it takes to get there. This always struck me as a lot of fiddly work -- trying to get to that distance, adjusting even smaller amounts of weight to get there, etc. -- never mind deciding the standard distances to measure so that there's some consistency from one RGC rater to another.

But how about doing the opposite? Instead of picking a distance and measuring the weight, what if we pick a weight, and then measure the distance?

Picking a fraction of the RGC rating (instead of a fixed weight) means that we can standardize this for any gripper no matter how hard or easy it is. It doesn't need to be 1/2, but 1/2 seems simpler than anything else.

For a given RGC rating, the smaller the distance between the handles (using 1/2 the RGC weight), the easier the sweep. For narrower grippers, this distance will be smaller, too.

And once there are enough measurements for different grippers, we might have a distance/number that will describe a gripper with an average sweep (for a given RGC rating).

A related use would be to test a phenomenon that I think (sorry if my memory fails) Daniel Reinard described: choked grippers losing strength in the sweep (even though the closing strength, or RGC rating, doesn't go down, according to testing by Mighty Joe and probably others).

Of course, this is easy for me to suggest, since I don't have an RGC set up. But I'm hoping someone who does a lot of RGC'ing (not to name any names ... ahh, what the heck ... Cannon, Eric Milfield, and Chris Rice come to mind ) might be tempted to try this out and see what kind of numbers and reproducibility they get.

This really won't be useful on the smaller grippers, but when you get closer to your limit, and you're having trouble finding the right gappers (low 170s comes to mind), then you could get incremental progression by picking something with the same RGC rating but a higher 1/2 RGC distance (HRD?) or a bigger jump in RGC but a lower HRD.

What do you think?

[Bearcat 74]

I don't know much about the workings of the RGC but picking a weight, 50% and 75% of the final number and taking a measurement sounds good in theory.

Sounds good to me.

[mightyjoe]

If you're one of those guys who thinks we spend too much time thinking about grippers and not enough time squeezing them ... this post probably isn't for you

For those of you who RGC a lot of grippers, what would you think about doing a second measurement? Load the gripper with half the RGC rating, and use calipers to measure the distance between the handles.

Here's my reasoning:

Up to now, RGC ratings have been the best way to objectively compare different grippers, especially different brands. One common complaint has been that even though the RGC number gives us an idea of how difficult the gripper is at the close, we don't get any information about the difficulty of the sweep. Some have used surrogates to make guesses -- gripper spread, spring mount, etc -- but there hasn't been an objective way to describe the sweep, or how one gripper with the same (or even lower) RGC rating as another can be harder to close .

One previous suggestion was to pick some intermediate distances (between spread and close) and see how much weight it takes to get there. This always struck me as a lot of fiddly work -- trying to get to that distance, adjusting even smaller amounts of weight to get there, etc. -- never mind deciding the standard distances to measure so that there's some consistency from one RGC rater to another.

But how about doing the opposite? Instead of picking a distance and measuring the weight, what if we pick a weight, and then measure the distance?

Picking a fraction of the RGC rating (instead of a fixed weight) means that we can standardize this for any gripper no matter how hard or easy it is. It doesn't need to be 1/2, but 1/2 seems simpler than anything else.

For a given RGC rating, the smaller the distance between the handles (using 1/2 the RGC weight), the easier the sweep. For narrower grippers, this distance will be smaller, too.

And once there are enough measurements for different grippers, we might have a distance/number that will describe a gripper with an average sweep (for a given RGC rating).

A related use would be to test a phenomenon that I think (sorry if my memory fails) Daniel Reinard described: choked grippers losing strength in the sweep (even though the closing strength, or RGC rating, doesn't go down, according to testing by Mighty Joe and probably others).

Of course, this is easy for me to suggest, since I don't have an RGC set up. But I'm hoping someone who does a lot of RGC'ing (not to name any names ... ahh, what the heck ... Cannon, Eric Milfield, and Chris Rice come to mind ) might be tempted to try this out and see what kind of numbers and reproducibility they get.

This really won't be useful on the smaller grippers, but when you get closer to your limit, and you're having trouble finding the right gappers (low 170s comes to mind), then you could get incremental progression by picking something with the same RGC rating but a higher 1/2 RGC distance (HRD?) or a bigger jump in RGC but a lower HRD.

What do you think?

I think it's a brilliant idea!!!

When I have some time or when I do some more RGC of my own grippers I will absolutely try this suggestion!

[bubba29]

interesting thoughts. i have often wondered if once you get through the sweep and to the close if you gradually remove weight to see if the sweep was actually harder than the final close. example, it took 170# to get through sweep to close but removing 5# kept the handles closed. one more pound removed and handles open. close rating 165#, sweep rating 170#.

[Cannon]

Ratings could be expressed a certain way so that both numbers are reflected. Like 170/35 or some punctuation between the numbers. 170# at close and 35mm between the handles with the % of weight.

I personally think the higher percentage will be necessary. Like 75% of the weight. Half the weight won't typically scratch the surface.

I like the idea but can't say I'll have much time to experiment. The way my weights and RGC are run, this would be a lot of monkeying with gear.

[climber511]

I think it's a great idea ............... for someone else! Doing a few grippers here and there is one thing but I did a few hundred grippers last year - and spent many many hours doing so - all for free. I know I would have no interest in spending that kind of time with it. But you all have fun with it .

[Andrew P]

I like the Idea enough to try it out. I'll test out a couple of grippers over the next week and get back with the results.

[bdckr]

Thanks for all the replies.

@Cannon: Yeah, you're probably right. Half the RGC weight would mean a distance more than half the starting spread.

@Mighty Joe, @Andrew P: Do either of you have 2 grippers with the same RGC rating which seem to feel a lot different in your hand? Can't wait to see what results you get.

Edited March 29, 2013 by bdckr

[bdckr]

Thanks for all the replies.

@Cannon: Yeah, you're probably right. Half the RGC weight would mean a distance more than half the starting spread.

The dangers of posting so late at night -- I think I've got that mixed up, and it's too late to edit my last post:

1/2 RGC would take you to a distance less than half the starting spread, wouldn't it? The problem with going for too high a fraction would be that the distances for different grippers would become smaller and closer together the closer you got to the actual RGC weight, making it harder to measure difference consistently. But then again, I have zero practical experience actually RGC'ing.

[Andrew P]

Thanks for all the replies.

@Cannon: Yeah, you're probably right. Half the RGC weight would mean a distance more than half the starting spread.

@Mighty Joe, @Andrew P: Do either of you have 2 grippers with the same RGC rating which seem to feel a lot different in your hand? Can't wait to see what results you get.

The best I can do is a GHP6@139.66 and a RB210@141.86. For myself I can walk up anytime and smash the RB210 but the GHP6 can feel like a brick depending on the day.

[jtaliani]

I think it is a great idea to be able to account for the difference in RGC difficulty.

Thanks for all the replies.

@Cannon: Yeah, you're probably right. Half the RGC weight would mean a distance more than half the starting spread.

@Mighty Joe, @Andrew P: Do either of you have 2 grippers with the same RGC rating which seem to feel a lot different in your hand? Can't wait to see what results you get.

The best I can do is a GHP6@139.66 and a RB210@141.86. For myself I can walk up anytime and smash the RB210 but the GHP6 can feel like a brick depending on the day.

I would personally love to see the results of your testing on the above two. I experience a similar effect where a lower level GHP can sometimes shut me down even when I'm mashing a higher level CoC.

[Cannon]

Yeah, like if you have a 180# GHP8 or something and you put 90 pounds on there, it's going close about 1/2" and that's all. It would still be almost entirely open.

If you put 135# (75%) on there it will definitely still be open way past parallel.

On most grippers, I would say closing it past parallel is a matter of fine-tuning the last 10% or so. In this case, the last 18 pounds or so.

If I would guess, I think 80 or 85% is going to be the right number were it puts you into a meaningful portion of the sweep.

Thanks for all the replies.

@Cannon: Yeah, you're probably right. Half the RGC weight would mean a distance more than half the starting spread.

The dangers of posting so late at night -- I think I've got that mixed up, and it's too late to edit my last post:

1/2 RGC would take you to a distance less than half the starting spread, wouldn't it? The problem with going for too high a fraction would be that the distances for different grippers would become smaller and closer together the closer you got to the actual RGC weight, making it harder to measure difference consistently. But then again, I have zero practical experience actually RGC'ing.

[climber511]

Years ago I was really into archery and made my own recurve bows. We would do what we called a force/draw curve. This meant we weighed the strength for every inch we drew the string (did this for compound bows as well). You could than use this to guesstimate the stored energy for that bow and compare it to another - giving an indication (and only an indication) of which bow would shoot the fastest. It also gave a good feel for how each bow would feel as they were pulled. This whole thing is very similar to what is being proposed here.

In reality I think all of us who have RGCed hundreds of grippers have a fair idea of what a gripper will feel like as we go through the process of adding weight gradually to the RGC. To do this "right" I think you would need to add weight slowly enough that you could graph out the force curve every quarter inch or so to actually tell us much about the process and give meaningful information.

[EricMilfeld]

Has anyone come across the following situation for a pair of grippers: identical calibration numbers (calibrated by the same person), same spread, same spring-set depth, similar knurling sharpness, and yet one of the grippers felt noticeably tougher to shut? Personally, I haven't. I always attributed sweep differences as mainly a combination of the above factors, when two grippers calibrate the same. Very curious now...

[bdckr]

Has anyone come across the following situation for a pair of grippers: identical calibration numbers (calibrated by the same person), same spread, same spring-set depth, similar knurling sharpness, and yet one of the grippers felt noticeably tougher to shut? Personally, I haven't. I always attributed sweep differences as mainly a combination of the above factors, when two grippers calibrate the same. Very curious now...

Completely agree with you here. What I'm hoping is that one number (the distance) can be used to sum up those factors (minus knurling sharpness, plus spring factors) that go into making the sweep harder. Of course it won't be nearly as accurate as what Chris described with his bows, but it would be a lot easier to measure.

[climber511]

Has anyone come across the following situation for a pair of grippers: identical calibration numbers (calibrated by the same person), same spread, same spring-set depth, similar knurling sharpness, and yet one of the grippers felt noticeably tougher to shut? Personally, I haven't. I always attributed sweep differences as mainly a combination of the above factors, when two grippers calibrate the same. Very curious now...

Yes - very much so but also no - very little - let me explain please. I do have two grippers the same - and both RGCed by me. If you "set" them to MMS - they don't feel much different at all. But TNS you can readily feel a difference - one is noticeably harder than the other.

[Randall Strossen]

Lots of interesting stuff here.

[bdckr]

Yeah, like if you have a 180# GHP8 or something and you put 90 pounds on there, it's going close about 1/2" and that's all. It would still be almost entirely open.

If you put 135# (75%) on there it will definitely still be open way past parallel.

On most grippers, I would say closing it past parallel is a matter of fine-tuning the last 10% or so. In this case, the last 18 pounds or so.

If I would guess, I think 80 or 85% is going to be the right number were it puts you into a meaningful portion of the sweep.

Had a chance to think more about this, and maybe this a good argument to use a weight no more than 75%. We definitely don't want it at or past parallel.

The most accurate description of a gripper from fully open to closed would be a curve with multiple data points for the same gripper over different distances. The obvious problems with this is the amount of work required and the inability to communicate this information easily.

Sure, you could graph it and integrate it for the area under the curve to give you one number that could be expressed easily, but it would be even more work, not less.

So if we're going to arbitrarily pick one measurement and one number to represent the sweep, then you want something that is well clear of the close (which is already well described by the RGC rating).

And if you want to find a measurement or a number that reflects the difference between the two grippers like Chris Rice describes:

Yes - very much so but also no - very little - let me explain please. I do have two grippers the same - and both RGCed by me. If you "set" them to MMS - they don't feel much different at all. But TNS you can readily feel a difference - one is noticeably harder than the other.

... then you'll want the ending distance to be well clear of parallel, too.

The added benefit of a smaller weight would be that the distances being measured are larger, so we're more likely to have a measurable difference between the two grippers that can describe objectively the subjectively felt difference in closing one gripper over the other.

Which of 50% or 75% would get you halfway between fully open and parallel? If we're going to pick one weight to get to a distance that represents the sweep, then whatever weight gets us closest to the halfway mark seems like the best way to represent the sweep with one number.

And maybe I'm thinking about it wrong (someone with better geometry and physics skills should chime in), but I'm not too worried that the linear distance isn't decreasing enough. We measure linear distance because it's easier to measure, but it's really the angular change that we're worried about with torsion springs. But since the angle is so hard to measure accurately, we're using the linear distance as a (less than accurate) surrogate. So that even if the angle between the handles drops in half, the linear distance between the handle ends will drop by a lot less than half, because when the spring twists to 0 degrees, the handles are still only parallel and ... what? ... 3/4" apart? And the spring seems to deform (and maybe behave?) a bit differently when you're going below 0 degrees.

Just took a quick look at one of my #3s: it has a linear spread of 3", the angle between the handles is 30 degrees, with a mounting depth of 1/16". So if we say the sweep is going from fully open (30 degrees) to parallel (0 degrees), then going halfway (or 15 degrees) would drop the linear distance to somewhere around 2"? What complicates things further is that the weight being used is exerting a force on the handle that isn't perpendicular to the handle, so that only a portion of the force vector is deforming the spring (and closing the gripper), with that portion gradually increasing to 100% when the handles are parallel.

So maybe the better question is which of 50% or 75% would get you closest to a linear distance of 2" between the handles? Which is where we want the average measurement to fall, somewhere close to half

I sure wish I had paid more attention in physics now.

[climber511]

It's called "REDNECK" gripper calibrator for a reason - this kind of stuff is fun at a sort of theoretical level but goes far beyond the accuracy level of this kind of equipment I think. But I have to admit I'm curious what you all find out when you do it.

[slazbob]

So it should be ...say, a gripper that rates 150. With a sweep of say 85. Just measuring what it takes to get it to parallel ? That could work...

[Cannon]

I experimented with this on one gripper really quick. It was a 170# Elite with a 2.644" spread.

One problem I noticed right away is that there is a difference in the measurement depending how hard you let the stack fall on the gripper. If the gripper has to rebound at all, the measurement is less. (Side note: When rating grippers, it's necessary to force the gripper shut to get the best rating. I kind of this this practice should be repeated for this process.)

Here is the best chart I can make. It's the weight added, the spread with the weight added on the open gripper, and then the shorter spread for the same weight when the gripper is forced shut and then allowed to rebound.

% weight spread rebound
0% 0# 2.644" 2.644"
50% 85# 1.244" 1.144"
60% 102# 0.950" 0.900"
70% 119# 0.745" 0.636"
75% 127.5# 0.619" 0.574"
80% 136# 0.514" 0.406"


Here are some picures:

[Cannon]

This was a lot of monkeying around by the way.

I have to say that the info is probably not worth the effort.

[climber511]

This was a lot of monkeying around by the way.

I have to say that the info is probably not worth the effort.