Rating Device

[John McCarter]

I've recently become interesting in how to rate grippers and the device/set up used. I was hoping people who have used this method could share some insight on how one should properly go about in the set up and variables you may encounter while getting things set up.

[Cannon]

I've got a lot to say on the topic. I'm on a mobile now, though, and will take a shot at typing some stuff out tomorrow.

[John McCarter]

I've got a lot to say on the topic. I'm on a mobile now, though, and will take a shot at typing some stuff out tomorrow.

Can't wait to see what information you have to share.

[climber511]

I'm pretty sure Matt and I and maybe Eric and Aaron talked about methods in a thread a good while back - no idea where but its on here somewhere if you can use the search better than I can.

[bencrush]

Edit: removed.

Edited August 14, 2014 by bencrush

[Cannon]

Okay, here goes. A lot of this is my opinion, drawn from experience. In no particular order:

1) It's not an exact science. There is a margin of error no matter how accurate and precise you try to be.

2) Don't deal in decimals. There is a write-up about why at the bottom of our ratings page.

http://cannonpowerworks.com/pages/ratings

3) Read Greg and Dave's article. However understand that most guys rating grippers (Me, Matti, Eric, Aaron, Chris, Jedd, etc) have rated exponentially more grippers then they ever did. CPW has rated over 1000 in the past 24 mos alone. My point is that we've learned more about getting repeatable results since they drafted that PDF.

http://www.software-henritzi.net/Articles/MortonGripperCalibrationDevice.pdf

4) You have to start with a clean and oiled spring. If the spring is grimy or rusty or dry, you will have no idea about the level of friction in the spring. If you take a rating it would be impossible to hope for those conditions again, making the rating irrelevant. But you can generally get back to a clean and oiled spring.

5) Ratings will change with gripper usage over time. To what extent I have no idea, but I have grippers I have been rating and using consistently for 8 years and they are getting lighter. And lately I have found compelling evidence that leaving a gripper in a choker for extended periods of time will reduce the rating. The lowest used #3, #3.5, and Elite I have ever rated all spent time in a choker.

6) The strap goes aligned at the end of the handle, not at the bevel edge or anywhere else.

7) A frayed or worn strap will generally result in lower numbers. The reason is that they tend to fray at the back because of the downward angle of the gripper handle when under weight. As the strap frays, it effectively gets "thinner" with respect to how the weight is hanging on the gripper.

8) The following issues will contribute to margin of error: spring condition, strap placement, strap condition, use of a shim, vertical alignment of the gripper, any swinging of the weight stack, your own judgment of the gripper being "closed."

9) There is judgment involved in declaring the gripper "closed." This is one place where I feel there is a learned "art" to rating grippers. This is also at the root of my advice not to deal in decimals. You don't want the handles touching because you can't be sure how much extra weight is pinning them together. Also, just before the gripper closes there will be some "bounce" to the weight stack. Ideally you want to find the 1# increment which will remove that bounce but not pin the handles together. At some point you have to decide "well, that's it" and declare the gripper closed either with or without that last pound. It's generally obvious whether or not you need that pound and dealing with smaller increments I believe is asking too much from the process. There is too much other "slop" to be that accurate.

10) You should shim the bottom handle so it fits tight in the device and doesn't tip downward. If allowed to tip, ratings will generally be artificially high. I have phenolic inserts for different size handles.

11) A brand new gripper shouldn't be rated without putting at least a few reps on there. The best example I can think of was a new HG300 I rated. It lost 1" on the spread with the FIRST close and stabilized after that. At CPW we do 30+ and usually in the neighborhood of 40-50 for every new gripper.

12) The gripper needs to be aligned vertically or the rating will be heavy. You'll notice some grippers have unique skews and are hard to balance. This is just the fun of unique grippers. Each one is a special snowflake. LOL. You want the handles directly above each other when the handles are closed. Like a number 8. You usually have to start out with the top handle farther to the right than you think so that once it pulls down with the skew of the spring they will line up. Every once in a while I get a weirdo gripper where it's hard to align the handles without the top handle touching the rating rig. These weirdo grippers generally are also harder grippers.

13) Don't take a rating with a preconceived idea of what rating you "hope" to get. Try to be objective every time.

14) Practice makes perfect.

15) Leverage is your friend. I have an iron pipe attached to a weight tree that I use as a lever to lift the weight stack. This is a huge win because it makes the weight feel like about 1/2 the actual poundage. Also, you can hold the weight at the top as long as needed to place the strap perfectly with your other hand. Sometimes I'll redo the strap placement 4-5 times until I'm satisfied. The leverage bar is attached by a chain and then an S clip so it can be detached during the rating.

16) Watch out for non-knurled handles. The weight will slide off on to your foot. I put double-sided tape under the strap if necessary on heavier grippers.

17) Keep your face away from top handle when under load. I had a loading pin break on me which sent a #3 handle flying back up without notice. Had my face been there, you're looking at a shattered jaw, lost tooth, black eye, broken cheek bone, or something bad.

18) Weigh your weights at the post office, but still have some perspective for what that means. They are "duty bound" to keep those scales accurate, but that doesn't mean the customer before you didn't rage on it or that some unattended kid didn't knock it on the ground or jump on it. I've weighed my weights at different offices and got different numbers. Yet another reason not to deal in decimals. I use them when adding up my weight stack, but once I get a total I'm back to dealing with that issue of "do I need another pound or not?"

19) I recommend using a round strap spacer. I have found blocks to make pressure points in the strap that can change how the strap pulls going over the top of the handle. I use a piece of PVC. Remember to weigh the spacer along with the strap and pin and anything that will be hanging. That's part of your rating total.

20) Cross-rate with other people. If you get significantly different numbers, talk about that and try to understand why. It won't be possible to match numbers all the time. I would say if you're off by more than 2 pounds then there is something to talk about. It could be the process, it could be the equipment, it could be the condition of the gripper. Just try and find an answer.

21) The rating process tells you "pounds at the close" and little else. The gripper could feel different in your hand for any number of reasons. Also remember that rating a gripper tells you more about THAT gripper, not ALL grippers. Be careful about drawing conclusions about groups of grippers or grippers from certain eras. Any one gripper could have any rating and you don't know until you rate THAT gripper.

22) Generally I put about 80% of the expected rating on the weight stack and use loose weights for the rest. Once you hang weight on the gripper and get it aligned, force it shut with your finger and see if it rebounds. If it does (which it will or you've got too much weight on the stack), pile loose weights around the stack as evenly as possible to remove that rebound. Keep forcing it shut and see if it rebounds each time you add weight. Make sure the handles stay aligned. I've bailed out of rating and started over because I didn't like the alignment. The goal is to get to what I describe in #9. Once you've deemed the gripper closed, you should still lift on the weight stack, take most of the pressure of, then let it back down. Force it shut again and see if you still like that weight. If you're not still in that closed "sweet spot" you might need to back off some weight, lift again, force shut again, and keep going until you're satisfied you have the right 1 pound increment on there or not.

Possibly you can see why I started by saying "this is not an exact science." It can be a fairly reliable and repeatable process but there a many variables. I've found that grippers which are 5lbs apart definitely feel different in the hand and we give this advice on our site. I wouldn't really want to have a 143 Grand Master and a 145 Grand Master. That's the same gripper as far as I'm concerned. There might be other reason which would motivate you to keep both; like maybe one is narrow, or one is filed, or one has better knurling, or has sentimental value. But in my opinion you're not really far enough outside the margin of error for them to be reliably two different strengths.

I hope this is helpful. If I think of more I will edit. Ask any questions. Pardon lame typos. If nothing else this is a good recap of the experience that is backing your $5 rating service through Cannon PowerWorks.

[John McCarter]

Thanks Matt, I'll keep all these concepts in mind when I get closer to have a rig set up.

[climber511]

Excellent post Matt. You have added a few things I never used - shims for example - so my readings should have been higher than yours I imagine. I never found grippers changing over time until I started checking ones I had held in chokers for quite a while - for a long time I did not find any change - just needed more time I guess. I didn't round up or down, I just wrote down what the weights added up to - of course I didn't believe we were actually getting that close but it was what is was. Postal scales weigh in oz on the smaller plates so when converting to tenths, you get decimals to hundreds is where all the weird numbers came from - at least for me.

One thing I did find value in was a "feeler gauge" I think the one I have is for setting "points' on an engine (everything now is electronic ignition but things used to have points that needed set. I have a .001 gauge that helps me tell when things actually touched or not. I no longer rate but feel the process does have value. You didn't mention this but I always did each gripper more than one time - usually 3 or until I had a few readings that came out the same - as you mentioned even the smallest of changes can matter.

[Cannon]

Thanks Chris! I feel the shim is important for repeatable results. I feel like I can ensure the gripper is level more consistently than I can rely on exact placement for a consistent certain amount of tip. As an added benefit, the knurling is protected.

[acorn]

Most excellent post Matt! Though my rating setup of the last couple years is quite significantly different from the original design and no longer uses weight plates but a digital load cell instead I continue to get consistent results with your ratings, my old tests and others by following all that is still relevant from what you just put forth. Most excellent!

-Aaron

[Cannon]

I've been very interested in a number of digital options and have drawn up about 3 different designs. From a theoretical standpoint, I don't see why your hanging scale method wouldn't give good, consistent results. I was gifted a mig welder so I just might be able to build one of my designs at some point. I just need to learn to use the dang thing.

[mightyjoe]

WOW! Amazing post Matt! Just a couple of observations from my own experience and with the digital dyno method. Several of your concerns are of no issue with the method I use. For example, weight bounce and determining if the handles are shut. Lastly, I experimented with shimming for level and it really made no difference except when it was several degrees unlevel. Even then the amount was under a pound high.v

Again, these are my own observations with a digital setup and conducting my own tests. Not knocking anything you,'ve shared here.

Thanks for all your time and effort in writing such a helpful post!

Superb!!!

Edited August 15, 2014 by Mighty Joe

[Mikael Siversson]

Matt,

Regarding point #5 below, do you see this drop with all brands (with regular usage, not choker)? My certification #3 which you recently rated at 137lb has always

felt far below an average #3 in strength, even brand new and its been closed several thousand times (never been in a choker though). If its dropped in strength it must have been almost insignificant based on how it felt brand new compared with other #3's.

5) Ratings will change with gripper usage over time. To what extent I have no idea, but I have grippers I have been rating and using consistently for 8 years and they are getting lighter. And lately I have found compelling evidence that leaving a gripper in a choker for extended periods of time will reduce the rating. The lowest used #3, #3.5, and Elite I have ever rated all spent time in a choker.

[Cannon]

Mikael,

I just have no other explanation. I've seen it with IronMind and Tetting for sure. I have a #3 that started out around 153 and I've used consistently for about 5 years and it's been dropping. It currently rates about 145.

Same with a Grand Master I have used heavily. It has dropped 8-10 pounds in 7 years of use.

Also other instances where I rated someone's grippers years ago and then had another chance to rate them again later after much use.