Comparing the handle spread

[jimwylie1]

I was comparing a friends #3 and #4 grippers tonight and I noticed that there is marked difference in the spread of the handles of these two grippers.  The #4 handles are much wider apart than (well a few mill! ) than his #3.  I find that this makes positioning the gripper much harder and can't help but think that a larger hand may be advantageous in closing this monster.  Has anybody else noticed such a difference and what is you opinion on this factor contributing to the grippers reluctance to be closed?  I'm sorry if this has been covered in previous posts but I tended to skip a lot of the posts in the past that have covered 'gripper physics'.

To those that are currently training with the #4, what would you consider a reasonable attempt at closure? 3cm? 2cm?  

Thanks

Jim

[Guest CanadaCrush]

The spread on my handles is about the same. As far as a good attempt, it's greatly dependant on the calibration of the gripper. I don't know what my 4's are at in inch lbs, but the best I've managed is a mediocre, 3/4-7/8" close.

-Mark

[John Szimanski]

Good eye, Jim. Actually, there are several dimensional variations that have not been monitored by quality control in most grippers. Most have been discussed in previous posts. We have been (painfully) mastering each of them, as we became aware of them.  Here they are so far:

1. The included angle, designated IA; this is a measurement of, as you describe, the spread between the handles. We found common grippers with IAs ranging from 25 to 37 degrees. IMs cover the range and BBs are typically high making them quite a challenge for those with small- to normal-sized hands. We have set this dimension and tolerance for SOS grippers at 30 degrees +-2. The included angle contributes to the degree of difficulty in getting your hand around the grips, setting up, starting the close, and total closing distance.

2. The skew, designated S. Look at the head of the coil with the handles facing away from you. The skew describes the angle the handles diverge to the sides. We have documented a range of S from 10 to 17 degrees for common grippers. We have set this dimension and tolerance for SOS grippers at 13 degrees +-2. The skew contributes to the degree of difficulty in the same way as the included angle with something additional. With a moderate skew the primary work effort is winding up the spring. As Pat points out, the larger the skew, the further you must do additional work to pull the handles crosswise over the coil.

3. The overall handle length, designated OHL; this is the measurement from the top of the coil to the tip of each handle when the handle is held at 90 degrees vertical. We found this all over the map, even between the two handles on the same common gripper. We settled on 5-5/16” +- 1/64 OHL for SOS grippers. Shorter handles provide less leverage and a higher degree of difficulty.

4. The distance from the bottom of the coil to the top of each handle, designated BCTH. We have found this all over the map for common grippers, like the overall handle length, even on the same gripper. It is a different factor than OHL, but correlated. We would expect grippers with the same wire size to have the same BCTH.

5. The severity of the dogleg, designated DL. We found these varying considerably but did not realize the impact until we found the extremely pronounced DL on one of Luke’s BBs. The DL is inherent in the spring winding operation but can be controlled. The DL does not act like a fully formed spring leg, as found on the opposite side. It creates a shorter lever arm on the coil and increases the degree of difficulty.

6. The wire diameter, designated Phi. Phi primarily determines the inch-pounds (IP) of closing torque. When a common gripper model number (implying that all similar model numbers are equivalent) denotes a gripper’s strength level, we would probably expect the Phi to be the same for all of the same model, as a minimum. This has not been the case. And, due to difference in steel characteristics, all Phi still have a range. We have sidestepped these issues altogether by calibrating the SOS grippers and stamping them with their true IP.

If you have a collection of five grippers of other brands, perhaps two will be the same on one or two dimensions. The rest probably vary considerably and significantly among each other and, as applicable, within themselves. We don’t believe that’s how it should be. We selected our specific SOS dimensions based on field-testing and feedback. We focused on tolerances so that any SOS gripper will generally feel the same as any other, except for the IP. Grippers fabricated under strict quality control offer a valid comparison between personal strength levels and effective incremental training tools.

A recent common catalog states their brand grippers are not calibrated and implies that calibration is not important. Unfortunately, a similar attitude carries over to covert design changes and a complete absence of quality control. So, the undocumented gripper ratings are meaningless, but it’s OK because they’re not measured anyway. And, no need to have their eyes open when they put them together. Otherwise you can’t get a double-3. Not exactly rational, much less ideal circumstances for a rating scheme. Still, the gripper game is fun and we love to see the COC list swell. We’re tickled to help when we can and excited to see folks get there. Now if Heath would get busy on the 4!

John