CPM differences due to clamping length, grips and head wt.
TECH NOTE 25: Sometimes a shaft or club will be tested on two different brands of analyzers and two different results will be obtained. Clamping pressure is one of the factors and has been discussed in an earlier tech note. There are other factors, which cause variations such as clamping length, grips or the test weight used.
Most frequency analyzers use a five-inch clamp however there are some that are different. I've heard of both 3" and 4" clamping lengths. A variation in clamp length is basically a variation in the length of the shaft. In an earlier Tech Note the formulae for frequency shows there is a strong dependency on the length of the shaft. Here's a brief table of clamping length vs frequency for a typical iron and wood shaft.
| Clamping Length (inches) | Frequency (cpm) | |
| Iron | Wood | |
| 3" | 289 | 218 |
| 4" | 297 | 223 |
| 5" | 306 | 228 |
| 6" | 315 | 233 |
Notice that the frequency increases as the clamping length increased. This is obvious because the unclamped portion of the shaft is effectively getting shorter. This effect is greater on the iron shaft since it is being shortened by a greater percentage that the wood shaft. The frequency of the iron shaft is increasing about 9cpm per inch whereas the longer wood shaft is increasing by 5 cpm per inch. The Club Scout Clamping Unit can be modified to vary the clamping length to 3", 4", and the standard 5". If anyone is interested give me a call.
The weight on the end of the club also effects its natural vibration frequency as shown as well in the equation of Tech Note 1. It is not quite as easy to show the effect of weight increase on frequency as it is clamping length because you have to be very careful to increase the weight without changing the center of gravity of the weight. By altering the cg you are effectively changing the length of the club. To run this test I used on of my weights, which can be adjusted without changing its cg. (If you just took a standard 3/8" chuck and screwed a bolt into it to change its weight you'd also be moving its cg away from the butt and therefore increasing the clubs effective length. This would slightly exaggerate the apparent effect of the increased weight.)
| Tip Weight (grams) | Frequency (cpm) | |
| Iron | Wood | |
| 202 | 305 | 218 |
| 225 | 290 | 208 |
| 255 | 274 | 197 |
The iron varies about .6 cpm per gram. The iron about .4 grams per gram. A half a cpm per gram is probably a good figure of merit to use when concerned about the effect on frequency of adding lead to altering swing weight. As a rule of thumb increasing the swingweight by a point will decrease the frequency by about 1 cpm.
Variations due to a grip are somewhat harder to quantify. The grip will always cause the frequency to go down due to its dampening effect. The effect however is a function of the softness of the grip and the amount of pressure applied by the clamping system. In a future Tech Note I plan on comparing the frequency of a raw shaft with the frequencies of that same shaft with a number of different gripped installed. I'll use the Club Scout with its slip clutch to apply a constant force on these grips. I'll also measure the frequency on a Club Scout with a toggle clamp installed that can apply a great deal more pressure to the grip.