Davai said:
. . . The clamp off time is almost immediate in both cases - so whatever string relaxation occurs it does so under conditions that are no longer influnced by the tensioner. The big assumption here is that both heads reach the exact same tension when they lock/beep. Therefore unlesss any string will lose a radical amount of tension in one second the difference is insignificant. . .
Typical nylon strings do lose significant tension immediately. From a chart labeled Clamping Off Creep Tension Loss from Chapter 33, p. 304, of the Physics and Technology of Tennis, I've extracted the following data:
Tension /Total Tension lost /Time in seconds after clamping
55 0 0
51.1 3.9 1
48 7.0 2
46.6 8.4 3
45.1 9.9 4
44 11.0 10
40.4 14.6 60
From the above actual real laboratory data you can see that in less than 2 seconds after clamp-off the string has lost more than 10% of it's original tension. Any constant pull electric or electronic with a hysteresis less than 5.5 pounds would already be repulling.
Bret mentions doing several tests with different Gamma machines at his disposal and testing the resulting string beds with the RA tester showing what is commonly accepted in the industry that CP machines (both dropweight and electric(onic)) produce stiffer stringbeds than the crank machines. A common misconception that permeates this and all similar threads is that a higher stiffness number (RA or RDC) is better.
The actual figure of merit or Quality Factor is the deviation (or the statistical number - standard deviation of the RA or RDC) of the same frame, string, tension, etc, done many times over.
Hypothetically if one were to string the same racquet five times in succession under the same conditions on a dropweight, CP electronic and crank machine and the RA data were:
DW: 72, 75, 74, 76, 74 Avg= 74.2 SD= 1.483
CP El:74, 76, 77, 79, 78 Avg= 76.8 SD= 1.924
Crnk: 66, 65, 66, 67, 65 Avg= 65.8 SD= 0.837
You would conclude that even though the DW and CPEL strung tighter stringbeds than the Crank machine, the overall consistency as measured by the Standard Deviation was better on the crank machine.
The above data was made up, purely hypothetical, but presented to make the point that consistency is the mantra. But wouldn't it be nice to see some actual field data (like the above) showing what various machines are capable of in this department?