PDA

View Full Version : Lower tension gives more power is a myth....


ricardo
03-18-2011, 09:59 AM
According to TW String DB, all strings (nat gut, multis/synthetic guts, and polyester) are more powerful at 50-60 lbs than an 40 lbs.

Since there is no data above 60 lbs, i assume that power declines above 60 lbs. Data supports the contention that power declines below 50 lbs.

So this is good news for people with arm problems: string lower than 50 lbs for more comfort and less power for more control...

AirK
03-18-2011, 10:49 AM
I'm sure many people have experienced differently?

danno123
03-18-2011, 11:02 AM
You might be right. Slow motion videos of a topspin stroke show that the face of the racket is actually neutral or slightly closed (i.e. pointed down). Watching the videos makes it clear that what makes the ball go up is the pocketing of the ball in the strings and the force imparted on the ball by the strings on the bottom of pocket as the racket swings up. It seems to me that if the strings are strung at a lower tension, the pocket is deeper and more upward force would be imparted. Therefore, it seems logical to think that with two identical rackets that differ only in string tension, the one with the lower tension will throw the ball higher (and therefore further) on a topspin shot. This might be interpreted by the player as "more power."

Of course, I could be completely wrong.

edited to add: TW University needs to do some testing on this.

JT_2eighty
03-18-2011, 11:11 AM
It seems to me that if the strings are strung at a lower tension, the pocket is deeper and more upward force would be imparted. Therefore, it seems logical to think that with two identical rackets that differ only in string tension, the one with the lower tension will throw the ball higher (and therefore further) on a topspin shot. This might be interpreted by the player as "more power."

This is exactly it. Lower tension is not more powerful as the myth has been. But, lower tension is responsible for higher trajectory off the racquet, which makes balls go long, which is then interpreted as more power.

While the OP is correct, lower tension is better for comfort; control is another can of worms, because altering the trajectory off your racquet is going to affect control. Many people are not used to controlling their shots at lower tensions, but some can and do, given they practice and like that "feel". Thing is, tension can be so subjective that things like "feel" etc, affect our strokes and how we control our shots, so it's easier said then done to "lower tension for more control".

The book Technical Tennis also describes this pretty well (and I think the info is also somewhere in TWU if you know where to look).

weksa
03-19-2011, 02:58 PM
On a similar note, I have a question. Let's say two of the same racquets have the same strings but at different tensions. Racquet A, which has the higher tension, is played with for x number of hours until its tension is the same as racquet B (never played). The primary difference now is string elasticity (unless I'm missing other factors), and racquet A's strings has lost much of its elasticity.

How does the elasticity affect the trajectory of the ball in racquet A vs. B?

DonDiego
03-23-2014, 05:52 PM
I, too, have recently experienced more control (less power?) with the same setup (Black Widow 17 crossed with Intellitour) at 52 than at 58. Might have been in my head, but next time I'll string at 52 again, or even 50, to check that theory.

LeeD
03-23-2014, 06:14 PM
Generally, lower tensions give more "easy" power, power with an easier stroke, than higher tensions.
But, higher tensions can hit as hard or harder when you swing full speed.
Question becomes, how often do you block the ball? How often do you swing full speed? How often to you reduce your swingspeed at times?

Muppet
03-23-2014, 06:23 PM
According to TW String DB, all strings (nat gut, multis/synthetic guts, and polyester) are more powerful at 50-60 lbs than an 40 lbs.
Since there is no data above 60 lbs, i assume that power declines above 60 lbs. Data supports the contention that power declines below 50 lbs.

So this is good news for people with arm problems: string lower than 50 lbs for more comfort and less power for more control...

I haven't experienced this myself, but there was some discussion saying that at around 40 pounds the various frequencies from the strings and the racquet cancel eachother out. This gives the racquet a 'dead zone' where you get very little power or feel for a short stretch of tensions, differing a little from racquet to racquet.

Bartelby
03-23-2014, 06:41 PM
There was other data on TWU which showed that the power peak for these very different types of string was quite different.

Poly seems to be at its most powerful in the mid to high 40s from the graph that I originally found in the low tension thread.

So poly might be getting less powerful at 40, but not necessarily at 45.



According to TW String DB, all strings (nat gut, multis/synthetic guts, and polyester) are more powerful at 50-60 lbs than an 40 lbs.

Since there is no data above 60 lbs, i assume that power declines above 60 lbs. Data supports the contention that power declines below 50 lbs.

So this is good news for people with arm problems: string lower than 50 lbs for more comfort and less power for more control...

Shroud
03-23-2014, 08:24 PM
I haven't experienced this myself, but there was some discussion saying that at around 40 pounds the various frequencies from the strings and the racquet cancel eachother out. This gives the racquet a 'dead zone' where you get very little power or feel for a short stretch of tensions, differing a little from racquet to racquet.

Hi Muppet,

Do you have a link to that? I would LOVE to find that spot where it all cancels. Were these full beds or hybrids??

Chotobaka
03-23-2014, 08:44 PM
According to TW String DB, all strings (nat gut, multis/synthetic guts, and polyester) are more powerful at 50-60 lbs than an 40 lbs.

Since there is no data above 60 lbs, i assume that power declines above 60 lbs. Data supports the contention that power declines below 50 lbs.

So this is good news for people with arm problems: string lower than 50 lbs for more comfort and less power for more control...

Data suggests that you ride the short bus.

Muppet
03-24-2014, 06:09 AM
Hi Muppet,

Do you have a link to that? I would LOVE to find that spot where it all cancels. Were these full beds or hybrids??

I think they were talking about full beds of string, but I see no reason why it wouldn't apply to hybrids as well. But it was a while ago and I'm having difficulty finding that thread. Sorry about that.

ChicagoJack
03-24-2014, 06:16 AM
According to TWU String DB, all strings (nat gut, multis/synthetic guts, and polyester) are more powerful at 50-60 lbs than an 40 lbs.

1. Slight Misinterpretation Of TWU Data : It's no biggie, but I think I know where the confusion is. The OP has probably arrived at this partially correct, yet grossly oversimplified conclusion by taking a quick drive by the energy return digits found in the TW University Data base, and doesn't fully understand the of context of that data column. The testing is done with steel impact hammers, not tennis balls. (See Screen Grab Photo Below)

http://i252.photobucket.com/albums/hh11/olmo21/TW%20Forum%20Stuff/TW%20Forum%20-%20ACOR%20Flex%20Master/TWU_EnergyReturn_zps593d764c.jpg (http://s252.photobucket.com/user/olmo21/media/TW%20Forum%20Stuff/TW%20Forum%20-%20ACOR%20Flex%20Master/TWU_EnergyReturn_zps593d764c.jpg.html)

2. Impact Hammer Testing, Energy return, Max Power Tension : Impact Hammer Testing (this is where we get the energy return digits in TWU) is useful in that it takes the biggest factor out of the equation, (ball deformation) so that we might see slight differences in strings more clearly. But viewing this data column without proper context, can be misleading. Yes, energy return can rise with increasing tension, but it does so at the expense of rising stiffness, which contributes to increased ball deformation, and the ball is where most of the energy loss occurs. Increased impact energy loss means lower rebound ball speed.

This higher energy return at higher tensions thing, often creates confusion, even amongst those making an intellectually honest inquiry. The phrase "Energy Return" seems like it would offer direct relationship to rebound ball speed but it does not. This is not a flaw in the study of racquet science. The testing with steel balls and impact hammers is incredibly useful in that it allows us to see the level of energy loss created by the string, and the amount of energy loss inherent with tennis balls separately. As it turns out, all string is pretty efficient. The type of string and the tension will make slight differences in steel ball bounce height, or impact hammer bounce speed, but almost all strings are roughly in the neighborhood of 97-95% efficient, with the test hammer returning to 97-95% speed, and steel balls returning 97-95% of the bounce height.

3. Max Power Tension Will vary Depending Upon String Stiffness : Impact hammers don't deform, tennis balls do. This explains why the tension that gives you the most ball velocity will be different given the stiffness of the string. Gut is easier to figure out because stiffness increases only slightly as tension increases. Max rebound speed for most gut will be probably be in the 55-62 lbs range. But poly is a whole nuther can of worms. The trade-off is more extreme because poly gets much stiffer as tension increases, while energy return rises with tension. Studies indicate that max rebound speed for most poly is probably in the 20-35 lb range. If anybody wants to go swimming in the deep end of this discussion, and you'd like to know more about the max power tension for dif kinds of strings have a look at this link (http://tt.tennis-warehouse.com/showthread.php?p=4544608#post4544608) here. For more on dwell times, force, and deflection, you can find more here (http://tt.tennis-warehouse.com/showpost.php?p=4526102&postcount=164http://). But you might want to take a triple macchiato with you. These are not easy reads.

4. Tennis Balls Are 55% Efficient : More elastic strings, or lower tensions create slightly more rebound ball speed because the ball compresses less, and the ball loses less kinetic impact energy. The rules of tennis dictate that when you drop a tennis ball from a height of 100 inches onto solid concrete it must bounce to a height of 53-58 inches. If the ball bounced back to 100 inches high, then the ball would have been 100% efficient at preserving the impact energy. This bounce height of 55 inches or so, tells you that tennis balls are designed to convert 45% of the collision energy to friction, heat and other things not very useful to a tennis player. Tennis balls are designed intentionally to be very bad at preserving kinetic impact energy.

5. String Beds Are 95% Efficient : So... what we want for maximum ball velocity is to have the ball squash less, because the ball has been designed to be not very good converting impact energy into outgoing velocity. String however, is roughly 97-95% efficient.

6. String Beds And Ball Impacts : When one drops a tennis ball onto on clamped racquet from a height of 100 inches, it will bounce to a height between 75-80 inches. Wen you drop a ball from the same height onto solid concrete, an approved ball will bounce 53-58 inches (this is according to the rules of tennis). What this tells you is that the string stored up a little energy when it deformed like a trampoline, the ball squashed less, and the string bed returned some of the energy to outgoing velocity when it regained shape. This is why lower tension creates slightly more ball velocity. It's not because the strings have more "power", it's because more elastic strings (or lower tension) means the ball squashes and deforms less. It's about the ball not the strings.

Links:

TW Professor : Energy Return, String Stiffness, Ball Velocity
http://tt.tennis-warehouse.com/showpost.php?p=5379231&postcount=2

TW Professor : Energy Return Charted To Stiffness, Gut-Nylon-Poly
http://tt.tennis-warehouse.com/showpost.php?p=4544608&postcount=271

TW Professor : Poly at Extremely Low Tension
http://tt.tennis-warehouse.com/showpost.php?p=4526102&postcount=164

-Jack