Sports Net Tension Gauges for Tennis and Volleyball; Training Tools for Volleyball Setters
Sports Net Tension Gauges for Tennis and Volleyball; Training Tools for Volleyball Setters

Please visit this page often, for the latest on the progress of the TNT Gauge System -- coming to a tennis facility near you!


2016:  Architects are adding TNT Gauges to the specs for new courts, recognizing that the presence of a certified net tension indicator tells players, "the net is correctly tightened," and avoiding over-tensioning that damages net post foundations.
The US Open used TNT Gauges on ALL the competition and practice courts, for the 5th straight year!


January, 2015:  USTA's Friend at Court has published the new Comment 1.1, with the first-ever net tension recommendation for all competitive tennis matches.   It's on page 4, with Rules of Tennis, Rule 1, or click here to see the excerpted page.


January 1, 2015:  Please note that the main contact email for Cable Tension, LLC and David Glass is (an additional "G" character over the prior address).  Super-spammers discovered the prior address, and overwhelmed the Inbox.


August 2014:  We worked with the facilities crews setting up the nets for the 2014 US Open, the 3rd consecutive year of all-court use at the Open.  The tournament purchased additional units to pre-load alternate net systems, and for all 5 practice courts this year.


August 2014:  The TNT Gauge is used for the 4th year on all the competition courts at the 2014 Western&Southern event in Cincinnati.


April 2014:  USTA's Executive Committee voted at the Annual Meeting to accept language that will recommend use of a net tension measuring device, such as the TNT Gauge, for sanctioned events and tournaments, beginning with publication in the 2015 Friend at Court.  The recommended tension range is a narrow 400-450 pounds, with all courts at a facility within 25 pounds of each other.


June 2013:  ITF has published a net tension recommendation, at this ITF Technical page, based on work with the TNT Gauge!  As USTA moves forward with evaluation of proposed language in the US, we look for positive results, even as the Emirates Airline US Open Series kicks off in July, with the TNT Gauge on most of the venues' courts.


March 25, 2013 update: The NTTF is suggesting language that will standardize the net tensions for college and sanctioned events and tournaments, for publication in Friend at Court.  This language was finalized at the USTA Annual Meeting, for submission to the affected committees.  Our hard work and proven TNT Gauge may be making a difference in the game!


January 2013:  David has been asked to actively participate on the USTA Technical Committee's Net Tension Task Force, recognizing that use of the TNT Gauge has created an important, new body of knowledge as regulators work toward a net tension guideline and rule.

October - December 2012:  Both USTA and ITF are in preliminary discussions about a net tension rule, in part due to the long-sought availability of a compact, inexpensive device to accurately measure the tension:  The TNT Gauge!

The French Open is testing a TNT Gauge, for this year's tournament.


September 12, 2012:  The ATP World Tour has announced a 3-month experiment with playing let serves, in the early 2013 Challenger Series, across the world.  This suggests even more value to standardizing net tension, and the TNT Gauge Pro System is the only proven, available solution.


September 5, 2012:  Jeff Archer of Knoxville CBS affiliate WVLT produced a story (no longer available on the station Web site, introduced on the 6:00 news by Sports Director Rick Russo.
The same day, Steve Megargee of Associated Press Sports uploaded this well-written
article, which was picked up by most US and European newspapers and online services (unfortunately for the print editions, it was the same day Andy Roddick announced his retirement).


September 2, 2012:  In phone conversation with Andrew Jarrett, the tournament referee for the Wimbledon Championships, he requested samples of the TNT Gauge be sent to Mr. Neil Stubley, Grounds Manager for All England Club, so that they might study the best net tension on grass courts.


August 13, 2012:  Installation of the TNT Gauge Pro System began at the National Tennis Center, in preparation for the US Open.  In discussions with the tournament's referee Brian Earley and his Operations crew, tension settings were established for the Open.  The reception to the product here has been amazing, and the crew is very friendly and dedicated to their tournament.  Big news will be here, in conjunction with the tournament.


July 25, 2012:  The Atlanta Open concluded last Sunday, with strong reviews and comments from the officials and operations crews.  This marks completion of testing of the new TNT Gauge Pro System, which improves the weather durability, accuracy, and calibration of the device, in addition to better lubricating tape for grooved post caps.  The ATP World Tour's heavy-duty net was no problem, but we all learned that this net requires more tension than normal nets, just to bring it to the center strap due to its weight.  For doubles, a good setting is 475-500 lb; with singles sticks in place, the net plays well at 425-450 pounds.  We are most grateful to Bob and Brad Bryant, the Tournament Director and Operations Managers respectively, for their hospitality and enthusiasm for the TNT Gauge, which marked its first anniversary in pro tennis at Atlanta.

July 7, 2012:  All six courts at the BB&T Atlanta Open are now equipped with the new TNT Gauge Pro Systems.  Using the bolt-on model, we adapted them to the Putterman net posts supplied by Signature Tennis, the court builder for this great new midtown Atlanta venue.


June 14, 2012:  Joining Cincinnati as additional ATP 1000 events, Tennis Canada is equalizing all the nets at both Toronto and Montreal Rogers Cup events, part of the US Open Series!  The TNT Gauge will be returning to the competition courts for the Emirates US Open Series, beginning with the BB&T Atlanta Open in July.


May 16, 2012:  The Knoxville area chapter of SCORE (Service Corp of Retired Executives) has been our business adviser since the startup in 2011.  Today they recognized Cable Tension, LLC as the Chapter's "Small Business Client of the Year."  Judith and I accepted the award from counselor Richard Jenkins.  SCORE's guidance has been invaluable, and I recommend their free service to anyone starting a business.


May 11, 2012:  Jimmy Hyams and Lenny Simpson updated their Tennis Hour audience today on The Sports Animal radio WNML, with a very generous summary of the latest news on the TNT Gauge.  Listen by clicking here.


May 9, 2012:  Link here to the NEWS RELEASE about the 2012 NCAA D1 Championships installations.  The University of Georgia installation:


May 7, 2012:  The Retail Referral Rebate (3R) Offer begins:  Get 10% back from the cost of your previously purchased TNT Gauge Systems bought directly from Cable Tension, LLC for each referral that becomes a direct retail sale.  The rebates are cumulative, and could result in 100% of your cost returned!  See the "Retail Rebate Offer" link at left.
1/17/2013 note:  The Retail Rebate Offer has expired.


May 5, 2012:  Installation of 16 units at the beautiful University of Georgia tennis complex is complete, with all their courts for the Division 1 NCAA Tournament equalized.  UGA's logo is prominent on their Gauges, as in this photo!  Downloads: A close-up photo if their logo Gauge is here, wider view of an outdoor net here.


April 27, 2012:  TNT Gauges are in place for yet another USTA/ATP Pro Challenger, this time at the Savannah Challenger at The Landings Club.  They used the direct-mount, bolted model.  Downloads:  Installation photo here, wider view of the Challenger play is here.

April 24, 2012:  The 2012 NCAA Tennis Championships will use TNT Gauges on all the courts at University of Georgia.  Pro Challengers are accepting them too, for their competition courts.  (Note to potential distributors:  these are sales, not comps)


March 18, 2012:  A presentation was made to the USTA Technical Committee about the engineering and science of net cord tension measurement.  That presentation in PDF form is available for download by clicking here.


February 26, 2012:  We joined Century Sports/Har-Tru (now merged) at the PTR Symposium Exhibitor Show in Orlando.  Great enthusiasm there for the TNT Gauge System!
See it at Century Sports HERE.


February 2012:  The science of net tension measurement will be a featured agenda presentation at the USTA Annual Meeting on March 18, by David Glass, inventor of the TNT Gauge System.


January 2, 2012:  The New Year opens with an article in the January issue of Racquet Sports Industry's RSI News.


December 3-5, 2011:  The TNT Gauge is featured in the booth with JA Cissel Mfg. Co, at the ASBA Technical Meeting in Palm Springs, CA.  The attention there from people in the court construction and maintenance business was very encouraging.


November 27, 2011:  The Tennis Channel premiers a "Court Report" (download) about the TNT Gauge (and its inventor).


November 18, 2011:  The US Open had tested two TNT Gauges on outer courts at the 2011 Open, and has decided to buy 18 more, to equip all of the US Open courts for 2012!  Check received from United States Tennis Association on November 27.


November 13, 2011:  University of Kentucky purchased 10 TNT Gauges for their indoor and outdoor courts.  The four indoor courts have TNT Gauges installed!


November 7-13:  The USTA Pro Challenger Series was in Knoxville at UT's indoor facility, using the TNT Gauges on Tennessee's nets.  We met with several senior officials and USTA reps, and got very positive comments and contacts for future business.


October 11, 2011:  For the use of tennis clubs, a cost justification or Cost Benefit Analysis exercise is available here.  It will show that upgrading your courts to Pro level can actually make money for you!


October 6, 2011:  After the UT Tennis Program was presented with 12 TNT Gauges with their logos, the Tennessee sports web sites wrote articles, and posted them on-line at the UT Vols and Lady Vols web sites.


End-September, 2011:  The TNT Gauge (and its inventor) were featured this month in the Atlanta tennis association's Net News magazine, and on the front page of my hometown newspaper, the Morristown, TN Citizen-Tribune.  (10/11/11: not available on-line after 10/1.)


September 23, 2011:  Judith and I joined Century Sports and Wilson to present the TNT Gauge to the industry at the USPTA World Conference on Tennis' Buying Show, at Saddlebrook near Tampa.  Despite a thunderstorm strong even by Florida standards, turnout was in the hundreds, and interest in the TNT Gauge was excellent.  We made the best possible set of media, dealer, and club  and facility owner contacts.


September 15, 2011:  Century Sports sponsored my presentation to the national sales conference of Wilson Sporting Goods' Racquet Sports Division at Kiawah Island, SC.  The TNT Gauge is now represented for Century Sports by  Wilson.  Links for dealers to the Cissel page, and the Wilson catalog page will be here soon.


August 29, 2011:  We signed the contract today for Century Sports/J.A. Cissel to be the first national distributor for the TNT Gauge, and are proposing the same terms to another!


August 25, 2011:  The TNT Gauge is on competition courts 14 and 15 at the US Open, and on the net of the new Stadium Court in the Winston-Salem Open, the final Olympus US Open Series event


August 23, 2011:  The TNT Gauge was a success in Cincinnati.  The Facilities Team changed at least 2 nets on their own, and reported that the TNT Gauge finally made them certain how tightly the cords had been set.  Judith and I were on-court for major league tennis, monitoring the net cord strikes, and seeing the world's top players in action, close-up.   Chair umpires for the ATP World Tour and WTA have been trained to use them, so that testing can continue in the Asia and Europe legs of the hard court season in September.


August 9, 2011:  TNT Gauge in the Cincinnati tournament!  After a post-L.A. update to the Operations Manager of the Western & Southern Olympus US Open Series Masters and Women's Open event in Cincinnati, he called and I am there, actually installing TNT Gauges onto the nets for all 8 competition and 8 practice courts for this highest-level professional men's and women's combined event;  The TNT Gauge has made it to the Bigs -- virtually all of the world's top men and women players are coming to Cincinnati for next week's main draw in this ATP 1000 event, and they will be playing on courts with equal net cord tension across the entire facility.  We're being treated so well... Judith and I have court access credentials, to assist with net cord settings, and access to the leaders of the tennis game and industry.
We are installing the "short-tail" versions onto Douglas Premier and Elite net posts, learning as we go, but no real installation issues at all!  This tournament is going out of their way to ensure the success of the TNT Gauge, since it benefits them too.


August 3, 2011:  Cable Tension, LLC reached an agreement-in-principle today with the first of our planned 3-5 national distributors.  The company name will be linked here as soon as the Agreement is final.  This is the biggest business step so far, and an encouragement that the TNT Gauge will be a commercial success as it builds its global resume.  The current strategy is for us to sell at only two market levels:  retail (from here) and through qualified distributors, that is, companies who will actively market the TNT Gauge through their sales channels such as a dealer and construction contractor network.  Cable Tension, LLC will not sell directly to Dealers, instead referring them to their choice of qualified Distributors.


August 1, 2011:  The Farmers Classic U.S. Open series event in Los Angeles concluded yesterday, and TNT Gauges were used all week.  The men's professional Tour supervisor sent very positive results, suggesting now that 475 pounds tension is a good compromise between doubles (without the singles sticks) and singles with the sticks.  They may choose not to set the tension differently between singles and doubles when one quickly follows the other on-court.
AUDIO OF BRAD GILBERT'S ESPN2 COMMENTS in Atlanta are here.  Still working on a new video from Atlanta, that will include before-and-after videos of a net cord that was WAY too tight, and the semis and finals when it had been adjusted.
Meanwhile, here's a temporary transcript of Brad Gilbert's comments and conversation.  It happened after the first net cord, off a forehand by Gilles Muller against John Isner, when the ball stayed fairly in play:


Isner serving, at 0-1, 15-0 first set.  A forehand by Muller hits the net cord, stays in play, Isner dumps a backhand into the net.


Gilbert to booth:  “Guys, I just got a note handed to me.  It’s called the TNT Gauge, it is a net cord gauge, and a guy heard us yesterday on TV and said the net strap was ‘way too tight.  They let him re-adjust the cord, and it will not be as lively.  So he has – it’s called Cable Tension (LLC), introducing the TNT Gauge.”

Cahill:  “OK!”

Gilbert:  “And he says the ball will not hit the tape and jump ‘out’.”

[Isner serves, “Fault” called]

Darren Cahill:  “That’s after the comment you made about the difference between here and Wimbledon.”

Gilbert:  “Yeah!”

In a follow-up e-mail exchange with Brad Gilbert, he said that I “had made a big difference in the Atlanta tournament.”


July 25, 2011:  We and the TNT Gauge had a great experience at the Atlanta Tennis Championships, an ATP World Tour 250 event.  Many new contacts, new leads, and fans of the idea and its execution; but the highlight of the last weekend has to be meeting Brad Gilbert of ESPN2, showing it to him the day after he had commented about the super-tight nets the day before.  I had been allowed to do the net tension setting for the televised Saturday matches, and Brad did a full 30 seconds of plug for the TNT Gauge, just after the first net cord of the semi-final singles match!!!  He did a nice job of representing the Gauge, even as the sideline camera guy Jeff tried unsuccessfully to get his giant lens focused on the TNT Gauge only 6' away from him.
We're on the way now, and even with the successes in NCAA and World Team Tennis, this Atlanta ATP World Tour event will likely be the watershed moment for the TNT Gauge.


July 21, 2011:  The TNT Gauge continues its successful competition testing at the Atlanta Tennis Championships, to very favorable comments by chair umpires and Tour supervision.  They get it:  the TNT Gauge has the potential to equalize tennis courts sufficiently to eliminate the let serve from our game!  The Tour will continue testing in the next several weeks, at tournaments around the world.  Next stop:  TNT Gauges on the grandstand and stadium courts at the ATP Tour's Olympus US Open Series event in Los Angeles, the Farmers Classic.  Not yet sure about the Masters event in Cincinnati, and the Tennis Operations guy here in Atlanta wants to take it with him to Winston-Salem in late August.
My biggest challenge:  educating the users, showing them that there is a way to set the tension, without just cranking the net as tightly as possible.  It's making a difference, and the educated users are quickly comfortable with it, once they know the Gauge is in place.


July 15, 2011:  The TNT Gauge is being tested on the ATP World Tour!  Invited by the tournament director, we installed TNT Gauges on all three competition courts, and three practice courts for the Atlanta Tennis Championships.  The tournament runs from July 16-24, with some big names coming in.  The tournament web site is here.


July 5, 2011:  The TNT Gauge made its debut in pro tennis tonight, at Kastles Stadium in Washington, DC!  In the opening night of the new stadium, World Team Tennis'  Washington Kastles played the Kansas City Explorers, and the TNT Gauge was there.  I flew up to meet Bryan Hicks, supervisor of officials for WTT, and the two of us installed it in 3 minutes, including the instructions.  A photo is here.  When we arrived, the net was very soft, about 300 pounds tension, and it played well at 420 pounds during the match.  Bryan is taking 3 more TNT Gauges to other cities in WTT, to use them for their no-let play.  I am grateful to Ilana Kloss, CEO of WTT, and to Bryan for giving us the opportunity.  Next stop: the ATP World Tour  US Open Series event in Atlanta, July 18-24, for TNT Gauges on 3 competition and 3 practice courts, for continued play-testing at the highest level of tennis.


July 1, 2011:  David's appearance on Knoxville radio station WKRL99's Sports Talk, with John Wilkerson, Jimmy Hyams (also a tennis player and author of the News Sentinel article), and their tennis expert and former pro Lenny Simpson.  MP3 audio of the 6-minute interview is here, and a photo with the radio guys will download here.


June 30, 2011:  The final report of destructive testing, that determined the ultimate strength of the TNT Gauge, is here for reading or downloading.


June 27, 2011:  The agreements are in place:  the TNT Gauge has made it to the pros!  Beginning with the US Open Series ATP World Tour event, the Atlanta Tennis Championships will have the TNT Gauges on the competition and practice courts, and we are working toward competition testing at other US Open Series events as well.

World Team Tennis will be playing no-let this year, so they want to try the TNT Gauge in four cities, beginning at the Washington Kastles event in DC, on July 5.  I will be there to demonstrate, install, and support the first use of the TNT Gauge by top pros!


June 22, 2011:   All remaining components of the 100-lot production run are in hand.  The finish machining pass added by Applegate Machine made the hard-coat anodized surface by Norco Metal Finishing much cleaner and more "polished."  Assembly is in progress.


June 19, 2011:  The Knoxville News Sentinel printed and posted a nice article about the TNT Gauge, which may be found here.  Jimmy Hyams, the writer, is a leader on the local afternoon Sports Talk radio program, and has invited me to his show on July 1.


June 9, 2011:  In the Materials Science Lab at Tennessee, we did the Destructive Tests today on two TNT Gauges that had been uprated to the production hardware configuration.  As expected, the first failure mode in slow, near-dynamic linear pull testing was the Quick Link attachment ring, which opened without catastrophic failure (no ejected components) at 1,588 pounds, a margin of almost 3X the maximum indicated tension of 550 pounds.  This proved that the Quick Link is the equivalent of an electrical circuit fuse, as intended.

A second TNT Gauge from the production qualification run was tested with a more dynamic load, simulating an adult-size person running into the net at speed, and putting full weight on it.  Pulling at a rate of 6 inches per second, the Quick Link on this unit stretched but did not open, and the two TNT Gauges failed by releasing the top loop cable at 2,124 and 1,912 pounds respectively, a safety margin of greater than 3.4X the rated load.  In both tests, there were no other component failures or compromises noted, that were not the result of the impact of releasing the compressed spring in the device failure, and with the exception of the top cable loop, all components were safely and entirely contained within the housing.  The test report will be posted at this site when completed.
     This concludes the qualification testing for the TNT Gauge:  it has proven through certified and play testing to be accurate, repeatable, weather-proof, durable, and safe.

June 6, 2011:  We're performing pull tests this week to determine the yield and ultimate strength of the production TNT Gauge, which so far has withstood everything we've thrown at it, including sitting and bouncing 50 times full-weight on the center of the net.  To know its ultimate strength and failure mode, we're taking two of them to a certified lab for test-to-destruction.


May 31, 2011:  Our target date for taking orders was May, 2011, and as of today, we made it!  Production quantities are ready, the business is formed, we can take credit card and check orders, and ship immediately.  The TNT Gauge is available in three models:  standard (long lower loop for Edwards, Lee / Hartru, Douglas, and most Courtmaster posts), short (for Douglas Premier, some Courtmaster posts and the French Open and Wimbledon), and the bolt-on model with no lower loop (for OEM and permanent hook replacement).


May 29, 2011:  The first production quantities of TNT Gauges are ready for immediate shipment.  School or Club logos may now be added to the space above the indication label, to customize the product and show that you care about the upgrade to your courts.


May 15, 2011:  The NCAA Tournament first and second rounds in Knoxville were completed today, with TNT Gauges on all six courts.  Weather forced some play, including the men's second round indoors, to move indoors, where the TNT Gauges were ready to demonstrate the equality and "Fairness" of the courts.  Officials and coaches had high praise for the product and performance.  In preparation for outdoor play Sunday, all six TNT Gauges were relocated from the indoor facility to the outdoor courts, with the move, installation, and calibration taking only 30 minutes by two people!
Technical update:  Another advantage of using the TNT Gauges became apparent during the 5 days of use for the NCAA's.  Showing the same effect on net cord tension as would happen without the Gauge, the nets lost about 25 pounds of tension when the court temperature increased 15 degrees during the day, due to thermal expansion of the length of net cord.  By simply taking up additional cable at the crank post, the tension was returned to the desired level.  Similarly, lowering the tension in the next morning's cooler air was just as easy!


NEWS UPDATE May 12, 2011:
TNT Gauges approved for use in NCAA Regionals in Knoxville, May 13-15 (Men and Women)
Installed and calibrated - all six courts are now equal.  After seeing it in use, the head coaches from Tennessee, Vanderbilt, Virginia Tech, and Radford men's teams accepted it with enthusiasm, and both the NCAA representative and meet referee have authorized use for competitive play at this level.


May 11, 2011:  TNT Gauges are installed and adjusted to the same tension on the six outdoor courts for team practice at the University of Tennessee, in advance of the NCAA Regionals, for coaches' review and opinion.
Also:  The TNT Gauge is ready for sale - "early adopter" specials for NCAA members through June 30.


May 9, 2011:  The ITF Technical Commission meeting is Tuesday, May 10, for their first official discussion of the TNT Gauge.  We look forward to their impression and continued testing toward acceptance.


May 5, 2011:  Machined first-articles are good, so production units are under way.  Six of the first lot will be presented to the University of Tennessee tennis program, where all the development has been done on the indoor and outdoor courts at the Goodfriend Tennis Center.  "Thanks" to Sam, Mike, Andrea, and the UT teams for their patience and acceptance!  Their enthusiastic cooperation and encouragement made the product possible.  We are offering the first official use of the TNT Gauge:  the first and second rounds of the NCAA Division 1 tournament, at UT May 12-15.  The local USTA referee and officials have given us optimism for success, with their encouragement too.


April 26, 2011:  ITF received their sample TNT Gauge today after a 17-day "Priority" transit.
Over the Easter weekend, a TNT Gauge was checked on the newer Har-Tru net posts at Sun City Hilton Head's excellent clay court facility -- no fitting issues, much curiosity about it.  This is a good target market, since these courts get a lot of Senior play by people interested in the quality of the court environment.  The encouragement is unanimous -- It's time to move into the business side.


April 21, 2011:  Engineering drawings have been updated, and given to Applegate Machine in Knoxville, to make the first 100 production units!  All other material on order.  The Knoxville supply community has been very generous with their material and knowledge, from nuts and bolts to anodized coatings; so the first production awards will be local.  It's the right thing, and I appreciate my new network.
We finalized the "hysteresis" issue with posts that have grooved caps vs. pulleys:  A 4-5" piece of PTFE (Teflon) tape in the groove makes it behave as a pulley.  The only requirement is to push down firmly near the net center, to release the system hysteresis, and the cord moves smoothly from then on.


April 8, 2011:  We shipped a pre-production TNT Gauge (P8B) to the International Tennis Federation today, for their testing.  ITF will review the test results in their May meeting of the Technical Commission.  It would have been even more exciting if I could present it to them in person... in London.  They only want to test it for accuracy and repeatability, which have proven to be excellent.
I had a very informative phone call today with the lab testing guy at USTA, who is excited to see the product.


April 7, 2011:  Downloads from the USTA Annual Meeting last weekend indicate very positive comments about the product's potential, from the USTA Competition people and members of the Technical Committee.  They're deferring formal tests to ITF, who make the Rules of Tennis.

At East Tennessee Scale Works this morning, we tested 3 pre-production TNT Gauges (P8x) at 200, 300, and 500 pounds.  The indicated force was dead on, so they provided a "no error" certificate of conformity -- a validation of the accuracy!

More of the history will be added, but the latest is added at the top!

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Court Report
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MP3 audio file [331.7 KB]
News Sentinel article
Adobe Acrobat document [434.4 KB]
MP3 audio file [5.7 MB]
Adobe Acrobat document [471.3 KB]
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"TNT Gauge", "TNT Gauge Pro", "Tight Right", "Set Right", and "Tempo Right" are trademarks. Sports Net Tension Gauges are protected by US Patent No. 8,806,952; other patents pending. c2011-2018 David Glass