Home  Home
   
Forum  Forum
FAQ  FAQ     Search  Search     Downloads  Downloads     Memberlist  Memberlist     Usergroups  Usergroups
Private Messages  Log in to check your private messages  
Register  Register   Log in  Log in  


Post new topic  Reply to topic Goto page 1, 2  Next
 Trackman Numbers... « View previous topic :: View next topic » 
Author Message
Anthony
PostPosted: Thu Jan 17, 2008 10:15 am    Post subject: Trackman Numbers... Reply with quote

Trusted user

Joined: 11 Jun 2007
Posts: 19

Hello Once Again,

Winter is still with us, but it won't be long now - 5-6 weeks.

Anyhow, I reieved a spam e-mail from Trackman yesterday. In it there was an article concerning AOA. Boiled down, they say that for 2 drivers swinging at 90 mph - one with a 5 degree AOA and the other with a -5 degree AOA that their optimum launch parameters are;

*-5 deg: 10 degrees/3100 rpm

*5 deg: 16 degrees/2200 rpm

I do not come up with numbers as iseal using trajectoware especially trying to keep the descent angle somewhere in the 35-40 degree range.
Any thoughts?
Back to top
View user's profile Send private message
dtutelman
PostPosted: Thu Jan 17, 2008 2:32 pm    Post subject: Re: Trackman Numbers... Reply with quote

Site Admin

Joined: 09 Apr 2007
Posts: 105
Location: New Jersey, USA

Anthony wrote:
Winter is still with us, but it won't be long now - 5-6 weeks.

Anthony, you're from New Jersey, right? Why wait 5-6 weeks? I live in NJ, too. Yesterday I played (walked) 29 holes at Bey Lea Golf Course in Toms River. A little cold and windy, true, but isn't that what the Scots had in mind?

Quote:
Anyhow, I reieved a spam e-mail from Trackman yesterday. In it there was an article concerning AOA. Boiled down, they say that for 2 drivers swinging at 90 mph - one with a 5 degree AOA and the other with a -5 degree AOA that their optimum launch parameters are;

*-5 deg: 10 degrees/3100 rpm

*5 deg: 16 degrees/2200 rpm

I do not come up with numbers as iseal using trajectoware especially trying to keep the descent angle somewhere in the 35-40 degree range.
Any thoughts?

I do not get what they did either. I got slightly lower launch angles (1-1.5 deg lower) and considerably higher spins (800-900 rpm higher).

I tried a few other things, and even had trouble understanding their results, much less duplicating them.

For those who want to try it on their own copy of TrajectoWare, here's what I did:

(1) I set the clubhead speed at 90mph and the angle of attack at +5 or -5. Then I varied the loft to find the maximum carry. Those are the numbers I reported above.

(2) At Anthony's suggestion, I reduced the loft (to reduce angle of descent) enough to lose just one yard of carry (assuming I'd get back more than that in runout). This brought down the launch angle 1* and the spin 200rpm. That's a move away from what Anthony attributes to Trackman.

(3) I set the clubhead speed and AoA, then -- leaving the ball speed the same -- changed the launch angle and spin to the Trackman numbers. The overall carry didn't change much, just a fraction of a yard. But... Don't forget that TrajectoWare Drive computes back the AoA and loft if you change launch angle and spin. The result was an Angle of Attack that was much higher than the initial +5 and -5.

What might have caused the difference? I don't know. It's probably too much of a difference to be due to the ball. It's almost certainly too much to be due to a head/shaft that is higher launch and lower spin than the "typical" built into TrajectoWare Drive. Bottom line: I still don't know.

Cheers!
DaveT
Back to top
View user's profile Send private message Visit poster's website
dtutelman
PostPosted: Thu Jan 17, 2008 3:13 pm    Post subject: Re: Trackman Numbers... Reply with quote

Site Admin

Joined: 09 Apr 2007
Posts: 105
Location: New Jersey, USA

A couple of additional points....

(1) There's an amazing amount of misinformation about trajectory, even in the minds of people who should know better! On television this weekend, Nick Faldo made a statement that is just plain wrong, but probably believed by every TV golf commentator. (BTW, I like Faldo, and feel he gets it right more often than most of the talking heads, especially Kostis.)

During a break in the action, Faldo showed a segment from the Pro-Am earlier in the week. It had Kevin James (a TV actor) hit a driver, with some Trackman data. The data was something like:

  • Ball speed = 140mph
  • Launch angle = 5.5*
  • Spin = 3900rpm

Faldo's reaction was, "Wow, he has to get that spin down!"

Wrong! With a 5.5* launch angle, any reduction of spin will LOSE distance, not gain it. First he needs to get his launch angle up to a reasonable number. Then, and only then, will a reduction of spin help.

You can play with this in TrajectoWare Drive yourself to get a better feel for it.


(2) Anthony, please tell me more...

Anthony wrote:
... I reieved a spam e-mail from Trackman yesterday. In it there was an article concerning AOA. Boiled down...

Questions:

  • Was this an email from Trackman? Or from a Trackman dealer? Or from some other organization? Who?
  • If you don't boil it down, what does it say? I'd really like to know what they did. If you can't or don't want to post it to the forum, please send their whole message to me in a private message.


Thanks.
DaveT
Back to top
View user's profile Send private message Visit poster's website
fschmidberger
PostPosted: Thu Jan 17, 2008 3:40 pm    Post subject: Reply with quote

Site Admin

Joined: 10 Apr 2007
Posts: 57
Location: Ravensburg, Germany

Hi Dave,

it's probably this document, Anthony is talking about: Trackman newsletter

Cheers
Frank
Back to top
View user's profile Send private message
dtutelman
PostPosted: Thu Jan 17, 2008 4:44 pm    Post subject: Reply with quote

Site Admin

Joined: 09 Apr 2007
Posts: 105
Location: New Jersey, USA

fschmidberger wrote:
it's probably this document, Anthony is talking about: Trackman newsletter
Frank

Thanks, Frank!

Very interesting article. (It's the second article in the newsletter, the one by Fredrik Tuxen on "Focus: Attack Angle".) I agree with many of his points, if not with all his numbers. Here are a few points perhaps worth discussing further:

  1. I cannot duplicate his numbers, for the particular angles of attack that Anthony pointed out. (Bottom of the first page of the article, page 03 of the newsletter.) If I hold the clubhead speed at 90mph and the angle of attack at +5 or -5, I can only get one of the other three parameters Tuxen cites (loft, launch angle, spin) at a time. I can't even get two of the others together, much less all three. That means that his formula for going from impact conditions to launch conditions are very different from mine. VERY different! I don't know what his are. Mine are spelled out -- together with corroborating data in http://www.tutelman.com/golf/design/swing2.php#launch
  2. In Tuxen's article, he speaks about two different lofts, which he calls "spin loft" and "dynamic loft". To confuse matters further, our (TrajectoWare's) "dynamic loft" is Tuxen's "spin loft". Bear that in mind when reading his article.
  3. I was very surprised at the magnitude of the attack angles (both positive and negative) generated by the pros. I don't have any data to dispute them, but I do have a few points of reference to put them into perspective:

    • He cites a few pros who achieve an angle of attack between 8 and 10 degrees. Think about the geometry this would require. For an 8* AoA on a driver, you'd need the ball to be struck 6" after the clubhead passes the lowest point of the swing. Not impossible at all, but it is a lot. (BTW, the 6" is kind of a minimum number. It assumes a relatively short 44" driver and the hands motionless at impact. With more realistic assumptions, it's probably more like 7" or 8".)
    • If such large positive angles of attack were possible to get efficiently (that is, without much loss of clubhead speed), you would certainly think the long drive champs would be doing it. But the two measured points of long drive data in my article at http://www.tutelman.com/golf/clubs/CompareTrajectoryPrograms.php
      show angles of attack under 1 degree. These competitors (Zuback and Lastowka) apparently felt that they were willing to accept less-than-optimal launch angle and more-than-optimal spin, and it got them to the ReMax finals in 2006.


Food for thought,
DaveT
Back to top
View user's profile Send private message Visit poster's website
Anthony
PostPosted: Thu Jan 17, 2008 7:28 pm    Post subject: Reply with quote

Trusted user

Joined: 11 Jun 2007
Posts: 19

Man you are quick,

Thanks for the prompt respones.

First off, I am not the golfing machine that you are and therefore have not been out, but during that short warm spell I did manage to get the Zelocity out and later visit the putting green. This is the time of year when I usually spend more time formulating all my screwball golf ideas for the upcoming season. Currently I'm putting out some feelers to see if I can put together a "tour van" of sorts and have some regular visits at the local links. Unfortunately, I think everyone is at the PGA show. In the meantime, I will be in attendance at a 2 day USGA rules class in beautiful Far Hills, NJ at the end of this month.

As for the article, the one that Frank linked is the one I recieved in the mail - only I recieved the html version.

Finally, I'm glad to see I'm not the only one having issues with this. One thing I wonder about though. Is was my understanding that the trackman tracks the ball the whole flight. If this is the case, are they still very dependent on formulas for their solution? I would think they are and still have a margin for error although I,m sure their PR folks would never admit it. I had heard somewhere that for some parameters, the Zelocity was actually more accurate than the trackman-although I don't remember which ones.
Back to top
View user's profile Send private message
dtutelman
PostPosted: Thu Jan 17, 2008 8:57 pm    Post subject: Reply with quote

Site Admin

Joined: 09 Apr 2007
Posts: 105
Location: New Jersey, USA

Anthony wrote:
First off, I am not the golfing machine that you are and therefore have not been out, but during that short warm spell I did manage to get the Zelocity out and later visit the putting green.

Hey, I'm 66 years old. I had to drop out of the volleyball league over a dozen years ago. In the winter, golf is my main exercise -- except when shoveling snow has to be my exercise. Smile

Quote:
I will be in attendance at a 2 day USGA rules class in beautiful Far Hills, NJ at the end of this month.

A friend of mine, David Hayes, teaches a lot of those. If you run into him, tell him I said "hi".

Quote:
One thing I wonder about though. Is was my understanding that the trackman tracks the ball the whole flight. If this is the case, are they still very dependent on formulas for their solution? I would think they are and still have a margin for error although I,m sure their PR folks would never admit it. I had heard somewhere that for some parameters, the Zelocity was actually more accurate than the trackman-although I don't remember which ones.

The Trackman uses doppler radar to track the ball in flight. That means they should be very reliable for ball speed, launch angle, carry, maximum altitude, angle of descent, total distance, and other things that depend on where the ball is at any given moment.

I don't know how they get spin or impact parameters. They may have to do that from formula. They might use the radar for clubhead speed and even angle of attack (though the latter might be hard). Loft and spin are probably either computed or measured by something other than the radar.

Does anybody have any real facts about this?

Cheers!
DaveT
Back to top
View user's profile Send private message Visit poster's website
Anthony
PostPosted: Fri Jan 18, 2008 11:38 pm    Post subject: Reply with quote

Trusted user

Joined: 11 Jun 2007
Posts: 19

Here is the info that came with my Zelocity regarding spin measurement:

Ball Spin is the total spin in revolutions per minute (RPM) that a golf ball rotates around a single axis. Total spin is predominantly comprised of back spin but to achieve pure back spin the golf ball would need to be perfectly struck with zero movement in either direction (i.e. perfectly straight). Since this rarely occurs, the club imparts varying amounts of side spin when the club is either open or closed at impact. The open or closed club face starts the ball on an offline path which thereby offsets the axis of the golf ball from being perfectly straight to having a tilt.

Note: The PureLaunch™ Doppler radar technology measures the entire golf ball as it leaves the clubface after being struck. When a golf ball is struck the top part of the ball moves faster than the bottom part of the ball as it reaches maximum velocity after impact. Radar technology is able to measure the delta of speed between the top and bottom of the ball which is used to determine the spin rate of the golf ball during its flight.
The PureLaunch™ Doppler radar technology collects approximately 100,000 readings per second on the golf ball as it travels. The radar tracks the ball to various lengths which are dependent on ball velocity. The higher the ball velocity, the longer the radar tracks the ball to ensure the initial launch readings are accurate. These “measured” readings of the difference in speed from one part of the ball to the other are used to determine the spin rate, ball velocity and spin rate decay as the ball travels.

The PureLaunch™ relies primarily on the spin measurements when tracking the golf ball outdoors over a significant number of yards. Indoors, the PureLaunch™ can only collect data based on how much ball flight room is available and therefore must use the measured spin values along with additional calculations to determine a correct ball spin. The indoor readings are remarkably close to those achieved outdoors.
Back to top
View user's profile Send private message
dtutelman
PostPosted: Sat Jan 19, 2008 2:34 am    Post subject: Reply with quote

Site Admin

Joined: 09 Apr 2007
Posts: 105
Location: New Jersey, USA

Anthony wrote:
Note: The PureLaunch™ Doppler radar technology measures the entire golf ball as it leaves the clubface after being struck. When a golf ball is struck the top part of the ball moves faster than the bottom part of the ball as it reaches maximum velocity after impact. Radar technology is able to measure the delta of speed between the top and bottom of the ball which is used to determine the spin rate of the golf ball during its flight.

That's VERY cool!
(Though they got the top and bottom backwards. A ball with backspin has the bottom moving faster.)

I didn't think they could get tangent-velocity readings from a spinning golf ball. If they can, then they can certainly measure total spin. It depends on golf balls all being the same diameter, but they are all within a percent or two anyway.

I guess I should have accepted that research assistantship Doc Edgerton offered me back in 1962. Then I'd know all that good stuff about radar. Smile But, at the time, I was preparing for a career in computers and telecom. Now, retired from 40 years of computers and telecom and doing golf club engineering, it would help to know the things he was working on.


Quote:
The PureLaunch™ relies primarily on the spin measurements when tracking the golf ball outdoors over a significant number of yards.

Also very interesting.

Thanks,
DaveT
Back to top
View user's profile Send private message Visit poster's website
Anthony
PostPosted: Sat Jan 19, 2008 11:42 pm    Post subject: Reply with quote

Trusted user

Joined: 11 Jun 2007
Posts: 19

Well that's what they claim they are doing anyhow. Who really knows.

Another question I have for those radar guys is "I wonder why the trackman can track the ball its whole length and the Zelocity makes no claim as to that". I guess a stronger radar.

And a final note, I think Trackman claims to read spin the whole time because I remember an article, I think Tom Wishon, who said that although higher lofted wedges spun the ball a whole lot more initially, by the time they landed there wasn't that much of a difference in there spin rate.

Happy MLK Day.
Back to top
View user's profile Send private message
NYKnuckleballer
PostPosted: Thu Jan 24, 2008 5:27 pm    Post subject: Reply with quote

Trusted user

Joined: 17 Apr 2007
Posts: 19

[quote="dtutelman"]
Anthony wrote:
Note:
Quote:
The PureLaunch™ relies primarily on the spin measurements when tracking the golf ball outdoors over a significant number of yards.


Also very interesting.

Thanks,
DaveT


Per some convos with Leith Anderson of Max Out Labs, his feeling is that no radar based LMs can track spin to a high degree.

Paraphrasing some words of his from memory, prior to October of so of last year - before Trackman upgraded some software - a reflective strip was required for indoor use with the Trackman.

Spin readings outdoors were always north of the readings indoors. Per his estimates, we're talking to the tune of 3,000 rpms outside, 2,500 rpms inside. Some of his outdoor readings were with skilled golfers, hitting low bullets that were turning over. Hardly the shot shape of a typical drive with spin readings north of 3,000 rpms.

These convos all took past late in the summer last year. I've heard from the PGA show and those shopping for new monitors for their businesses, a lot of upgrades are coming down the pike this year....so the above info may be inaccurate going forward.

That's it. I'm out of ammo.

Later,
David
Back to top
View user's profile Send private message Send e-mail
NYKnuckleballer
PostPosted: Thu Jan 24, 2008 5:47 pm    Post subject: Trackman inventor says.... Reply with quote

Trusted user

Joined: 17 Apr 2007
Posts: 19

Have you found any discoveries during your investigations of attack angle?

Yes! It turns out that if you hit down or up on the ball with the same club, the spin rate will be more or less identical if you impact the ball on the same spot on the face. This is in contradiction to the myth saying that hitting down on the ball increases the spin rate.


Frank and I have a conversation about this last summer as well. He stated that the only factors that effect spin off the driver are loft at impact or "dynamic loft", speed, and COG effects. I countered with what about the "increased friction" that may occur from a downward angle of attack. He said no. Laughing I thought you were crazy. Looks like you were right! Kudos.

Later,
David
Back to top
View user's profile Send private message Send e-mail
Clubdoctor
PostPosted: Wed Jul 23, 2008 7:08 pm    Post subject: Reply with quote

Trusted user

Joined: 01 Jul 2007
Posts: 8
Location: England

DaveT:

I logged in to the site for the first time for many moons and came across this thread.

Don't take this as a criticism (because I think that the software you & Frank have created is REALLY good), but what you and others seem to overlook when comparing, as in this case, TrackMan (or indeed other LM data) with the outputs from TrajectoWare drive for various inputs, is that I believe you have modelled only one type, or even only one model, of golfball.

Some years ago, comparative golfball data was available FREE via the equip2golf website; now it has 'gone commercial' and a subscription to their Golf Ball Selector service is required.

However, fortuitously I came across a still-active link to one of their old test results pages - go to:

http://www.equip2golf.com/oldsite/news/2002/2002golfballreport.html.

Balls are in three groups (Premium, Mid Range & Budget), and various balls in each group are tested for, amongst other things, spin & launch angle for a standard driver, #6i and wedge.

If you look at the driver data for premium golfballs, for example, you will find that the spin rates for different makes/models of ball for the SAME driver and the SAME clubhead speed vary by over 900 rpm (from 2765 - 3678 rpm).

Similarly, the Launch Angles vary by 1.5º (from 15.7º - 17.2º), again for the SAME driver & clubhead speed.

The data is some years old (2002), but I cannot see any reason to suppose that different golf balls now launch & spin the same for the same impact conditions.

IOW, it strikes me that it is perfectly possible for the Trackman data to be valid, even if you can't exactly replicate it with TrajectoWare Drive.

Richard Kempton

PS I can certainly confirm from personal observation that different golfballs can launch on visibly different angles with wedges.

Some years back, I picked out 6 balls at random from my practice bag and hit them into my net with a SW. Five hit the net near the top, but one was a good 3ft lower, which I put down to a bad swing.

I raked all 6 balls back and hit them again - same result: one ball launched about 3ft lower and again, I assumed it had been a bad swing. When it happened a third time, I marked the one that launched low.

It wasn't my swing - that ball DID launch consistently lower than the others; 3ft lower flight in something like 8-10 ft of travel is a LOT ....
Back to top
View user's profile Send private message
Clubdoctor
PostPosted: Wed Jul 23, 2008 8:56 pm    Post subject: Reply with quote

Trusted user

Joined: 01 Jul 2007
Posts: 8
Location: England

dtutelman wrote:
Anthony wrote:
Note: The PureLaunch™ Doppler radar technology measures the entire golf ball as it leaves the clubface after being struck. When a golf ball is struck the top part of the ball moves faster than the bottom part of the ball as it reaches maximum velocity after impact. Radar technology is able to measure the delta of speed between the top and bottom of the ball which is used to determine the spin rate of the golf ball during its flight.

That's VERY cool!
(Though they got the top and bottom backwards. A ball with backspin has the bottom moving faster.)


Er ... I'm confused. Wouldn't that depend on how one interprets 'moving faster'?

Strictly speaking, I guess that the top of a spinning golf ball will be rotating at the same rate as the bottom about its centre, so I presume that you are referring to the speed of rotation relative to the direction in which the ball is travelling.

OTOH, if Zelocity mean that the AIR (what I think is called the 'boundary layer'?) is moving faster over the top of the ball than it is over the bottom, isn't that what creates the lift that keeps the ball in the air?
_________________
Richard Kempton
Back to top
View user's profile Send private message
dtutelman
PostPosted: Wed Jul 23, 2008 9:53 pm    Post subject: Reply with quote

Site Admin

Joined: 09 Apr 2007
Posts: 105
Location: New Jersey, USA

Hi, Richard, and welcome!

First, about the variation with the model of ball...
We discussed this in a different thread. We recognize that there is variation with the ball, which the program does not address. It is on our list -- but probably not for the next release. And who knows when that will be; Frank and I are pretty busy these days with other things.

That said, I have gotten feedback from real live golfers, that says TrajectoWare Drive gives results that agree with their experience. Just this weekend, a clubmaker phoned me to remark how closely the program's output matched TrackMan data he took the previous day.

On to the other issue...
Clubdoctor wrote:
dtutelman wrote:
Anthony wrote:
Note: The PureLaunch™ Doppler radar technology measures the entire golf ball as it leaves the clubface after being struck. When a golf ball is struck the top part of the ball moves faster than the bottom part of the ball as it reaches maximum velocity after impact. Radar technology is able to measure the delta of speed between the top and bottom of the ball which is used to determine the spin rate of the golf ball during its flight.

That's VERY cool!
(Though they got the top and bottom backwards. A ball with backspin has the bottom moving faster.)


Er ... I'm confused. Wouldn't that depend on how one interprets 'moving faster'?

Nope!

We're talking specifically about spin measurement using doppler radar, which measures velocity. So the interpretation is determined. It is the difference in speed between the top of the ball and the bottom of the ball, those two speeds measured relative to the fixed radar antenna. When a ball has backspin, the bottom is moving faster (away from the radar antenna) than the top.

Hope this clarifies it.

DaveT
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic  Reply to topic Goto page 1, 2  Next Page 1 of 2

Jump to:  



You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


DAJ Glass (1.0.9) template by Dustin Baccetti
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © Frank Schmidberger and Dave Tutelman - 2007