c903

http://www.dartonarchery.com/Nock%20Travel.htm

Black Frog

Dave Barnsdale has started making some awesome new twin cams where the upper and lower cams wheels are slightly different diameters. And this is with a shoot-through cable system. The different diameters in the cams account for the upward slope of twin cam nock travel. I got to play with one a bit this past weekend, awesome bows.

Len in Maryland

FranK:

What video is showing you is how the system operates under the 'BEST' conditions. That is, shooting a bow out of a machine. The loose mechanical 'grip' will have a minimal affect and allow the rest of the bow to 'float' to compensate for nock travel problems. We all know that a shooting machine will shoot 'absolutely' better.

Now take into consideration the human element. Do you really think even a small percentage of archers shoot like a machine?

This is why I will stay with the test method I use. It compares bows, one to the other, and it therefore doesn't necessitate the interpolation of the human elements.

Don't get nock travel and nock positioning confused. Nock positioning is something that Dave Barnsdale is addressing when BF talked about different diameter cams. He is trying to get a TRUE center shot bow in both the 'X' and 'Y' axis. This will enhance overall performance and tuning.

Although the outcome of nock positioning can really be construed as nock travel, what we have always addressed as nock travel has been the added affect of caming.

I hope this helps you understand my reasoning better.

Black Frog

Len, you're correct.

Dave's new wheels seem to compensate for the difference between the true vertical center of the bow and the placement of the grip, but don't provide the level travel. My mistake! []

PABowhntr

Len,

Thank you for the response. Thank you c903 for the link.

I do have a question about this quote though. Wouldn't the loose mechanical grip more closely emulate what actually occurs when a person is shooting a bow as compared to a more fixed riser position device? I would think this would demonstrate a more realistic representation of what a typical shooter can expect in terms of how nock travel may affect accuracy.

I understand where a fixed position device like an Apple Tuning machine would be more useful when comparing two bows strictly from a mechanical/engineering standpoint but would it not loose some value when attempting to predict how any given bow would perform in the hands of a human shooter?

I apologize for the myriad of questions but this subject has me very interested lately.

Pinwheel 12

Frank-

There are many variables that CAN come into play, but most of the time the shooter is trying to emulate perfection, therefore we must have a constant with which to start and go from square one. if you put one bow in a machine that has dead-straight and level nock travel, and another that is terrible, they will both still shoot arrow after arrow into the same hole. You can take a bow that has a cam on one end, a wheel on the other, a straight limb of 50lbs on one end, and a recurve on the other at 80lbs, and still get a tune. Think about that for a minute![8D]

BUT, they hold and shoot like garbage. No forgiveness when actually held and felt by human hands. So when we come to the question of straight and level nock travel and what it can do for you as an individual, the answer is easy---it will make your shooting experience much more pleasant, regardless of your form or stature. Cam rotation is symmetrical, as is the limbtip travel back to brace. Paradox is effectively reduced to a minimum, which makes for a faster responding arrow, making it easier to tune, and more accurate downrange. Fixed blade broadheads will tune without incident when youa re not starting out high. low, or porpoising. We all remember why the mechanicals came to be so popular in the early to mid 90's, and it wasn't because they penetrate better! LOL Certain designs simply had terrible nock travel and thus it was very difficult to tune fixed blade heads.

Twin cams do not have straight and level nock travel. They have straight but not level. Solocams had terrible nock travel early on, but some designs that do not have modules or adjustments on the cam can exhibit S&LNT at CERTAIN drawlengths. Keep in mind there are few that do. Some of todays' hybrids offer the best nock travel in both planes I've tested to date, while others are really not that good. When choosing a cam design, one must take into account not just whether or not the bow exhibits S&LNT, but that it does so with everything working in tandem. Throw your preferred bow into a crankboard and run it out to full draw---pencil around the limbtips. Back it down about halfway, then pencil around your limbtips again. Let the bow down and measure between the marks. Is it the same? If so your bow is performing at it's best with everything working in tandem. Some of you may be surprised. when doing this simple test as to how some designs actually impair perfromance and accuracy by exhibiting poor dynamic balance during the shot.

That should keep you thinking for awhile. Good shooting, Pinwheel 12

Len in Maryland

Frank:

Quote: "Wouldn't the loose mechanical grip more closely emulate what actually occurs when a person is shooting a bow as compared to a more fixed riser position device?"

Really, how many archers really use a loose grip. That's something we're teaching constantly in the shop. A "typical shooter" does not utilize a loose grip. Also, the loose grip only partially compensates for the problem and makes it appear not to exist. And, just because you can't 'feel' it or 'see' it doesn't mean it doesn't exist in the mechanical world. How many bad arrows can't be seen by the average archer???

Quote: "I understand where a fixed position device like an Apple Tuning machine would be more useful when comparing two bows strictly from a mechanical/engineering standpoint...." Good, that's a start in truly understanding what I'm trying to convey.

Quote: "...but would it not loose some value when attempting to predict how any given bow would perform in the hands of a human shooter?" All bows "loose some value....in the hands of a human shooter." This is why I choose to analyse the basic mechanics in a bow.

This is why I made the statement above "Studying nock travel, unless you have the equipment and expertise, if a mind-blowing task and is not definable via this medium."

I really would like to explain this so that everyone understands the problem. It might be slightly possible if everyone was in a room for a live demonstration. But then you'd still have the nah-sayers who would expound on their personal feelings rather than try to understand the engineering data. It's a subject where it's so easy to arbitrarily disagree. You're more than welcome to stop by to see a demonstration and analyze the results of comparable tests.

PABowhntr

Kevin, Len,

Thank you for taking the time to answer my questions. I am going to continue to look into this issue wherever I can find good information like that which you both provided.

I will probably be down your way again next summer Len. Logan loves your shop.

jmac_or

The problem I have found is there is not much GOOD information around. I have been looking for weeks now and I have found bits here and there. I would love to see a technical paper or something done by independant testers using various bows of today, but it just is not there. Also, finding unbiased and unemotional information on the internet is at best a gamble, with your odds lying somewhere between slim and nil. My search goes on......

JMAC

Straightarrow

If we actually saw some engineering data, it would be much easier to understand the problem. Up until now, all I've seen are opinions and we all know how reliable opinions are and who has them. Even Darton's website info, although interesting, qualifies as nothing but a sales pitch. Unbiased engineering data would be a great start, but even then, one has to judge the validity of any concern, by real life experiences. If I was having tons of trouble tuning broadheads out of today's single cams, I'd be a lot more likely to think there was a significant advantage to one cam style over another. However, I'm not experiencing such problems. I'm willing to bet, that some day a technical report from an independent test on the importance of S&LNT will emerge and then we can all form our opinions on data, rather than on someone else's opinion.