Flat nock travel

geoffretired

Supporter
Supporter
I assume flat nock travel is a good thing.Perfectly matched wheels/cams with perfectly matched limbs should do the trick so long as the wheels/cams are timed properly.( that's just an assumption)
One cam bows, I think, were an attempt to remove the worry of having wheels out of sync. Hybrid cams were another attempt to keep the cams in time with each other all through the power stroke( neither could get ahead or behind by the way they are connected)
However, one cable links to the limb and it seems this can upset the flatness. Is that because a limb mismatch can cause a geared up/ amplified mismatch on the one cam?
Binary cams are the next step. There are no cables attached to either limb.
Is this as good as it gets? I'm only curious, but I'd love to know!!
 

greydog

New member
The single cams still have a power cable which transfers the holding weight at full draw, and is attached to the top limb by a yoke, this is the cable that takes most of the 75% poundage you don't hold at full draw( depending on let off). Even though it's the only cable attached to a limb I don't think a limb mismatch will cause any problems as the cam is essentailly slaved to itself via the idler by the shooting string, which also acts as a control cable.
Nock travel is built into single cam bows at a specific point, so you'll usually get the flattest nock travel if your arrow lines up through the berger hole.

The hybrid system works in the same way, but the control cable is seperate, allowing you to fine tune nock travel, by way of changing the rotation of the cams in relation to each other. This allows you to have level nock travel below the berger hole if you wish, just creep tune the cams.

Binary cams take the limb yokes out of the mix but otherwise work like a twin cam, I think that they are supposed to be more efficient as their rotational energy is kept more within the system and you don't have to worry about cam lean. Of all of them, the binary would probably suffer most from a twisted limb as there's no yoke to straighten the limb tip, that said, you can only do that on the top limb of most single and hybrid cam bows anyway.

You can't go wrong with any of the systems on the market at the moment, it mainly comes down to how much you like to tinker :D
 

jerryRTD

Well-known member
IMO Oneidas have it right the cams are locked together by a steel cable they can not go out of sync. Any slight mismatch in the limbs causes a small power transfer through the timing cable to compensate and correct. There is no way the nock travel can deveiate with out breaking the control cable.
 

geoffretired

Supporter
Supporter
Thanks for the input. I like tinkering but I like to know the truth even more.
The Oneida is a great piece of kit, Jerry. I may give mine a second chance??
 

Marcus26

Well-known member
Nock travel is determined by the shape of the cam, not the cam type.
Of the bows I have tested the Bowtech Binary cams, Mathews Single cams and PSE/AR NRG cams have the straightest nock travel. The hybreds are pretty ordinary, but not bad, Hoyt's are not great. Of them all in order of preference I would take

Bowtech Binary/Mathews
PSE/AR single cam
CPS Cam
Hoyt Cam 1/2
PSE/AR hybred
Twin Cams
 

geoffretired

Supporter
Supporter
Marcus, You're back! I thought you would have an input if you were around.
Thanks. I understand what you say about the shape controlling nock travel. I was getting a bit confused over the different systems and how some gave better control in practice. All systems seem as if they should give flat nock travel until they are put to use. Is it just to do with accuracy in the forming of the profiles, or are there forces at work , like friction, that pulls one way more than another? Are some systems more able to resist these forces?
I just like to know.;):boggled:
 

Merlin Archery

New member
Ironman
There is a difference between describing nock travel as 'straight' and describing it as 'level'. A nock path which is both straight and level is the ideal, but is harder to achieve.

Of all cams designs, its easy to design a twin to give perfectly straight travel. i.e the nocking point travels without bumps or dips from brace height to full draw. (assuming they are synchronised at full draw) That is because the top and bottom cams are exact mirror images of each other. They are both wrapping up equal amounts of cable and bending the limbs the same. In fact, you have got to try pretty hard to design a twin cam not to give straight travel. However, nearly all conventional twins don't have level nock travel. It rises slightly as you draw. This is a combination of grip pressure below the centre of the bow and the draw point above centre. This can be corrected if need be by making the cams slightly different sizes.

Solocams and hybrids are another ball game. Much harder to get them straight. Even when Hybrids have string tracks that are identical does not mean they will create a straight path. This is because there is one power cable, and one control, or 'let out' cable. (The string on a solocam acts as the let out cable, as well as being a bowstring, but essentially they are doing the same thing) As the power cable wraps up around the power track the control cable is let out to rotate the top cam. (Or how much string is passed over the idler and at what speed) The power track is not a consistent shape and rotates at different rates through the draw, so judging how much, and at what point the control cable is let out is the hard part. This is why many hybrids and solocams, especially in the early days had terrible nocking point travel. You can also fit a pair of level travel cams on one bow, put them on another with different bow centres and they will cease to become level. Changing cam rotation and draw length can throw nock travel off. Poorly matched limbs create a curving effect to the nocking point as they bend different amounts through the draw.

A well designed hybrid, solo or twin cam can all give straight and level nocking point travel, but I have tested a lot of bows that claim straight and level, and I can tell you they are not. Another example of false advertising that seems to be the norm in the archery business.
 

geoffretired

Supporter
Supporter
Thanks for all that info,Ben. It is good to know these things, I find. I remember my Max 2000 had twin cams and I noticed the nock lifted at the end of the draw. I did a Heath Robinson on it and put a thin strip of tape in the top cam's groove. I thought that would make the
top cam slightly bigger so it would pay out more string from the top and lower it back down to equalise things. I think it levelled things a little.
 

Marcus26

Well-known member
It's purely based on how and when the cam feeds string during the draw cycle.
Remember, you have a cam shaped item feeding out string as you draw back, if not designed right it will give to much string and the nocking point will raise or not enough and fall.
As Ben said even if it is right, if you change the rollover charateristics of the draw it can throw that out.
Basically there are 3 parts to nock travel
1) How straight it is through the draw
2) How level it is through the draw
3) What it does as you pull harder into the wall

#1 will determine how easy the bow is to tune. People using a bow with a straight nock travel report that they usually get bullet holes out of the box.
#2 will determine nocking point height. If the nocking point angle up as you draw the bow you may well need a higher nocking point to clear your rest.
#3 is the accuracy one. If the nocking point moves up or down as you pull harder into the wall then you will get high-low shots depending on how you shot that shot. This is something you can tune out with a hybred or dual cam but are screwed if your single cam doesn't have straight travel at this point. (all modern singles are very good here though)

geoffretired said:
Marcus, You're back! I thought you would have an input if you were around.
Thanks. I understand what you say about the shape controlling nock travel. I was getting a bit confused over the different systems and how some gave better control in practice. All systems seem as if they should give flat nock travel until they are put to use. Is it just to do with accuracy in the forming of the profiles, or are there forces at work , like friction, that pulls one way more than another? Are some systems more able to resist these forces?
I just like to know.;):boggled:
 

geoffretired

Supporter
Supporter
Thanks again. I feel much better now. I knew there was a lot to this but it is good to get some much clarification. Thanks again
Geoff
 
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