# cam sync vs. stop timing???



## GCOD (Nov 24, 2006)

what kind of bow are you shooting


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## shooter76 (Nov 27, 2006)

oh....forgot to mention that.....hoyt vtec cam and half.

thanks


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## TailChaser (Aug 13, 2005)

I think bow manufacturers still design their cams like you are pulling them from the exact middle of the string, but you aren't, so it never works just right. I'd get them to stop at the same time, so they would be out of sync at full draw.


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## highdeehoo (Apr 10, 2005)

*Timing/Tuning*

Look at the sticky in bow tuning from Javi


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## shooter76 (Nov 27, 2006)

i read and did the sticky by javi but still cannot see how i can adjust one without adjusting the other. thanks


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## JAVI (Jun 19, 2003)

shooter76 said:


> i read and did the sticky by javi but still cannot see how i can adjust one without adjusting the other. thanks


Sit back and study the control cable... it moves the cams in oposite rotational directions and at different rates of rotation. Then look at the buss cable it only moves the bottom cam.. 


Now drink a cold one and think about this....


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## LEADWORKS (Apr 6, 2006)

thought about it, but was too drunk to get it. Break it down for us please Javi. I still don't understand how you can change the sync without changing the timing.


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## francis (Jan 18, 2003)

ttt


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## LEADWORKS (Apr 6, 2006)

to the tizzzzop


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## ymanarchery (Nov 10, 2006)

The bus cable hooks from the top limb to the bottom cam therfore only effecting that cam.The control cable hooks to both cams.Help me out Javi.Is this close?
Yman


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## shooter76 (Nov 27, 2006)

the only way i can see where the stop timing and cam synch could be adjusted separately is if the rotational speed can be differed between the two cams. i dont think this can be done.....hopefully somebody that knows the hoyt cams will chime in........oh javi...where art thou!!!


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## gad (May 8, 2006)

Same problem here with a hoyt powetech 2006. Draw stop are in time, but cams are not in sync.


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## JAVI (Jun 19, 2003)

ymanarchery said:


> The bus cable hooks from the top limb to the bottom cam therfore only effecting that cam.The control cable hooks to both cams.Help me out Javi.Is this close?
> Yman


Yep and the control cable is routed to affect the cams in opposite rotation and at different rates... 

Keep at it guys... if you look hard enough you'll figure it out...

another hint.. measure the distance from the nock to the top axle and compare it to the distance to the bottom axle.


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## nccrutch (Feb 26, 2003)

I'm just about ready to call BS on this whole "timing"/"sync" issue. I've read thru that "sticky" for over a year now and it still doesn't seem right. It says:

"The control cable should be used to sync the rotation of the cams while doing this. If the cams are in sync at this point the reference holes will be equidistance from their respective cables and the tiller will be even".

OK, i've got that part. Now the cams are "in sync". Well now we go to "draw stop timing" and it says:

"using a draw board or similar device, when the bottom cam’s draw stop is just touching the buss cable, the control cable should lay flat in the groove of the top cam. If the cam is under rotated you can put a twist in the buss or untwist the control".

Now if i do this, and make adjustment to the control cable to get the stop right, then how can the sync remain the same?


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## JAVI (Jun 19, 2003)

nccrutch said:


> I'm just about ready to call BS on this whole "timing"/"sync" issue. I've read thru that "sticky" for over a year now and it still doesn't seem right. It says:
> 
> "The control cable should be used to sync the rotation of the cams while doing this. If the cams are in sync at this point the reference holes will be equidistance from their respective cables and the tiller will be even".
> 
> ...


You're right it is just a cruel joke...


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## shooter76 (Nov 27, 2006)

ok.....when i look at those cams and cables it looks so simple yet there are a million of things going on there. my brain is overloaded now!!! why cant this stuff be more simple!:twitch:


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## JAVI (Jun 19, 2003)

shooter76 said:


> ok.....when i look at those cams and cables it looks so simple yet there are a million of things going on there. my brain is overloaded now!!! why cant this stuff be more simple!:twitch:


Then anyone could do it... 

Now get a piece of string and starting at the peg the string is hooked on wrap it around the cam until you get to the juncture where the string leaves the cam... do this on both cams... and measure the difference.


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## gad (May 8, 2006)

JAVI said:


> Yep and the control cable is routed to affect the cams in opposite rotation and at different rates...
> 
> Keep at it guys... if you look hard enough you'll figure it out...
> 
> another hint.. measure the distance from the nock to the top axle and compare it to the distance to the bottom axle.


The distance between the nock to the top axle and to the bottom axle on my powertech is about 1 inch less to the top. ukey: 
So the cams are not in synch but the draw stop is ok. How it could affect my shooting?


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## JAVI (Jun 19, 2003)

gad said:


> The distance between the nock to the top axle and to the bottom axle on my powertech is about 1 inch less to the top. ukey:
> So the cams are not in synch but the draw stop is ok. How it could affect my shooting?


The original cam & 1/2 didn't have draw stops... it relied solely on synchronization of the cam rollover (start of a certain location on both cams) .. Think of it as the timing of the cam and crankshaft in a motor.. Two different diameters which must rotate at different speeds, but be in synchronization for the motor to operate to peak efficiency.


Explain to me again why I need to defend my post....


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## Campo (Sep 20, 2006)

*A little clarification Javi...*

First of all, I would like to say "Thank you" to Javi for posting all this info.
I too am confused about the correlation and correction between stop and sync.

One question though....If you were to paper tune a bow from very close, and get a perfect tear, does this mean that the cams are in sync and stopping in the right location? Or do you still have to run the diagnostics in order to figure out if something is going on?

I am about to try and get my vector cams in tune this weekend, and any additional information you could give would be most excellent!


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## JAVI (Jun 19, 2003)

Campo said:


> First of all, I would like to say "Thank you" to Javi for posting all this info.
> I too am confused about the correlation and correction between stop and sync.
> 
> One question though....If you were to paper tune a bow from very close, and get a perfect tear, does this mean that the cams are in sync and stopping in the right location? Or do you still have to run the diagnostics in order to figure out if something is going on?
> ...


When I tune a hybrid cam bow I look for four things; cam synchronization, draw stop timing, draw weight and draw length all other measurements are only reference and a good starting point. Once I have those items set to the way I hold the bow, (and yes draw stop timing is affected by how you set your grip, and nock point) I will set my rest height and center-shot position and depending on my mood and available time I might shoot through paper to see if I have any gross problems. If not I proceed to walk-back or French tuning and group tuning at various distances. For hybrid cam bows and two cam bows I recommend creep tuning after checking center-shot and nock height, but before proceeding to WB or group tuning. 

Of course this assumes I've done my due diligence and have a properly spined arrow with the correct rest set to the proper spring tension.


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## gad (May 8, 2006)

JAVI said:


> The original cam & 1/2 didn't have draw stops... it relied solely on synchronization of the cam rollover (start of a certain location on both cams) .. Think of it as the timing of the cam and crankshaft in a motor.. Two different diameters which must rotate at different speeds, but be in synchronization for the motor to operate to peak efficiency.
> 
> 
> Explain to me again why I need to defend my post....


Oh, sorry, I just mispelled when I said "draw stop". I want to say that both cams hit the cable at the same exact moment when reach full draw. But on the top cam, the cable lies inside the reference hole, on the bottom, it is far away about 5 mm from the reference hole.


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## LeEarl (Jun 1, 2002)

All of this cam&1/2 tuning, timing sync what ever makes me think back to the post Dave Cousins posted here back in 2002 (I think it was 02) about how this system shoots so well out of sync and how he could still hit the same spot at 60m with it out of sync. Just a little reading I found from the archives......

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This a brief excerpt from my report on the Cam&1/2 system:

Session 104 shows a high right grouping centered in the area of the X ring at 1 to 2 o?clock. When shooting this plot of 60 arrows I had taken notice of the bottom cam creeping out of time statically (cable attached to bottom cam was elongating). This started about 20 arrows in to the session and continued till the session of 60 arrows was complete. The bottom cam had moved .125? from its original position. Although the bottom cam had moved and was clearly out of time with the top cam I was unable to feel this difference when coming to full draw. It was also difficult to visually notice a timing difference in the cam system when approaching full draw. If I had been shooting my current bow set up with Command Cam+ this would be considered a major amount of cam movement and would be very evident when coming to full draw. A difference in impact point at the target would have been seen. I most likely would be shooting low and need to fix the timing problem as soon as possible to maintain proper impact point.
Before starting the second plot of 18 arrows (session 105) I pressed the bow and put six full twists in the cable yoke to bring the cam back to the mark. This made the cams in time statically but I was still unable to feel or see a difference in cam position coming to or at full draw.
Without changing any sight setting I proceeded to shoot and plot session 105. The plot shows a very small move down and to the left in the group centers. I found this to be very surprising when compared to the impact effects of the Command Cam+ going out of time and being set back into time. Simply put, I have not seen that much movement in any cam system I have ever shot and had similar impact results as the prototype cam!


Keep in mind this testing was done in very hot tempters with new strings. I?m not trying to tell you that the Cam&1/2 moves more that other cam systems. The new strings and high heat were necessary parts of the test in order to make the cam system move this much.

The sessions referred to in the above are Target Plot sessions for the palm hand held computer. The target used was a 60cm face at a distance of 60m. The size of the X-ring on a 60cm face is 3cm or a little over 1 inch. This should give you a little better idea of how much impact difference I?m talking about.

When was the last time you put 6 full twists in one yoke and still hit the same spot at 60m with your bow be it a two or one cam. Well I never have till now! And that?s a fact!

Get right down to you have got to get your hands on one and find out for your self!!!

Dave Cousins

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Just food for thought :shade:


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## JAVI (Jun 19, 2003)

See I told you it was a cruel joke...


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## LeEarl (Jun 1, 2002)

It was supposed to be such and easy system to shoot and maintain. What ever happen to that?

Javi, your right, there is way to get this system to shoot at its peak performance. Some just get way too worked up about it :shade:


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## JAVI (Jun 19, 2003)

Even completely out of tune the system will shoot better than most of the worriers, but it will also kick, buck, jump and make all kind of noises. But is very smooth, solid, and quite if properly tuned.  

It's still a cruel, cruel joke...:angel:


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## zenarch (Aug 3, 2002)

JAVI said:


> Even completely out of tune the system will shoot better than most of the worriers, but it will also kick, buck, jump and make all kind of noises. But is very smooth, solid, and quite if properly tuned.
> 
> It's still a cruel, cruel joke...:angel:


JAVI,
You're having way too much fun with this.   You're going to have to "switch back " (oops, dark side words) to Hoyt to get back your guru status.  
Joe B.


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## nccrutch (Feb 26, 2003)

zenarch said:


> JAVI,
> You're having way too much fun with this.   You're going to have to "switch back " (oops, dark side words) to Hoyt to get back your guru status.
> Joe B.



Yes! Even the hybrid gurus have switched to the single cam offerings.


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## JAVI (Jun 19, 2003)

nccrutch said:


> Yes! Even the hybrid gurus have switched to the single cam offerings.


On the serious side for a moment, before the rumors fly... My switching to a Mathews had nothing to do with the cam design.


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## JAVI (Jun 19, 2003)

zenarch said:


> JAVI,
> You're having way too much fun with this.   You're going to have to "switch back " (oops, dark side words) to Hoyt to get back your guru status.
> Joe B.


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## LeEarl (Jun 1, 2002)

Nice catch Javi :shade: 

Ohhhh and he is safe at home base :star:


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## LEADWORKS (Apr 6, 2006)

So, since the bottom cam is smaller than the top cam, there is a specific length of buss and control cable that will get the cams moving together at the same speed and hit the draw stops at the same time? So, there are many different cable lengths in which the draw stop timing is the same on top and bottom, but only one cable length sweet spot where both the rollover speed and timing coincide correctly?

And this is to account for the fact that the nock is above center on the Hoyt bow? Because the string needs to come out of the cam quicker on the top cam to give level nock travel. So, even if you don't get the sync perfect, you can compensate for it by putting your nock higher or lower on the string, and find the sweet spot that way?


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## LEADWORKS (Apr 6, 2006)

So, bottom line is, get the ATA and brace height into spec, and get the draw stop timing to coincide, and the cams will already be close enough in sync.

It seems to me, that the cams being in sync isn't really that influential on things. As long as the control cable is there, it's going to do it's job and control the rollover rate no matter how long or short it is set. The draw stop timing is more important. The hoyt manual says that it doesn't matter if the reference holes line up with the cables the same distance. But, if you have everything into spec, they will be.

This system is not easy to tune. Seems that there is a specific setting for your cables _and_ nock height that will give you perfect nock travel, and if you are off on either one, you get porpousing. So, you have to constantly tinker until you find the sweet spots.

What was wrong with the normal cam system with two identical cam sizes and buss cables that instigated a switch to a hybrid cam? The two regular cam bows I have tuned were very easy to tune, it took five minutes to get a perfect tear.


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## JAVI (Jun 19, 2003)

LEADWORKS said:


> So, bottom line is, get the ATA and brace height into spec, and get the draw stop timing to coincide, and the cams will already be close enough in sync.
> 
> It seems to me, that the cams being in sync isn't really that influential on things. As long as the control cable is there, it's going to do it's job and control the rollover rate no matter how long or short it is set. The draw stop timing is more important. The hoyt manual says that it doesn't matter if the reference holes line up with the cables the same distance. But, if you have everything into spec, they will be.
> 
> ...


Well... it takes me about 2 minutes to tune a cam & 1/2


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## LEADWORKS (Apr 6, 2006)

rub it in why don't you! LOL

Actually it probably wouldn't be such a pain if I had a real bowpress instead of the portable Bowmaster Press! Screwin that thing in and out is what takes so long, man I hate it.


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## NMP (Aug 6, 2003)

Anybody could tune their cam.5 that quickly with the right equipment.:shade: http://www.archerytalk.com/vb/showthread.php?t=414850


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## TX Bowhunter (Dec 13, 2004)

JAVI said:


> Well... it takes me about 2 minutes to tune a cam & 1/2


It's true I've seen it :eek2: :eek2:


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## LEADWORKS (Apr 6, 2006)

Tell me if you agree. It occurred to me that in the cam & 1/2 system, the control cable only works to keep the top cam in sync with the bottom cam, not the other way around. This is because of the way that the control cable is attached differently on the top cam and bottom cam. 

So, if the bottom cam is under rotated at release (or the top cam over rotated) and tries to roll over quicker than the top cam, the control cable will yank the top cam with it, so the bottom cam will pull the top cam up to the same speed.

Now if it happens the other way around, and the top cam is under rotated at release, the control cable will not be pulling the bottom cam with it. If anything, some tension will be taken off the control cable, and the system acts like a regular cam system with both cams moving independently.

This is significant in that when you are setting your cam timing, you would need to make sure that either both cams are hitting the stops at exactly the same time, or with the top cam slightly over rotated. The system only works to correct the situation where the top cam is over rotated, but won't do much to help if it's under rotated. I can see now how there could be a lot of bucking and vibration in this system if the cams are too far out of time.

Am I seeing things right?


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## shooter76 (Nov 27, 2006)

it makes sense to me



LEADWORKS said:


> Tell me if you agree. It occurred to me that in the cam & 1/2 system, the control cable only works to keep the top cam in sync with the bottom cam, not the other way around. This is because of the way that the control cable is attached differently on the top cam and bottom cam.
> 
> So, if the bottom cam is under rotated at release (or the top cam over rotated) and tries to roll over quicker than the top cam, the control cable will yank the top cam with it, so the bottom cam will pull the top cam up to the same speed.
> 
> ...


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## mntngrown (Sep 17, 2005)

*hybrid*

Today I set up a used Pearson Gen II that the seller told me was shooting great. I found the cam and control wheel on this bow were on different letter posts, the timing lines were not on the same letter and the control/ upper wheel had serious lean. I also determined that the slide was on backwards. I changed the draw length module for me, got the timing marks on, and twisted one side of the yoke to get the wheel lean out. I went to Javi's creep tuning section on the Pearson site and used the horizontal tape/ pull hard into the stop test after light pull shots. I was shooting bulls at 20, 30,40,and 50 in no time. I must agree with Le Earl and Mr. Cousins if the other guy thought it was shooting great the way I received it.


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## KenL (Dec 1, 2005)

04 UltraTec...cam 1/2...winners choice strings/cables....cam sync is good, draw stop is good, peak weight and draw length are correct, but the cables are a full 3/16" below the bottom of the timing holes. Is it possible this is correct?


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## francis (Jan 18, 2003)

KENL....

mine is the same way 

draw stop timing is good, but at rest both cams have the cables at quite a large disatnce from the timing holes

i cant get it any different, so I just decided that timing at full draw is what I figured is most important and just adjusted it for that

I am not using the original cables and string, maybe that has something to do with it i dont know?


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## LEADWORKS (Apr 6, 2006)

KenL said:


> 04 UltraTec...cam 1/2...winners choice strings/cables....cam sync is good, draw stop is good, peak weight and draw length are correct, but the cables are a full 3/16" below the bottom of the timing holes. Is it possible this is correct?


How about your Axle to Axle length and Brace Height? Are they to specs?


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## bassman409 (Jul 19, 2006)

Mine is 1/8 off the hole too! I was looking at the Hoyt manual on pg 17 and it says the cables will be off the holes slightly.


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## KenL (Dec 1, 2005)

My manual says they should at least be covering part of the holes. With the holes/cables the way they are.... the cams are very under-rotated, athough in sync.


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## LEADWORKS (Apr 6, 2006)

I agree, your axle to axle is probably not in spec either. If it's too short, untwist the cables and the string. If it's too long, twist up the cables and the string. Then tweak them to get the timing set again. If you lengthen the string and the cables at the same time, it shouldn't change your draw length and weight very much because the affects cancel each other out.


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## pyroarch57 (Jul 13, 2006)

LEADWORKS said:


> Tell me if you agree. It occurred to me that in the cam & 1/2 system, the control cable only works to keep the top cam in sync with the bottom cam, not the other way around. This is because of the way that the control cable is attached differently on the top cam and bottom cam.
> 
> So, if the bottom cam is under rotated at release (or the top cam over rotated) and tries to roll over quicker than the top cam, the control cable will yank the top cam with it, so the bottom cam will pull the top cam up to the same speed.
> 
> ...


 This may be of interest. To get zero nock travel at full draw my cables ended up at this position. But the top cam looks like this. Having both cables centred between marks gave me 10mm nock high travel.


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## shooter76 (Nov 27, 2006)

wow.....i would think that there is something wrong with that cam being overrotated like that.


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## pyroarch57 (Jul 13, 2006)

shooter76 said:


> wow.....i would think that there is something wrong with that cam being overrotated like that.


 yes, me too, on first thoughts, but i`m waiting for someone to prove that it is.


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