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Discussion Starter #1
Could anyone advise me what the effect of the top cam lagging behind the bottom cam would be. i.e, vibration, poor grouping, noisy bow etc.
i'm currently shooting 55lb ultratec, 29.5 inch draw and top cam appears to be lagging and i'm suffering all the above problems plus more.

also what would the recomended arrow spine be, 3.39 acc shoot approx 2-3 feet left at 50 to 60 yards when centre shot and sight all in line. could this be incorrect spine or just poor setup.

thanks.
 

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I have the same rig and if the top cam is underrotated you will get noise and vibration and also the draw valley will jerk the string out of your hand. You probably have factory strings that have stretched and need to be tightened up or replaced. The buss cable needs a twist or two. I use 2216 aluminum.
 

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Here you go ........



Hybrid Cam Sync & Timing
By Mike Javi.... Cooper



The timing system on the hybrid cams is somewhat different from other systems.

The cams need to be in synchronization and in draw stop timing; these are two entirely different issues but interconnected. It is possible to have the cams in sync, but not in time and visa versa.

The string is for all practical purposes, just along for the ride, the buss cable (yoke) controls the bow, and it is used to set the axle to axle (limb) preload and takes most of the weight of the limb deflection at full draw. The control cable (slave) ties the two cams together so that they rotate at the required speeds.

The reference marks or holes (depending on the cam) are there to provide a visual reference to cam synchronization not draw stop timing. I find that tiller is a more precise indicator of cam sync; if the limbs are bottomed out the tiller will reflect the position of the cams better than the reference holes (marks).

To adjust the cams, I back the string off until I’m sure it isn’t affecting the axle to axle (usually ten twists will do) then adjust the buss cable to bring the axle to axle measurement to a ¼” longer than the specifications for that particular cam/limb combination (see Hoyt tune charts). 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 (limbs bottomed out).

Now is the time to adjust the draw stop timing, using a draw board or similar device (you can draw the bow and have someone else look at the cams) 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, I determine which I do by the draw weight and draw length of the bow. Shortening the buss cable will lengthen the draw and increase the draw weight. Shortening the control cable will decrease the draw length and decrease the draw weight.

At this point, I measure the draw length (using AMO standards); it should be long and the draw weight should be higher than spec for the bow. I will then twist the string to bring the draw length to spec; this should also bring the draw weight and axle to axle into spec.

I double check everything and tweak a half twist here or there to fine tune it.

Finally I use the hybrid cam creep tuning method to set the bow to my shooting style.

If you follow this method you will have a very solid wall and the bow will be practically vibration free.

A note: the regular cam & ½ should be tuned in the “D” draw length slot for best performance. You can then set the module to your required DL and tweak the DL using the string.
__________________
The eye follows the mind, the arm follows the eye. Focus with your mind the arrow will follow.


Javi....

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Discussion Starter #6
thanks for the replies,
i'm relatively new to compound shooting, and have a new ultratec, i recently noticed the top cam seems to be lagging the bottom cam.
after measuring a few setting, a-a is 37 7/8", chart shows should be 37 1/2", B/H currenty 7 1/4", chart shows should be 7".
having never attempted to adjust cables or strings before was after some guidance on what to adjust as a first attempt to see if i can bring back into align without making too many changes.
from what i read, it would seem a twist or 2 on the bus cable will bring the cam timing back, and a-a down a bit (3/8" maybe not?).
but how will i get the b/h to 7", as string already seems too long (only a few twists (maybe 10). bow has always been a bit noisy probably because of poor setup.
 

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I would take it to a pro shop and have them look at it. If you are relatively new to compounds then you probably dont have the equipment to do it with.
Just my opinion.
 

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Well, I would also suggest you look at the manual. It is available online.

The top cam is a slave to the bottom. So, if you adjust the control cable it affects the top cam. If you adjust the buss cable it affect both. The string keeps the settings of the two cams.
 

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Discussion Starter #10
had a go at this last night, 5 twists in bus cable brought cam timing back, sync seems ok as alignment holes on cams are still about the same. slight difference in position, but both holes are over the string.
but a2a and BH both about 3/8" too long.
From what i read twisting string will bring a2a down, but will take BH up.
any suggestions.
this is the first time i have attempted any adjustments on the string/cables on a compound so please forgive what may sound like silly questions.

Another quicky, used a bowmaster portable press, with the large #6 cams on my bow the split limb adapters actually touch the string until the bow is compressed quite a way, is this ok?

many thanks.
 

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Discussion Starter #11
forgot to ask, what is the affect of doing any tuning with limbs not wound fully in, if both were wound out an equal amount (at my shooting weight) how would this affect anything.
And if timing and sync were set on the D setting (where i shoot) why is this not be better than doing it on E, then putting it back to D?
sorry probably another couple of silly questions, but if i dont ask i'll never know.

thanks.
 

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scruffy, BH cannot be corrected measured unless limbs are fully down. Turning the limbs out will slightly affect BH and ATA. You most likely should tune your bow in the D slot. Go to the hoyt tune charts and you can check that.
When I used a Bowmaster I had the same thing with the string and the adaptor, that is common.



Mark
 

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If you put the Bowmaster split limb adapter under the string and then over the limb tips it seems to work much better. There's still some contact with the cables but it eases off fairly quickly.
 
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