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As with all advice on this website, if you
are not comfortable or experienced with pressing and working on a bow,
take your bow to a proshop or have an experienced person help you. Compound
bow failures can be very dangerous and even fatal. Safety first!!
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.
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