Published by bowgod on 03 Apr 2008 at 02:47 pm
Here is VERY simple time tested method that I use for tuning most of the newer cam systems that Hoyt has introduced over the last few years. This method will also work with the popular cam 1/2 and cam 1/2+ systems as well as other hybrid cams (except binaries) with just the possiblility of a little more work than outlined here.
The fist thing that need to be is you need to determine all the advertised specs for your paticular bow/cam combination. (find all the specs on the hoyt tune charts under the customer service link on Hoyt’s web site) you need to know string and cable lengths as well as draw length, draw weight, axle to axle and brace height measurements. Write all the numbers down on a peice of paper and keep it handy.
Now onto the tuning process.
STEP 1: press the bow and remove the string and cables. You want to measure each cable and twist it down to where it measures 1/8 of an inch shorter than the listed lengths (be sure the string is straight and stretched out for this measurement often times the ends are still bent where the end serving wraps around the cam these need to be straightend). with each cable twisted 1/8 shorter than listed specs put the cables back on the bow and move onto the string.
STEP 2: Basically you want to do the same thing with the string but with the string twist it down to 3/16 of an inch shorter than listed length, then put it back on the bow.
STEP 3: From this point everything is going to be close, take the bow out of the press and start checking all the specs. First tighten both limb bolts all the way down, then check the performance marks on the cam. (in every bow i have worked on excluding the regular cam 1/2 the performance marks are right on by this point, with the cam 1/2 you may need to mess with the control cable just a bit to get the performance marks right) Now that the performance marks are on check your ATA and brace height, in most cases the ATA will be right on and the brace may run just a little on the long side, once you check this move onto draw stop timing. using a draw board or have someone draw the bow for you and watch the cams. The draw stop on the top cam should hit the cable at the same time as the draw stop on the bottom cam. If the bottom is hitting before the top your top cam is under rotated, and vice versa, if the top cam is hitting first. From here more than likely you will need to make some minor adjustments, if the top cam is under rotated you can either add twist to the buss cable or take twist out of the control cable. I always use the control cable for under rotated top cam unless my ATA is coming in on the long side or if the brace height is coming in too short (for me either of these are a rarity) i say this because twisting and untwisting the bess cable will have a greater impact on the ATA and brace height than messing with the control cable. Now if the top cam is over rotated you basicaly do the opposite either take twist out of the buss cable or add twist to the control cable. (for these adjustments i ussually use the buss cable because as previously stated the brace height may be running a little long and untwisting the buss cable will fix that, if the ATA and brace height are already on then i will use the control cable for this as well. Make these adjustments in small increments it don’t take many twist to get it right.
STEP 4: Now that you have that all done you need to check the AMO draw length and make sure it is at spec. To do this draw the bow and have someone mark your arrow right at the center of the rest hole (AMO draw length measurements are measured from the nock groove to the pivot point of the grip wich happens to be right in line with the center of the rest hole so measureing to the rest hole just makes this a little easier.) Now measure from the inside of the nock groove to the mark on your arrow and then add 1.75 inches to that measurement, this will reflect the AMO draw length of the bow. Twist or untwist the string from here to get the AMO draw length set right to where it needs to be. If your measurement is saying it’s too long then add a few twist to the string if it’s too short take a few out (5 twist either way = aprox. 1/4 inch) once you get the AMO draw length set right double check the max weight of the bow and from here you should be done.
If for any reason you get to any step and notice that something is way off from where it is supposed to be start over at step one because more than likely one of the measurements was off. If the problem still isn’t fixed feel free to contact me on WWW.ARCHERYTALK.COM under the username BOWGOD and i will gladly walk you through it the best i can.
I have been personally using this method for years now and in every case this method has gotten me so close to perfect the first time around, just a few small adjustments after you put it all back together after step 2 and the bow is ready to rock. I have tried several tuning methods over the years and this is by far the easiest way to get my bows tuned right into their sweet spot with no headaches.
Good luck and shoot straight.
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