idler lean

[jray57]

Trey I have a question regarding idler lean. I have a 60# left hand Drenalin. The bow maxes at 63#. I shoot GT XT hunters 5575 27" shaft length. I use cb unis and a g nock. 100gr tips and 3 2" blazers. The bow shoots good thru paper and walk back is good also. When I put on the broadheads ( muzzy Phantoms 100 gr) I am grouping good but about 2 to 3 inches left of field tips at 40 yds. Your tuning guide suggests that to correct a left impacting BH that you twist right cable yoke. I thought this might be the best option due to the fact that bow is doing good thru paper walk back is good, arrow spine is good and bow is set to factory specs. Now to get to the question (finally). I am a litle confused on how the idler should be oriented at rest. Should the bottom of the idler be pointed towards the roller guard or away from it? Right now the idler is straight at rest , ata is same on both sides. If I twist right yoke this will make the bottom of idler point towards roller guard. Remember this is a left hand bow and I guess that is part of the reason for my confusion. At rest should the ata be shorter on the shelf side or the riser (roller guard) side and if so approx. how much. Also should the ata on the short side be 35" or should it be 35" on the long side. I tried the arrow on the idler alignment procedure and this only tells me that the idler is straight at rest. I am new to these roller guards and need help understanding how they affect the idler and what I should look for to get best tune. I hope this is understandable and I hope you can give me some insight. Thanks

[Trey Lawler]

jray57 said:

Trey I have a question regarding idler lean. I have a 60# left hand Drenalin. The bow maxes at 63#. I shoot GT XT hunters 5575 27" shaft length. I use cb unis and a g nock. 100gr tips and 3 2" blazers. The bow shoots good thru paper and walk back is good also. When I put on the broadheads ( muzzy Phantoms 100 gr) I am grouping good but about 2 to 3 inches left of field tips at 40 yds. Your tuning guide suggests that to correct a left impacting BH that you twist right cable yoke. I thought this might be the best option due to the fact that bow is doing good thru paper walk back is good, arrow spine is good and bow is set to factory specs. Now to get to the question (finally). I am a litle confused on how the idler should be oriented at rest. Should the bottom of the idler be pointed towards the roller guard or away from it? Right now the idler is straight at rest , ata is same on both sides. If I twist right yoke this will make the bottom of idler point towards roller guard. Remember this is a left hand bow and I guess that is part of the reason for my confusion. At rest should the ata be shorter on the shelf side or the riser (roller guard) side and if so approx. how much. Also should the ata on the short side be 35" or should it be 35" on the long side. I tried the arrow on the idler alignment procedure and this only tells me that the idler is straight at rest. I am new to these roller guards and need help understanding how they affect the idler and what I should look for to get best tune. I hope this is understandable and I hope you can give me some insight. Thanks

Roller guards cause a good bit more limbfork torque than a cable slide at full draw. On large idler roller guard bows (like most Mathews including the Dren) its normal to see the shelf side ATA about 1/16" shorter than the off side. It does not matter which ATA is on spec. A 1/16" either way is not enough to have a negative impact. At rest the idler will not be straight, but that is fine. It will rock way to the other during the draw cycle as the cable yoke angle changes and the forces increase. I bet if you shot a bare shaft through paper at 6' and 12' you'd see a right tear at both distances. The same does not hold true for small idler bows though because it can require a dangerous amount of yoke imbalance to get a response from small idler bows.

[jray57]

So I should try twisting the right (shelf) side a little as per the tuning directions? This will cause the ATA to be approx. 1/16 shorter than the riser side. I never did try a bare shaft thru paper, kinda hard for me to read the tear. Maybe I could try putting something with some color (maybe carbon black?) on the tip. Thanks for the help. I'll put my new string and cable on and get back to work.

[Trey Lawler]

jray57 said:

So I should try twisting the right (shelf) side a little as per the tuning directions? This will cause the ATA to be approx. 1/16 shorter than the riser side. I never did try a bare shaft thru paper, kinda hard for me to read the tear. Maybe I could try putting something with some color (maybe carbon black?) on the tip. Thanks for the help. I'll put my new string and cable on and get back to work.

Twist the arrow shelf side yoke. What you are accomplishing by twisting the yoke is moving the string relative to the rest. In otherwords the nock travels horizontally toward the riser during the shot. If the yoke is not preloaded (i.e. straight idler at BH) then the string ends up too close to the riser. This positions the back (nock end) of the arrow too far to the left of the center of gravity of the arrow (i.e. rest position). The result, during a shot the nock end of the arrow swings out toward the center of gravity. If the misalignment is too much the arrow will over shoot and cause a right tear. That is also why moving the rest to the left corrects a right tear (i.e. position the center of gravity of the arrow behind the nock/string). In some cases fletching clearance will not allow the rest to be moved in close enough to the riser so the yoke must be adjusted such that the top of the idler is moved over to get the string further away from the riser to provide sufficent clearance for the fletchings to clear the riser and the center of gravity to be lined up with the nock/string to achieve straight flight. To further complicate it, hand torgue on the riser or anchor torque on the string can affect horizontal nock travel also. If you find that you cannot get the bow to tune in the horizontal, the rest is as close as it can get to the riser, and you have preloaded the yoke to the maximum safe limit (i.e. for Mathews and Ross I consider that right at 1/16") then hand or anchor torque are the cause if the arrow is spined correctly. Depending on the horizontal tear direction you can move your hand more toward the riser or further from the riser to correct the tear. If there is too much face contact with the string or fletching that will also cause an uncorrectable horizontal tear. Often that is caused by too long of a draw length.

[jray57]

Trey, Thanks for the explanation. I think I understand how it works now.