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View Full Version : MOAB cam lean????



racknspur
12-01-2009, 05:31 PM
Just picked up an '09 MOAB off AT and noticed a spot where the cam seems to be chewing through the string. After further inspection, the cam is leaning to the left(from rear) and it is obviously the reason for the pressure on that spot of the string. Is there any adjustments I can make? What are the chances Martin would warranty to the second owner if there was a problem? This is my first martin and I do like the looks and feel. Also @ 15yds. my arrows are 6-8" left even though my centershot is at worst very close and I've had to move my sights WAY left of the centershot to try to bring my groups in.:(

bfisher
12-01-2009, 06:56 PM
When we speak of cam lean we are usually referring to the idler wheel (top limb) as this is the only one that can be adjusted.. If I interpret your post correctly yours is leaning right to left, with the top of the wheel to the right? This is quite common with many single cam bows. here's how to adjust it:

You need a bow press to relieve the pressure on the string, or you can back out the limb bolts far enough to relieve the pressure. Watch the threads of the limb bolts through the barrel nuts in the riser. When you see some daylight you should be close to that point. This usually occurs after you've taken about 10 turns off the bolts.

OK, now you need to slip the left branch of the split cable yoke off it's mooring, paying attention to which direction the twists are in that branch. Then add more twists to that side. Star with 5 to 7 full twists.

Put it all back together and take a look-see. If it needs more do it again. It's pretty much trial and error till you get it right. Now how do you know when it's right? Hold an arrow shaft or straight edge against the side of the wheel and parallel with the string. It should run parallel with the string.

Hope this helps. Let us know how you make out.

racknspur
12-01-2009, 07:38 PM
Yes, the idler was/is leaning,but so is the cam. I did adjust the idler by taking twists out of one side and adding twists to the other, it's much better now, the cam is still leaning but maybe because the CSS is pulling the string and cable it's creating an optical illusion. However the adjustment I made to the idler as well as center shot seems to have brought things more in line so I'm on the right track. Thanks.

bfisher
12-02-2009, 09:49 AM
The cam leaning is not an optical illusion. That's what cable guards and roller guards do. To pull the cables out of the flight path of the arrow they are pulled to the side. This creates torque on the limb tips which causes the cam to twist.

Some bows with dual cams that anchor at the limb tips can be adjusted to reduce or eliminate cam lean (limb twist).

Single cams can only have the idler adjusted, as you have done. You can't do anything about the bottom cam.

Binary cams anchot on the opposite cam so nothing can be done with them if things are too far out of whack except limb replacement or whatever magical solutions the factory might come up with.

With the adjustments you made the bow should be a little easier to tune and be more consistent. If so then come back and let everybody know.

racknspur
12-02-2009, 10:28 AM
O.K., I've been working 12hr. shifts so I've only had a chance to eyebal tune. After going back and taking and adding twists to each side of the yolk to make idler lean better-not perfect and centershot about so the nocked arrow splits the center of the string w/ sight lined up over the arrow, I'm packing them in the bull @ about 15yds. Here's one thing I don't get, on my old Mathews it was recommented to set the idler so the string was tracking straight off the idler @ full draw but was tracking off to a side @ rest????? That bow tuned like a dream!

bfisher
12-02-2009, 03:26 PM
If you're so inclined you might try tweaking the idler they way Mathews suggests. Ya never know what you'll come up with.

I was under the understanding that Mathews suggested to lean the cam a little more toward the cable/roller guard. On a right handed bow that would mean a straight edge held on the left side of the idler would be angled to intersect the nocking point at rest. I can understand this somewhat because as you draw the bow more force is applied to the cables, which would make the cam lean the other way and possibly make it straighter at full draw. Here again this is just a guess.

Don't know just where you have the rest set for centershot, but mine lines up just about 7/8" (center of the arrow) from the VEM pad attached to the sight window.

If yours varies much from this it might be because of a spine issue. We haven't gotten into that yet. What poundage and draw length (measured) is the bow set at and what are the specs of the arrow?

racknspur
12-09-2009, 01:08 PM
I'm not going to tweak the idler any more as I'm satisfied how it's shooting in the basement @ 20yds. right now. My Field points and broadheads are dead nuts bullseye. By the way, I don't have a draw board yet, I use a digital scale mounted to the floor joists to see cam sync and solo cam position. I had to put the 26" mod. in the MOAB and it feels great, but I'm usually a 27" do they run a tad long?

bfisher
12-09-2009, 01:32 PM
I'm not going to tweak the idler any more as I'm satisfied how it's shooting in the basement @ 20yds. right now. My Field points and broadheads are dead nuts bullseye. By the way, I don't have a draw board yet, I use a digital scale mounted to the floor joists to see cam sync and solo cam position. I had to put the 26" mod. in the MOAB and it feels great, but I'm usually a 27" do they run a tad long?

Yeah, my Moab ran long too. I think with the F1 mod in it it should have been 26", but mine came up at 26 5/8". If need be play with the draw stop. If it's not set short enough the end of the draw will feel pretty mushy.

If you have target points and broadheads hitting the same POI right now I'd say you're on your way to success. Keep up the tinkering.

racknspur
12-09-2009, 06:32 PM
Yeah, my Moab ran long too. I think with the F1 mod in it it should have been 26", but mine came up at 26 5/8". If need be play with the draw stop. If it's not set short enough the end of the draw will feel pretty mushy.

If you have target points and broadheads hitting the same POI right now I'd say you're on your way to success. Keep up the tinkering.

Yup. Got her right where I want now. Feels great. I'm sure it will be a KILLER hunter even though it will prob. be the backup when my Alien X gets here.:D

LondonDave
12-13-2009, 01:24 PM
Can this be a problem on the 08 Moab's also? I just traded my son's 08 Moab because he just wasn't using it. The guy I traded it to just contacted me saying the top cam (idler) is bent or warped to the point the the string jumped off when he shot it. He got this info from a shop (non-Martin dealer) that he took it too.

Thanks,

Dave

copterdoc
12-13-2009, 01:54 PM
Can this be a problem on the 08 Moab's also? I just traded my son's 08 Moab because he just wasn't using it. The guy I traded it to just contacted me saying the top cam (idler) is bent or warped to the point the the string jumped off when he shot it. He got this info from a shop (non-Martin dealer) that he took it too.

Thanks,

Dave
If the idler is bent or warped, it is from dropping or dry-firing the bow.

bfisher
12-13-2009, 01:55 PM
It's possible that the cam is bent, but this would be quite obvious and is not the same as cam lean. Probably the best way to check to see if it's bent is to loosen things up till the string can be removed, or press it, and just spin the idler to see if it's spinning true.

Any decent shop should have been able to do this if they wanted to take the time. And it doesn't have to be a Martin dealer. When it comes to stuff like this a bow is a bow is a bow.

Not being able to see the bow it's hard to make an accurate assessment. I know I have seen short ATA bows drawn with fingers and the string torqued badly enough to roll the string off the cam or idler, especially when letting down. I have seen a bow that the string did come off when shot, but this was a carbon riser HCA bow that had some very extreme cam lean issues. Oh, yeah, I saw it on a PSE Nova once, too. In this latter case I just gave the customer a new bow and sent the bad one back for replacement.

LondonDave
12-13-2009, 02:17 PM
If the idler is bent, what would the replacement cost be....any idea? It sounds like the string might be pooched too from coming off.

Thanks,

Dave