Limb bolt noise

[McDave]

One of my bows started making a vibrating noise when I shot it, or if I would smack the back of the handle.  Or maybe it has always made it, and I just never noticed it before due to my poor hearing or that I was shooting it in a quiet location with my hearing aids in.

Anyway, in trying to track this down, it seemed to be coming from the area of the limb bolts.  The first thing that occurred to me was that maybe the limb bolts were bottoming out, so even if they seemed tight, they really weren't tightening the limbs against the handle.  So I ground a little off the bottom of the limb bolts, and made sure they were really tightening up the limbs against the handle and not just bottoming out.  The noise stayed the same.

Then, after some head scratching and other thoughts that didn't pan out,  I examined the beveled fitting in the handle that the limb bolts screw into.  I found that the anodizing had worn off the very bottom of the beveled section, but had not worn off higher up the bevel.  This means that the angle of the bevel of the limb bolts is sharper than the angle of the bevel of the receptacle, so contact was only being made at the bottom of the beveled section.  There is a tiny gap between the beveled limb bolt and the beveled receptacle for much of the length of the bevel, which makes a vibrating noise when the bow is shot or pounded.

To fix this, I put electrical tape on about the top 2/3 of the beveled part of the limb bolts.  When I screwed them back in, voilá, no more vibrating noise.  The photo below shows the tape sticking out around the limb bolts where I put it.  I will trim this off, but left it on for this photo.  I don't know if electrical tape is a good permanent solution, but at least I have identified the problem.

In looking at beveled limb bolts on the Internet, they seem to come in two angles: 82* and 90*.  I suspect the receptacles on my bow are 90* while the limb bolts are 82*, which is why they don't mate along the entire bevel.

Just thought I’d pass this along in case anyone else has this problem.

[4dogs]

Good troubleshootin Dave!

[Crooked Stic]

Just a matter of gettin the right bolts.

[McDave]

Just a matter of gettin the right bolts.

Possibly. I’m not sure they actually used two different sizes of bolt and receptacle when they made the bow.  It’s possible that the sizes are the same, but manufacturing tolerances may have allowed enough difference in fit to cause the chatter.  This isn’t a bow I’m very likely to take down, so the electrical tape fix will probably suffice as long as it continues to work.

[trad_bowhunter1965]

If your bow is a Bob Lee I would call Rob they will take great care of you.

[McDave]

Yes, Bob Lee has always been top notch to deal with.  However, I didn't want to box up a bow that is more than 5 years old and send it to them saying only that it was “noisy.”  Now that I’ve isolated the cause of it, they could probably either replace the limb bolts or the bushings and fix the problem.  I have other Bob Lee bows with identical limb fastenings that are quiet, so I know it is not an inherent characteristic of the bow.  But for the moment I’m happy with my electrical tape fix.  I am sort of puzzled as to why I didn't notice it before.  I'm not THAT deaf.

[trad_bowhunter1965]

Maybe your hearing has  improved 

[Crooked Stic]

If you have a nut and bolt vendor they could get the right bolts for you. I would think no more than $2 A piece.

Sent from my SM-T550 using Tapatalk

[McDave]

Probably be easier than sending the whole bow back to Bob Lee.  I might try that.