String breaking at top knock?

[Cheezer]

So I have a mid 70's 50lb Darton Magnum that has broke 2 strings so far this year. The first time it was last years string, figured it was just old. So I made a new one a couple of months ago and it broke too, 12 strand flemish B55.

After the second break I checked it for burrs or rough areas, didn't really find much, but sanded it down a little anyways.

My question is could brace height being too tall cause this? I found an old Darton catalog which states BH should be 8 3/4" to 9 1/4", and I had it tuned around 9".

I made another string yesterday, 14 strand, and the BH settled into 8 1/4" and I think I'm just gonna roll with a lower BH for now. Really just want to see if anyone else has had issues with these low AMO bows busting strings at the knock?

[NothingHappenedToday]

I had a Bear Ausable that had the same problem. One of the corners in the string groove was really severe, so I rounded it down with some sandpaper and that fixed it. Also, if your arrows are too light it may be rough on the string

[kenneth butler]

Brace height is not a concern. If the string is breaking in the loop there is something abrading it. You probably have it taken care of now. It doesn't take much just a a piece of grit or bubble in the finish.>>>---> Ken

[LBR]

Not the brace height.  Some spots are so minor you won't feel or see them, but they cut strings.

[monterey]

Also, you could pad the loops but you probably already thought of that.

[Lowrider]

Run an old pair of pantie hose or similar material thru string grooves an see where it catches. Got to be a rough spot somewhere in the string grooves.

[Cheezer]

I have made padded strings before, but that just delays the inevitable.

I used a cotton swab when looking for the defect, found nothing, so maybe pantie hose would be a better option, never thought of using that.

[HornHunter]

another thing people dont realize keep super glue away from any string, specially the ff material it will melt that stuff instantly creating a hard spot
even the fumes will cause problems, yours sounds like a fiberglass issue, maybe cracked and only split open when it is drawn had that happen

[madmaxthc]

I had a similar issue, on the top loop. I tried to smooth the tip of the limb a couple of times with no success. Eventually I asked a cobbler to cover both tips with a small leather hood. That worked. I've had them in place for 6 or 7 years by now, they didn't give me any problem.
Hope this helps.
Max

[madmaxthc]

Sorry, I've just read your question again, you're breaking at the nock, right? As some said before me, 1) it's probably the nocks too narrow. Do you use a serving on your strings? 2) could be  superglue, if you put it on the serving/nocking point knots

[Eric Krewson]

I have told this story before; I was shooting 2114s out of a 70# bighorn and breaking B-50 strings at the top nock right and left.

I asked for help on the old Stickbow site, Dan Quillian said "you are dry firing your bow with the light 2114s, this is causing your strings to break".

I thought, "you old goat what do you know" and kept shooting my 2114s for a while and breaking strings. I was getting 205fps out of the bow.

That year for hunting I changed to a heavier 2018 that was about 100 gr heavier than the 2114s, I never broke another string.

Old Dan knew what he was talking about and I had to eat a major helping of crow.

[V I Archer]

I have a PSE Heritage series longbow which wore thru strings rather quickly.  I took to wrapping the loop with b-50, much like serving an endless loop.  May have slowed it down a foot or two but I would get a year plus out of a string rather than a week.

[Cheezer]

I'm flinging some ICS hawks at around 450 grains, so I would hope that's heavy enough.