String dampener????

groundpounder · Post by **groundpounder** » Sat Dec 09, 2006 9:50 am

I like the ideas of filling the voids in the stock with material. Has anyone tried the "foam STUFF" used for sealing cracks in your house. I've seen material similar to this in stocks before. Don't know how it would hold up in an xbow and might be a pain to remove if it doesnt work. But I just might give it a try. As far as your string stoppers, Looks like a really good idea but will this type of thing affect your warranty on the xbow. I would think it would.

GaryL · Post by **GaryL** » Sat Dec 09, 2006 9:52 am

Stay away from the foam, any voids you want to fill use silicone works great and they be afew that can be filled....

Leonard Hawkins · Post by **Leonard Hawkins** » Sat Dec 09, 2006 11:07 am

how do you bolt the dampeners to the bracket? do they have a hole thru them ?

sumner4991 · Post by **sumner4991** » Sat Dec 09, 2006 1:13 pm

The bracket I purchased had two pre-drilled holes on each side of the elbow. . .it's a standard 2 1/2 inch elbow bracket. I used a hacksaw to cut one side off just above the first pre-drilled hole and that's the side I attached the Sims Split Limbsaver. I think the other guys used a strip of bendable metal and glued the limbsaver on. Only the split limbsavers will bolt on and I drilled the holes out to 1/4 inch on the bracket.

Matthias72 · Post by **Matthias72** » Mon Dec 11, 2006 4:27 pm

I have done some test with an audio analyser, to test my Crossbow Absorbers; I used a 393 grs arrow and Exocet 200 crossbow.

With Absorber System the speed is 324.6 fps, without is 321.0 fps
In brown the noises in common.
In red the major noises without Absorber system.
In green the major noises with Absorber system.
I have done 4 tests to be sure of results, and this is the result:
I have got an important noises decreasing and in the same time I have got 3.6 fps more.

grandtrout · Post by **grandtrout** » Mon Dec 11, 2006 5:02 pm

Matthias,
Cool results!

I'm having a bit of trouble figuring out quanties based on your scale.

It looks like your system shows about a 20% reduction in total loudness? Is this interpretation right?

It also looks like the sound disipates quicker (has a shorter duration) Is this an acurate finding?

Hi5 · Post by **Hi5** » Mon Dec 11, 2006 5:12 pm

Can you measure in decibels, with and without absorber?

I'm not sure that it would make much difference to a deer what the frequency level of the sound was. I assume that some frequencies of sound are absorbed more than other frequencies.

Cedrus · Post by **Cedrus** » Mon Dec 11, 2006 7:32 pm

Need references and scales for both X and Y axis. Time and db (log scale) respectively.
You have a great web site. Keep up the good work.

Matthias72 · Post by **Matthias72** » Tue Dec 12, 2006 3:08 am

Ok, on the vertical scale (Y axis) you can find the Total Sound Intensity (all the frequencies) and the horizontal scale (X axis) you can find the Time. So this graphic is the exact sound image of one crossbow shoot. With the graphic you can see a noticeable noises decreasing during the fist part of the shooting,(normally the phase of maximum string stress),
and after the Absorbers disipates also the sound quicker (has a shorter duration).
Do you know the terrible "metallic" sound that the crossbow does using light weight arrows?
This Absorbers kills complitely the "metallic" (I apologize all high frequencies) sound, the sound becames soft and shorter, the same sensation if you use not a 393 grs arrow but a 550 grains.

grandtrout · Post by **grandtrout** » Tue Dec 12, 2006 8:30 am

Interesting results! Thanks for sharing them with the group.

Just a theory here...

Looking at your graph the noise a crossbow makes could be broken down into two componets. Sound during the shot & sound after.

Sound during,
I suspect this volume comes primarily from the friction created when the string and bolt travel down the rail. The high frequency part of this sound is most likly coming from the bolt itself - actually the last inch or so becuse the rest of the bolt is suspended in an upward expression of the archers paradox. Just a theory here but if you shoot a bolt that is crested and the crest wrap covers the metal nock you should see further reduction in high frequency sounds (metalic noises) but not likely a substantial reduction in volume (loudness). Rail lube might help here too but it sort of makes a mess if you put enough on. I'd also be curious to see just how much fletch type contributes to this portion of the bows noise - if at all.

Sound after,
This is the anoying part of the whole deal becuse its difficult to identify with the ear. However, I think there a few easy things you can do to further reduce this sound both in frequncy and duration.
-put rubber on sturrup, a cut up innertube wrapped around the sides seems to work well.
-Stick one of the sound stoper strips on the bolt holder - its amazing the twang this actually makes if released independatly of the bow going off.
-There are also a host of things you can do to that stock that are mentioned previously in this thread.

Just my two cents - thanks again for the test data.

JB

grandtrout · Post by **grandtrout** » Tue Dec 12, 2006 8:56 am

One other thing.

I think overall loudness is improtant in reducing the chance of a string jump but I also think frequency is just as important if not more critical. There are very few if any high pitched loud noises in the deer woods. There are lots of loud noises, branches falling, small animals crunching about etc. I droped a rattling antler out of the tree within 20 yards of a doe a few years ago and it reacted by looking up not bounding off - I figure this is because the loud noise wasn't something that a deer would fear. The same doe would have likely tore off if I would have touched an aluminum arrow to a metal riser or a tree stand- totally unusual sound for a deer to hear in the bush. No way to know if this is true or not, however I make every effort to set up all my hunting gear so that there is no chance of making a metal on metal contact. Frequency, and paricularly high frequency counts for me anyway.

Matthias72 · Post by **Matthias72** » Tue Dec 12, 2006 9:17 am

The graphic shown is a "compact" graphic where you can see the complite
sound image, but is not so detailed. I have much more detailed graphics, where you can see perfectly the noise when the arrow is in move.
Now I'm in office and I don't have this material with me, but I can show you with a paint, the "real" sound graphic:

The first part is when the arrow is in move on the crossbow riser. No diffrences with/without Absorbers. The Brace H. with absorbers is 0.8" shorter, so the first big noises, caused by string extensions, arrive a little after.

The total noises intensity on the first string exstension are the same: I think the only way to drecrease them is: 1. one heavier arrow weight. 2. A crossbow with less poundage 3. A string more elastic..

After this point the Absorbers begin to work, and they suppress the energy of second and succesive extensions always better, decreasing maximum sound intensity and total sound duration.

I don't know in the grafic where are the high frequency noises, but sure the "metallic" sound (it seems to be an high frequency sound) with Absorbers now is killed.

Crossbolt · Post by **Crossbolt** » Tue Jan 16, 2007 12:06 pm

I am happy to see that some of you are liking my invention.

I believe that you will all continue to find that it does in fact produce the results that I have posted to several of you here and in the couple of topics in which I made everyone aware of its existence.

The device is patent is pending and we plan to produce a commercial version of the product at some point in the near future, so any ideas for improving the basic design will be appreciated.

You will find that the Limbsavers last far longer than any other dampening device that has yet been produced by the market for Excaliburs. In fact my two test bows still have the original dampeners that I fabricated on them a year ago and show no visible damage after a full season of shooting almost daily.

Bolt speed is not affected as some have suggested.

If properly installed there is no adverse impact to accuracy either as some have posted in this thread.

We believe that the design is rock solid and will be producing it commercially at some point very soon...so stay tuned for more!!!

Best regards to all.

-Crossbolt

Crossbolt · Post by **Crossbolt** » Tue Jan 16, 2007 12:15 pm

BTW, Sims SVL wraps are good for wrapping the stirrup and can also be wrapped around the quiver mount also...although the bicycle inner tube idea may produce similar results however the softer durometer SVL materail should be superior to cycle tube material.

Any rubber that you can add to the hollow aluminum rail and hollow plastic stock both are going to have a positive impact.

Our riser mounted string stop/dampener stop is by far the most noticeable improvement to sound and shot recoil reduction that we've yet found however.

Best,

-Crossbolt

Leonard Hawkins · Post by **Leonard Hawkins** » Tue Jan 16, 2007 12:48 pm

I have set my Vixen up the same MATTHIAS72 and also filled the forearm of stock with silicone. havent done rail yet but this works great for me. No notice in the way it shot, still on zero at target. Much quieter. Hawk