380 vibration noise

[ThunderXB]

I could use some experienced thoughts on this.

I have a BD400 and just got a 380 Blackout.

Both use same arrows, 18" zombies weighing 418 gr ready to go.

The BD has airbrakes, Dr S silencers & bumpers, a JBK string, rubber pads under the strings at the limb tips and a wrapped stirrup.

It's pretty quiet, just a medium whuump! at the shot, no residual noise or vibration.

Yesterday, my 380 was pretty stock, using a Matrix 1992 string and Dr S bumpers and was louder than the BD400 with a loader whaackk! at the shot.

Had two guys stand with their backs to me this weeked as I shot both and both giuys identified the loader bow as the 380.

SO, today I put airbrakes on it, Dr S silencers, rubber pads under string tips and a stock extender kit.

When I shoot it now the initial noise is softer, more of a whuump than a whaack, BUT now I get a residual waaangg vibration type of noise.

So, sort of a whuump..waangggg.

I hear this after the arrow is gone and at the target.

I every screw on this bow has been locktighted and rechecked this afternoon.

I don't recall hearing this vibration noise before I put all the "noise dampening gear" on it.

As it comes later in the "stroke" I don't think it will bother animals, because they'll be dead or gone by then.

ANY THOUGHTS???

[vixenmaster]

String

[mmc]

.... SO, today I put airbrakes on it, Dr S silencers, rubber pads under string tips and a stock extender kit.

When I shoot it now the initial noise is softer, more of a whuump than a whaack, BUT now I get a residual waaangg vibration type of noise.

So, sort of a whuump..waangggg.

I hear this after the arrow is gone and at the target.

I every screw on this bow has been locktighted and rechecked this afternoon.

I don't recall hearing this vibration noise before I put all the "noise dampening gear" on it.

As it comes later in the "stroke" I don't think it will bother animals, because they'll be dead or gone by then.

ANY THOUGHTS???

Yeah, the waangggg is all that new sound deadening stuff vibrating. You changed the vibrational frequency is all....

On Edit: I didn't mean to come across as a smarty pants.... Was referring to the physics... how/why it works. The sound dampening stuff don't actually kill (or absorb like a magic trick) the vibrations that cause the loud noises when a 380 is shot... rather those intense vibrations are met with more mass and more transfer points for those vibrations to travel into, with each leading further away from the "source". The differing materials encountered (and the increase in distance from the source) extend the "time' factor, thus altering the frequency during those several transfers of energy. Make sense?

On Edit again... By extending the distance from the vibration source you are extending the time that it takes to complete a "cycle". Energy travels through a material (or materials) from the source to its furthest point away (distance) from source, then "bounces" or reflects back onto itself, behaving like a wave, which it is.... an energy wave. A short distance allows the vibration to complete cycles sooner, thus energy will dissipate sooner as the time factor is short. A longer distance for energy to travel allows the extended time for a vibration to exist before dissipated and that energy is spent.

Adding mass to increase the distance for energy to travel sometimes leaves a portion of the source free to vibrate independently from the rest.... like vixenmaster said, check your string... or another xbow part extending distance and/or time, such as a quiver and bracket singing solo with the choir.

[ThunderXB]

No worries, I appreciate the feedback and understand what you're saying.

Based on the transient displacement of the vibration frequency, it likely is finding the point of "easiest" energy release and that is most likely, the string.

I just wonder how much a different string will alter the noise without costing too much in the way of speed?

VIXENMASTER, any thoughts on the last comment? What impact do your 8190 flemish strings, especially the 38 or 40 strand, have on speed and noise?

[acreek]

Thunder, of your Bulldog mods, can you pinpoint which one turned the crack into a thud? I've taken the metallic twang out of mine by wrapping the stirrup and placing traditional rug rest material on the retention spring. So far so good, but I still have a loud crack at the shot. Do you remember putting any single piece on your Bulldog and saying, "Oh yeah, that did it."

[ThunderXB]

Thunder, of your Bulldog mods, can you pinpoint which one turned the crack into a thud? I've taken the metallic twang out of mine by wrapping the stirrup and placing traditional rug rest material on the retention spring. So far so good, but I still have a loud crack at the shot. Do you remember putting any single piece on your Bulldog and saying, "Oh yeah, that did it."

I honestly can't pinpoint one thing.

The BD still makes noise when shot, it's just less metallic and more of a "thud", with no residual twang.

I was sort of surprised with a similar set up, the 380 developed the twang, although the firing noise did get muted a little more, still the 380 is using a factory Matrix 1992 string and the BD is using a JBK string.

I have a spare JBK string I'll try on the 380 tomorrow or Saturday to see if there is a difference.

Truthfully, even in a hunting scenario I could use the 380 very comfortably as it is now. It is drop dead accurate!!

[W.Miguire]

Thunder , Do you have the whole DR. Stirup set up or just the bumpers. I am asking because I have a 380 and do not have your problem . I am using the whole set up with shrink rap on the arrow spring with a Flemish string. seem ok to me. check on Gaston's web site and he goes through the process on bow vibration. maybe this might help . my string is only a 30 strand.

[Eck]

A string made of Force 10 material by Vixenmaster (Mike) made all the difference on my 380.

[flightattendant100]

They are supposed to sound like that! Hope us get it figured out. You can take one thing at a time off and find it. But I know that's a pain in the backside

[vixenmaster]

Light weight strings don't absorb the energy that a heavier thicker string does. Its a trade off, speed or abit less speed n abit less energy left in the string. Its the same when usin a light arrow n goin heavier arrow will make the sound n vibes change. What string is on now the factory or the other JBK ?

[SEC-ond 2 none]

T XB; Did you wrap the 380 stirrup and arrow hold down spring ? I used simms and shrink tubing on my retainer spring, simms and vet wrap on foot stirrup, used wildcatters method of installing dense Foam/Rubber material in the rail and installed pieces of same material under the cheek piece. My M380 is "Much Quieter" and still Very fast and extremely Accurate.

NOTE: I Practice from a bench/rest. I still have a Twang after my shot BUT that is generating from my Caldwell DFT Lead Sled.

Stephen

[ThunderXB]

The string currently on it is the factory 1992 matrix string.

(I'm going to try the JBK string today, seems to work great on my Bulldog 400, but I think it is similar construction to

VIXENMASTER, why don't you PM me and we can discuss which string you think may be quieter without sacrificing speed, thanks.

The arrow spring retention holder IS covered with shrink tubing.

I did do a "temporary" wrap on the stirrup to see if that helped and it didn't.

(I have a Dr S stirrup coming to try)

[ThunderXB]

Problem mostly solved.

As surmised above, it was the string vibrating.

I put on the new JBK string, and while that helped a little, the vibration noise was still there.

I left the JBK on overnight and this morning it had stretched just enough to be lightly touching the Dr S bumpers.

On the shot, the Dr S bumpers now stopped the string noise/vibration.

Shooting good too!! Pounding a 1/2" dot at 20 yds.


One thing I did notice is that the JBK strings middle serving is about 9 1/2" long meaning that it is the serving that contacts the bumpers, not the string strands themselves.

In comparison, the Matrix string middle serving is 3 3/4" long.

Don't know if that means anything, but it was just something I noticed.

I am also going to try a Force 10 Flemish string for both quiet and speed retention. Be my first flemish and I'm interested to see how it goes as many seem to favor them.

[W.Miguire]

Glad you got it figured out . you should let your string indent those bumpers about 1/16 " the Flemish string will make a world of diff. you won't get rid of all the noise . it will be the last noise the deer will hear. good luck hunting this year.
W.M.

[ThunderXB]

Thanks.

Always meant to ask, do you hunt out on the Island??