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Bow hair tension
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Mat Roop
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Joined: 24 Mar 2007
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Location: Wyoming Ontario

PostPosted: Sun Dec 13, 2009 4:29 pm    Post subject: Bow hair tension Reply with quote

Is there a tension measuring device for bows?
The issue is that some bows are softer than others and that means that a soft bow cannot pull hair tight as effectively as a stiff bow. Therefore a soft bow needs less hair.....but how much?
1- Is there a device to measure a bows ability to tension hair and
2- Is there a device to test measure an amount of hair to match the bow's ability to tension?
Thanks!!... Mat
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Andres Sender
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PostPosted: Sun Dec 13, 2009 9:12 pm    Post subject: Reply with quote

The only device I am aware of is one that measures the deflection of the stuck for a given weight. Some people are using this to track stick stiffness. The device is being called a "Stroup Gauge" because they were apparently made and sold at one point by a fellow named Herman Stroup. Some basic information about them can be found with a Google search.

With this sort of gauge all you'd need is to calibrate by keeping track of the relation between stick stiffness and amount of hair in a large number of bows that work well, and you'd be all set to determine what to use in a strange bow.
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Mat Roop
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PostPosted: Tue Dec 15, 2009 9:28 pm    Post subject: Reply with quote

Thanks Andres.... That was helpful... Mat
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Mat Roop
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PostPosted: Wed Dec 16, 2009 12:48 am    Post subject: Reply with quote

Andres... would you know what the approximate tension range would be on an average bow hair ribbon?
I am thinking that there is a way to take direct measurements from the bow along the tension path rather than the Stroup method which is to my thinking a quasi surrogate measurement. And it follows that there should be a way to easily and directly measure the tension resistance to exactly match the bow's ability to tension.... maybe better folks than I have tackled this issue, but I'd like to give it a go.... so your advice on the question above will help me get started.
Thanks... Mat
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Andres Sender
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PostPosted: Wed Dec 16, 2009 7:59 pm    Post subject: Reply with quote

Mat--I agree that this might be an interesting thing to explore, but I am not aware of anything. Probably someone has an article in a back issue of the VSA or some other violin maker's organization on this subject but I haven't run into it.

I've mulled the idea over in the past--something with cord acting as hair, with a support for the bow, maybe a small pulley to run the cord to a good scale.

But then you are left with how far to tension the stick. Should all bows have their tension measured with the hair a pencil width away from the stick? (I expect not.) I am sure different degrees of tension create different behaviors on different bows, so that one bow may be at its best at a lower tension, and another at a higher tension.

Ultimately I think recording the stick's characteristics is the way to go, and linking that to evaluation of the bows' behavior. I think learning how to do the latter is simply necessary if one is to reach any reasonable level of skill in bow work.
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Janito
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PostPosted: Thu Dec 17, 2009 7:58 pm    Post subject: Reply with quote

Mr Joe Regh showed an interesting device at the Nov VSA meeting which he uses to measure stick displacement for defined weights.

He would be the person to ask.
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Stradsman
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PostPosted: Fri Apr 29, 2011 12:56 am    Post subject: Reply with quote

Is it true that for orchestral playing tighter hair is used, and looser for solo performance? I've heard this from a few professional violinists but find it a little odd.
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Mat Roop
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PostPosted: Wed May 04, 2011 11:29 pm    Post subject: Reply with quote

Well, my understanding is that bow hair tension is entirely up to the player, the nature of the music being played and the environment that they are in. I am not a player, so take what I say with a grain of salt. I know some players will play with a soft bow while another will like it tight... both playing in the same place at the same time.
Clear as mud Rolling Eyes
Cheers, mat
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FiddleDoug
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PostPosted: Fri Jun 10, 2011 9:20 am    Post subject: Bow hair tension Reply with quote

I can envision a device to measure tension, but it wouldn't involve the hair. Imagine a loop of nylon cord that would hook over the bow tip. Put a small luggage scale, attached over the frog, at the other end of the loop. Tension the bow to the "normal" camber, and you should be able to read the tension directly on the scale. Claims on any patent or royalties that come out of this. Cool
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Mat Roop
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PostPosted: Sat Jun 11, 2011 1:18 am    Post subject: Reply with quote

Doug... you have got the idea!
I have been working on this for the past month or more and there are some challenges...
1-it must be a digital scale as the others have too much travel distance for the frog.
2-The digital scale must be small enough to allow the "simulated hair" (the cord) to be in the same plane as the real hair. I have researched custom digital scales and they are about $200-300
3-the nylon cord will have too much stretch to it and the frog will run out of travel space getting up to tension.... it will also indent the wood as it wraps around the bow head. The tension is in the order of 2 to 5 kg (4.4-11lbs) depending on the bow and the camber
4- Every bow is a different length and the cord (wire) will need some sort of non slip cinching device to accomodate all the different lengths
5-Then there is the problem of calculating a correlation of bow tension to amount of hair required for the bow. I read somewhere ( I wish I could remember where Confused ) that someone had tested bow playability and tone generation and concluded, as I recall, that less hair to approx 140 hairs for some bows seemed to be optimal.... and rarely over 200 hairs were necessary.
6-I think the amount of hair required for a bow will vary by the type of hair. I use only premium Siberian Stallion hair ranging in thickness of 0.12-0.17mm Diameter.. so all my testing will be with that hair.
I do believe I am getting close to some solutions.
In the next few weeks I will be doing the measurements and rehairing several bows with the calculated quantities to see if this really works.
When (if Razz )I get good results, I'll post some info and pics... and where to buy it!
Having gone thru 1 patent, for the Rezx resonance modulator, This one will be tough to patent!
Next challenge... how do you measure a hair bundle to precision? The herdim hair guage is too vague for me ... that will be my project after the tension tester Smile
Cheers! Mat
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FiddleDoug
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PostPosted: Sat Jun 11, 2011 7:15 am    Post subject: Hair Tension Reply with quote

Mat,
You can get inexpensive digital luggage scale on Ebay for about $5 or so. I have one that is about 2"x3"x3/4". It goes in up to about 70 lbs, and will read in ounces. I was envisioning something that didn't use the frog screw to create the tension. That way, the hair could remain on the bow, in the frog forward position, but you could still tension the bow itself to the correct camber. Hope this makes sense.
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ctviolin
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PostPosted: Thu Aug 23, 2012 1:34 pm    Post subject: Reply with quote

My opinion is this;
When rehairing from the tip first (which is how I happen to rehair) you'd get the hair tied in front of the bow mortice in front of the frog, for the hair and then , after combing out the hair, pull it back to the appropriate distance behind the mortice to fit well and allow the knot to go around the plug and seat at the bottom of the mortice.
At this point, your bow will be in the vice and the tightness of the knot going into the frog will depend entirely on how the bow tension feels to then rehairer.
Experience is the only way I know to arrive at such a conclusion, and yet practice must start somewhere. By doing.

I do not believe that there is any type of trick or guage that will let you know how and where to tie the final knot (for me, the frog knot) other than doing it a few times - then you start to ge a correct feel for how it goes.

This is merely one small steap in the process - and the process is one learned by trial and error and realizing, up front, the properties of the particular bow in hand....
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ctviolin
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PostPosted: Thu Aug 23, 2012 2:56 pm    Post subject: Reply with quote

And there many techniques in rehairing - that work fine. So I wouldn't pass up anyones idea of what will work - it's sort of like making violins in this respect.
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ctviolin
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PostPosted: Wed Oct 10, 2012 11:35 am    Post subject: Reply with quote

Redo;

My opinion is this;
When rehairing from the tip first (which is how I happen to rehair) you'd get the hair tied in front of the mortice in front of the frog last (or, the final knot is second, after the tip has been done),
that is, aftert securing the tip hair first, putting a rubber band around the tip ribbon on the tip - keeping the hair corectly and tightly in place on the tip first.
after combing out the hair from the tip back to in front of the frog, (until it is even and untangled and straight), tie a knot in front of the frog mortice on the ribbon (at this time, only TIE the frog knot, but do not glue it or cut the hair ribbon to the final length yet.

It needs to be positioned correctly behind (not in front of) the frog mortice in order to allow the hair to still be compleatly loose with the frog in the full foreward position - so, finally, it must be pulled back to the deapth of the frog mortice, so that the final knot is now BEHIND (the bow screw side - not tip side side of the frog) the mortice, and not be tight in any way yet when finally wedged in.
.
After combing the hair out from the tip back to the frog knot, pull the thread knot back, a slight distance more - to an appropriate distance BEHIND the mortice, in order for the frog's mortice knot to fit well, allowing the knot to go around the frog's plug wedge, and seat the actual knot itself at the bottom of the mortice. then cut and glue the knot on the ribbon, and place and wedge it in the frog.

Make sence?

This is trickyest move in the process, because the hair must still be even and loose at this point - when the frog is fully mounted and foreward - but only "just loose" when the plug is in the frog, and the frog mortice goes on & the final wedge is installed, it (the ribbon of hair) must immediately just start to tighten the ribbon of hair somewhat evenly when the frog gets moved back using the bow screw.

then there is the flaming process. Shown here, to finalize everything properly.


The entire ribbon of hair should all loosen up evenly at the frogs full foreward position, and all start to tighten quickly and evenly, when the bow screw starts turning.
At this point, your bow will probably still be in the vice, (depending) and the tightness of the knot going into the frog, will depend entirely on how the bow tension feels to the rehairer - at that point.
It's not dependant on the bows "wood strength" at all. it is a mechanical process of the rehair that should be the same for any bow being rehaired. Full relaxation in the foreward position on the frog - tightening quickly as the frog is pulled back by the screw.
Experience is the only way I know to arrive at such a tension conclusion regarding the final knot's fit, and yet practice must start somewhere.
By doing.

I do not believe that there is any type of trick or guage that will let you know how and where to tie the final knot (for me, the frog knot) other than doing it a few times - then you start to ge a correct feel for how it goes.

This is merely one small steap in the process - and the process is one learned by trial and error and realizing, up front, the properties of the particular bow in hand
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ctviolin
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PostPosted: Wed Oct 10, 2012 6:18 pm    Post subject: Re: Bow hair tension Reply with quote

Mat Roop wrote:


1- Is there a device to measure a bows ability to tension hair and
2- Is there a device to test measure an amount of hair to match the bow's ability to tension?

Thanks!!... Mat


Your hand and the feeling of the bow - I do not believe that these two things can be fortold by a guage or tool of any type.

Nor does a bows stiffness decide much if anything, of what needs to be done with the hairs in a rehair. (the only real variable is the amount of hair - which can often dictate playing qualities.

Again, an ability that arises from practice only.

From fully and evenly loose at the forward position, to a fully tight ribbon quickly enough, is what you are looking for on just about any bow.

all hair tension matters, have more to do with how large the gap is between the stick and the hair ribbon at playing tension, and the amount of screw left, to adjust for (if needed) to either add additional tension to the ribbon amount chosen, or retract for less playing tension in the chosen ribbon... which is not calculated before the rehair, as far as I know - other than getting used to rehairing in general.

it's simply an adjustment of the bow screw.
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Last edited by ctviolin on Thu Oct 11, 2012 12:05 pm; edited 1 time in total
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