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Andreas Preuss

self made useful tools or templates for violin making/repair

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57 minutes ago, David Burgess said:

No. Here's my thinking on this:

The total downforce on the saddle will be the same, no matter where the "break point"  or ridge is located. Since the most common situation is for a saddle to roll forward if it comes unglued (raising the rear of the saddle), I like to put the downforce more to the rear of the saddle, helping to hold that part down, by putting the break point closer to the perimeter of the outline.

Does that make any sense? :blink::)

29 minutes ago, Davide Sora said:

It would take an engineer who makes the right calculations, I don't venture further...:unsure:

OK, I can take a hint.

As it turns out, the defining geometry is pretty well set by the saddle height and the angle of the tailgut on either side of the saddle.  Reducing the saddle to the ridiculuous limits:

IMG_2358.JPG.ac638b77fbe639d308ae1668e733cd72.JPG

The resultant force vector magnitude, angle, and location are the same no matter where you put the breakpoint... as long as the "effective" saddle height is the same (the actual saddle height of the one in the right diagram would be slightly lower to get the same effective saddle height, i.e. the same tailpiece geometry).  

The diagram is for a mostly frictionless condition, but adding friction wouldn't change the result.  Vector b would be larger, and a would be reduced, but there would be no difference between the two saddles as to the resultant vector.

The crucial thing to me would be to keep friction down, by having a very smooth curve.  Lubricating the saddle with wax or something should help avoiding the levered-out problem, which would be mostly due to friction.  Naturally, a higher saddle height also would add to the problem.

 

 

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1 hour ago, Don Noon said:

The resultant force vector magnitude, angle, and location are the same no matter where you put the breakpoint... as long as the "effective" saddle height is the same (the actual saddle height of the one in the right diagram would be slightly lower to get the same effective saddle height, i.e. the same tailpiece geometry). 

Oh alright then, dangit! I'm back to this, which requires no cutout of the top, no time consuming diddly-fitting of a saddle, and no glue. But I haven't had the nerve to send it out on a customer fiddle yet. :lol:

https://maestronet.com/forum/index.php?/topic/328110-look-ma-no-saddle/

spacer.png

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1 hour ago, Don Noon said:

OK, I can take a hint.

As it turns out, the defining geometry is pretty well set by the saddle height and the angle of the tailgut on either side of the saddle.  Reducing the saddle to the ridiculuous limits:

IMG_2358.JPG.ac638b77fbe639d308ae1668e733cd72.JPG

The resultant force vector magnitude, angle, and location are the same no matter where you put the breakpoint... as long as the "effective" saddle height is the same (the actual saddle height of the one in the right diagram would be slightly lower to get the same effective saddle height, i.e. the same tailpiece geometry).  

The diagram is for a mostly frictionless condition, but adding friction wouldn't change the result.  Vector b would be larger, and a would be reduced, but there would be no difference between the two saddles as to the resultant vector.

The crucial thing to me would be to keep friction down, by having a very smooth curve.  Lubricating the saddle with wax or something should help avoiding the levered-out problem, which would be mostly due to friction.  Naturally, a higher saddle height also would add to the problem.

Thanks Don for coming to our rescue.:P

I suspected that even distribution of the curve and friction were the crucial point, but a more authoritative confirmation frees the field from any controversy.

What the heck, I'm just a luthier, my reasoning is something more like: if it doesn't come unglued, it works...:lol:

While we're at it, do you think making the saddle more inside than the purfling as I do can compensate for a greater height? Compared to a lower one but flush with the purfling?

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4 hours ago, Don Noon said:

OK, I can take a hint.

As it turns out, the defining geometry is pretty well set by the saddle height and the angle of the tailgut on either side of the saddle.  Reducing the saddle to the ridiculuous limits:

IMG_2358.JPG.ac638b77fbe639d308ae1668e733cd72.JPG

The resultant force vector magnitude, angle, and location are the same no matter where you put the breakpoint.

 

I agree that the Resultant vector sum is the same but the point of application  of R does not look to be the same. If both diagrams were drawn to scale R in the first diagram is lower than the R in the second diagram and so there might be a small difference

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I'm starting to have second thoughts about Don's drawing. It shows a roughly 45 degree combined force vector. But the longitudinal forces are actually much larger than the vertical forces, and that might change some things. I may need to do some "drinkin' and thinkin' " , and may even need to do some actual experiments to sort all this out. :blink:

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1 hour ago, catnip said:

I agree that the Resultant vector sum is the same but the point of application  of R does not look to be the same. If both diagrams were drawn to scale R in the first diagram is lower than the R in the second diagram and so there might be a small difference

Don mentions "effective height" that means (If I understand correctly) that the lines of vectors a and b coincide if you overlay the drawings. Real height of the saddles follows the dotted line of vector b in the first drawing.

In ideal world without friction the force vectors a and b are same.

But I see one flaw in Don's reasoning. If one of the force vectors increases (due to friction) then the direction of the resulting vector DOES change (alebeit only  little unless the difference is significant). If the vectors are same, then the result bisects the angle but, once one of the forces is larger the resulting vector shifts towards the larger one.

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7 hours ago, Davide Sora said:

While we're at it, do you think making the saddle more inside than the purfling as I do can compensate for a greater height? Compared to a lower one but flush with the purfling?

Cutting the saddle in past the purfling line will give it a wider base and definitely be more resistant to torquing out.

For all the other folks... those diagrams were freehand on a scrap of paper.  Not to scale at all.  But the basic idea is that the external force vectors on the saddle (tailgut) are the same no matter how you shape the saddle, and therefore the resultant force vector will not be different... with all else being equal (tailgut angles and location, and friction).  Friction WILL change the resulting vector, but with the same friction and same tailgut geometry, the shape of the saddle doesn't enter in.

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11 hours ago, Don Noon said:

Cutting the saddle in past the purfling line will give it a wider base and definitely be more resistant to torquing out.

Thanks for your confirmation, that's what I thought when I decided to make the saddle more inward. Maybe there is no need, but raising the saddle it seemed appropriate to do so, even if many consider this an imperfection:o:)

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On 11/13/2020 at 5:28 PM, Davide Sora said:

 

..... I like to make pretty tall saddles .....

Hi Davide... curious about why you make tall saddles? Do you adhere to the "standard" 158 degree string angle over the bridge? 

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17 hours ago, Mat Roop said:

Hi Davide... curious about why you make tall saddles? Do you adhere to the "standard" 158 degree string angle over the bridge? 

I rise to the saddle precisely to stay in the 157 ° / 158 ° range, mainly to compensate for the higher arching I make.

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Just starting a new cello, so I thought I'd share this. Not a self-made tool, but I find this method of holding and positioning the cello mold while fitting ribs very helpful. The mold rotates into any position. Veritas carving vise attached to a two piece mold.

IMG_3383.thumb.jpeg.578014e4259d2cf9b880256f01331666.jpeg

IMG_3382.thumb.jpeg.564141c1a9dd1960d020555052100010.jpeg

IMG_3384.thumb.jpeg.38693c1d2763202a136763535a484658.jpeg

IMG_3385.thumb.jpeg.42734a2ed38ff72c60f359c9181f93da.jpeg

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5 hours ago, arglebargle said:

Just starting a new cello, so I thought I'd share this. Not a self-made tool, but I find this method of holding and positioning the cello mold while fitting ribs very helpful. The mold rotates into any position. Veritas carving vise attached to a two piece mold.

IMG_3383.thumb.jpeg.578014e4259d2cf9b880256f01331666.jpeg

IMG_3382.thumb.jpeg.564141c1a9dd1960d020555052100010.jpeg

IMG_3384.thumb.jpeg.38693c1d2763202a136763535a484658.jpeg

IMG_3385.thumb.jpeg.42734a2ed38ff72c60f359c9181f93da.jpeg

That's cool, Arbargle. I've been using a couple of easily repositionable holding fixtures for about 40 years now. 360 degrees rotation on two axis, plus 90 degrees on a third. They've gotten pretty pricey now, but at this point in my career, I have absolutely no doubt that they have paid for themselves many times over.

https://www.amazon.com/Wilton-16240-301-Mechanical-Pow-R-Arm/dp/B00101WGMI

Perhaps some of their less expensive models would work for some things too?

https://www.amazon.com/Wilton-16120-344-Veep-Pow-R-Arm/dp/B001AZPA0O/ref=pd_sbs_469_15?_encoding=UTF8&pd_rd_i=B001AZPA0O&pd_rd_r=ad15d3bf-6790-4e5d-bd66-d656e0305389&pd_rd_w=Xh9wx&pd_rd_wg=XH7Qp&pf_rd_p=ed1e2146-ecfe-435e-b3b5-d79fa072fd58&pf_rd_r=KXCRNHB48M9HYC1CY7BZ&psc=1&refRID=KXCRNHB48M9HYC1CY7BZ

And:

https://www.amazon.com/Wilton-16180-343-Junior-Pow-R-Arm/dp/B002RNVMXM/ref=pd_sbs_469_2/138-0405833-5071504?_encoding=UTF8&pd_rd_i=B002RNVMXM&pd_rd_r=d91d4ad6-1607-4061-acf6-366ad4646882&pd_rd_w=IPqSV&pd_rd_wg=4M0u7&pf_rd_p=ed1e2146-ecfe-435e-b3b5-d79fa072fd58&pf_rd_r=5DSX1AWX6QVBEKQZRARC&psc=1&refRID=5DSX1AWX6QVBEKQZRARC

 

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On 11/16/2020 at 9:06 PM, Andreas Preuss said:

And one more I forgot to post at the beginning.

It is a device to plane a soundpost from short pieces of split wood. 

image.jpeg

image.jpeg

image.jpeg

I am intrigued by your jig. Is the plate under the plane glass or plastic? Thanks for posting and answering my question.

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4 hours ago, violguy said:

I am intrigued by your jig. Is the plate under the plane glass or plastic? Thanks for posting and answering my question.

Thanks for your interest.

There is neither glass nor plastic used in the jig. See the technical drawing below.  

Some useful hints for making it:

The 1mm plywood is needed too get the plane blade as close as possible to the wood surface.

the trickiest part is adjusting the holes where the needles fixture is inserted.

the holes shold match the size of the needle. the thicker the needle the better. if you find 0.6mm it is suffcient 0.7 would be better but seems hard to find.

For fine adjustment I first drilled the needle holes and then planed the ebony piece to adjust the distance to the rail basically by trial and error making test sound posts.

 

 

image.jpeg

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On 12/2/2020 at 3:20 PM, David Burgess said:

 I've been using a couple of easily repositionable holding fixtures for about 40 years now. 360 degrees rotation on two axis, plus 90 degrees on a third. They've gotten pretty pricey now, but at this point in my career, I have absolutely no doubt that they have paid for themselves many times over.

 

 

Those look pretty nice. Of course, we all know what I really need is a monsterball vise. Unfortunately, I just don't have the room. Someday.

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34 minutes ago, arglebargle said:

Those look pretty nice. Of course, we all know what I really need is a monsterball vise. Unfortunately, I just don't have the room. Someday.

The bench model Monsterball vise looks nice too. I'd have to think long and hard about dropping $1500 on one though. :o

http://www.monsterballvise.com/benchmodels.htm

 

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I thought a bit about making my own "monsterball" device using an old bowling ball and a solid wood frame... but it seems overkill.  A duckpin or candlepin ball would probably suffice (David might need the bowling ball version).    But I don't really need it anyway, and have far too many fixtures and jigs cluttering up the shop.  And I need to make a bunch more CNC fixtures.

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On 12/2/2020 at 6:51 PM, Andreas Preuss said:

Thanks for your interest.

There is neither glass nor plastic used in the jig. See the technical drawing below.  

Some useful hints for making it:

The 1mm plywood is needed too get the plane blade as close as possible to the wood surface.

the trickiest part is adjusting the holes where the needles fixture is inserted.

the holes shold match the size of the needle. the thicker the needle the better. if you find 0.6mm it is suffcient 0.7 would be better but seems hard to find.

For fine adjustment I first drilled the needle holes and then planed the ebony piece to adjust the distance to the rail basically by trial and error making test sound posts.

 

 

image.jpeg

Thank you for clarifying. Everything is much clearer now.

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3 hours ago, Don Noon said:

I thought a bit about making my own "monsterball" device using an old bowling ball and a solid wood frame... but it seems overkill.  A duckpin or candlepin ball would probably suffice (David might need the bowling ball version).    But I don't really need it anyway, and have far too many fixtures and jigs cluttering up the shop.  And I need to make a bunch more CNC fixtures.

Don, the frame does look pretty easy to make from wood, maybe a half-day project if one was after utility, and wasn't anal about appearance. To secure and release the ball, my fist thought is that I would use a wedge pushing the ball up from the bottom, with the wedge attached to a screw to force it in and out. But if I thought about it a little more, I might be able to come up with a simpler and better way to clamp and release the ball. :)

A friend of mine recently purchased a high-performance boat from the person I had originally sold it to. The original hull (produced by a high-performance boat manufacturer) incorporated many parts made from wood, including balsa-core skinned with fiberglass. But I added many other parts made from wood.

So my friend, shortly after purchasing the boat called me up, after discovering that so many of the parts I had added and fabricated were made of wood, teasing me about that, since he has known for at least least 30 years that I am a violin maker.

I love stuff like that, jokes between friends, with no intention whatsoever of hostility. The current owner of this scary-fast boat and his partner are some of the most wonderful people I have ever met.

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On 11/16/2020 at 9:06 PM, Andreas Preuss said:

And one more I forgot to post at the beginning.

It is a device to plane a soundpost from short pieces of split wood. 

image.jpeg

image.jpeg

image.jpeg

Does one of the pins fit into a hole in the back plate?

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