Sideways bend in bass bar?


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53 minutes ago, arglebargle said:

This is a bass bar jig (early) I made a while ago. The design if from Sharon Que, published in The Strad. 

My violin/viola jig is somewhat similar, but my locating arms are on the other side of the bar, where it will resist the downhill slide.

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17 hours ago, Don Noon said:

The clamping method could also be a contributor.

I didn't notice anyone mentioned this, so excuse me if I missed it, but I've found orientation of the clamps also rather important.

In violin making school we were taught to make and use wooden "spring clamps" (those ones that look like kind of like wooden clothes pins) which  were applied from the bass side of the plate. I have to admit I discarded them after school  and  have use light screw clamps  since, alternating the application on the bass and treble side. I found this method allows more control in the amount of pressure applied and where the forces "go". Especially combined with locator studs, things tend to go quite smoothly.

If a plaster cast exists as part of a restoration, I sometimes glue in the bar using it (especially if there are repairs near  the bar; see below). I also have aluminum plate rings that I can use to stabilize a free plate when necessary.

BBincast.jpg

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4 hours ago, Tostra said:

Sure looks helpful! Keeping the plate from moving without a frame is difficult, so I have often considered making a sturdy plate for keeping it flat. That design doesn't look bad, is it stable enough?

It is stable enough for me. My violin and viola jigs are made from really thick plastic and are more stable. Aluminum would be great. This is a jig I made fairly quickly out of necessity. I always intended on re-doing it, but it works well enough that I've never gotten around to it.

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7 hours ago, arglebargle said:

 

1697991107_PhotoJan2384530AM.thumb.jpg.01b905b39554fb0966b93fe18ade3149.jpg

This is a bass bar jig (early) I made a while ago. The design if from Sharon Que, published in The Strad. I also have one for violin and viola.(they look a bit more sophisticated) The two arms move to adjust the bar while the platform holds the plate flat. The bar rests agains the arms at 90 degrees. Make on and never look back.

Thank you for the photo. How thick is the ply that supports the top?

With a slightly sprung top, I have needed a second person. But now, it is an issue of installing more of the taller cleats in the middle. Takes more time... The bar would like to move down slope, the way it's chalked. 

 

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4 hours ago, Jeffrey Holmes said:

...I've found orientation of the clamps also rather important.

I didn't think if it since I don't use clamps, but seeing them it becomes obvious... the overhung mass of the clamps will put a torque load on the clamped parts, and pull the bar in the direction of the clamp.  That may or may not counteract the tendency to slide downhill, depending on how much clamping force is used and which side the clamp is on.  But in any case, using side locating supports on the bar is the main thing.

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18 hours ago, GoPractice said:

Thank you for the photo. How thick is the ply that supports the top?

The plywood is 3/4 inches, 18mm.

Here are some pictures of the violin jig, since there seems to be some interest. Again, all credit goes to Sharon Que for the design. I tried to find the original article, but no luck. I believe she made it while working for Joseph Curtin. Her plastic frame was much thicker, but this was all I could find at the time. Works for a violin/viola, but probably too thin for a cello.

IMG_3571.thumb.jpeg.d9c080e2ec34cb039ce00b14ed593556.jpeg

IMG_3572.thumb.jpeg.aa04248ee1a672c241186231d4cabdb6.jpegIMG_3573.thumb.jpeg.687b9729c6358823044c72b94033c1e9.jpeg

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Looks like each of those 200 violins has received a lot of love and attention, really gonna be some lovely instruments with their own peronality ;-)

Seriously though, I don't see why that wouldn't work, in theory, if the bar really fits perfectly and nothing moves. But I don't think it would go well in reality...

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This (the video) is the way I was taught, and have done a few this way.  If I did as many as she does in a day, that might be the way to do. I only do about 5-7 BB's a year and I find Sharon's jig works the best for me.  BTW, I use a swing arm on the treble side that works well.  I glue the BB in the jig so the treble side arm keeps it from sliding downhill......Trick is to fit the bar well and NOT clamp the crap out of it.

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