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Vacuum Bridge Clamps
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Author:  Bob Garrish [ Fri Nov 23, 2007 4:15 am ]
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OK, a few people mentioned in the vacuum tools thread that they'd be interested so here's the offer on vacuum bridge clamps. They can be made in guitar or UKE sizes.:

If eight to ten will sell, then I can do them at $50 each. If it was 15 or more, I could do them for $40, but that's a lot of bridge clamps. Quantities under eight are doable, but the pricing goes up pretty quickly, so we'll figure that out if it happens.

The clamps are 3.5"x8.25" inside and 2.5"x5.25". They're made from 3/4" acrylic plate with a 1/8" neoprene foam gasket on the bottom and a neoprene vacuum membrane on top. They come fitted with a barb of your choice for 3/8" or 1/2" hose (outer diameter). And they really suck!

Author:  JohnAbercrombie [ Fri Nov 23, 2007 5:08 am ]
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Bob-
I'm interested-very.
Are you talking about a 'group buy' sort of thing here, with the total number of orders being 10 or 15? I think you should get there fairly easily.

I assume you'd have to add on some money to the shipping charges to cover packing materials and time? Any idea of that cost?
Are the gaskets and neoprene sheet replaceable? Spares available?

Cheers
John



Author:  Rod True [ Fri Nov 23, 2007 5:40 am ]
Post subject: 
Is that US$ or CAN$ Bob?

I'd be interested if there are enough people to hit 15 units.

Are these curved on the bottom?
Author:  Bob Garrish [ Fri Nov 23, 2007 6:08 am ]
Post subject: 
John:
You could consider it that. At one point, I offered these as retail items in an online store but I don't generally hold stock on items and the setup ended up eating up any profit on making them. So, to make a profit on them I need to batch them.

Shipping would be cost plus $5 for the packaging. I can get more of both the gasket and the neoprene sheet. In theory, you should never really wear out either of them (especially the gasket). Replacing the neoprene is just a matter of slicing off the old stuff with a razor blade and gluing new stuff on. At the price, though, you can probably just buy another one in fifteen years :)


Rod:
Currency doesn't really matter. Pick whichever one is cheaper for you on the day you pay.

They don't need to be curved on the bottom as, over the width of the clamp, there's only 0.05" of bow even in a 15' radius (and 0.125" of gasket). It's good on anything up to around probably an 8 or 9' radius, which would be one heckuva dome. I can make them with thicker gasket, as well, if someone's doing something really crazy with them, but it'll cost a bit extra.
Author:  Ricardo [ Fri Nov 23, 2007 6:52 am ]
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I'm in for $50.  I think my compressor hose is 1/2".
Author:  JohnAbercrombie [ Fri Nov 23, 2007 7:33 am ]
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Bob-
Sign me up for one, thanks!

John
Author:  Rick Hubka [ Fri Nov 23, 2007 7:55 am ]
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I'm in for 2. one guitar and one mandolin.

Thanks
Author:  letseatpaste [ Fri Nov 23, 2007 8:59 am ]
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I'm in for a guitar one.
Author:  Joe V [ Fri Nov 23, 2007 9:27 am ]
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Bob,

I will order one for guitars.

Joe Volin
Author:  Bob Garrish [ Fri Nov 23, 2007 10:14 am ]
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That's seven so far at Joe V if I'm counting right. I'll leave it open over the weekend and I'll tally up where we are on Monday, set the price, and order the materials.
Author:  BruceHerrmann [ Fri Nov 23, 2007 10:57 am ]
Post subject: 

I'll take one for guitars, the 1/2 barb will be fine, I assume they are standard fittings, if it turns out I need 3/8 I'll just switch it out.  Have not finished my vacuum system yet but am planning to use 1/2 inch hose.


Bruce
Author:  GregH [ Fri Nov 23, 2007 11:24 am ]
Post subject: 
I would buy a guitar bridge clamp at $50.
Author:  chewy63 [ Fri Nov 23, 2007 11:38 am ]
Post subject: 

Hi Bob, I have a pneumatic flow over pump for my stripping operation.(the girls love it)


Will it work as a vacum?  I am looking for a reason to buy one of these, and also another application for my pump.


Just a thought.  If someone knows if it will work i will take one.


chewy
Author:  Rod True [ Fri Nov 23, 2007 11:53 am ]
Post subject: 
I guess I didn't specify,

Guitar bridge clamp with barb for 3/8" hose.

Thanks Bob
Author:  Ricardo [ Fri Nov 23, 2007 1:24 pm ]
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Bob, will I be able to use the guitar one for my ukes or will it be too big? Rich
Author:  GCote [ Fri Nov 23, 2007 1:50 pm ]
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Hey Bob...
I will take a guitar 3/8" too

Thanks Gary
Author:  Bob Garrish [ Fri Nov 23, 2007 4:47 pm ]
Post subject: 
[QUOTE=chewy63]

Hi Bob, I have a pneumatic flow over pump for my stripping operation.(the girls love it)


Will it work as a vacum?

chewy

[/QUOTE]

You got me. The only vacuum pumps I know of are the rotary vane type and the venturi type. I have one of each, I only use the venturi when I need CFM.

Author:  Bob Garrish [ Fri Nov 23, 2007 4:54 pm ]
Post subject: 
[QUOTE=Ricardo]
Bob, will I be able to use the guitar one for my ukes or will it be too big? Rich[/QUOTE]


The interior of the clamp is the dimension I put in the original message at the top. You need at least that much area and a smidge more underneath the clamp or you won't get a seal. If you have enough space on your uke top (3.5" by 8.25" plus at least 1/8" all around for a seal) then there shouldn't be a problem.
Author:  Ricardo [ Fri Nov 23, 2007 5:27 pm ]
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Bob, whats the interior dimensions of the mando clamp?  Ukes range from around 6 inches across to around 8 for the 3 smaller sizes. 
Author:  chewy63 [ Sat Nov 24, 2007 3:13 am ]
Post subject: 

Thanks for the reply Bob.


It was just a thought.


chewy
Author:  Howard Klepper [ Sat Nov 24, 2007 3:44 am ]
Post subject: 
Vacuum bridge clamping strikes me as an example of thinking that higher tech must be better. With a good pump and seal, you won't get more than 10-11 psi, which is a small fraction of what any glue manufacturer recommends (OK, they all recommend much more than is really needed, but in any case you can easily get 3-4 times as much with clamps). Plus the vacuum will tend to pull the glue out of the joint. I won't dispute people saying they haven't had problems, but they are having success in spite of the clamping system, not because of it. Why give up your margin of safety unnecessarily, when it is so easy to clamp a bridge in the traditional way?
Author:  JohnAbercrombie [ Sat Nov 24, 2007 5:00 am ]
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[QUOTE=Howard Klepper] Why give up your margin of safety unnecessarily, when it is so easy to clamp a bridge in the traditional way?[/QUOTE]
Good points, Howard.
I've done a few lattice-braced tops (where the lattice runs over the bridgeplate) and just find it a PITA to make up a caul to properly fit, and then stick it in there, and remove it later. I was also thinking (while recently working inside a guitar with CA and transducers) that it would be a lot easier to install the K&K pickup transducers before gluing on the top, if they were part of the plan from the get-go.
For situations like that,I thought it would be handy to get/make a bridge vacuum clamp. I agree that the clamping force with vacuum (perhaps 80lbs total?) is not as great as with several screw clamps, but it's comparable to using 8-10 go-bar sticks, which seems like plenty to me.
I also hate using clamps through the soundhole, as it's easy for me to 'ding' the soundhole edge- I'm kinda clumsy, I guess.
BTW, I already have a vacuum pump for laminating jobs.

Cheers
John
Author:  Bob Garrish [ Sat Nov 24, 2007 6:12 am ]
Post subject: 
[QUOTE=Ricardo] Bob, whats the interior dimensions of the mando clamp? Ukes range from around 6 inches across to around 8 for the 3 smaller sizes.
[/QUOTE]

Ahh krunk...that explains it! I accidentally wrote 'mandolin' instead of 'uke' in the original post. The second clamp size is specifically for ukes! My bad!
Author:  Bob Garrish [ Sat Nov 24, 2007 6:38 am ]
Post subject: 
[QUOTE=Howard Klepper] Vacuum bridge clamping strikes me as an example of thinking that higher tech must be better.
...
Plus the vacuum will tend to pull the glue out of the joint.
...
Why give up your margin of safety unnecessarily, when it is so easy to clamp a bridge in the traditional way?[/QUOTE]

I think it's an example of people considering the forces at work and choosing the simplest solution. On a properly fitted glue joint with glue properly spread on both mating surfaces, the goal of the clamp is to push the mating parts together while evacuating ALL excess glue except that which is required to coat the surfaces. The strongest glue joint is a chemical bond, and that requires the thinnest glue line possible.

Clamping pressure accounts for errors within the parameters above. Too much glue in the joint? More clamping pressure to evacuate it. Poor fit on the joint? More clamping pressure to force the parts together.

I agree that a margin of error is lost, but the margin in this case is accounting for sloppy work, not the requirements of a good bond on a properly prepared joint.
Author:  Ricardo [ Sat Nov 24, 2007 7:04 am ]
Post subject: 
I don't know how else you would glue a bridge on if you don't have a sound hole or its too small.  I've used a whole body clamp, but I don't like putting clamping pressure on the body. Seems like the vacuum clamp is an ideal solution.
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