Official Luthiers Forum!

Well I have my vac/press system up and running, I have built a press for bracing and I would like to build one for the bridge. I hate to fork out $100+ for LMI does anyone have pics of bridge clamps they have built

thanks
Richard

Richard, check out the tutorials section, there is a recent thread there with a plan to download and pictures as well. here's a link for you viewtopic.php?f=10117&t=23895

I'd like to see some pictures of you vacuum set up as I plan on setting up soon as well. I have a Gast pump, an old compressor with a blown motor (I'll be using the tank as a reservoir) and nothing else, so I'd love to see pictures of your set up.

Cheers

_________________
My Facebook Guitar Page

"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

_________________
Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

That's some nice minimalist engineering, right there. A vacuum clamp is just a membrane, a seal, and some way to get the air out.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Well, I didn't mean for it to be "end of subject" when I posted that pic. That's one way to do it. Let's see some more!

Dennis

_________________
Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Dennis,

Where did you get the white plastic fitting for the end of the vacuum hose?

Kathy

Hi Kathy,

That came from FiberGlast. They sell the vacuum film as well as the valve.

The Vacuum Connector (valve) is about half the way down on this page: 891-A Vacuum Connector

The vacuum membrane is on this page : 578-A Nylon Bagging Film about half way down, and the 581-A Gray Sealant Tape is near the bottom of that same page. That tape came off cleanly from KTM-9 finish, and I know it comes off cleanly from other finishes as well.

Dennis

_________________
Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

great job dennis.

Mine isn't quite as minimalist as the one Dennis posted.

Mine is made from a scrap of lexan (1/4 thick). For the membrane, I cut the end off a exercise rubber band they sell for pilates and yoga (my wife bought them at a garage sale). The gasket is a bit of a foam rubber yoga mat with a hole cut in it (no butt seams to leak like with using weather stripping) - again from a garage sale. The only new part was the brass hose connector which is screwed into a hole I tapped for the threads. The membrane and foam rubber are attached to the lexan with a bead of super glue. Total cost was less than $5.

John Cross

Thank you for the links, Dennis.
John, your design is also quite simple and good - thank you for posting.

Kathy

What pump or motor setup are you guys using?

_________________
“If God dwells inside us like some people say, I sure hope He likes enchiladas, because that's what He's getting”
-jack handy

John, this looks interesting. Good (re)use of cheap resources!

Can you go into more detail about how you made yours? You've got a piece of Lexan with a hole big enough for any bridge you make, and onto the bottom of the Lexan, you've glued a piece of rubber yoga mat of the same shape as the Lexan. (I've made vacuum templates/jigs for a pin router, so I "get it" when I see the hose connected, but you may want to explain that in detail for others that may be interested in doing it your way. I used quick-disconnect air hose fittings for the connector - I can't see yours very well in the photo but it seems like you used the same or similar.)

Looks like you've also glued an additional piece of the membrane material onto the bottom, covering the yoga mat/gasket. Did you seal the edges where the membranes meet at the exterior?

Thanks,

Dennis

_________________
Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

john can you go into a little more detail about it. I like the design.

Here is a bit more detail about how I made mine.

The lexan scrap is about 4x9 give or take. I cut a hole bigger than the bridge I use offset to one side (about an inch clearance for the bridge all around) and eased the edges so there were no sharp corners to catch the rubber membrane. In the side that didn't have the hole for bridge clearance, I drilled and tapped a hole to fit a standard brass fitting (since it is a pipe thread, make sure you tap it from the same side as you will be attaching the rubber mebrane and only go deep enough to have the brass fitting go almost all the way through the frame). The brass fitting I used has pipe treads on one side and barbs on the other so you just press your vacuum hose onto it after it is threaded in (wait to thread it in until after all the other pieces are glued on). Run a bead of super glue all around the bridge clearance hole (but not the hole for the brass connector) and put on the rubber membrane taking care to make sure it wets out the glue all the way around and there are no wrinkles. You don't need a lot of glue - just enough that there is a continuous bead. While that's curing, take the foam rubber mat and cut a piece the same size as the lexan scrap (i.e. 4x9). Cut a big hole in it so that the edges are about a half inch wide all the way around. Run a bead of glue around the edge of the rubber mat ring and press that onto the other side of the lexan frame. After that cures, screw in the brass connector and attach you hose (which has a quick connect fitting on the other end to actually attach to the vacuum pump).

I drew up a picture of the parts if that isn't clear enough.

As for the vacumm pump I use, I got a diaphram pump from Joe woodworker because I wanted something quiet. If that wasn't a issue, there are cheaper otions.

Thanks, John.

I guess what's so surprising is that superglue holds the membrane onto the Lexan. I think of superglue as drying pretty brittle. I'll have to try and see if thick CA will hold the Nylon film that I have. I like the clear Nylon membrane, as you can see if anything has shifted during clamping.

It still appears to me that you have glued the green membrane both to the top (which is the part that stretches and gets vacuum sucked down), as well as an additional membrane covering the yoga mat (thin neoprene?), or does the yoga mat just happen to be the same shade of green?

Vacuum Pumps:
I did some research to see which Gast vacuum pumps would pull at least 25 to 28 inches of mercury (in Hg), because that is what Grant Goltz told me would be adequate clamping pressure. (Grant also builds drop-dead gorgeous kayaks, vacuum forming veneers with epoxy resin and cloth.) Once I knew how strong the pump needed to be, I watched Ebay until I found a used one for (I think it was about) $30 + shipping. They are way too expensive to buy new, for most non-full-time pro luthiers. The other thing I bought was a vacuum gauge, so I would know when the vacuum was at or near the 25 to 28Hg range. I found it to be critical, because without a gauge, you won't know if the seal is tight, and you may be pulling less, for example if you were pulling 15 inches Hg, the membrane would be stretched, and you would have no way to know that you got inadequate clamping pressure (until the bridge popped off later.)

Dennis

_________________
Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

CA will hold it. It's by far the best glue for the application, actually. I think it gets a bad rap for the combination of being harder to use properly than hide glue and less traditional than epoxy, but it's a really great adhesive for many things if that doesn't scare you off

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Dennis said "It still appears to me that you have glued the green membrane both to the top (which is the part that stretches and gets vacuum sucked down), as well as an additional membrane covering the yoga mat (thin neoprene?), or does the yoga mat just happen to be the same shade of green?"

The rubber yoga mat and the stretchy membrane are the same colour (just luck - not intnetional). The stretchy membrane gets glued to the top of the lexan frame (same side as the brass fitting threads into). I don't know what kind of rubber it is but it is pretty tough. The yoga mat gasket gets glued onto the bottom of the lexan frame. No second layer of membrane.

My first version of this looked more like the one LMI sells (i.e. bolted together) and used weather stripping as the gasket. It was a complete failure - leaks, took a long time to build, looked even uglier than this one. This version will hold a vacuum for about 25 seconds after I turn off the pump.

Dennis-
Thanks for the FiberGlast link- I had been looking around for latex and other stretchy materials for a while. It looks like the Stretchlon material will do the trick (500% stretch).

Cheers
John

John, If I knew you really well, then I would tease you about being excited to have found a latex store. I would also warn you not to make your suit too tight. However, I don't know you well enough, and so will have to hold off.

Dennis

_________________
Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Dennis-
Yeah, well on second reading it does sound a bit like the fetish thing, I admit. I should have said 'I had been looking around for latex and other stretchy materialsstrictly in small quantities for vacuum guitar jigs', I suppose.
There's a whole bunch of stuff I just 'don't get' in life.....

Cheers
John

Do you think something like this would work for a larger top brace in dish clamp?

_________________
Pat

This is actually the setup you would use to vacuum bag a 60ft fibreglass yacht! (slight scale difference though )

Dennis, doesn't the tacky tape mess up the finish? The stuff I've used is really hard to get off once you've stuck it down properly.

Edit: sorry, should have read the whole topic

_________________
"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

I'm in the "use what's at hand" camp.
Just a tuberculin syringe barrel stuck into the vacuum hose, a three way IV valve, and hypodermic needle. The needle is sealed to the bridge clamp with silicon caulk.
I recently had to clamp multiple bent strips on an undulating mold for a prototype for a guitar stand. For the port through the rubber membrane, I just cut out the injection port from an IV fluid bag and glued this to the membrane with Locktite Vinyl Fabric & Plastic Flexible Cement. Worked great for multiple clampings...just stuck the needle through the IV bag port, and your good to go.

For a pump I use the compressor out of an old freezer, an old propane tank from the BBQ (flushed out with Nitrogen first !) as a reservoir, and the control stuff which you can get from Joe Woodworker site. Quiet as a mouse.

I did a tutorial on one. It's in the tute section.

_________________
Steve Smith
"Music is what feelings sound like"