talkFestool  

Go Back   talkFestool > Manufacturers & Vendors of Fine Tools > Bowclamp

Bowclamp Modern technology used to realize an age-old idea: a perfect bow shaped arc. The Bowclamp's patented design - made possible only with the help of computerized, numerically-controlled cutting technology (CNC) - allows for equal clamping pressure along the entire length of the glue line... with only one clamp at each end!

Reply
 
LinkBack Thread Tools Display Modes
  #1 (permalink)  
Old 04-29-2010, 04:15 AM
CraigFeuerzeig's Avatar
Member
 
Join Date: Sep 2008
Location: Montclair, NJ
Posts: 526
Default "oh... you've exceeded that".

That was the quote from the guy doing the testing... when he asked... "what was your target pressure?".

I answered... "My goal was 150 psi".

I spent the whole morning with these guys.

Pressure Indicating Film and Pressure Sensitive Film

I wish I knew about these guys before yesterday. How funny that they were only a half hour away.

And boy did I learn a lot... please allow me to explain.

This is the product... it's like litmus paper, except it measures pressure. The paper changes color depending on the pressure. It records the maximum pressure applied. You can see on the bottom left where I pinched it to make sure it was oriented properly. It's actually 2 pieces working together, and they need to be facing the right way.



The deeper the red color the more pressure applied. It's typically used to measure torque and machining tolerances in engine components and material handling components used in industry.

They loved the idea of the Bowclamp and were more than willing to help. This stuff is scary expensive however... $700 for a 20' roll. So use will have to be sparingly.

The film comes ready to measure different pressure ranges. There are 6 different grades measuring from 28 psi -50,000 psi.

I bought "super low pressure"... measures 70-350 psi. And crossed my fingers.


My Bowclamp testing was done with "Super low"... 70-350 psi.



Clamped between 2 pieces of 1/4" mdf and 2 bowclamps picked at random off the top of the pile.

Here's a close-up of the middle. You can actually see the grain... or is it sanding marks?


And the corresponding graph... I'm instructed to use line C based on local conditions:




That's about a .7 ... 250 psi. Computer imaging to follow.

Thanks for looking.
__________________
Bowclamp "good caul"

Last edited by CraigFeuerzeig; 02-21-2013 at 11:18 AM.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #2 (permalink)  
Old 04-29-2010, 05:12 AM
RWeber's Avatar
Member
 
Join Date: Jul 2008
Location: Lincoln, NE
Posts: 1,212
Default Re: "oh... you've exceeded that".

Thats cool. And interesting. Do they make strips that mount to your back, so you can actually verify when your wife . . . oh never mind.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #3 (permalink)  
Old 04-29-2010, 05:24 AM
EijiFuller's Avatar
Member
 
Join Date: Aug 2008
Posts: 1,536
Default Re: "oh... you've exceeded that".

I never doubted it. Nice test.
__________________
Help me by liking www.facebook.com/fullerbuilt
www.fullerbuilt.com
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #4 (permalink)  
Old 04-29-2010, 05:25 AM
EijiFuller's Avatar
Member
 
Join Date: Aug 2008
Posts: 1,536
Default Re: "oh... you've exceeded that".

You should be selling the bench top too.
__________________
Help me by liking www.facebook.com/fullerbuilt
www.fullerbuilt.com
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #5 (permalink)  
Old 04-29-2010, 05:32 AM
SRSemenza's Avatar
Member
 
Join Date: Jul 2008
Location: Fingerlakes Region, NY State
Posts: 1,178
Default Re: "oh... you've exceeded that".

That is cool stuff Too bad it isn't cheap enough just to try out on things around the shop.

Seth
__________________
If you know where it's comin' from ...... You can tell where it's goin'. ========> ======> =====> ====> ===> ==> => > > >>>
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #6 (permalink)  
Old 04-29-2010, 06:01 AM
MichaelKellough's Avatar
Member
 
Join Date: Jul 2008
Location: The northernmost end of the southernmost county of New York
Posts: 4,525
Default Re: "oh... you've exceeded that".

That is a neat material. I have no doubts about Bowclamps but so far the pressure film is demonstrating the high heel shoe idea (concentrated pressure resulting from points) rather than indicating the pressure the Bowclamp delivers. You'd have to somehow average the red and white zones to figure out what the pressure really is in the tests so far.

The film is very sensitive to texture. You have to find a way to eliminate texture to get an even color in the film since it is so prone to illustrating the high points in the cauls. Try a caul that is totally smooth like a 1/4" strip of acrylic. You might have to back that up with a strip of neoprene so the pressure is even enough for the film. Actually a medium to soft neoprene might be all you need (omit the acrylic). Seems like you need a caul that's softer than the film or smooth as glass.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #7 (permalink)  
Old 04-29-2010, 01:19 PM
CraigFeuerzeig's Avatar
Member
 
Join Date: Sep 2008
Location: Montclair, NJ
Posts: 526
Default Re: "oh... you've exceeded that".

While I agree that it shows me the importance of getting my auto-shaper on line to get rid of the milling marks I've wanted to get rid of for a long time... it's actually just the nature of the beast I think. This stuff finds the high spots on finely machined metal parts. A close up of an crank-case joint would look very similar. We're simply never going to get flatter than that with wood. Think about the 40,000 psi photo. All the pressure in the world wan't going to bring those faces together completely. I think you have to consider that this represents what's happening in the real world... albeit it a bit more glaringly than any one of us would like to believe, perhaps. I went with 1/4" mdf. I think it's about as flat as we are going to get in our woodshops. The computer imaging will show that there are areas that exceeded the paper (350 psi). We will always be working with averages... and the pressure being distributed through the material we're gluing.

Another thing I should mention... The day before yesterday I spent a good part of the morning on the phone with the senior technical consultant at Franklin (makers of titebond). Boy, does he love me!

I learned an awful lot from him as well.. but the take away bit of information was this quote... " while it would be difficult, it's absolutely possible to over-clamp and starve the joint".

And 150 psi really isn't that tight. In fact if I had to give it a (relative) word... I'd have to call it "snug".

The other thing that I think is really cool... is, if anything... I'm I'm comforted to know that, as suspected all along...

The squeeze-out doesn't lie.
__________________
Bowclamp "good caul"
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #8 (permalink)  
Old 04-29-2010, 02:07 PM
MichaelKellough's Avatar
Member
 
Join Date: Jul 2008
Location: The northernmost end of the southernmost county of New York
Posts: 4,525
Default Re: "oh... you've exceeded that".

Quote:
Originally Posted by CraigFeuerzeig View Post
While I agree that it shows me the importance of getting my auto-shaper on line to get rid of the milling marks I've wanted to get rid of for a long time... it's actually just the nature of the beast I think. This stuff finds the high spots on finely machined metal parts. A close up of an crank-case joint would look very similar. We're simply never going to get flatter than that with wood. Think about the 40,000 psi photo. All the pressure in the world wan't going to bring those faces together completely. I think you have to consider that this represents what's happening in the real world... albeit it a bit more glaringly than any one of us would like to believe, perhaps. I went with 1/4" mdf. I think it's about as flat as we are going to get in our woodshops. The computer imaging will show that there are areas that exceeded the paper (350 psi). We will always be working with averages... and the pressure being distributed through the material we're gluing.

Another thing I should mention... The day before yesterday I spent a good part of the morning on the phone with the senior technical consultant at Franklin (makers of titebond). Boy, does he love me!

I learned an awful lot from him as well.. but the take away bit of information was this quote... " while it would be difficult, it's absolutely possible to over-clamp and starve the joint".

And 150 psi really isn't that tight. In fact if I had to give it a (relative) word... I'd have to call it "snug".

The other thing that I think is really cool... is, if anything... I'm I'm comforted to know that, as suspected all along...

The squeeze-out doesn't lie.
Those are all good points Craig. I'd be comfortable using the Bowclamp directly against my workpiece. My point is that the pressure sensitive film is too sensitive to texture to determine the pressure the Bowclamp is delivering, unless you make some additional effort to reduce the texture in contact with the film.

To measure the force of a Bowclamp I'd make a jig with a spring scale

\

rigged so that straightening a Bowclamp stretches the scale.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #9 (permalink)  
Old 04-29-2010, 04:17 PM
Poto's Avatar
Super Moderator
 
Join Date: Jul 2008
Location: San Diego, CA
Posts: 8,999
Default Re: "oh... you've exceeded that".

That's really cool, Craig. I'd be interested in a test in which you put the tape perpendicular to the bowclamps, and clamped two pieces of wood, to see how the pressure fell off with horizontal distance away from the bowclamp. If you tried it with different thicknesses of wood, you could test your 45 degree hypothesis - see how the force radiates away from the caul to create pressure laterally.

As for averaging the signal on the tape, there's lots of programs that will take your digital image and average the data over a selected area. I doubt it will change your conclusions much.
__________________
I don't have as many Festools as Fred. Or Marcou's, or Brese's, or Lie-Nielsen's, or Lee Valley's, or Blue Spruce's, or Harold and Saxon's, or...
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #10 (permalink)  
Old 04-30-2010, 01:48 PM
CraigFeuerzeig's Avatar
Member
 
Join Date: Sep 2008
Location: Montclair, NJ
Posts: 526
Default Re: "oh... you've exceeded that".

Actually Michael the spring test would not be effective for the same reason I tried to explain that the scale test was flawed. I would not be flattening the bowclamp... just bending it in one spot and pulling the ends down to meet it. In effect I would end up with an arc and an arc... not a straight line. In the scale test, only the area of the caul making contact with the scale are flattened... resulting in an arc, a straight (touching the scale), and an arc.

I think this is significant... to say the least. In order for the spring test to work I would need continuous springs along the length. I'd like to think that since the arc is continuous, 4 scales would read the same.

And Peter yes, I'd like to do that test as well. I'm saving up for the paper.

But it's not exactly my theory... I'm sure I read it wrong, but :smad:

Stress (mechanics) - Wikipedia, the free encyclopedia




Maximum and minimum shear stresses

The maximum shear stress or maximum principal shear stress is equal to one-half the difference between the largest and smallest principal stresses, and acts on the plane that bisects the angle between the directions of the largest and smallest principal stresses, i.e. the plane of the maximum shear stress is oriented from the principal stress planes. The maximum shear stress is expressed as
Assuming then
The normal stress component acting on the plane for the maximum shear stress is non-zero and it is equal to
__________________
Bowclamp "good caul"

Last edited by CraigFeuerzeig; 04-30-2010 at 02:47 PM.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump


All times are GMT +1. The time now is 10:21 PM.