Official Luthiers Forum!

Maybe true in some cases, but maybe not. There are folks like Sylvan Wells and Ervin Somogyi that have made it clear that they want financial compensation for disclosing (at least some of) their ideas. Every one of the folks I listed could have done the same (well, Roger Siminoff did write books - probably lost money on the venture though.) It costs very little to have a website with some protected pages, available only to those who have paid a subscription fee. So, no great outlay of cash or time, or legal hassles, or manufacturing woes involved. I have had conversations with most of the folks I listed, and happen to know Grant Goltz pretty well, and I can tell you that at least some of the folks I listed offered their knowledge freely simply because they wanted to share. I think people that have a "giving" spirit themselves get what I'm saying, and those that don't, don't. Filippo, your own spirit of sharing is reflected in my drill press table, with its horizontal and vertical T-track, and even the intersections between T-track pieces hogged-out the same way you showed. I just wanted you to know that I know that you do "get it."

Sharing is fun, it feels good, it fosters friendships and a sense of community.

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Brad,

It looks like (in ur picture) that the waist caul mechanism is welded at some angle, perhaps optimum for your body (your guitar body!) shape. Maybe this is not an issue. But it would seem that being able to adjust that angle might be a good thing. I was thinking about its physical location as well, much harder to design that in. But then, of course, the user can (I think) slide there mold back and forth for alignment. But I cannot jusdge from the pictures how this might work out since I am unsure how the band works off the lower bout.

As for the stretcher, I was being a bit self centered with that suggestion since I like to build harp guitars. Unfortuneately, there is little in the way of symmetry to take advantage of. So two molds are built. The upper mold includes the harp arm which would not work with your current design. The stretch arm might even need to tilt up some (after extended) to work properly with the harp arm side.

To make matters worse, there is the bottom of the harp arm as well. But I do have ideas for that. It just requires an even longer steel belt or slat if that is what your are calling it.

Dennis, Just be thankful for what people are sharing for free. And those who you mentioned have shared many of their thoughts and ideas for free. There isn't anything wrong with them wanting to make a living from Lutherie. Perhaps they just don't give away the farm as much as you would like. You don't work for free do you?
I can tell you from experiance that it gets a little old at times when I make a video and then someone says something like "show us how you do" and not even a, " can you or thanks." At what point is someone to be compensated for the time and money and energy and creative thought they put into it? The Thanks is nice but in the end it ain't putting food on the table. Just be thankful for what you've gotten shared and don't expect more. Times are hard if you are unemployed.

Interesting - I went to Sylvan's site today and found that he is charging to view the tutorial he did on making my version of a precision router base .... I remember when it used to be free ....

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

It's been that way for sometime Tony. Since no one was contributing a donation to the Tips page he now charges something like $20 for access. But my YouTube is still up for the Precision Router Base.

Dang that bender could make me start building again. Great job Brad.

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Chris Paulick: WORD!

Brad and Nelson, I was curious about the bending process. In the prototype, the lever arm comes down and there were knobs to lock the arm in the horizontal position prior to pressing the waist shoe. In the current iteration, it doesn't appear to have a similar lock. How does one seat the waist, particularly in the cutaway configuration, without having locked the arm set?

One other thought is that in your CAD drawings the rear uprights are square to the table. It might be nice to have these set at a back angle so that when the arm is in the upright position its own weight keeps it upright because it's leaning back away from its hinge point.

I also think its a mistake to leave out the horizontal registration bars for the molds. That seems to me to be a good way to make mold changes consistent.

I think that the fixture should accommodate a slightly taller molds so that there is more meat on the re-curve area of the cutaway, unless there is more support under the mold at that area so it can't flex, or even crack from the repeated heating and cooling.

One could also improve the waist caul by having vertical rods and sleeve bearings that help keep the caul flat as it comes down, and doesn't rack.

I'm also curious as to what the two arms are coming off of the armature on either side of the cutway horn in the photo of the current version.

Another addition would be the use of ejection pins to change the armature locations for full and cutway configurations, locating the waist shoe, as well as elevation on the back posts for different height bodies so that the armature remains parallel to the centerline when using the cutaway arm.

Ejection pins are ubiquitous in the sound industry for rigging speaker cabinets and setting their angles, so they're quick and incredibly strong.

Correct me if I'm wrong here but what makes this bender really function at bending well is the tension on the slats? And do the air cylinders provide the amount of tension depending on the of air pressure that is applied applied to the cylinder or is the cylinder rated for that?

Pneumatic cylinders pull proportionally to the pressure, but they have maximum rated pressures, as well. The cylinders I have here are rated max 125PSI (which means the 150-175 straight from my compressor could ruin the seals) with a 1.5" bore. 0.25*Psi*Pi*bore*bore gives you the amount of pull, which is 0.25*125*3.1415*1.5*1.5=220lbs per at 125PSI for my cylinders.

It's linear, so if I was using 90PSI then it would be 90/125*220=158lbs per. I wonder how much force they're using at Taylor?

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Dennis, just for curiosity what are the differences between the Fleishman and Goltz neck joints?

Thanks Bob, I haven't seen that Taylor video in a long time but I think they may have said 300lbs.

He says 300 lbs in the video.

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http://www.chassonguitars.com

But that is with two cylinders isn't it?

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Canada

I'm watching it now and he says 300 and there are 2 at each end of the bender slats. So we talking 75 lbs. per right?
http://www.youtube.com/watch?v=I1XZwLA5 ... re=related

Yes Chris, that's what it means.

What is interesting about the Taylor design is that piston travel does not do the bending work, it's the swing arms that do it. The pistons simply keep the slat tension constant at 300 lbs.

The second prototype has bolt that lock the mid arm to the frame. The bolts are ok but it would be better with cam clamps. The first design worked but I thought it could be improved.



A good idea! The current design just uses a locking pin to keep the frame upright which works well.



You might need to explain this...not sure I understand.



In the waist cut away area the re-curve area has no pressure since it is on the outside of the bend. During my tests I didn't even have the area on the mold (cut it off) and all pressure was just on the cutaway block.



Would be a nice touch.



They are used to secure the upper arm assembly to the mid arm assembly.

Thanks for the feedback.

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Brad
Avon, OH

Another good point. I also think they would work well....just didn't get time to add these nice touches to the prototype.

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Brad
Avon, OH

Brad, on the original prototype it appears that you had two pieces of bar stock running underneath the mold at both ends, registering it in position. Now you're doing it differently. It would be better to have them register on something so they go in the same place quickly, every time.

It doesn't show in the pictures but I located the mold with 3 pins on the bottom side that lock into three holes on the frame of the bender. Both methods are just as effective I just found it easier to drill holes with a hand drill than using a table saw to cut the slots.

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Brad
Avon, OH

Brad, instead of the bolts or cams as you suggested, why not tabs that come up from the upright that have holes in them. A matching pair of holes in the lever arm to match, and then a pair of ejection pins.

So what ever became of this bender thread?
It was a good one that showed a lot of interest...

Gary

Wow, thanks for reviving this. For a moment, I thought there might be an offering of the plans. Or something.

Mike