4" Pipe Too Big For Side Bending?

[pariah223]

I have recently built a nice bending iron using a thermal couple to control the heat and a 200W lightbulb inside to heat it up. It works great and maintains whatever temp i want with ease. however, i am finding it hard to get the bends right at the waist and stuff and im wondering if its because my pipe is too big. i have a 4 inch diameter steel pipe that is perfectly round so it dosnt have a wider side and a more narrow side. I am just not sure if its too big or not. The waist radius is not that tight and im not doing any cut aways. The plans i am using are from Kinkaid's book which im sure some of you have.

[fryovanni]

I have recently built a nice bending iron using a thermal couple to control the heat and a 200W lightbulb inside to heat it up. It works great and maintains whatever temp i want with ease. however, i am finding it hard to get the bends right at the waist and stuff and im wondering if its because my pipe is too big. i have a 4 inch diameter steel pipe that is perfectly round so it dosnt have a wider side and a more narrow side. I am just not sure if its too big or not. The waist radius is not that tight and im not doing any cut aways. The plans i am using are from Kinkaid's book which im sure some of you have.

Whether or not the diameter will work relates to the bend, actually having a diameter that suites your bend well has the added advantage of great support and even heating. You of course have to have a smaller pipe for tighter bends.

I am suspicious of a 200 watt bulb being able to keep up during bending(much less require control) and get the wood up to proper temperature. My 3.5" pipe has a much higher wattage heating element and runs full on, and I can cool it if I don't take my time and allow it to keep up. Remember your going to be targeting a wood temp. of about 300 degrees(pipe temp will need to be a fair bit higher, as it is basically a big heat sink wanting to cool).

Peace,Rich

[pariah223]

ill have to post a picture of my setup. i am using a thermal couple which is a quite expensive unit that monitors the temperature and controls the heat source to keep it at whatever temp you specify. In the case of the lightbulb, it will actually cause the lightbulb to turn on and off to maintain the temperature. It actually learns how many time it has to do so to keep the temperature and holds it. Once i start bending, it turns on longer to cope with the water and the wood sucking the heat away. I have it set on 350 right now, and the whole time i bend it never drops below 347. Maybe i need to turn the temp up? The pipe is almost the exact diameter of the bend i need to make... but dont you have to overbend to allow springback? or should it stay put once i bend it if i have the heat set right?

[fryovanni]

ill have to post a picture of my setup. i am using a thermal couple which is a quite expensive unit that monitors the temperature and controls the heat source to keep it at whatever temp you specify. In the case of the lightbulb, it will actually cause the lightbulb to turn on and off to maintain the temperature. It actually learns how many time it has to do so to keep the temperature and holds it. Once i start bending, it turns on longer to cope with the water and the wood sucking the heat away. I have it set on 350 right now, and the whole time i bend it never drops below 347. Maybe i need to turn the temp up? The pipe is almost the exact diameter of the bend i need to make... but dont you have to overbend to allow springback? or should it stay put once i bend it if i have the heat set right?

Well it sounds like you have the heating under control, as long as it holds that temp. and you allow the temp. of the wood to come up(are you monitoring the temp. of the wood somehow?, it is a good idea to check it to see how long it takes the wood to get to temp. with your rig, and then you will get a feel for the timing in the future) it will hold the bend. One thing that is very helpful with pipe is to use a good slat to hold the wood to the pipe evenly. It also acts to keep the temp. of the wood even, and greatly reduces the chance of cracking.

I use heat blankets to bend to a form. It has no significant over bending going on. I bring it to temp, bend and lock it to the form, thencook it a little longer to dry the wood well. Leave it in the form till it cools and bam, it is bent(no significant springback).

Peace,Rich

[pariah223]

hm, so if i have springback, the wood just didnt get hot enough? ill have to try that. thanks!

[fryovanni]

hm, so if i have springback, the wood just didnt get hot enough? ill have to try that. thanks!

Depending on the species, you will notice a little springback. What little springback you may have is not a problem per sey, as long as it conforms to your mold with just a tiny bit of pressure(by that I mean you can say use light finger pressure to move it into position). Even with a bit of springback it should pretty much hold the correct shape. If it is straightening out it did not take the bend, likely not hot enough, or it cooled without being held in the correct shape.

When the wood reaches the correct temp it will soften the lignin. Lignin is kinda like HHG in that it softens at higher temps and as it cools it resets. As long as you soften the lignin and shape the fibers as you want them(without ripping the structure apart) and hold it there while the lignin resets, it should hold the new shape permenantly.

On tuff to bend woods you may want to try something like supersoft(fiber softener) to help make the fibers more flexable and less likely to rip apart. Water acts to do this a bit also, as well as carries heat into the wood better.

Peace,Rich

[pariah223]

i just gave it a shot with the pipe turned up a bit and i also used an aluminum strap behind the wood because i heard that makes it even hotter.. it seemed to have been quite successful i had much less springback and strangly enough, i burnt the wood LESS with more heat. I also used alot less water then i did the first few test bends.. i think i was oversaturating the wood. If i had a dry spot, i immediatly sprayed it with a squirt bottle, but this time i didnt add any water after the initial soaking. I have it clamped in the mold i will keep updated on how it holds once it is done. Also, if it dosnt perfectly conform to the mold, but with a little bit of pressure (very little) it does, that is good enough (i hate that phrase) and i wont have an problems in the future?

[fryovanni]

i just gave it a shot with the pipe turned up a bit and i also used an aluminum strap behind the wood because i heard that makes it even hotter.. it seemed to have been quite successful i had much less springback and strangly enough, i burnt the wood LESS with more heat. I also used alot less water then i did the first few test bends.. i think i was oversaturating the wood. If i had a dry spot, i immediatly sprayed it with a squirt bottle, but this time i didnt add any water after the initial soaking. I have it clamped in the mold i will keep updated on how it holds once it is done. Also, if it dosnt perfectly conform to the mold, but with a little bit of pressure (very little) it does, that is good enough (i hate that phrase) and i wont have an problems in the future?

No, your not stressing anything to speak of, so there is nothing to become problematic. The hint of possible stress that could be introduced to other components(top/back) would be so slight it would be nothing compaired to stresses from seasonal expansion and contraction.

Glad to hear the bending is going better As soon as you get a feel for how your equipment works you will be golden, I know it took a little bit for me to get used to my first Fox bender(bulbs and heatgun), as soon as I worked it all out it worked pretty well(not as well as the heat blankets I use now, but pretty reliable).

Rich

[pariah223]

well, i have both of my sides cooling in the mold now and i am feeling very optimistic.. things went better than i could have hoped (bending was my biggest fear for this guitar so i have a big weight off my chest). I have some slight burns in the mahogany but there not bad and i think they will sand out. Even if they dont, this is my first build and im not going to worry about a little burning just yet.. Actually, i remember reading, but i dont know where about some kind of stain or rust remover that does a good job on burns, so ill have to research that. Anyway, im going to go take some pictures of my progress and make a thread with pics of my jigs and my tools and my progress thus far... so until then..

Edit: Im going to post my bending iron in this thread just because it makes more sense since i was asking about it here. Here is a picture of the bender while it is heating up.

And here is a picture of it after it has heated up and i have been using it. The top number is the temp of the pipe, and the bottom number is the temp you want it to maintain.

Edited May 12, 2008 by pariah223

[scab]

wow man! that looks really nice! so you made this? how did you get the temperature to adjust like that?

Mike

[pariah223]

it adjusts itself, the thermal couple is a thing my dad happened to have laying around. It attaches to the pipe (its hidden in the pic) and it monitors the temp. the device then learns how much it has to turn the heatsource on and off to maintain a given temperature. In this case, the lightbulb goes on and off once it reaches temp to hold the temperature. It stays within 1 or 2 degrees. Not a cheap solution if you dont happen to have one around though.