Steam Bending

[Cal]

20 hours ago, lew said:

 

 

 

 

 

Effortlessly, at least twice she said it

[jthornton]

I bent a piece of white oak 3/23" x 1" x 24" and the plumbers tape is only 3/4" wide so there was some splitting at the edge. This tells me the wood need 100% support when bending such a tight radius.

 

After I put a radius on the edges the splits were gone.

 

I'm working on a 1" wide 0.007" bending strap now...

 

JT

[4DThinker]

3 minutes ago, jthornton said:

I bent a piece of white oak 3/23" x 1" x 24" and the plumbers tape is only 3/4" wide so there was some splitting at the edge. This tells me the wood need 100% support when bending such a tight radius

JT

Yep.  Although how much/bad splitting occurs varies depending on the species used. Red oak vs white oak vs ash vs...

After 40 years of teaching and usually one or two projects that used steam bent parts we got pretty good at predicting spring back, splitting degree, etc..   Our college shop had a metalwork section so usually we would make a custom support metal strap for each unique projects. Hooks on the ends to keep the outer face in compression around the bends. 

[jthornton]

2 hours ago, 4DThinker said:

Our college shop had a metalwork section so usually we would make a custom support metal strap for each unique projects. Hooks on the ends to keep the outer face in compression around the bends. 

 

What type of strapping did the shop use for the compression strap?

 

I could only find some 0.007" shim stock in 1" wide rolls... all other rolls of shim stock are 6" wide so I'd have to cut it which would not be fun.

 

JT

[4DThinker]

Depending on the project, we had a wide metal shear and typically cut strips from some thin sheet metal. We had a local metal supplier also (now retired and closed) who would provide strips of any width if we didn't have anything in our store room to use.   The advantage of a university shop with just about every tool we imagined we needed.  

[jthornton]

 

[Grandpadave52]

By golly, I believe the turkey is done to perfection JT.

[Cal]

[jthornton]

Well the 0.007" strap is too thin it broke on the second bend. Gotta find or make a strap with thicker material.

 

JT

[Grandpadave52]

5 hours ago, jthornton said:

Well the 0.007" strap is too thin it broke on the second bend. Gotta find or make a strap with thicker material.

 

JT

Wonder if the heat from the steamed wood transferred enough to effect the temper? Would plastic plumbing hanger strap work? May not since it's generally only 3/4" wide.

 

HD Plastic Hanger Strap

Edited February 19, 2024 by Grandpadave52

[jthornton]

On 2/18/2024 at 9:17 PM, Grandpadave52 said:

Wonder if the heat from the steamed wood transferred enough to effect the temper? Would plastic plumbing hanger strap work? May not since it's generally only 3/4" wide.

 

HD Plastic Hanger Strap

Plastic will not work because it will stretch and if it stretches any at all the wood will splinter. I used 3/4" metal plumbing hanger for the first few tries.

 

I may try to double up the 0.007" shim stock but that seems to be a bit of a challenge to get the holes perfect in both strips...

 

JT

[lew]

I remember using stuff similar to this when I first started in construction

 

https://www.amazon.com/Galvanized-Perforated-Strapping-Commercial-X-Bracing/dp/B0BPH7CMMN?th=1

[jthornton]

That just might be the ticket it's 1 3/8" wide and 0.040" thick and has holes in it!

 

Thanks @lew

 

JT

[Gerald]

Kinda late on this , but why not use solid wood as an outside loop and just drive the outside loop into the inner.

 

Second idea still in solids . Cut the outer loop into thirds at the curve. Then clamp in two directions to close the corners. Yeah lousy drawing but maybe better explanation of idea.

[jthornton]

I "think" I know what you're suggesting... but maybe not.

 

The wood would just split out at the corners if you allow it to expand in length on the outside of the bend. The strap and blocks keep the wood part from expanding in length so all the fibers must compress as they bend.

 

JT

Edited February 20, 2024 by jthornton

[jthornton]

On 2/20/2024 at 10:14 AM, lew said:

I remember using stuff similar to this when I first started in construction

 

https://www.amazon.com/Galvanized-Perforated-Strapping-Commercial-X-Bracing/dp/B0BPH7CMMN?th=1

I ordered some 1 3/8" perforated strap and it should be here Wednesday... so we will see what it does.

 

JT

[lew]

2 hours ago, jthornton said:

I ordered some 1 3/8" perforated strap and it should be here Wednesday... so we will see what it does.

 

JT

Hope it works for you!!

[John Morris]

one thing that jumps out at me JT while testing, it appears you are bending flat sawn wood, it will separate and split far more than quarter sawn. Quarter sawn is much better to work with, you don't have those flat sawn flakes coming off the outside curve.

Just in case you were not aware, if you are aware, then disregard what I just blabbed on about!

[jthornton]

14 hours ago, John Morris said:

one thing that jumps out at me JT while testing, it appears you are bending flat sawn wood, it will separate and split far more than quarter sawn. Quarter sawn is much better to work with, you don't have those flat sawn flakes coming off the outside curve.

Just in case you were not aware, if you are aware, then disregard what I just blabbed on about!

 

Actually I just grabbed a bit of white oak and didn't pay much attention to the grain direction. I'll have a look and see what I used.

 

Gotta build a new steam box as the last one exploded... well it looked like it exploded on the bottom. Gotta figure out a way to allow the wood the steam box is made  from to expand as it takes up.

 

JT

 

[kmealy]

On 1/3/2024 at 4:05 PM, jthornton said:

 

Thanks for the photos. I don't think you can get the steam temperature above 212 unless you have pressure.

 

JT

Not sure that's right.  While liquid water (without impurities) won't go above 212 at atmospheric pressure, I think steam (gaseous water) can go higher.  Isn't that like saying that ice can't get below 32 degrees?  https://van.physics.illinois.edu/ask/listing/1799#:~:text=Is it true that water,and colder than 32 degrees%3F&text=A%3A,up much hotter than that.