hmmmm, pallet timber WON"T steam bend? [Archive]

malb

30th May 2015, 08:27 PM

Steam bending is normally used to form material around gentle curves. Your form looks to be fairly sharp at the bend point and I doubt that anything would bend around it happily, including 3mm laminations. Also you need a lot more clamp points set into the form. The normal approach is to drill a row of holes that can accept the fixed head of clamps around 120 to 150mm back from the face of the form, and separated by about 150mm. The work is then steamed, and quickly clamped at one end of the form, then fed around the form in the shoe, with clamps applied progressively as the timber contacts the form, then finally pulled up tight. By having a lot of clamp points drilled into the form, it is easy to set each clamp to pull at a tangent to the form at the point where the clamp is located, eliminating the tendency for the clamps to slide and loosen. In your first pic, the clamp nearest the camera would tend to slide along the back of the form as you tightened it, making for fairly ineffectual clamping.

Master Splinter

30th May 2015, 10:46 PM

Some pallet timber has also been heat treated, which might further interfere with the ability to bend it.

fletty

31st May 2015, 12:03 AM

I think you've hit the nail on the head MS. I will give it one more go with the proper steel straps but it felt like the lignum had already been set by age or, more likely, kiln drying?

Thanks too Malb, the clamps you noted were only added as a last minute (desperate?) gesture when the polyester straps didn't pull it around the former as it normally does. Also, the "CRACK" when it broke was the sound of dry, brittle timber not timber that had been in the steam box for 3 hours!

fletty

Master Splinter

31st May 2015, 12:11 AM

The heat treatment is not like kiln drying...it takes it to a much higher temperature...200 degrees or so -

http://en.wikipedia.org/wiki/Thermally_modified_wood

Old-Biker-UK

31st May 2015, 05:45 AM

A bit of searching before I built this box (http://www.woodworkforums.com/showthread.php?t=181725) came up with info on bending timber. Best to worst was - green, air dried, kiln dried with heat treated just about a no no.
The mahogany veneer I uses was kiln dried, only 1/16" thick but still didn't want to go round the curves even after 2 hrs in the steam box.

Mark

Bushmiller

31st May 2015, 08:23 AM

It could also be that some timbers are not suitable for bending. Bootle's book lists good bending timbers in the description of properties. The difficulty with pallets is that almost any timber can be used so identification is a problem.

Regards
Paul

fletty

31st May 2015, 11:00 AM

The heat treatment is not like kiln drying...it takes it to a much higher temperature...200 degrees or so -

http://en.wikipedia.org/wiki/Thermally_modified_wood

Thanks for that link MS, it explains a lot. I chose the pallet because it looked like it was made of some beautiful, dark hardwood BUT I now believe it is 'thermally treated' something-or-other and is now well beyond bendable!

A bit of searching before I built this box (http://www.woodworkforums.com/showthread.php?t=181725) came up with info on bending timber. Best to worst was - green, air dried, kiln dried with heat treated just about a no no.
The mahogany veneer I uses was kiln dried, only 1/16" thick but still didn't want to go round the curves even after 2 hrs in the steam box.

Mark

Mark,
I LOVE that box, or is it a chest? It looks like a shaker box with punk and attitude! I did a lot of research on timber bendability in the thread below .....
http://www.woodworkforums.com/showthread.php?t=184893&page=4&highlight=fletty+chair
...but I hadn't come across the effect of thermal treatment before. Normally I can steam bend green timber easily with just the polyester strap clamp but yesterday's encounter with thermally treated timber (and medieval police :;) has confirmed your comment about a bendability no-no. It didn't even make a decent crossbow ... strong enough but too brittle!

It could also be that some timbers are not suitable for bending. Bootle's book lists good bending timbers in the description of properties. The difficulty with pallets is that almost any timber can be used so identification is a problem.

Regards
Paul

Hi Paul,
In the chair thread above, I even found that timber from different parts of the same tree bent differently? I had, on one hand, a book extolling the bendability of Australian red cedar and, on the other hand, a bin full of snapped Australian red cedar chair slats!
Rather than waste another 4 hours like yesterday (2 hours to get the boiler up to temp and 2 hours of steaming), I think I'll finally get a moisture meter and put some science rather than hope into it?

PS, congratulations on the article, you look EVEN younger!

fletty

wheelinround

31st May 2015, 02:45 PM

I bet you didn't soak it ........and I don't mean pouring Red into you, try give back some moisture before steaming

Crossbow looks good little ruff but it'll impove

Skew ChiDAMN!!

31st May 2015, 05:24 PM

Green timber makes the best ballistae arms anyway. :innocent:

fletty

31st May 2015, 05:52 PM

..alright, alright ...it WAS me that gave the cops your address!

fletty

Old-Biker-UK

1st June 2015, 08:35 AM

Ray - my mahogany strips had a week in a rain barrel before steaming but still didn't want to bend.
I've found a nice piece of fresh cut ash for the next try.

BTW a crossbow is on my to-do list, but with a steel bow. I could forge the ends but would need to find a blacksmith willing & able to temper it for me!
Either that or I could shape one out of an old leaf spring with my trusty angle grinder trying not to lose either the steel or my temper in the process....

Mark

Robson Valley

1st June 2015, 08:59 AM

Water in wood is in two places:
a) "free water" in the empty volumes of the wood fiber cells
b) "bound water" which is a part of the structural matrix of cellulose, lignins and pectic substances on the wood cells walls.

"air-dried" under cover to a constant weight, the residual water (MC approx 12 - 14%) is the bound water. The principle of a steam box is to use hot water vapor as the energy
transfer to get the bound water (and free water, if present) to heat up. This in turn heats the pectic substances which are not fiberous. Instead, they behave like waxes and plastics which soften with heat. NOW, you do the bend.

I can think of several reasons why your steam-bending effort was so disappointing:
1. Some of the air dried MC was cooked out in a kiln ( rare to suppose it can be replaced.)
2. Whatever species the pallet wood was, the hardwood fiber was of such a short length that the bends passed the bursting strength.
You can't compare what you did to the ease with which conifer wood can be bent >90 degrees. Great fiber length.
Plus, when you look at the magnificent bent-wood boxes of the Haida people, the actual bent wood layer in the corner is about 3mm thick.
3. Despite the dimensions, the wood was not hot/wet steamed for long enough.
4. The wood was not face-sawn to ease the bend. Radially cut or quarter-sawn woods, even conifers, are wicked to try to bend.
Pallet woods are cut, even here, to maximize the yield from the saw log. Certainly not with any artistry in mind!

fletty

8th June 2015, 06:21 PM

I'm not the sort of person that gives up and so my bending rig is getting more and more 'complex' ...Heath Robinson has nothing on me?

349482

I fired up up the boiler this morning and went for a run (city to surf is in 8 weeks :o), roughly cut a piece of hairy oak that I know has only been air dried and put it in the yum cha steamer after it got up to temperature.....
"you haven't forgotten that we are going out today?"
"no, of course not but I have forgotten the details :;......."
"oh yes, that's right, of course I'll be ready in an hour......:C......"
shave...
shower.....
dressed....
steam bend......
out......
and, when I got home.....

349485

OK, the obvious issues are that this isn't a random piece of pallet timber AND it is supposed to be a 'U' not a 'J' but it IS progress!

fletty

wheelinround

9th June 2015, 11:44 AM

I like the new toy Fletty can we have more info please? :2tsup: That digital gauge thingy looks like some smick trammel.

fletty

9th June 2015, 01:25 PM

.......That digital gauge thingy looks like some smick trammel....

it could be either

The $6 meat thermometer in the steamer
the brass element cover from your Mum's (?) laundry boiler OR...
the new shiny ratchet spanner that came with the Veritas steam bending kit?

Or, it could be the 10 digital indicators on the gloves :roll:...

fletty

wheelinround

9th June 2015, 02:43 PM

it could be either

The $6 meat thermometer in the steamer
the brass element cover from your Mum's (?) laundry boiler OR...
the new shiny ratchet spanner that came with the Veritas steam bending kit?

Or, it could be the 10 digital indicators on the gloves :roll:...

fletty

:doh: just realised its the Beasy Clamps

You mean Sue's boiler stored at her mums

Ok what steam bending kit? Ok just googled it ???? All that steel banding laying round factory creates and such and you bought that :doh:

fletty

9th June 2015, 03:12 PM

:doh: just realised its the Beasy Clamps

You mean Sue's boiler stored at her mums

Ok what steam bending kit? Ok just googled it ???? All that steel banding laying round factory creates and such and you bought that :doh:

....and the ratchet spanner!!

fletty

9th June 2015, 10:44 PM

Time is running out for the pallet competition so ....I've had to resort to SCIENCE because there are no INSTRUCTIONS!

I selected a slat from a pallet and noted the marking

349580

I now know that IPPC = International Plant Protection Convention and...
HT = Heat Treated which is 56degC for 30 minutes (BTW, MB = methyl bromide fumigation)
This heat treatment was for the purpose of insect protection NOT changing the structure or property of the timber.
I fired up the boiler when I got home tonight, machined the slat, steamed it for an hour and bent it with the steel strap in tension. The whole idea of the strap is to stop the outside surface from going into sufficient tension to split AND to balance this against too much compression on the inner surface which displays as compression failure on the inner surface. Well, I got massive compression failure on the inner surface....

349587

but, it did bend, it didn't split on the outer surface and I have a bent, heat treated, pallet slat... of sorts?

349588

the next step is to reduce the tension on the strap or maybe remove the strap altogether and see if I can minimise the inside compression failures without splitting the outside .....I love a CAUSE!

fletty

Bushmiller

10th June 2015, 01:25 AM

the next step is to reduce the tension on the strap or maybe remove the strap altogether and see if I can minimise the inside compression failures without splitting the outside .....I love a CAUSE!

fletty

Or two straps: inner and outer? ( Edit: on second thoughts, your former serves the purpose of an inner strap.)

I remember somebody telling me that similar results to steam bending could be achieved by immersing timber in water. I am not suggesting this entirely, but I did wonder how you would go wetting the timber before steaming (perhaps for 30 minutes). This would impregnate the timber more rapidly and the timber would not absorb your steam so readily as the moisture is already there.

Once conventional techniques are failing, I think you can adopt the radical with a clear conscience.

I have to say my only attempt at steam bending was a dismal failure as the concrete pipe, with it's 25mm thick wall, absorbed all the steam I generated. So please feel free to ignore my suggestion :) .

Regards
Paul

IanW

10th June 2015, 10:10 AM

...I remember somebody telling me that similar results to steam bending could be achieved by immersing timber in water. I am not suggesting this entirely, but I did wonder how you would go wetting the timber before steaming (perhaps for 30 minutes). This would impregnate the timber more rapidly and the timber would not absorb your steam so readily as the moisture is already there...

Paul, while wetting helps soften the cell walls of wood, and may allow a teeny bit of sliding of cells against each other, it usually won't be enough to get it to bend successfully without heat. You can bend many woods 'green', certainly, but usually not as extremely as you can when they are heated. I think a lot of folks imagine the steam wetting the wood, but what it's really for is to heat it. Heat plasticises the wood material, which allows it to deform much more easily. It also permanently changes the material - I read somewhere, probably in Hoadley's book, that stem-bent wood is typically 40% weaker than the original material. The art in bending is to get it hot enough to take the deformation you want, but not hot enough to weaken it beyond practical usefulness. You might improve your success rate by soaking the wood til it is thoroughly wetted (which would take substantially longer than 30 minutes, I think). I've read somewhere that adding a bit of detergent to your soaking & steaming water helps.

I think one of the main advantages of thorough soaking would be to increase the rate at which the wood heats up in the steam box. Wet wood is a much better conductor of heat than dry wood. From my own limited experiences of wood-bending, it takes much longer than you think to heat even a skinny bit of wood right through.

Fletty, my lad, you are betting on on a hiding to nothing, trying to bend unknown woods! There are many woods that simply will not bend, no matter how you cook 'em.......

I admire your stubborn tenacity! :U
Cheers

wheelinround

10th June 2015, 02:17 PM

Its nice to see you are still doing your Pallates :U

Bushmiller

10th June 2015, 02:19 PM

I think one of the main advantages of thorough soaking would be to increase the rate at which the wood heats up in the steam box. Wet wood is a much better conductor of heat than dry wood. From my own limited experiences of wood-bending, it takes much longer than you think to heat even a skinny bit of wood right through.

Ian

I admit I don't fully appreciate the physics of steam bending, but I was advocating the use of water as well as heat: Not instead of. I think you may well have a point in the problem of getting the heat into the timber in the first place.

This would be down to the capability of your steam generator and the ability to retain the heat.

Just a charlatan's thoughts.

Perhaps I should make up a pallet out of spotted gum, send it to Fletty and then he would be right! Actually I did supply some spotted gum to a pallet manufacturer once, but they had to increase the air pressure for their nail guns as it was too hard for their normal settings! SG is one of the good bending timbers :wink: .

Regards
Paul

fletty

10th June 2015, 07:26 PM

Perhaps I should make up a pallet out of spotted gum, send it to Fletty and then he would be right!

Regards
Paul

ooooh, you are wicked .....but I like it! :;

Fletty

Scally

10th June 2015, 10:40 PM

Hi Fletty
I only opened this thread because I wanted to see how YOU would build a crossbow.

What a disappointment.

As I continued to read.......I was shocked to find that you DON'T own a moisture meter? and you have so many other interesting toys/tools.

Have you given up on your pallet timber bending folly yet?
Your persistence is admirable but........

Just make a square box out of the pallet. Add a raised panel if you want.

Then get some Spotted Gum from Paul and steam bend to your hearts content......and buy a moisture meter.
Maybe a crossbow could be your first project?

Bushmiller

10th June 2015, 11:13 PM

Scally

One of the definitive books on the crossbow is the book "The Crossbow" by Sir Ralph Payne-Gallwey.

It covers everything the average backyard bowman could wish for as well as a section on catapults and trebuchets, which is so handy if you have an annoying or pesky neighbour.

Ralphy (pictured below) died in 1916, but his book is still available through Amazon, which is where I got mine. A very interesting read even if you are not planning (immediately) to take somebody out.

349621

I will be sending Fletty the spotty pallet as soon as I can get in touch with Doctor Who to fit it into a 5Kg Aussie Post bag.

Regards
Paul

fletty

10th June 2015, 11:18 PM

Have you given up on your pallet timber bending folly yet?
Your persistence is admirable but........

Hey Scally, it's been a long time between gallery openings!
Alright, I confess, I've been trying to steam bend DRUMS to compete!
I was going to send you off on a wild goose chase with some cock-and -bull yarn about furniture but NO .... It' drums, Drums, DRUMS!
Yes, of course I have a moisture meter, my tongue can pick a dry red from 10 metres!
see you on the weekend mate?
fletty

fletty

10th June 2015, 11:24 PM

Hi Paul,
That fabulous book cover reminds me. My sister is travelling soon by train from Scotland to London on the Caledonian Sleeper. In this age of political correctness, she was reduced to hysterics when she read that, on THAT train, you can travel with your dog and SHOTGUN!
She asked if the shotgun was compulsory because she was currently shotgun deprived?
ya gotta love this World!

fletty

Bushmiller

11th June 2015, 07:03 AM

Fetty

That picture is actually a caricature that was published in Vanity Fair. This is the book cover:

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Still, at least we know how to travel in Scotland now and the necessary apparel :) .

This is a link to the book itself for any pirates and mercenaries out there:

https://glow420.files.wordpress.com/2014/03/book-of-the-crossbow-the-by-sir-ralph-payne-galloway-ocr.pdf

All the best for the pallet. I hope people won't misunderstand if you tell them you are going on a bender over the weekend.

Regards
Paul

Scally

11th June 2015, 03:38 PM

You guys are so helpful

But I really don't need any help finding more interesting projects!!

I have some instructions and some funny videos about making Trebuchets. (All my neighbours are on the list!!)

I know a guy who makes a few drums. I have even invested in a Nova lathe to replace my home-built Router lathe. Mostly I let the Africans chop out the drum shells.

A mate of mine just built this Atabaque. His father has a strange affliction with trying new projects too.
They cut the staves.....glued, nailed and strapped the bottom s of the staves together first. Then they used a variety of methods to steam the rest of the staves while using ropes to wrestle them together.
I think he tried a few methods before he had success.

Looking forward to seeing you at the Show tomorrow.

Cheers

wheelinround

11th June 2015, 03:38 PM

A thought most of what all are saying including me is Water/moisture yet Fletty is using Aussie timbers which are oil more than water. I wonder if you drop it in some 20W-50W........ you should have plenty on the drive or just leave it under the RR for a few days then attempt a bend.:p

fletty

14th June 2015, 09:17 AM

Robson Valley

14th June 2015, 09:23 AM

The water has very little to do with it other than being a heat exchange mechanism.
It is not the hot water which bends any wood.
The hot water softens the plastic-like pectic substances in the wood.
Then the wood bends. Held in service it cools to a new shape.
Water is convenient. OIl would work well to heat the bound water in wood.
That, in turn, heats and softens the pectic substances.

The more water that there is in the wood, both the bound water and the free water,
the more heat energy holding capacity is available to heat the pectic substances.

Not hard to imagine that the concentration of those pectic substances varies from one soecies to the next.
Everything else does.

wheelinround

14th June 2015, 12:38 PM

In case there are any impressionable young people reading, I have put the above viewer warning on this thread. After using a steam bending set-up yesterday that included

A laundry boiler
steam box
bending former
200 x 50 x 2400mm hardwood plank
a 5000 kg capacity 4WD winch
2 convenient nearby trees ( and tree protectors)
a 2.4T Land Rover (in low range)
spring steel strap AND
2 consenting adults ....( and people protectors)

...my quest to steam bend random slats from random pallets, HAS FAILED! As a sign of mourning, I will not be cleaning the shards of tortured timbers from the back window of the Land Rover for the traditional 7days.
thank you,
Fletty

:oo: I guess that means no show today ??
Pity the safety offices didn't video it.

Bushmiller

14th June 2015, 10:34 PM

In case there are any impressionable young people reading, I have put the above viewer warning on this thread. After using a steam bending set-up yesterday that included

A laundry boiler
steam box
bending former
200 x 50 x 2400mm hardwood plank
a 5000 kg capacity 4WD winch
2 convenient nearby trees ( and tree protectors)
a 2.4T Land Rover (in low range)
spring steel strap AND
2 consenting adults ....( and people protectors)

...my quest to steam bend random slats from random pallets, HAS FAILED! As a sign of mourning, I will not be cleaning the shards of tortured timbers from the back window of the Land Rover for the traditional 7days.
thank you,
Fletty

Fletty

At the risk of sounding defeatist, could you laminate instead of steam bending? 3mm to 4mm strips perhaps. You would need a bandsaw as a circular saw is going to cut as much wood as you end up with. (My understanding is that you can only use a single pallet.)

Regards
Paul

PS:That Spotted Gum pallet is looking very attractive :- :D .

fletty

15th June 2015, 12:18 AM

PS:That Spotted Gum pallet is looking very attractive :- :D .

VERY attractive indeed!

No Paul, you are looking at a beaten man here! I have redesigned my entry, some use Sketchup, I use Sup-up (the back of a beer coaster) and it is all now VERY straight, VERY geometric and those around me, who helped with the beer coaster, have tried to console me with claims of its new beauty ....but all I see is defeat!

I will resurrect the curvy one when I find a supply of usable, recycled, nail pockmarked 4x2's .....

http://www.woodworkforums.com/showthread.php?t=195628&highlight=fletty :roll:

fletty