OK, I have a project in mind and its going to involve steam bending some timber.
What I need is cheap ideas for building a small unit that I can steam stuff in!
I already plan on using a wallpaper steamer to provide the steam and the unit doesn't have to be bigger than 4" across and 4' long.
Many thanks
...
the unit doesn't have to be bigger than 4" across and 4' long. ...
Not familiar w/ the actual output of those steamers so can't comment on the volume or all but there are many plans that just use PVC for the basic volume...
doesn't have to be bigger than 4" across and 4' long.
Might grab a piece of 4-6" dia schedule-40 PVC pipe (schedule-80 is even better), cap one end using PVC glue (do not use threaded pvc joints at these temps) and slip cap the other. Drill and tap the center of the pipe tube for a connection to your homemade steam genny. Drill a few evenly distributed holes in the top (1/8 - 3/16) for pressure relief, and add a ball valve at fixed end to serve as drain and added safety valve.
Open slip cap (cover), insert stock, replace slip cap, open steam input valve for 30-40 minutes and check for doneness. Use heavy barbecue gloves, tongs, and wear thick clothing and eye protection. Warning!! Do not stand in front of removable slip cap while cooking or removing cap cover.
Simple, cheap, can be varying lengths/ widths to accommodate stock sizes. Easily mounted at slight down angle (to facilitate draining of condensed water) on upright cinder block or just about any sort of home brewed support. Should safely handle temps up to about 140 deg. F; steam is much higher in temp, but with low pressures, adequate venting, and ambient external skin temperatures the pipe won't exceed its maximum. If concerned, add an inexpensive temp gauge and monitor aggressively.
Lee Valley used to sell an electric tea kettle for use as a steam generator.
See page 6 of the below PDF file.
OK, I have a project in mind and its going to involve steam bending some timber.
What I need is cheap ideas for building a small unit that I can steam stuff in!
I already plan on using a wallpaper steamer to provide the steam and the unit doesn't have to be bigger than 4" across and 4' long.
Many thanks
=======================
You wife always wanted one of those hanging clothes steamers anyway. They work like a charm!
"Digger" wrote
I've found that it helps if you insulate the tube.
And to prevent condensation onto the tools, do it outside the workshop!
Jeff
I've also been planning on doing some steam bending, and have no experience whatever with the process. What I do have is a steam unit called a "Ladybug". It is a semi profesional unit, which generates a smaller quantity of very high temperature steam.
My question is....... Which is the better condition for bending wood, High temperature with low moisture content, or lower temperature with more moisture? What is the best temperature range for bending wood, and what is the best moisture content? Should I pre-soak the wood before I place it in the steamer, or just start with dry wood, and rely mainly on the temperature to make the wood pliable?
Anyone have any thoughts or experience with this?
I am no expert!! So, I can only express an opinion based upon my own limited experiments...
My thought, and again I am not a fluid physics major, is that steam is
212 deg F, period! Unless one uses some sort of additional process, pressure and super heating, to force higher temperatures (danger Will Robinson), steam remains steam and the temperature is relative only to the type and design of generator used. Water boils at a 212 deg, which remains fairly constant in free space at sea level. Volume (or density) of steam produced is a whole different discussion and would vary with type and settings of burner combined with method of containment and surface exposure.So, I would think, simply brainstorming for discussion, that given a relatively fixed temp, moisture content and absorption rates become a function of time, exposed surface area and pressure, variables easily controlled. Rates will also differ based upon cellular density and stock sizes; hardwood vs soft pine...open porous stock vs close grain etc.
One can soak stock in a body of water for months and probably achieve almost the same capability of radius bend as steam, but the whole point of using steam is speed. I see no advantage to pre-soak and would think it might add weeks to fixing/ curing. Just my best guess, but I do know it takes much longer for water soaked lumber to dry and become workable again than simple steaming. My sense is stick with cured lumber.
Nothing stops steam from exceding 212F. WATER cannot exist above 212 at normal atmospheric temperature, but it is possible to produce steam over 350F
Another time proven method of bending wood is "hot pipe" bending - and there you DO soak the wood - the roughly 300 F heat of the hot pipe turns the water in the wood to steam. It is the heat, more than the moisture, that allows the wood to bend, as it loosens the lignen? in the fibers, allowing them to slip.
Never said steam could not be heated to higher temps, but, as stated above, it would take additional effort to achieve elevated temperatures. As water boils at 212, steam is (theoretically at least) immediately directed to the containment vessel due to venting, without additional heating or other post process. We are talking about the simplest form of a steam genny aren't we? But, perhaps I am wrong.
Not familiar with "hot pipe" process as such -- perhaps an aka might ring a bell -- and have only played with the simplest forms of steam bending. Sounds logical though, but more like a commercial process rather than homebrew backyard project. However, never too late for me to learn something new. Keep in mind, yours truly is only a hobbyist at best, not a pro or expert.
Cheers,
RE: Subject
A little basic heat transfer.
To raise temperature of 1# water 1 degreeF requires 1 BTU.
Thus 180 BTU/# of water are required to raise the temperature from 32F to 212F.
To convert 1# of 212F water to 1# of 212F steam requires 144BTU/#.
This is known as the "Heat of vaporization".
To raise the temperature of steam above 212F requires 1BTU/#, and requires the steam to be above atmospheric pressure.
This is known as super heated steam and forms the basis of every fossil fueled electric steam powered generating station.
(Damn, you never forget that stuff.)
More the 50 years ago, passed the Ohio PE exam solving heat transfer problems.
All of which has very little to do with most steam bending rigs for wood.
The steam in the steaming chamber is at atmospheric pressure and will be 212F.
BTW, I have always been told to use "green" lumber for steam bending.
YMMV.
Lew
wrote
According to the Uk Forest Products Wood Bending Handbook, 'wood at 25% -
30% moisture content contains enough moisture as is necessary to render it compressible when heated.''Wood is in the best possible condition for bending when it has been heated right through to boiling point.'
'........for the most part the effect of steaming is to heat the wood, not to inject steam into material as is sometimes supposed.'
Jeff
Double boiler?
Pot with a vegetable steamer to keep the wood away from the water.
Aging eyes misread the post this morning and saw inches instead of feet.
Gotta get a new prescription.
Ok, good deal. I feel much better now!
Thanks for the clarification Lew,
I was going to say! How big are the double boilers in where you are?
Thank you for the suggestions. Most useful.
A question though? Is it OK just to leave the timber on the bottom of the pipe or should it be raised so it doesn't sit in any water/block steam input/block water run off?
My own experience is just use a sacrificial piece (or scrap pieces) as the bottom layer, mostly because it is then easier to retrieve other layers. However, anything wider than a half inch would not be of concern anyway due to the rounded nature of pipe -- I did once try wire mesh and the adjacent wood became discolored and took an imprint of the mesh. Real pain to remove all of that after bending.
As suggested earlier however, I would tilt slightly downward at valve or relief end and if water becomes an issue, perhaps you may add a large reducer between ball valve and vessel to act as a temporary reservoir.
Just as a precautionary note, try to avoid steaming dissimilar woods in the same batch as it can cause spotting, streaking or minor discoloration through leeching.
Good luck,
unit doesn't have to be bigger than 4" across and 4' long.
You could use 4' sections of snap-together galvanized round ductwork with a couple of end caps. Wrap the duct in scrap rebond carpet padding for insulation. You want the steam to circulate around the wood, so use some scrap wood to make a ladder-arrangement that will slide inside the duct and raise the wood to be steamed so it's not touching the duct.
RArmed with all this new information, I contacted the manufacturer of my LadyBug Steam Cleaner. I was assured that the steam leaving the boiler is at
290Degrees, but cools slightly as it travels through the delivery hose. The main question now is the amount of thermal gain required to heat a given size chamber, the efficiency of the chamber's insulation, and the method of distribution within the chamber. I had no idea I was entering into a physics dilemma! I was also told that the machine is intended for cleaning with superheated steam, rather than what I plan to use it for. Does a good job cleaning, so why not see if the little "Bug" is up to the test.I'm just going to make a test chamber with pvc pipe, insulate the heck out of it, measure the temperature of the exhaust, and do a few trial runs. Nothing ventured, nothing gained. I'll try to remember to post my results when I get around to doing the test. If it works, I can imagine that more than one Steam Cleaner is going to find it's way out of the vacuum cleaner closet, and into the workshop! :)
Kevin
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