I’m looking to build a steamer for bending. I plan to use 3″ pvc pipe with a water heater element in the bottom for the boiler and 4″ PVC for the steaming chamber. I’d have a relief valve set way below the operating pressure of the PVC. Any suggestions for improvements to the attached drawing?
Edited 4/17/2008 3:54 pm ET by Quickstep
Replies
There's a good chance you will melt the PVC with a heater inside. You didn't put in any dimensions. Steam boxes need a lot of billowy steam, that means a fair amount of water at boiling temperatures. Small boxes can work with a wallpaper streamer but larger ones are often powered by a propane buner and a 5gal. can. You shouldn't have to worry about pressure. A small relief hole 3/8" is enough to keep the door cap from blowing off. Use gloves when you open the door. You will want something to keep the work up and off the PVC. Condensation will just make things wet. You can expect the PVC to deform if you have a long session. It usually goes back in shape when cooled.
Mine has worked well for bending up to mid size pieces. An improvement might be strapping the pipe to V shaped boards. I use a strip of aluminum soffet vent to keep the work up.
Beat it to fit / Paint it to match
The softening temperature of rigid PVC is 80°C (175°F), well below the boiling point of water. 'Nuff said.
You could possibly use CPVC, although it's hard to find in large sizes, and you'd be running dangerously close to the glass transition temperature, which would eventually make the plastic very brittle.
-Steve
Your kind of on the wrong track here.
No pressure required or wanted. What your after is constant and prolonged wet heat.
Here is a basic set up-
Plywood box for steam chamber, insulated is better, and sealed is good.
A container with a lid and an out spout you can attach a hose to.
A radiator hose.
A heat source you can run for hours.
Hose goes from can to the bottom of one end of box ( opposite the door)
Cut a one inch hole in the top of opposite end from the hose.
That's all you need. Constant flow of steam. The pressure thing can result less flow into the chamber and actually interrupt the process. Besides being a pain in the xxx to make and deal with.
Hey Quickie, It is interesting to see where your intuition is leading you, but as stated by the others, there are flaws that your lack of experience is failing you at.
Here is a link to a free pdf. that would be good for you to read, before you get too far into this. There are a lot of little things involved in steaming that ALL have to be done right. Missing only one little thing will up the chances for failure. Steam bending wood is really frustrating when you take the re-invent the wheel approach.
You would likely boil off all of your water before you got the wood hot all of the way to the center. Starting over with filling the tube would loose what you had already done, etc.
It would be a really good thing to read this before you get started.
http://www.leevalley.com/wood/page.aspx?c=1&p=31161&cat=1,45866,45867&ap=1
One thing to remember -- do not lay the wood you are steaming on the floor of the steam box. You want the board to be out of the water but in the steam -- so put in a screen or shelf.
A bad day woodworking is better than a good day working -- yes, I'm retired!
PVC will work but I've had pretty good luck w/ a plywood box. For smaller items I use a
8" x 8" x 24" box and an electric steam kettle. For thicker and larger pieces I use a 10" x 10" x 24" box powered by a kettle and turkey fryer burner.
Hi, It depends on the size of the wood you want to bend. I'm bending slats for the back of a chair now. They are 19" long, 2" wide and 1/8" thick. I use an elongated pot used for cooking whole fish. I insert some empty tin food cans to keep the strips out of the water and cover the pot. I then boil the water on high for 3/4 hour. Presto a PRIMITIVE steamer that works. In preparation I drew the pattern I wanted on a piece of hardwood, drilled holes where I wanted the bends to go and inserted dowels in the holes. Presto a form for drying. A few hours for drying and it's done. No need to worry about excess pressure (though I do line the cover with aluminum foil to minimize the amount of steam that escapes) or melting materials. All you need then is a cooerating wife who's willing to lend you her fish cooking pot. As for bending wood that's bigger than that? I'll leave that to the woodworkers with more ambitious plans than mine. Best of luck, Shalom
At least for now, I'll be bending pieces 3" wide by 36" long by 1/4" thick. Also, Since I'll be doing this in my shop, I'd prefer not to have any type of flame for the boiling operation.
I tend to do larger batches so I keep it outside. The steam is a bit much indoors.
But an Electric hot plate is where I started. They take longer to boil, yet you never have to worry about running out of fuel.
To me running short on water is one of the classic goof ups. One other thing I've found is to elevate the chamber so you don't
get a face full of steam every time you open it up.
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