The hood sticks on my French 1923 "T" are full of woodworm and some are broken. I have to make a new set. I have been told to use ash timber and to steam the bends. Has anyone done this, and would the steam produced by a wallpaper stripping tool be enough to feed a steam tube?
Any ideas or advice would be welcomed.
Steam bent pieces are usually made of White Oak.
Dave S.
Ian & David - I have heard that Ash is preferred for many applications where steam bending is done; top bows for sure. (???)
David is correct, white oak is best for bending. Powder post beatles prefer ash. Hard to keep them out of it unless treated. Apparently the oaks don't taste real good.
I have original ford drawings on some of the wood bows and every one of those drawings specifies the wood to be used as WHITE OAK. Ian I don't think that you will get enough steam in your box with a wall paper steamer but I could be wrong. I have done enough steam bending to at least give you some warnings about what NOT to do.
Don't try to steam bend a board more than once. Steam bending actually dries out the wood something awful and if you try to steam bend twice you will have a lot of pulp. You need to steam wood in a chamber surrounded by steam which then maintains that chamber at 212 degrees. You must not let the chamber fall down temperature wise except when you are ready to open it up and take out the wood. You steam bend EXACTLY 1 hour with chamber at 212 per inch of thickness. You need to start your timing when the chamber reaches 212 but you don't want to have steam all around the wood with a long time delay before the 212 is reached. This is why I think your small steamer may not work. You need to have your form ready and waiting and all your clamps ready and waiting and already preadjusted so that you can install all of the clamps in very very fast time. Get as many people to help you as you can so that everyone has clamps ready to go. Start pre bending the piece the moment you have it out of the steam chamber and take it directly to the form as you are bending it depending on the type of form you have. You need to get it fully on the form in a matter of seconds. If you don't - toss it away and try another piece - don't try to resteam it. The rosin in the wood between the wood fibers will remain soft and pliable only for a very short time before resetting to the new shape. Think through your entire process of steaming, chamber opening, movement to form and clamping. Do not put several boards into the steam chamber if you have only one form. What I did was to pull a single piece of wood out of the steam chamber and shove the next piece in at the same time. I then took the hot piece directly to the form while bending with my hands to get it going right away. I then clamped the piece to the form and let it cool while the next wood piece was in the steam. When the piece was about 10 minutes from being ready in the chamber, I unclamped the first piece and got all my ducks lined up for the next piece. Think assembly line and you will have success. I find there is a lot of misinformation on the internet about steam bending that appears to be posted by people who either never actually did any steam bending or had zero success at it but posted their method anyway. One guy filled a chamber with wood and then steamed a lot of pieces but took them out one at a time to clamp and cool and left the others in there to cook - no way that works!!! You get ONE shot at each piece of wood. Take it out too early and it won't bend - wait too long to take it out and it will fall apart as pulp - wait too long to put it on the clamp and it will take a new shape but not what you want. - been there - done that.
Hey John, not to drift the thread as it may help Ian but did you generate steam inside the chamber or externally then pipe it in? Was it regenerative? Happen to have pictures of your setup?
John has posted some good info on steam bending wood.
However, I can say from experience that ash is an excellent choice for wood which is to be bent. I built several Windsor chairs in a previous life. The preferred bending wood used by the early American chair makers was Ash. I used a Coleman stove and water in an old pressure cooker with a piece of rubber tubing going from the top of it into the steaming box. It worked quite well. It probably will take a few trial efforts to determine how much bend to put into your bending forms, since the wood will spring back some after bending and drying overnight. Bend it slowly around the form, and use lots of clamps.
At the time I tried it I was a "new be" to wood bending (still am) and the Model T. I used what I thought wood might work. Lucky it did. I was using pine lath,clamps and hot towels(soked in the bath tub) and only broke one.
There still looking good. Now that was in 1980.
Bob
I wonder why Elm wouldn't work. Elm's cells are long and I know it does a lot of bending (dry) before it'll break.
Bob:
Judging by the method you described (hot towels and soaking) and the size of your ribbing holding the lathe - I respectfully suggest that the wood was not "steam" bent and the wood fiber locations were not altered permanently. It is possible to bend wood to an arc and hold it there mechanically and it will work fine but when steam bent the top lathes for my Delivery car simply laid in place and were only tacked down. There was no stress still in the wood. I had no clamps holding the front edges down.
There are 2 ways to bend wood. One is to use thin lathes alone or laminated to make thicker parts and the other is to steam bend. The rosin in the wood will not soften until it has been steamed at 212 and all of the rosin has been softened in the piece which takes a considerable time. The fibers in the wood will then shift and when the rosin cools and again is hard - the wood has been permanently bent to a new shape and there are no latent forces still in the wood after the "spring back" has relaxed when the board is released from the mold. If you take a laminated curved piece of wood and cut it parallel to the laminations with a band saw you will see that the 2 pieces will immediately separate and go their separate ways as the stress in the wood shows its presence as it relieves itself by the cutting. If you do the same to a steam bent piece of wood it will rip right down the center of the curve but both pieces will go right back together without any force holding the cut pieces together. Steam bending makes a permanent change to the shape of the wood. Laminating or soaking does not relieve the stress in the wood and it is still there and in some cases can cause trouble later with parts not fitting together if the glue weakens.
Ken:
I got my basic setup via a simple diagram I found on the internet somewhere. I have the setup still but I dismantled it and put it up in the attic for future product so I can't shoot a picture of the whole setup but I can describe it. I don't think it practical to generate the steam in the chamber for a hobby setup but it could be done I guess. Like Mike I used a Coleman stove but I used a 5 gallon gas can for my kettle. Now for Pete's sake don't use anything but a brand new can that has never had gas. The thing you need to do is be able to add water to the kettle without having to take the whole setup apart. The gas can was one of those with a large cap in the top center and then a pouring spout with a large screw on cap on that and a smaller screw on cap in the center of that. My steam chamber was a fairly long length of 4" PVC drain pipe with a screw on cap at each end as per the internet sketch. At the kettle end I used a 4" to 2" PVC drain pipe adaptor thingee I found in the Home Depot plumbing rack normally used to tee in a 2" drain pipe to the 4" drain stack. I then stopped at the local auto parts store and bought a 2" diameter radiator hose. I used radiator hose clamps to clamp the 2" radiator hose to the large output size pouring spout of the gas can (I ditched the large cap and small cap both) and the other end went to the 2" tap on one end of the steam chamber. At the other end of the steam chamber I drilled a small hole to insert a Turkey baster thermometer to thus give me the temperature in the far end of the chamber. I also drilled another small hole there to let the steam out and I just caught the dripping in a bucket. My steam chamber was long so I didn't try to return the water or steam to the kettle. The gas can sat on the double burner coleman camp stove that was on the floor. The thing that you have to watch out for is to prop the plastic pipe up in lots of places since it gets pliable when it gets to 212 degrees and it starts to sag but it still worked OK since I had a wooden board under it and had that board sitting on saw horses. I was bending long lath pieces for my Delivery Car roof. You need to have lots of water in the steamer since if the steamer runs dry during the steaming time then you lose the chamber temperature and that piece of wood is ruined since you can't start over. If you add water you must do so before you put wood in the chamber. You steam the chamber and when the thermometer reads 212 you are ready to put a piece of wood in. You do it quick so you don't loose much steam. Then you wait till the temperature again returns to 212 and then start your timer. I was steaming 5/16 thick slats so the timer was set to 20 minutes.
I found that for hard maple that I was bending that spring back was about double thus to end up with a 36" radius I had to steam bend to about 18" radius on the form. White oak being easier to steam bend will likely not spring back as much. It takes some fiddling to get the form right.
Mike:
I respectfully disagree that you should place the wood on the form slowly. You need to get it on the form as fast as you can since you have less than a minute before the wood rosins will begin to harden. You probably have more time for thicker wood since the heat internally will remain for a bit but there is no advantage to be gained by working slowly. If bent right away I could easily bend a piece of oak into a tight 9" diameter elliptical shape which is what I had to do to make the window glass retaining strips for my Delivery Car. One must work very fast when steam bending or you will break lots of wood.
I also put some stainless steel bolts through the 4" pipe (cross wise and below center line) about every 2 feet to hold the wood lath pieces up into the center of the chamber to let the steam completely surround the wood.
A common mistake is thinking that the steam is a good thing and the hot water softens the wood. It is true it does do that a bit but that is actually bad and has nothing to do with steaming wood to bend it as far as I understand it. It just turns out that 212 degrees is as hot as the chamber will get with steam in it and it will be a constant 212 temperature applied everywhere to the wood via the steam. It is the 212 temperature that softens the rosin without damaging it and lets you then shift the fibers of the wood around while the rosin is soft - get it? As soon as the rosin begins to set up hard again you better have had the wood on the form a long time before that.
FWIW - I learned how to steam bend by spending a lot of time reading on the internet how to do it and discovered a lot of folks actually didn't "get it". I then spent a lot of nights reading old patents on steam bending apparatus used to make wood felloe wheels and then it all began to make sense. The wetting of the wood is not good but a necessary evil in softening the wood rosins. Since the steam had to be there for a long time to get the internal rosins soft inside a board I wondered if something like a microwave oven wouldn't work without water to allow me to bend a piece of wood since the microwave oven actually heats things from the inside (where the moisture is) toward the outside. I put some small wood pieces into my kitchen microwave and YEP they bent rather easily. Since the Microwave oven was too small to put anything practical in there - I saw no future in using it but it does look like it could be used to bend wood but not sure if it could provide a steady temperature in the wood which is critical to being able to not only bend the wood but have it not be structurally weakened by the process.
Ian,
Here is a video showing a person using a wallpaper steamer to bend some wood strips. Seems to work fine.
http://www.youtube.com/watch?v=OOIJXDZXB3g
Jim
Jim;
Quite interesting.
Hugo Richter of our Lone Star Model T Club built his own top bow steamer using pieces of galvanized gutter to form a steaming chamber that would heat quickly and evenly with a length of top bow wood inside. He made a burner from a piece of 1/2" iron pipe with 1/8" holes drilled every 6 inches. It worked very well. Hugo built all the top sockets and bows for his '13 touring. They are perfect.
Of course Hugo is a rocket scientist (literally) so you must realize your results may vary.
I did the sticks for my '09 a couple of years back using a wallpaper steamer and an old drainpipe. The steamer reservoir was a bit too small to do the full time, so I boiled up a kettle to top it up. I got some green (i.e freshly-cut) oak from a boat building supply co. and it worked very well. My wastage for experiment was about 20%.
The important bit I found was that if you simply try to bend around a former the outer fibres of the bend stretch and split; you need to make the inner fibres compress. I did this by having a flexible metal strip on the outer side along the length of the stick with an end stop either end, so the stick could not stretch. Also you need to make your curves on the former a bit tighter than needed 'cos it will spring back a bit once you take the clamps off.
Also I did not attempt to make a full double bow to go right across the car - I made each in 2 halves with a splice joint in the centre.
here's some photo links
https://picasaweb.google.com/100465155247781991498/Ford#5305903012622535490
https://picasaweb.google.com/100465155247781991498/Ford#5305903042094600658
https://picasaweb.google.com/100465155247781991498/Ford#5305903095237453282
https://picasaweb.google.com/100465155247781991498/Ford#5305903173825811954 This shows tearing due to insufficent compression.
"I respectfully disagree that you should place the wood on the form slowly. You need to get it on the form as fast as you can since you have less than a minute before the wood rosins will begin to harden."
John -- You are correct that one has a short time to bend the wood after removing it from the steaming box. I too would recommend getting it to the form as quickly as possible. What I meant was that the actual bending should be done in a slow and steady continuous movement, rather than very quickly. I guess I didn't explain that part very well. Maybe you bent it quickly and it worked for you; I don't know. If so, great. Maybe it's not that important to bend it slowly.
The whole process works better with help. I would take the steamed piece to the form and have a helper clamp it at the center, then I steadily bent both sides around the form at the same time while someone else applied clamps as we went through the length of the piece. As you say, you have only about a minute before the piece cools too much to cooperate.
The books I read about bending wood when I was learning about it 30 years ago said to bend it slowly and steadily, as it was less likely to break that way. That's how I did it, and it worked well for me. Here is an example of some steam-bent parts I did back then.
I made a set of 6 Windsor dining chairs for a customer, and then made this writing arm chair for myself. The arm and loop are ash; the cherry crest also is steam-bent.
For those of you considering steam-bending for the first time, the most important thing you can do to prevent having the piece split out is to have continuous grain all the way through the piece. Grain which runs out the edge of the piece will likely split away when you bend it.
BTW -- I just read Jem's post where he mentioned getting green lumber from a boat-building supply company. That reminded me of another thing which has to do with steam-bending, and that is that kiln-dried wood doesn't bend well and is more likely to break. The KD process bursts the cell walls of the wood and it's not nearly as strong then. I haven't tried steaming green wood, but I always used air-dried wood, not KD.
Thank you so much for all the advice, this has been most helpful. I now have a much clearer idea of what to do. I wish we had a Forum like yours in England. Sadly nobody uses the "Guestbook" on our website. Your Forum provides a wealth of information, advice - and humour - every day. Thank you!
John, thank you for your wonderful explanation and tips. I have a question.
If I'm making top bows, which are bent at both ends, I can see how making a steam chamber long enough to steam the entire piece is possible, but how do you suggest bending and clamping both ends at once? If the working time is very short, doing both ends simultaneously seems like it would take so many people that they would get in each other's way. Any tips?
Peter,
You can use a 10' length of 4" PVC pipe for the steam chamber. That should be long enough. PVC is a better thermal insulator then stove pipe (steel) and you could even improve the PVC by insulating it with some kind of insulation or blankets.
When done steaming and ready to bend you could also use some type of cover over the hot soft wood to prevent it cooling too fast. Maybe some bubble wrap or most anything that will slow the cooling. Other then that you just have to have a plan and work fast when bending and clamping.
Jim
Jim,
Just a thought here but might work. I'm pretty sure the top bows are straight across the center part, only bent on the ends. I think I would make a form with one side exactly the bend radius you want, and the other side with a tighter bend radius to account for the spring back. I would modify the end cap of the steam pipe so that the wood could stick through it. I would then stick one end of the wood into the steam pipe and seal around the piece with some insulation. When that end is ready, take it out and bend it around the tighter radius end of the bend fixture and let it cool. Then steam the other end. This time when you put it in the fixture, clamp the already bent end into the correct radius side of the fixture, then bend the other end around the tighter radius. If you don't steam all the way to the center you will not be steaming the center part of the wood twice.
Just a thought.
Dave S.
Dave S.
Yes, I think just doing one end at a time is a good option.
Jim
Mike W.;
That chair is beautiful.
Lots of great info. Thanks John and everyone else for contributing.
I don't much care for PVC above 100 degrees. I had a bad experience with it. Of course, it probably didn't help that the solution I was using was caustic.
PVC would probably not work for a full time steam chamber for ongoing production of things but for a set of steamed long parts now and then it works fine if you remember to support it to prevent it from sagging and bending on you. It too will not spring back when it cools. It stays "lumpy" and "humpy" from the steam being in there again and again but the end result was excellent for me and that is all that really mattered since in truth it was very cheap to build.
David S.
The top bow drawings in fact show that for all of the bows there is a slight crown in the middle of each bow. It is not stated that it is desirable but just is shown in the drawings that the center of the bow is definitely not straight across and I suspect it is a remnant of the steam bending operation and that the crown is there when the part comes off the bending form.
I saw a "production" bending jig for top bows. It consisted of a full form for the the entire under side of the bow with sharper radii as the corners to allow for over bending and then later spring back. The entire form and clamp was laying flat on the ground and mounted to a sheet of either steel plate or thick wood. The clamping action was provided by one long heavy spring steel band that was longer than the wood piece and had a single chain attached to each end. That chain formed a loop to the ends of the steel band. The chain loop came forward to a ratchet lever that could quickly ratchet the chain center forward and tightly clamp the steel band against the surface of the wood and sandwiching it between that steel band and the form. It took only a few seconds to clamp the steamed wood piece to the form completely. I think it had some sort of wedge in the center behind the steel to push its center down a bit tighter but it was really fast and I saw it done in a video somewhere and was done by an Amish wood worker. I remember it and the wood was really hot and steaming when that ratchet lever was cranked tight.