Bending Copper Tubing

To stop the kinking and flattening fill the tube with sand and plug the ends. As to forming it, I'll leave that with you.

Try loading sand into 65 feet of copper tubing that is in a coil. I can't get to the other end because it is in a coil 2500 feet long. The wall thickness is .016 and it cannot be 'played' with. It has to come off the coil and on to my jig in one smooth operation.

Why not go to your local Refrigeration warehouse and purchase a roll of 1/2" copper soft instead of annealing it. It comes boxed in a roll. It is dehydrated and easier to form with a 1/2" pipe bender, or soft spring bender that you can purchase a the same warehouse.

Easy, same wall thickness, and less work in the long run.

Did you see this from the OP?

" I can't get to the other end because it is in a coil 2500 feet long. The wall thickness is .016 and it cannot be 'played' with. It has to come off the coil and on to my jig in one smooth operation."

That is why they make couplings to attach the rolls. Or better yet if you are going to purchase 2500 feet of copper tube why not purchase the soft tube before it is cut into lengths, and run it on the jig.

Simply put the soft copper is annealed at the manufacture to make it playable for may types of installations.

My 1/2" copper tubing bender is at work rather than here, but I'm pretty sure the radius is less than 3 inches. This bender is the type with a "shoe" that supports the inside radius of the bend; I don't think that the inserted spring types work as well. I would guess that your coil would need similar support until the radius gets to 6 inches or so, and then you can just wind the tubing on.

Sand might help as internal support for a few turns of your coil, but then it would have to be fished back out. Water might also work, so long as the tube ends are tightly capped, and it would readily drain out.

I'm sure this is totally impractical, but if you could just freeze that water, you could get kink free bends.

I watched a Discovery 'how it's made' programme a while ago which showed trombones being made. To bend the brass pipe they filled it with a mix of water & (I think) soap which they then froze. This mix supported the pipe during bending but was slightly compliant & just melted out after processing. Obviously you would need a long freezer or would have to work in sections but it might be worth looking up the programme.

Automotive tailpipe manufacturers use this frozen water method to maintain a consistent wall spacing when bending dual wall exhaust pipes. The space is filled with water when the tubes are still straight and then frozen. That's why I was aware of it.

Maybe you should post your jigs, might help to figure out why it isn't working.

I was working recently with hand-bending jigs to make cuffs. I made a couple of jigs with different sized pipe and dowel. I had the same problem of kinking when working with a concave piece that was overly work hardened as well. But you've said that the material is soft. I found that the solution to the kinking problem is technique. Very gradual bending is the key, ie making very slight and gentle bends at increments of a few mm. Then you go back over the same area to increase the bend gradually until it is as you want it. I think the second solution for bending a pipe shape would be to customize the tool.

If I had to do what you're trying to do, by hand, I would modify a simple hand jig like the ones shown below, by cutting a semicircular groove less than half the pipe diameter. This would allow me to put even pressure on the inside of the curve. Maybe make a shallow groove in the bottom grip as well, and put a piece of leather over it to soften the impact but maintain the grip.

You could use a simple small hand jig like this, sliding it along the length of the coil of pipe, to make the spiral exactly as wanted. Very gradual bending is the key to avoid kinks. By the time you finished 65 feet of it, you'd be very skilled!

If I was working with a curve that was consistent over the length of the copper, your idea is worth investigating; although it would be time consuming. Remember that my final part is spiral and not concentric. Each and every section is of a tighter curve than the last. Also remember that the copper must come off the spool and into the shape I want. I cannot 'play' with the copper; it kinks, wrinkles and flattens far too easily. When that happens you can kiss that piece good bye.

I made a jig that would support the copper with posts but when the copper rounded the posts it just kinked and would try to go straight to the next post. I then bought some spring steel and was going to adhere that to my posts( eye bolts cut out to leave a 'C' shape to hold the tubing as it went around the jig; the eye bolts were then screwed into a base with each one 1/8 inch higher than the last. remember my copper raises 1 inch for each revolution and 2 inches less in diameter for each revolution). The posts were made of zinc and there is apparently no way to adhere spring steel( 3/8 x 1/16 ) to zinc eye bolts.

I am presently exploring having a machine shop use a very large lathe to make a solid jig that would support the copper as it is wound around. I will still need internal support to keep it from completely flattening. I will also need a copper rounder to round the copper as it comes off the spool.

The other alternative is the pancake copper coiler. These are not cheap.

It takes a very large lathe horizontal lathe to do the job. My max diameter for the production model is 72 inches. For the prototype I can get away with a 48 inch lathe.

Now you have some idea of the complexity of this task and why I have written to you experts in creative thought.

Actually, what you don't realize is that you can get any curve with a small hand jig, except a curve that's tighter than the mandrel. It is easy to get a gentler curve for your larger loops. You're certainly right that it would be time consuming for a 65 foot spiral ending in 48 inch diameter. However I'm not sure you will find a quick fix that works, unless you buy the dedicated pancake copper coiler.

The upper part of the spiral with the tightest curves is going to be the difficult part: I'd start at the top and work my way down if I were you. Once you put those tight curves in, the structure should be self-supporting, whereas the loose coil at the bottom will be barely work hardened in the process, if at all.

A small jig that's made for the purpose would be able to slide along the coiled pipe to any point that needs adjustment. The jig is a clamp that puts a controlled bend into each point where it is applied and work hardens in the process. Whereas your 'wrap around a big mandrel' plan is more apt to flatten and kink the pipe instead of hardening it into the shape you really want.

I tried the pipe bender like you envision. I did not have the internal support that I have now but I found it nearly impossible to hold the precision that I am looking for. This is not a onetime occurence. I will be making these over and over again so it needs to be efficient and exactly duplicatable. Doing it by hand does not seem to me to be very efficient or replicatable. The dimensions need to be held to a very minimum of variance. I can put a motor on a lathe cut jig and turn it very slowly to avoid wrinkles and the like (maybe).

If you are planning industrial production, invest in the dedicated machine. You can spend your money getting a huge cone milled on a special lathe to use as a form, I don't think it will work, you are better off getting what works.

I would like to know your reservations with the milled form.

As for your other comments; If I had unlimited funds, that is exactly what I would do. I hate to invest the money before I have had the unit tested and functioning. There is still a lot of time between where I am in development and planning on production quantities. That money can be spent on a great many things rather than sitting in a piece of production equipment. That is as long as making a form for the prototype is not prohibitively expensive. Then I have to make some painful decisions. In a perfect world your comment is spot on.

Michael,

I had a look around for some terms and resources to discuss the bending issues in a scientific way, and that led me to look back at the spec you're describing here and your bending needs. Do I understand correctly that your smallest bend has a centerline bend radius of 3 inches? A six inch diameter circle of pipe is not a very tight bend. But there is another reason for the material failure: the tube wall is thin.

Take a look at the description of "wall factor" in bending pipe here. The ratio of your tube's outer diameter (0.5 inch) to wall thickness (0.016 inch) is 31.25. Problems such as wrinkling and flattening are described for wall factor greater than 15, in a tight bend. This shouldn't be as much a problem for the relatively large bend radius for a six inch coil minimum, but the wall factor is very high all the same. See at the bottom of the same page, they discuss crown tooling to prevent flattening of the outside of the tube. The crown tooling is lacking in your plan to use a milled mandrel.

In view of your cost considerations, if you are in North America I would try these people or similar, who custom form all kinds of copper tubing. I'm sure they have the pancake coiler among their machines and could do your prototype form without a costly setup. Unless it is really not feasible with the spec wall factor, which I'm sure they'd let you know. I bet it may be cheaper to buy your copper already formed, than to have the big mandrel milled on the hope (but no assurance) that simply winding the pipe on a mandrel will change the problems you already have with the forming.

Artsmith,

Your comments are well taken. I was unaware of the correlation between bend radius and wall thickness. I was compensating for the flattening by inserting an internal support in the tubing. Because there is an out of round condition even with the copper on the roll itself, putting an internal into the tubine can be contentious. I have resorted to 3/8 inch support in either teflon, HDPE, or a specially spring I had made. Teflon works and even pushes past some of the flattened areas. I have not tested the HDPE as yet; a sample has been hard to come by; a 10 ft piece of the spring is in my possession and will be tested soon. Each has its advantages. The spring will not allow any compression but could be difficult to remove,although I suppose, I could theoretically unscrew it from the tubing. The telfon can 'stretch' past flattening, but will it eventually snap apart? and the HDPE has been recommended as it is used in Australia for the same purpose.

You are correct about the lack of support on the external surface, and I was depending on the internal support to do the job.

A great deal will depend on the prices for all things considered. I would rather have it made for me, at least for the prototypes.

Thank you for you input. CR4'ers are awesome.

Do you have any links on the 'internal support' process? Is it usually done with some kind of machine to get the support material in and then out? Or is it used for forming short pieces of tubing? I have serious doubts about getting 65 feet of support material into a half inch tube by hand, and then getting it out after the pipe has been coiled... you're looking at a lot of labor for that, if it is even possible.

Maybe you've tried this, but here's what I'd envision doing:

Take a 4x4 foot piece of plywood and attach a 6" dia piece of PVC pipe in the middle. Buy some expanded polystyrene foam sheets (say, 24 inch x 24 inch) and cut one strip that is a long triangular piece that tapers from 1/4 to 1 inch. Then cut the rest of the foam sheets into 1 inch strips. [Or, 1 inch minus the diameter of the tubing.]

Attach the copper tubing to the PVC pipe (leaving a tail piece that can be cut off later if need be) and start flat-winding the tubing around the PVC, using the polystyrene foam as a spacer to expand the diameter of the tubing. Once the first triangular piece is used, use the 1 inch wide strips as spacers for the rest of the copper coil.

You could mount the plywood on a lazy susan so you can spin the plywood as you make the coil. Once the coil is done, it should have plenty of 'spring' to let it move in the vertical axis to get the horizontal separation you need between the coils.

Can you do it in sections, then swage and silver (hard) solder the un-kinked or un-flattened part.

95-5 soft solder might be ok too for your application.

Part of the plus for my unit is the fact that it will remail solderless and as such needs that much less labor to assemble. But your thoughtful contribution is appreciated.

Take an iron pipe for electrical conduit, that has same ID as you OD or close enough, split it in half with the grinder, and bend it and beng it in shape on your existing jig. It will become the bending support for the copper pipe.

1. You obviously do not comprehend the OP. It's a cone.

2. The radius for this bend is constantly changing. Not to mention the twist.

Obviously, his present jig is for a conic shape. What I was describing is to bend first in that conical shape, half a pipe,(the inside one) without being afraid that it kinks, etc, and that can be hammered to get an adequate shape to serve as guide for bending the copper pipe. The copper pipe will be bend on top of the half pipe like CO,C being the support on the inside and O the copper pipe. After the bending is done, twist all the coil a little (is a spiral) and it comes out of the support. Good enough?

OK,

Good enough for me, but I wouldn't do it that way

The OP has 2600 feet of thin wall copper tubing on a giant spool that he needs to unwind into a spiral shape that is hundreds of feet long. He can't bend it on one mandrel and tweak it into the final shape. It's the ever changing diameter/radius that's the problem.

I am obviously ignorant of your methods, but "hammering" doesn't seem to me to be an option here.

Still learning.

You hammer the iron pipe till it gets in to shape, to form a perfect support for bending, and you fix it in place. You put the jig on a bigger lazy Lizzie, hook up the copper pipe starting from the smaller diameter, and turn the jig, coaxing the pipe to sit on the C with the hand/device. With the proper tension for un-spooling the pipe drum, and a little guidance, it suppose to sit by itself. That means that originally, the pipe is on a drum , free to turn like a spool.

For production, I'd be inclined to make a plywood jig to wrap the spiral on, and start winding from the small diameter. For high precision, you have to allow for spring-back; more toward the center. Starting with a small jig, out to 18" or so, would show how much tighter to make the final jig to a fairly close guess.

I'd also recommend against spending any time or money on patents until you have enough money to keep lawyers on staff.

Clayton in El Monte, CA makes steam generators from steel tubing/pipe and bend very tight pancake coils. They fill the tube with molten salt, I think it is sodium hypochlorite. Then they bend up the tube with this relatively rigid plug inside, and then heat it up and blow it out, rinsing out the residue.

Sand is a nice thought, but if you put sand in a piece of copper tubing and bend it to a tight radius without full support it will simply kink. Think of what would happen to it if you squeezed it in a vise, pretty obvious.

A nested frusto-conical tube stack for a monotube heat exchanger is now almost ancient history but still very appealing. I still prefer pancakes coils. What temperatures are you designing for, what fluid, flow rate, etc?

HI Karl Petersen,

Step up to the plate. Sounds like you know something about this.

Welcome.

I believe my design will generate more througput than any flat panel of equal size. Flat pancake coil is nice and easy but does not allow for that little bit of extra sunlight I can get from a cone shape. And the angle is critical. I never need to move the collector. It sees the sun in every season. A liquid center would be attractive because it comes out easily. Problem is that I will have 140 plus feet to fill while it is still on the roll. Then I have to get it back out again. I feel that a solid center like teflon, hdpe or a spring will be more effective. I have proven teflon on a small sample and it works. Just don't know about the longer length.

I will be testing the hdpe if I can get enough and the spring will be tested this next week. I am sure that I need a backing support when I begin winding it on the form. USB had a good idea and I have looked at that. I takes considerable work to form the 1/2 piece of any tubing to support the copper. and then there is putting it in place exactly! That is the rub. My design dictates that the copper be as close to exact in placement to work at its best.

I am becomming more convinced that I will either have the prototype done for me or I will have the form milled for me, at what cost I do not know. Again, depends on cost.

All of the ideas I have seen here are useful and most I have tried or discarded for one reason or another. I have been looking for that majic bullet that I had not thought of.

The initial support can be a pyramid of 2x4. You have to think that you will have some spring back that is unknown, so you have to have an adjustable support at the beginning, until you know exactly what shape the support has to have. The initial work to bend a split pipe made of iron in the coil shape it might be a lot, but you can adjust it, function of how much is the spring back. The split pipe can lean on nails stuck on the frame. If you want to order the jig to be made, you still have to give the dimension of the support, I don't think that is possible to say "and when it springs back after bending, it has to be in this shape".

I am designing for the most efficient unit I can produce. The flow rate will be determined by a series of inputs all fed through a circuit board. That means optimizing the delta T of both the collector and the inground storage tank. All my materials have been selected for the most through put possible. This is just the beginning of a very large project and it has taken me nearly two years to get this far. I estimate it will take another 3 1/2 years to complete each phase of the project and have a system ready for production.

The process you're describing would not be at all feasible for a home workshop, and I think you're mistaken about the molten salt being sodium hypochlorite (bleach). This 'melts' at 18 C in other words, a liquid at room temperature, not forming a rigid plug, and being a very corrosive and caustic material which decomposes to release toxic gases above 40 C. Heating it and 'blowing it out' would be a real party.

There's lots of documentation that sand has been used for internal support in pipe bending, and ordinary granulated table salt serves the same purpose and is easily rinsed out afterwards.

Cerrobend, Wood's metal, and the non-toxic Field's metal already mentioned in this thread are alloys that are solid at room temp but melt below the boiling point of water and would serve the purpose of internal support while being feasible to flush out with boiling water. Check out the video, looks like an ordinary coffee/tea boiler used to melt and easily pour the stuff. A bit more expensive for the non-toxic Field's, but re-usable and not generating any waste or hazard.

USB had some good ideas which can be improved on. Build a wooden jig in the shape of your cone, fasten the strips of R20 insulation in strips in the shape of a cone and attach to the wooden jig. If you use a pvc pipe through the entire center you can add reducers on the ends to say 1" pipe. Build another set of legs that can hold the completed jig in it's rough form. Bolt the entire unit to the floor in your garage.

Attach a motor to this to spin it at 300-400 RPM's. Then add a solid piece of either aluminum square tubing or other material the entire length from spindle to spindle. On this tubing build a slide around it to attach a tool bit to shape the insulation from it's rough form and begin turning this till you have a final cone shape in the exact diameter required for your end product using the motor to rotate the work.

When you have the final diameter from end to end. Reduce the speed to 2 FPM.

Mark a line on the cone so you can follow it with the copper tubing.

Setup your roll of copper on some type of holder also attached to the floor so you can leave it behind you. Attach the copper tubing to the large diameter end, operate the motor on a foot switch, and begin to wrap the copper and follow the line. 2 feet per min may sound slow, but you will need this speed when you get to the end.

Keep the copper tight and follow your line on the cone. What you are building is really a custom lathe. This will also likely be used after the initial coil is made and will work for quite a few coils till the insulation is deformed too much to use. Then replace the insulation or find a soft material to wrap the cone. You will have to cut this down with the tool bit once again to get the OD exact.

This is what I would do for a project of this magnitude.

To minimize kinking, you could possibly use a form with a properly-sized groove on the surface- sort of a "U" groove, deeper than the diameter of the tubing. For the tubing to kink, there has to be some place for the deformed walls to go. Since this is a conical shape, once the final coil is formed, the form will simply screw out of the center with a couple of turns (in the right direction).

A deep U groove is just what I have specified for the machined form. And of course unscrewing is the only way to remove it once it is in place. The solid internal support will add to the integrity of the final product. You understand the problem very well.

One factor I did not mention in the previous post- you want to maintain the tension in the copper tube at a minimum. Almost like pushing the tube (gently) onto the forming jig, making sure there is not a whole lot of drag from your supply reel...

The old method for bending tube was to fill it with damp sand.

Cut, or have cut for you, circular disks of wood to the same circumference
and depth of your copper pipe and join them through the centre to make a
stepped cone shaped former for the coils.

Gently wrap your pipe "on to and up the stepped layers" (steps of the cone)
in to the correct shape you require and lift off the former.

If you have thousands to make, centralise the former on a turning machine.
hand jig, or slow turning lathe. (or route the coil shape in a cone block of wood)

Hope this helps.

jt.

It's a misconception that onions are the only vegetable to bring tears to the eyes,
a turnip in the face works just as well. www.mycall.mobi.

I understand you're having issues getting the proper bends on your coil. I can tell you've spent a good deal of money on legal fees and you've obviously spent time and money making the shell that houses the coil. I understand the idea of not having to reposition the collector. My question is have you done any cost projections on what it would be to actually manufacture and market your idea? Inventions never come down to which one is most efficient or compact. Beta has far better quality than VHS but the box was simply too big. If it's too expensive or isn't the right fit sales will not follow.

There are plenty of collectors on the market right now. More and more designs are coming to market using parabolic mirrors or Fresnel lens to amplify heat. I understand your design is using the cone as a continuous collector, it's nice. But as someone who has also pursued patents in the past I wonder if you're looking at the business and marketing side of the equation. It will work but will it sell against the competition?

I wish you luck and I admire the simplicity of your design.

"I admire the simplicity of your design."

Simplicity is the key to affordability. Yes I have looked at the cost to manufacture. I have a 35 page business plan with 5 year projections, including markets, facilities, sales, management, everything necessary to step into production. The only issue remaining is money. The bank and others have told me that once I have a working prototype and have begun sales they are willing to loan me what I need. I have spent the last 3 or 4 months on this coiling issue alone. The rest is ready to go. My suppliers are all lined up and waiting.

Have you checked the price of Fields Metal lately? Scarey. As the copper is still on the roll, how do you suppose I am going to get it in. if I decided to do it that way. That is the problem with all liquids.

"..how do you suppose I am going to get it in." See the coffee urn in the video? Use a hose coupling to your pipe and the liquid metal will flow through. You might have to warm the coil to keep the metal flowing to the end, if it's slow.

I can't imagine that getting a solid or even a granulated material through 65 feet or more of coiled tubing is going to be any easier.

Price is a different matter, but if you are going to handle the fabrication process yourself, you will have to invest in something that you can repeat, and reliably produce your product.

Using Ostalloy 158, or an equivalent would be relatively simple. You also don/t need much.... just enough for a small number of coils per heat cycle..

Since you are working with relatively small diameter tubing with excellent heat transfer; melting and solidifying of the alloy can be accomplished rapidly by spraying with or dipping in hot water (~170F) and then cool water (~70F).

As long as you can form a low point between your supply and your coil form jig....

-the liquid metal can be poured into the tubing initially,

-then cooled with tap-temperature water,

-then coiled up and around the rotating coil form jig until just prior to reaching unfilled tubing,

-then heated by immersing in or spraying with hot water for a time sufficient to insure complete melting,

-once again cooled with room temperature water for a sufficient time to insure complete solidification,

-and repeating the process;beginning by coiling another appropriate length of tubing.

Many of these alloys expand slowly over a period of time after initially solidifying, which could be helpful.

I can attest to the ease and effectiveness of using low melting point alloys for things like bending very thin wall chromoly tubing. I have no experience using it with thin walled copper, but my guess is that it would be similarly easy and effective.

put high pressure air in the tube.

Please tell us you're kidding. Please, oh please.

You might consider using a 12-inch diameter for the first loop; the area lost would be all but negligible in the overall picture.

I will have to ponder that for a bit. Thanks

If you make a pancake coil of 1/2-inch OD tubing with 1/2-inch spaces between, a 72-inch overall circle would accommodate about a 323-foot coil (quickie arithmetic, so not precise or certain). A 48-inch circle would allow about 143 feet. I haven't yet estimated the flow and pressure drop for these lengths, but am curious as to possible issues.

ps.. re-submitted entry.

To stop kinking you could try e.g. candle wax.
To fill immerse tube in molten wax, bend, then re-heat and allow to drain.
Even water with tightly sealed pipe ends may work.

Hope this helps.

jt.

Entries deleted if I offer subjective entertainment, sorry, no can do.

If your need is only to support the inside of the tubing while bending, look into cerro-alloys (bismuth and other soft-low-temp melting metals which you can melt at hot tap water temperatures) and pour or inject into the straight copper tubing. Then, bend the tubing and heat it to melt out the cerro-alloy. Alternatively to cerro--alloy, you might try a newish plastic for the same function called (I think) Shape-Lock. Either of these materials will support soft copper tubing while bending and can be melted out after the bending process is complete. Experiment with short lengths to determine viability and how completely the internal support material is removed to avoid a thermal barrier from residual film on the inside of the tubing. PS, you may need to heat the copper tubing while filling to avoid premature freezing resulting in incomplete filling.

Please let us know how you resolve this problem.

PS... Why fill all the pipe?
Have a plug (spring) on a tie (string) fed into the length of pipe and fasten the other
end of the tie at a distance to the point of bending. As the pipe is bent, the plug will travel up the pipe, always being held "at the bending point" of the pipe by the tie, and eventually re-appearing at the end of the bending.

As the pipe is fed, and bends at the point of the short plug, which stays in the one
position, as it travels up the pipe.

Hope this helps.

jt.

I have been put off trying to entertain, and I'm sad now. I would not want
to be in a club that would have some one like me as a member. (Marks.)

What makes you think the plug is going to move at all? Why doesn't it just become 'stuck' because of the compression of the pipe at the point of curvature?

If I were doing it: the "plug" would be a loose fit, would have been "greased" to slide,
the "pull-through string" would be sufficiently strong, and the radius of the bends are
not that small. Correctly thought out I see no problem?

jt.

The "pullout string" probably needs to be straight (or at least not wrapped around many degrees of bend). It appears that the OP is winding off a coil and onto a desired coil; this probably defeats the "straight pullout" feature.

A coil admittedly could cause problems. I did not see the plug (bullet)
string actually pulling on the coil, rather the pipe sliding over the plug.

I assumed the op would cut the required length of pipe, feed the string
(probably weighted) down the length of the pipe, and secure the end.
The pipe is then bent around the wooden former with the plug sliding
along inside the pipe, as the pipe is drawn around the former.

The plug is not actually moving, only the pipe over it. If it could be
done with little or no drag upon the plug, may it even work from a coil. ?

Not much of a drawing, but workable? jt.

This is a good explanation. The "bullet" would be shaped like a football on the right half, to accommodate the curvature of the tube as it is formed.

This might lead to a two-step process. 1, insert the bullet for a few feet to support the tight-radius portion of the coil. 2, unwind most of the coil off the supply and onto a grooved cone mandrel.

Thank you for the support Tornado!
I think this would be a lot less hassle than filling the pipe with
candle wax (I mentioned earlier) or the frozen water/chemicals.

Who knows I may even get a credit for this one! (but not my jokes!)

Many thanks. jt.

What would an engineer call a nun sitting on a washing machine?
sistermmatic

The "bullet" just needs to be a standard internal pipe bending spring.

The only disadvantage of this method is that you do need to start with the full length of tubing straight, but, I think that's a price worth paying.

GA jt

Your HDPE comments seemed to suggest you are thinking about using HDPE in the full length of the tube. Don't you only need a few feet of HDPE rod in the small diameter end of the cone?

G'day,

Working in cu, means as you play with it tends to harden. I'm no expert but a jig made of steel to the desired shape that can be kept to a temperature such that it keeps the cu from hardening. This along with a former for holding the shape that can follow the the spiral jig as your continully heated cu tube is introduced to the jig should allow you to end up with your conical spiral. A couple of practices runs should give you a determination of required speed to operate at.

Michael,

A couple of thoughts:

1. you are taking it off a reel where it is coiled, in doing so you straighten it to some degree and then attempt to recoil it. Is there some way that you can make use of the existing coiling on the reel - maybe take an end off the reel and end feed it from the coil to your mandrel with minimal uncoiling along the way.

2. This would require some work to achieve but may work .... build a segmented cone your final size or very slightly smaller to allow for the spring of the pipe. weld to the cone a spiral flange 90 Deg to the cone surface with coils separated by the diameter of the pipe - allow gaps or a tapered join in the flange at the cone joins wide enough to inwardly dismantle the cone. Bend the pipe into the gaps between the flanges, then when complete dismantle the cone inwardly away from the completed coil.

Regards

Bill

My thoughts precisely - why un-coil?

If you buy the 'flat coil' configuration, just by picking up the outside, it falls to a cone.

If in fact this 'cone coil' fits inside that form; placing the flat coil on top, and a bit of a push, and it falls into the shape. A tweak or two - winding, or unwinding, the 'general curves' - done deal.

However, I share the concern that the proposed length will have excessive line loss, and I tend to question, why so much, and why copper anyway.

Michael, after reading all the posts and thinking about this for a few days. I think Dooglease had the best idea. Farm this out to someone that does this. He did post a link or 2 if I remember correctly. If you discuss this with them on the prototype and that many ore will be on the way is probably the best answer. This way you won't be frustrated with designing your own jig and you can concentrate on getting this off the ground. Good Luck on your venture.

Jim

jimh778,

After reading all the thoughtful posts I have come to the same conclusion, and will be calling some tube formers today. I will as I get closer to production, be buying my own eqipment. The cost of having it supplied is far greater that doing it your self, in most cases. The issues with most of the responses was that they did not fully understand that the copper was on the roll and because of the lengths it could not be taken off to work with. It flattens easily. So putting in sand or some other liquid is out of the question as it would not fill the tube and there would be no way to stopper the other end.

I will have to get a re rounder for the tubing before it is formed. And I will still need internal support. That I am testing.

Once done I am ready to build build build!

I wonder if you have looked at a typical hand pipe bender for 1/2" copper pipe?

No mandrel is required because the form is a semi-circle, preventing the sides moving out, and the wiper, also a semicircle - wipes.

I.e. you will get 'flattening' if you do not use a close fit groove.

A groove leaves the issue of springing it off your giant form, without it deforming significantly. Then the same issues installing a floppy 'spring' into your unit.

Of course if you take it off and set it on the floor - will it sag to a flat spiral?

If so, why not just make that?

If you don't mind working out a reduction to move 2 spindles at the time, I have the machine here for pick-up in the Bahamas. It is an old hoop forming 3 roller machine that was originally hand turned to fabricate the steel hoops that go around wooden spiked wheels. I have put a motor on it and have formed the most impossible combination with it. I brought it here from my shop in Belgium, where I rolled, pipes, T- channels, Z channels. The rolls are close to each other, stretch the pipe into the pre- formed profile cut of the rollers.

How it works:

When you rotate the handle, 1 0r 2 rolls ( my machine has only one) transport the pipe - on top sits a roller that is adjustable in height ( mine adjusts the distance between the two rollers) Think of a triangle with moving base (extending)

[p]

You start with the smallest diameter and make a first circle. An adjustable wedge on the machine creates the space between the cores - each revolution, you gradually bring the rollers further out of each other - and this drive determines how much the cone swells.

Peace of a (pan) cake.

This machine I bought 30 years ago, and it was already 50 years old.

It simply enabled me to buy a whole professional set of machines, CNC included.

For a prototype, I would make up a cone of concrete mounted on a turntable.

Mark the required spiral on this while the concrete is still green and easily sculpted, then make a groove the OD of the pipe and half the height of the pipe.

When the concrete has cured paint it to get a good smooth surface.

Cut off the length of pipe required for one full spiral, seal one end and pour in molten paraffin wax. When the pipe has cooled, seal off the other end.

Now fasten the end of the small coil and start bending the pipe into the grooves until the spiral has been made.

On completion, cut off the sealed ends and melt out the paraffin ready for reuse.

The coil can be removed by rotating the mold backwards and letting it drop down until the pipe clears.

I haven't tried this out but it should work.

If successful, the general process can be adapted for production.

I would have drawn diagrams to make this clearer, but my draftsmanship is atrocious and the result would probably be more a hindrance than a help.

I have done some copper tubing bending myself with the same kinking problems. The way I solved the problem was to fill the tubing with sand. Cheap, easy to put in and take out, no more kinks.

Sounds more like a still condenser to me though.

Wath about filling the tube with a fluor dougth (in example) capable to be piped out by compressed-air and washed lately with water.

Or use a magnetic ball wen you are bending doing some similar to this:
http://www.youtube.com/watch?v=BaBLwGu5Njk&feature=related

hope this helps

papablo,

Unfortunately, you don't have a clue.

The magnetic ball technique is genius! wow.

The right sized ball would be applicable to the big spiral. Take out every kink...

Thin wall brass with the surface area in the video...Yes.

1/2" copper 1/16" wall.....when it kinks has a tendency to push out at the corners of the kink, cracking, and actually fatiguing the copper causing leaks.

Ah.. The thin wall problem. I have cracked stuff by overworking it, but didn't know there is a possibility of copper pipe that cracks on the first time it's bent!

Oh well, I'll save that one for a beat up saxophone.

The wall thickness is 16 thousanths of an inch: thats( .016) NOT 1/16 of an inch (.0625).

That magnetic ball took out dents NOT a kink. They are worlds apart and the ball technique although appealing will not take out kinks. Once copper is kinked as with any other metal, good luck gettting it back into shape The idea is to form the copper to the desired shape WITHOUT kinking it.

It has the potential of rerounding the copper if it has flattened while being worked.

Is this something common to musical repair shops?

Look at this.

With the right rollers you can make whatever coil you want.

This machine is better than mine, because it has an open structure and also lets you

spiral wind.

I saw a way smaller smaller machine for about $6,000.00.

I tried to pass you a link.

Check youtube "walsmachine" - there is a spanish machine at work.

At the end with pipe.

That's rod, not tube--way different in crush behavior!

"It all depends on the form of the rollers"

I think that the point the OP has missed.

Equally it depends on doing in a properly dimensioned groove - (internal) mandrel or not.

<sigh>

The significance of work-hardening in the process has also been missed in much of the discussion. The roller machine, like metalSmiths bender, is a tool that hardens each part of the pipe into the shape intended in the process. This is the right approach. Whereas simply winding a dead soft annealed copper pipe onto a form will harden it only a little - not enough to make it a free-standing spiral. Using internal support material will harden it more, but whether it's enough, depends on the hardness of the material to begin with. If the material is already half-hard, it will spring back from the form intended. It would have to be hammered to get it to comply with a "wind-on" shape, unless it is dead soft. In which case, the spiral probably collapses. The proper tool work-hardens in the process of forming.

Open message to users who have posted in this thread

I have read and contemplated each and every post without regard to the nature of the information provided. I believe that each and everyone has something to contribute and I respect that. You can never know where the next tidbit of information will come from and sometimes it is a bit here and a bit there that completes the puzzle.

CR4 ADMIN: Deleted Post

Abuse/Attack: This post was deleted because it was an attack on another user. Please review the CR4 Site FAQ and the CR4 Rules of Conduct.

I never indicated anyway or another how the copper should be wound. I imposed no constraints other than those of the copper itself and the dimensions required to me adhered to,

That the copper needs to be in a groove is unquestionable from my perspective. Every jig I prepared had such a groove.

The right tube to do the job is the one that gives me the best thermodynamic performance, and the one I have chosen does exactly that. I believe that every problem (opportunity) has a solution. This one is difficult, but that is no reason to run from the solution and avoid the mental struggle required to resolve it.

For your information, today I took a specially manufactured 10 ft long spring and inserted it into the copper and it went in past some flattened areas and some dents. The tube was wrapped around some posts representing my form and it performed very well. The only shortcoming was that the posts caused excessive wrinkling on the inside wall of the tubing and created some difficult areas to remove the spring from.
With a solid backing from a 'groove' the test would have been completely successful.

In taking a suggestion from Dooglease, My copper supplier has offered to form the copper for me and to continue supplying the product as long as I wish. The only difference is that he is going to use a slightly more annealed product.

I thank you for your thoughtful input and each suggestion was insightful and helpful in its own way.

We should all thank lyn for the gentle humor sprinkled through out the thread.

There was nothing at all abusive in my comments to 34point5. I was responding to a direct insult on my knowledge and integrity.

The moderator should not have allowed that direct insult and I do not regret having made my comments. Perhaps the moderator should be more even handed in the future.

Thick skin and the realization that anonymity allows bluntness not encountered in personal contact will help you survive here.

Yours is an interesting problem and I wish you success with it.

Good Luck.

Well actually I agree and have said so elsewhere.

I hate it when I miss something said to me

Even more so, if I'm not sure it was to me or someone else. So thank you for clearing that up.

But no insult was intended to your integrity

And I'm very happy you have finally decided to take good advice, offered long before I entered the thread, and get the right material for the job and enlist the skills technical required.

What you do not realize is that the supplier, while well meaning can only provide for the prototype units. It takes a much larger bender that may even be available. I have a quote for making the jig I need and will use that for the production model. The tubing must be put through a re-rounder and in doing so it will become a bit more annealed, which is required for it to stay in place. I could have started with the slightly more annealed copper, but that would have altered my secondary objective.

The rest of the exercise was to gather information from intelligent, educated and creative thinkers about this issue. I have ulterior motives for doing so, which shall remain confidential.

I thank you for contributing.

HIp, Hip GA