I'm building an illusion for a client based on spec's in the client's Harbin book. One of the parts is fabricated from 0.25" x 2.0" aluminium bar stock, which the spec's call out as "bent" into a U-shape with critical dimensions. And there have to be 2 of 'em, completely uniform.

I'm a reasonably proficient metal worker, but I don't know of any way to do this bend cold. Just for fun, I jigged a scrap, made relief nothces, and tried making the bend with resultant failure. Harbin's author, Eric Lewis, mentions this bending merely in passing. It doesn't work within the context cited by the author.

[Knowing this, I fabricated the part using a rivetted configuration; TIG welding would have served as well.]

Harbin had a prototype...but based on the book's description, I don't know how he put it together.

Leland

Did you try heating it for the bend? A propane torch should provide enough heat to do the job. Aluminum can be pretty strong and brittle at room temperature.

Nah. I wanted to try building the project as described in the book. Lewis wrote nothing about heating, and even called the formed material "hardened aluminum" (impossible unless it's an alloy, which the text does not indicate) But who knew? Maybe I was wrong about the ductility of the aluminum bar, and Harbin/Lewis were onto something.

Anyway, tho' I was anticipating failure, I made relief notches at each end of the bend line with well-radiused edges. Didn't help. Fractures (compression and tension) began developing at about 30 degrees into the bend and failure occurred at 45 degrees.

I have a friend who is a metal worker and he bent 1" steel bar to a fairly tight radius for a circular table top, but he had a machine to do it. It was a rather simple looking contraption, but worked like a dream. I am sure a metal fabricator could do it for you no problem - I like to do as much of a project as possible myself, but I have found that for more complex metalworking, I am much better off subbing it out (fortunately, my friend and I often trade minor projects, so I don't usually have to pay out of pocket). Good luck -

Bill

Bill is correct. Look up a local machinist and ask him where you can have it done. Any place that makes wrought iron gates can do the bending. ( How do you think they get all those curves in the gatework? )

Best,

Tim

Virtually ALL aluminum available at the consumer level is an alloy of one sort or another (there are hundreds upon hundreds of different aluminum alloys).

TW

Fair enough, but the point remains that unalloyed aluminum can't be hardened (except as an undesirable result of deformation stress; i.e., work hardening).

I'm using a 6081, which forms probably the bulk of the Al stock at my local steelyard. Prolonged soaking at high temperature would induce minor hardness, but the term "hardened aluminium" to me indicates a copper, beryllium, or zinc alloy. Whether Harbin or his fabricator used one of those series is unknown.

:) "They" get those curves in their gates the same way I get them in mine: With a tubing bender - a machine that rolls a tube through opposing rollers to impose an arc. Unless I'm using solid stock, which is bent on the anvil with a scrolling fork - hot or cold, depending on size.

Thanks for the heads-up, guys...I'm really curious about what Harbin did or used on this one, and so far it remains a mystery.

Leland, ask Pete Biro, he knew Harbin very well and may know the backstory on this one.

Any good blacksmith can bend them by hand. weld a beginning point on your table to grip the bar bend the piece around (a piece of wood you cut with the desired curve)very important PULL stretch the bar as you make the arch. yes it is that easy, once you get the hang of it . and don't add heat , aint needed and it weakens your metal
Good luck
John

Hey, Ricker, thanks for the heads-up.

My original post was imprecise. The piece to be bent into a U-shape is not a simple arc (an easy task), but rather a long bar with two, 90-degree bends at each end (a difficult task). The finished products will resemble this: [ And 2 pair were atually required, not 2. All dimensionally consistent.

My solution was cutting pieces of 0.25 x 3 x 3 aluminium angle to width and rivetting them to the bars. Voila! Instant conformance to spec, perfect right angles, zero failure rate, and much less head-scratching during fabrication. That shiny spot on my scalp certainly doesn't need any additional scratching

Leland,

It is important to note that (at least this is my understanding, it has been a few years since I read my Harbin and the other books about him) that the "Harbin Book" was not a very precise text, and Harbin left out a LOT of particulars especially in the way of fabrication and materials. Many of the props described are missing whole elements like the Up-Side-Down production box.

I think a lot of this was discussed in the book Genius of Robert Harbin.

So I dunno if it helps you or not, but there is the strong possibility there were some major discrepancies in the text you are reading.

Can I ask what piece you are trying to build? I think I know from your question as I attempted to build. PM me if you would like.

Keith

Look for somebody with a good hydraulic press brake. it's doable, might be expensive, becuase some shops do have a policy about not working on specific matrials.

It's a scary thing but it happened a couple of times to me where I was bending a few pieces for a customer, convinced it was just mild steel. I was wrong, this was hardened material that shattered in my hands. (and yeah it hurt like none other)

But make a few phone calls, and a few favors will get you there.

I'm not sure on what you are building, but good luck with it.

Leland,

Where I work they have a machine to make rings out of flat bar stock like you are talking about. They call it a ring roller. it is all for cold bending similar to a sheet roller except the rollers themseves have grooves so that the bar stock won't twist durring the rolling action.

The bad part is we aren't allowed to do "goverment Jobs"

Mark

Okay, I may be way off the mark and I am sure that Café members won't hold back in letting me know here! Iknow nothing about metalworking etc but I do remember working on a project at school where we had to bend some aluminium bars.
We rubbed common household soap over the portion we wanted to bend and gently heated it till the soap started to blacken and then bent it. Apparently it wsa a way of telling when it was at the correct temperature but not too hot to damage the aluminium.
Hope it helps but maybe my CDT teacher was just a little wierd! I am sure that there will be a more qualified Café go'er on here to put you straight
Bri

If it does not have to be metal, you can use plastic or rubber. When it is painted with chrome color paint it looks metal.

Okay, the job's complete and the client is quite pleased with my effort. You can take a look at it by aiming your browser:



Click!

Please note that the buyer PURCHASED a copy of "The Genius Of Robert Harbin," which purchase included the right to build (or have built) the illusion depicted.

Enjoy!
Leland

The strongest aluminium is an alloy and comes under the title
Airplane aluminum or airplane grade. I have used a boileer maker
who bends pipe for factories.

Although this is an old thread, I will make a note here for historical purposes. I own the referenced bar bend illusion. I will not tip the method but I will say that a key assumption made in the above thread is incorrect and has nothing to do with this effect.

Sure, while you're at it, might I add that there are over 500 varieties of aluminum types used in the aircraft industry... so, how is the phrase "airplane grade" be clarified?

Would a Plumbers Spring be any good? Used to bend pipe without deformation.