Topic: Tube bending for the poor

[Quick Draw]

Originally typed for Colorado 4x4, but I'm putting it here since a couple people on Marlin had asked me about it:

Okay, I will be the first to admit that I'm poor.  I don't have any money for the awesome tools that I hope to purchase someday after I get out of college and find a real job. :rolleyes:  But I have found that with a little hard work and ingenuity, you can accomplish all sorts of crap for small fractions of the price that the "other guys" do it for.  So if you have $600 to spend, go buy yourself a real tube bender, and get out of my thread.  The budget for this project is $100.

Where do poor people turn for cheap second rate tools?  Harbor Freight of course!  NO...this is not the ever popular bending tube filled with sand in the Harbor Freight pipe bender.
http://www.youtube.com/watch?v=GWT3N3m4bE4

Instead I will be talking about Harbor Freight's other fine tube bending option... the tube roller!  Watch for sales and coupons, and you can pick one up for $100.  For some reason, the Chinese can't measure very well in inches...  But all you need to know is that it comes with 1.5" rollers marked as 1" or something.  It fits 1.5" HREW/DOM tubing perfectly.  It also comes with some other sizes, but they're pretty useless.
http://www.harborfreight.com/tubing-roller-99736.html

You may be saying, "But Quick Draw, that's for rolling large radius bends.   You'll never get a tight bend out of that thing."  Well I set out to prove that theory wrong, and I have been quite successful.

Right out of the box, the bender does as advertised.  It bends tube with big huge radii.  Great...  But if you try to bring the bend in a little tighter you're going to run into issues. 

First off, the big wheel is attached to the shaft using two set screws.  It doesn't take a genius to see that those won't last long under much pressure.  So step 1 is to weld the big wheel to the shaft...  Easy enough.  Don't have a welder?  Then what business do you have bending tube?

The center roller is also attached to the shaft with 2 set screws.  Unfortunately, the roller cannot be welded to the shaft.  So in this case, you have to drill out the set screw hole as big as you can, and go all the way through the shaft and the other side of the roller.  I think I ended up with about a 1/4" hole before it started getting a little close to the edge of the roller.  Now go out and find yourself a 1/4" diameter by 2" long hitch pin to put through the hole.

I know pictures are worth 1000 words.  I'll see what I can do later if people really want to see them.

After doing this, the bender is ready for the serious torque that you will be applying to it through the wheel.  Now you have to come up with some sort of stand.  Harbor Freight sells one... but who has money for that?  Also, I don't really have a place that I can bolt a stand down, so I had to get creative.  Originally I just mounted it on a piece of square tubing and pounded it down in to the ground... But as soon as the ground gets a little moist, you can run into some problems. 

Here was the 1st incarnation 2 years ago.  Back then I was just getting to know a girl and I taught her how to weld, and then let her have at it on the stand construction.  How many girls do you know that can stick weld off a (under-powered) generator?  Yep...she's still the girl friend.  I was impressed. :


Here is the stand pounded into the ground, and I got busy bending tube:


At that time we had an electric impact gun on the top bolt...but that proved to be pretty much worthless.  Real leverage is much better.  At that time I was also using a grade 5 1/4" bolt instead of a hitch pin to hold the center roller on.  All I can say is that if you're going to do that, you better have a big box of 1/4" bolts... They shear pretty quickly.

Here's a 180 degree bend with a 10" radius:

Here's that same tube bent in the opposite direction with a 7" radius:


Despite the initial bugs, I proved that this bender could easily do a 7" radius bend to 180 degrees if you had the patience (and enough 1/4" bolts) for it.  I got the job done, and I put the bender away for almost 2 years. 

Last week it finally came out of the garage again.  I couldn't find any 1/4" bolts, and frankly that sucked replacing those all the time.  The holes couldn't be drilled much bigger, so I went out and found hitch pins to put in the hole instead.  This is working MUCH better so far.  I haven't broken one yet.

I also found that pounding that stand into the ground again was just not going to work.  So in about 5 minutes I had that fixed with some random crap found around the backside of the barn!  Yep...I'm one of those types...  It's one thing to have pride in your work... it's another thing to get done in a timely manner.

As you can see, the stand is now mounted in a big steel drum using a tube across the top.  That tube is then jammed up against two other tubes that are pounded into the ground, to keep the drum from twisting.

Tune in next time for roller bending theory and techniques.

[Quick Draw [OP]]

Okay let's talk some theory. Using this bender will require using your head a little. Most benders have a fixed center line radius die. But with this bender, the radius of any given bend is a giant variable. So for all intensive purposes when I refer to the bend radius from now on, it is actually the inner radius of the tube that I mean. More on that later...

So I came up with an equation to help me bend tube. Later I found out it's a pretty common equation that some people use when bending tube. Mine is in a little different form the one you may have seen before though. Basically, you have 3 variables: bend radius (R), bend length (X), and bend angle (A). When bending a tube, you must pick two of these constraints in order to determine the characteristics of the bend. The final variable can be solved for using X=B*R*A, where B is the "bend constant" = 0.0175 This equation can of course be rearranged to solve for radius or angle, but this is primarily the form it needs to be in.

Let's say for example that you plan to bend a tube around the top corner of your cab. The corner of your cab has a radius of 9", and it bends a total of 83 degrees. So plugging that into the equation we get, X=(.0175)*(9)*(83)= 13.07. So that's close enough to 13 that we will just round it to a full 13".

Now you take your tube and using a scribe, mark a center line parallel to the axis of the tube. Ideally, you would have a special tool to do that, but I don't have one so sometimes I just use the weld line on HREW... You will also make a centerline mark on the top roller of the bender. As you're rolling the tube through the rollers these two marks should line up at all times. This ensures that you are always bending on the same plane and that the tube hasn't turned in the rollers...which it will probably do. Your job is to notice that the tube turned as soon as possible, and correct it. Fortunately, because this is a slow bending process, if you catch it early, you won't get too bent out of shape (no pun intended).  Now mark where you would like the center and end points of the bend to be. Remember, the two end points for this particular bend should be 13" apart. Make your marks on the top of the tube, as the top will become the inner radius, which is what we are measuring for.

Always start by lubricating the bender. Put a dab of grease on the threads of the bolt that goes through the top. Also, smear some on the rollers. Without lube, the rollers start to get marred up and the bolt becomes almost impossible to turn. Now place the tube between the rollers of the bender and hand tighten the top bolt to snug the top roller down to the tube. Roll to the center of the bend. Now take a big wrench and CRANK down on the bolt about as hard as you can. I have been using a torque wrench because it is a nice long 1/2" drive rachet...but I recently broke the racheting mechanism because it was too much torque for it to handle. So I would suggest a non-racheting socket driver with a big long handle, or a breaker bar nearby. The tighter you can get it, the less likely it is that the tube will twist in the rollers.

Now roll from one end point to the other, being careful not to stop short or go too far from the mark. The endpoint must roll all the way to center of the top roller to get the full length of the bend. You should now be able to get about another 1/8 turn from the top bolt. If it won't budge, roll from end point to end point again and try again. Eventually after a couple of cycles, you won't have to pay very close attention to the end points because the wheel will stop on its own at each one. Continue the cycle of rolling from end point to end point and stopping to retighten the top bolt over and over and over.... I recently did a 7" radius 75 degree bend, and I would estimate that it had around 30 or more cycles. Did I mention this is a slow bending process, that WILL give you a workout? 

Keep going until the bend looks pretty close to your goal. Now roll to the center of your bend. Loosen the top bolt so that the spring back of tube can be accounted for. Place an angle finder on the left and ride side of the bend to find an angle from horizontal (assuming the bender itself is vertical). Add the two angles together to find the total angle. The two angles should be the same if you are in fact at the center of the tube...

I have thought of making a gauge on the bender itself that would measure the progress of the bend. But rather than measuring the angle it would have to measure the degrees per inch of the bend. This is because the distance downward that the top roller travels does not take into account the length of the bend. Rather it is proportional to degrees per inch, which can be calculated by taking A/X. From the earlier example, this would be (83)/(13)= 6.37 degrees per inch. So in theory, the bender could have a scale next to the top roller that indicates these degrees per inch and you could stop bending when it reads about 6.3 or so to measure the bend. I would wager that the relationship is not perfectly linear due to deformation and stretching of the tube at various stages, so making the scale would probably have to be purely experimental.

Does this crazy way of bending tube sound like something you would like to try? For me it is totally worth it. I have come up with a list of advantages and disadvantages to this design from my experiences:

Advantages:
-Can bend a large range of radii, rather than being limited by die manufacturers
-Can easily bend to follow the curvature of a round fender opening or roof line. And it won't look like a series of small kinks like it does when you use a regular bender. If for example you wanted to build an exo cage for a Volkswagon Beetle, this thing would be awesome for that.
-The pressure of the rollers constantly going over the bend creates IMO a superior work hardening effect over regular benders. You can definitely tell when you look at the grain of the metal after a tough bend. Work hardening link: http://en.wikipedia.org/wiki/Work_hardening
-It's cheap!
-You get a workout!

Disadvantages:
-It's cheap! ...requires a decent bit of beefing up to really bend tube otherwise it will break quickly.
-You get a workout! ...seriously, you will be sore.
-It takes FOREVER to make bends compared to hydraulic benders. I have about 4 hours into a 10 ft section of tube containing 5 bends totalling about 210 degrees overall. This is however with some trail and error of my own techniques and tools.
-Likely cannot bend as tight as a 5.5" radius like some benders...altough I haven't tried yet... In theory, it could do as tight as 2" radius, but I fear that the force required to do that would probably require a whole lot of leverage and would end in something breaking catastrophically. Soon here I will experiment with how tight I can go.

Overall, I would love to have a dedicated tubing bender for constant radius bends AND this roller for more creative bends. But until then, I intend to prove that this bender could be a potential substitute for a real bender.

[4RunnerChevy]

Super Hokey, but much respect for what you making that POS do.

[emsvitil]

You mentioned work hardening.

I would think that would make bending harder and harder as you go along.


Have you thought of torching the tube every once in awhile to soften it up and then keep going (I know this works with copper) ?

[Quick Draw [OP]]

You're probably right, but I think using a torch would mess up the strength of it too much for anything structural.  If I didn't need the bend to be super strong and I wanted to speed up the process then sure, I could use a torch.

I can tell you that there is a point after about 10 passes that progress slows down A LOT.  I usually have to put a big long pipe over the wrench to keep it moving.  After another few passes, the effort gets much easier again, as the tube begins to stretch and deform some.  The bent section does get very slightly elipse shaped for bends under like 10" radius.  It's not terrible, but enough that you can feel the difference when you run your hand over the tube.

[4RunnerChevy]

annealing doen't really work in a low carbon state, in mechanical tube..  But it will let you bend it easier, but adding deathly weakness to the tube.

[junya92toy]

You mentioned work hardening.

I would think that would make bending harder and harder as you go along.


Have you thought of torching the tube every once in awhile to soften it up and then keep going (I know this works with copper) ?

You as you bend you work harden the part that bends, and move to new tubing thats unbent.

[Quick Draw [OP]]

You as you bend you work harden the part that bends, and move to new tubing thats unbent.

....  Not quite sure I follow ....

[Quick Draw [OP]]

Some updates on this:

I stripped out the top threads when I got a nice long breaker bar.  Then I found out that you cannot find a nut that will match square profile metric threads anywhere.  So I did some more "rigging", and threw one of those screw bottle jacks that come in Tacomas from the factory in there to put pressure on the top roller.  Apparently it takes more force to bend a tube than I anticipated, because I completely stripped that thing out about halfway through a bend.  I couldn't back the pressure off to get the tube out, so that was interesting...  And then I decided to throw in a hydraulic bottle jack instead, which seems to work well.  But it also seems to be pretty rough on my 4 ton bottle jack.  Anyway, bends are going much faster now that I'm getting the hang of it.  I'm still at about 15 minutes to get a 90, but I will take it.  I whipped this up last night.  Going to add more tubes over the next week or so to make a full front bumper.



I'm seriously considering doing my whole exo with this thing.  I already have my rear hoop basically done.  I had about 2 hours into it...  But hey, I've got the time... not the cash.

[nisota]

Awesome I totally support what you are thanks for helpin the rest of out who dont have cash but are willing to put in the time. 

[BadnewsBob]

  I like it bro.....Shade tree is a respectable term around these parts.

[OldGold3VZE]

It's one thing to have pride in your work... it's another thing to get done in a timely manner.

I can totally agree with this.  My bender has never been "properly" mounted.  It usually gets bolted to an old frame or buggy chassis sitting in the yard.  When I sell or scrap said chassis I have to find a new location for the bender, but I have managed to build lots with this setup!  Way to go, and thanks for the write up.  I think I'm going to get one of these for the fenders on my next buggy.

[junya92toy]

....  Not quite sure I follow ....

Once you bend something, it takes even more force then the last time to bend it more in the same spot.

[Braswell91]

Great write up! Im am goin to swing by harbour freight and snatch one up when it comes time for the new project!

[Carolina82]

Great write up, going to try to learn the art of bending soon. 

[At]

What tubing notcher do you use?  my father did metal fabrication and when I was younger I wish I would of paid more attention!

[junya92toy]

How much do you need to do? YOu could use a bandsaw, chop saw, angle grinder, a harbor freight notcher, or spend a few hundred for a nice one. A few notches and Id do it with a bandsaw, anymore Harbor freight is fine, and if youre doing a lot, like building for people get a nice one.

[At]

How much do you need to do? YOu could use a bandsaw, chop saw, angle grinder, a harbor freight notcher, or spend a few hundred for a nice one. A few notches and Id do it with a bandsaw, anymore Harbor freight is fine, and if youre doing a lot, like building for people get a nice one.

I'm a perfectionist so if I do something it's gonna be perfect. So to your question how much do you need to know, as much as I can to do the best job that's possible.

[junya92toy]

Well I do the best job I can do, but to be honest, you can make very good copes with the methods Ive talked about. Plus, any little gaps will weld out and you will never know the difference. Notchers dont make the best cut, if you are a perfectionist, then get a end mill notcher, should set ya back 5000$

[junya92toy]

This was done with a porta band

[chrisprojects]

Looks good

[<3 Low range]

Harbor great strikes again
 

[oldyotaholic]

Ive walked past that same roller and that thought went though my head...just wasnt sure how capable itd be.  How thick is the sidewall of the 1.5" tubing youre using?

[pumkin toy]

I have notched using many different methods, grinder, chopsaw, pipe notcher on ironworker (only works for 90 degree notches basically) mill with different sized end mills, and lastly the standard tube notcher with holesaw.
I have gotten the best fits possible with the mill of course, but that's way to expensive.  the fastest, easiest, and best tool for the money in my opinion is the standard tube notcher with holesaw.  Ive got a jd2 basic model and ive been using it a lot lately. I really like it.  easy to use and provides a great fit.