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Benders and Bending Which bender is best? How do you use a bender? How do you calculate bends? Everything Bender related...


Benders and Bending Which bender is best? How do you use a bender? How do you calculate bends? Everything Bender related...

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  #1  
Old 01-03-2013, 10:28 PM
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Scrambled Scrambled is offline
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How fast is your bender

I am in the process of making a lot of 90 and 122 degree bends in 1.25 pipe for some handrail I am making.

After spending all day watching my JD2 model 32 bend 90 degree bends, out of shear bordom I started timing my bends. It takes my hydraulic pump 2:45 minutes to make 1 bend.

I have to get something faster.

How fast is your hydraulic bender making a 90 degree bend?


Steve
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  #2  
Old 01-03-2013, 10:42 PM
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Margoville Margoville is offline
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I would have to time it to be sure but my bender will bend 70* in one sweep then re position. I would guess it takes less than 15 seconds to bend 1-1/2" .120 304 stainless to 70*. It is a JD2 I grafted onto a old Rino Iron Worker that has about a 24" ram.
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  #3  
Old 01-03-2013, 10:46 PM
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Diverbill45 Diverbill45 is offline
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I converted my JD2 over to hydraulics 2 years ago and did time it once. With a 24 inch stroke I can make a 118 degree bend without re-pinning and it takes 22 seconds to make that bend.

The retract cycle takes 17 seconds, with no load.
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Last edited by Diverbill45; 01-03-2013 at 10:48 PM.
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  #4  
Old 01-03-2013, 11:08 PM
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I can also bend to about 115 degrees without re-pinning the bender.

What GPM flow pumps are you using? What size motors are you using for these pumps (HP size).

Thanks

Steve
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  #5  
Old 01-04-2013, 12:02 AM
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TheBandit TheBandit is offline
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I love this question because I'm a geek.

The speed you can theoretically bend at is a function of your motor horsepower and the output torque required to bend your tubing. Let's say you have a 1hp motor and it takes 3,900ft-lb of torque to bend your tube (FWIW that's what I measured on my machine for 1-3/4x.120 chromoly). If you were able to match your gearing perfectly you would get:

[ 3,900ft-lb / (1hp * 550ft-lb/sec*hp) *2*3.14rad/360deg]= .12sec/deg = 11sec/90deg or 22sec/180deg

Now in the real worked we tend to deal with fixed displacement pumps and non-variable gear/machine ratios, so we really have to design around our worst case torque. In my case I designed a bender for 5,000ft-lb of torque and it uses a 1hp motor. I was able to size the cylinders, pump, and mounting points to optimize for that power output, so I theoretically get:

[ 5,000ft-lb / (1hp * 550ft-lb/sec*hp) *2*3.14rad/360deg]= 0.16sec/deg = 14sec/90deg = 28sec/180deg

I got pretty close to this when the machine was completed. If you look at this video, you can see I do a 45 in about 7 seconds which is pretty close to the calculation above. http://www.myspace.com/video/vid/1441790523

That machine was designed from scratch so I had a lot more flexiblity to put the cylinders where I wanted and match them to the pump/motor/power unit.

Ways to get faster bends:
- Increase power
- Make bender variable so smaller tube (lower torque) can be bent faster with the same power
- Reduce variation in geometry/leverage during cylinder stroke
- Do the homework to match components, geometry, etc
- Have someone else do it for you :)
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  #6  
Old 01-04-2013, 12:24 AM
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Clint, on my bender, the highest pressure I have gotten is 500 PSI on a 2 inch cylinder. This was when I was bending 1.25 solid round bar.

Usually on the 1.25 sched 40 pipe, the pressure is close to 200 psi on the gauge. The gauge is mounted directly on the back of the cylinder.

Steve
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  #7  
Old 01-04-2013, 12:33 AM
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Do you have any photos of your bender and do you know the specs on your pump & motor? I can give you some recommendations on how to speed it up. If you were able to bend the round bar at 500psi and your schedule 40 bends at 200psi, you can speed up your bender by about 2.5 so your 2:45 bends should go down to about a minute if you can size things better. There are a lot of ways to do this - it may be as simple as a multi-mount for your cylinder or as complicated as a 2.5x larger flow rate pump

Of course without knowing a lot more about your bender, I don't know how hard you're pushing things.
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  #8  
Old 01-04-2013, 12:38 AM
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Quote:
Originally Posted by Diverbill45 View Post
I converted my JD2 over to hydraulics 2 years ago and did time it once. With a 24 inch stroke I can make a 118 degree bend without re-pinning and it takes 22 seconds to make that bend.

The retract cycle takes 17 seconds, with no load.
The faster retract is probably less from the no load and more from the rod taking up volume on the retract side of the cylinder. Most motors and fixed displacement (gear) hydraulic pumps put out pretty close to constant flow between no load and rated load, at least from what I've seen in my limited experience.
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  #9  
Old 01-04-2013, 12:43 AM
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Clint-

I am using a 10,000 psi porta power pump. It is low flow, but high psi. I am not too shure what the GPM is, but I will try to find out.

I will try to find a picture or two for you.


Thanks


Steve
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  #10  
Old 01-04-2013, 01:21 PM
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Diverbill45 Diverbill45 is offline
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Clint, ..... Thanks for catching that. I'll admit, I made a mistake on the retract time. I was out in the shop last night and timed the return cycle. It wasn't the same as the extend cycle, it took a couple of seconds longer to fully retract.

I, for one, do not like to receive faulty info, so I always try to be correct in the info that I pass on. Even though this was a very minor mistake, it was in fact, a mistake, so with that, I apologize to all members reading this.

I guess my only defense is, I was having a senior moment again.

Now I'll just go and sit in the corner of my shop and think about it, for a while.
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  #11  
Old 01-04-2013, 02:52 PM
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zag zag is offline
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mine does 90 in ~6 seconds and from tooling to 180 is about ~1.5 minutes

http://www.youtube.com/watch?v=5NhP2ZKPjCM
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  #12  
Old 01-04-2013, 03:29 PM
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No fair Zag! Guess I gotta put a pull-start engine on mine to keep up with that power.
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  #13  
Old 01-04-2013, 10:11 PM
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CarterKraft CarterKraft is offline
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I have been designing a log splitter for myself and I am thinking about using a regenerative circuit on the extension stroke, a good description is here.

Of course if you are using a single acting cylinder and think you are then it won't work but I am posting this to possibly give others some ideas.
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  #14  
Old 01-05-2013, 01:15 AM
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My JD2 Model 3 Elect/hydro was fast, now I am using air/hydro. OMG it is slow. I can duct tape the pedal down and go pee, wash my hands and come back to the bender and it still not to 45 degrees. Just kidding but I have almost fallen asleep.
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  #15  
Old 01-05-2013, 01:58 AM
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Zag-

Do you have a link to a build log about your bender? I like the design.


Steve
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  #16  
Old 01-05-2013, 10:14 AM
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Bandit and ZAG -awesome! two of the best homeade benders in one thread!

ZAG-does the ram/sprocket extending out ever get in the way of the "next" bend?
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  #17  
Old 01-05-2013, 10:40 AM
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CarterKraft CarterKraft is offline
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While my air/over hf ram is slow but while bending I find it plenty fast enough that there isn't any wasted time during a bend. I acquired a directional SPX porta power power unit and have got about 80% of my elec/hydro conversion but I had to put the air/over back on because I needed to get some work done. I will do some time comparisons when I get done.
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  #18  
Old 01-05-2013, 10:57 AM
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Quote:
Originally Posted by Scrambled View Post
Zag-

Do you have a link to a build log about your bender? I like the design.


Steve
here is the build up

http://www.pirate4x4.com/forum/shop-...en-bender.html
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  #19  
Old 01-05-2013, 11:10 AM
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Quote:
Originally Posted by bullnerd View Post
Bandit and ZAG -awesome! two of the best homeade benders in one thread!

ZAG-does the ram/sprocket extending out ever get in the way of the "next" bend?
some times in my 1" die (small clr)if the bends are really close and i have to rotate first bend down.
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  #20  
Old 01-05-2013, 11:39 AM
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bullnerd bullnerd is offline
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Very good.

Do either of you think that you "overbuilt" your machines at all? Like ,could you have gotten away with thinner/lighter materials anywhere?
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