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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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  #21  
Old 12-16-2009, 09:58 PM
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balterbuilt balterbuilt is offline
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i wanna see this
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  #22  
Old 12-16-2009, 10:00 PM
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Domino2205 Domino2205 is offline
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well if Pirate 4x4 said it than it MUST be fact.......................
I always think not to get involved with threads that don't base on facts but
if pirate said it than you will be more than fine
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  #23  
Old 12-16-2009, 10:04 PM
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Quote:
Originally Posted by Domino2205 View Post
well if Pirate 4x4 said it than it MUST be fact.......................
I always think not to get involved with threads that don't base on facts but
if pirate said it than you will be more than fine

hahahahaha, i second that one
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  #24  
Old 12-16-2009, 10:18 PM
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lol... true!
I guess we'll see what happens. I'm lookin forward to seeing how this one comes out.
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  #25  
Old 12-16-2009, 10:54 PM
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Bender Specifications Information?

Here is a post that I posted over on the H.A.M.B. board some time ago and never got any response to the Question at the end of the post.

"I just bent a scrap piece of tubing on my Hossfeld bender and here is what I found. The tube is 2" x .120" HREW P & O material. The die set is a 6" CLR. I have a 36" stroke cylinder for doing 90 bends in one stroke that has a 2-1/2" bore. At the start of the bend (when the leverage is the lowest) my pressure gauge reads just at 500 PSI. As the cylinder extends, the pressure drops to a little over 400 PSI and then starts climbing as it approaches the 90 mark.



The area of the piston for a 2-1/2" cylinder is 4.909 Sq. In.. Thus the force exerted by the cylinder at 500 PSI is 2454.5 Lbs. The force is applied at a pivot pin that is 19" from the center pin. The pin that the wiper die is pivoted on is 8-3/4" from the center pin. Thus there is a ratio of 2.171 to 1 to add into the calculation. That gives a force of 5325.72 lbs at the wiper die pin.

Converting this to torque is where I get lost on this. Maybe one of the engineers on here can check my math and take it from here."

Here is some additional info about my setup. The motor is a 1-1/2 hp 1725 rpm and the belt reduction is 2 to 1. The pump is a vane pump that produced 1400 psi when it was new about 40 years ago. A 90 cycle take about 32 seconds...that is extended and retracted.

Hope some of this helps someone making their choices. All of the components of my system should be available at any good farm supply store.
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  #26  
Old 12-16-2009, 11:51 PM
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If you go with a GM Ham style pump, then you can pop out the relief valve, shim the spring for more pressure if needed, and drill out the hole for more flow. If needed. You dont have to take the pump apart to do it. The only thing to keep in mind is that from the 80's on up that pump uses a metric "bump tube" fitting. You will need to buy a bump tube to -AN adapter to hose it.
One other thing is that those pumps use 2 different size V belt pulleys. A large and small. Each will give different results. From there you could mate a cone pulley to the motor like the ones used on an old drill press. that way you could experiment with the speed to power ratio.
Other than that, there is no reason why it wouldnt work.
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  #27  
Old 12-17-2009, 12:07 AM
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well, I picked up a chunk of 3/4" X 4" flat bar today.. 9 feet of it. Time to make me some bender arms. I need to make up my mind soon on the style.
Anyone have any 7/8" and 1" 4140 cold rolled round bar they would sell me? Local Steel thief wants me to buy a whole stick of each since they don't carry it.
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  #28  
Old 12-17-2009, 12:31 AM
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At the start of the bend (when the leverage is the lowest) my pressure gauge reads just at 500 PSI. As the cylinder extends, the pressure drops to a little over 400 PSI and then starts climbing as it approaches the 90 mark. The area of the piston for a 2-1/2" cylinder is 4.909 Sq. In.. Thus the force exerted by the cylinder at 500 PSI is 2454.5 Lbs.
This is correct

The force is applied at a pivot pin that is 19" from the center pin. The pin that the wiper die is pivoted on is 8-3/4" from the center pin. Thus there is a ratio of 2.171 to 1 to add into the calculation. That gives a force of 5325.72 lbs at the wiper die pin.
These measurements are not really useful without knowing the angle between the cylinder and the arm. or the wiper and the arm. Ignore these for now.

Converting this to torque is where I get lost on this. Maybe one of the engineers on here can check my math and take it from here."
Torque is a function of the force and PERPENDICULAR distance. The distances and ratio you applied above give you incorrect results because you weren't dealing with perpendicular distances. You probably know from using a cheater bar or ratchet wrench that you have to pull perpendicular to the wrench handle. If you push along the wrench handle, no torque is generated. Also as you make the handle longer, less force is required to make more torque.

In the case of the bender, the same is true. Take a look at the picture below and you can get an idea of the torque the tube needed. Your force calculations above are spot on, but what you need to measure is the perpendicular distance (shown as "r") from the force of the ram ("F") to the center pin. You can do this by placing a 90degree square along the length of the ram and measuring to the center pin. This measurement will change as the bender moves through its range of motion, which is why the pressure in your cylinder also changes even if the torque to bend the tube may be roughly constant. Friction of course also accounts for some variation.
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Last edited by TheBandit; 12-17-2009 at 12:33 AM.
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  #29  
Old 12-17-2009, 02:33 AM
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Quote:
Originally Posted by idahoaj1 View Post
"With 1000 psi pump pressure exerted against a 12 square inch piston area (approximately 4" diameter), a force of 12,000 pounds is developed by the cylinder. The speed at which the piston will move is dependant upon the flow rate (gpm) from the pump and the cylinder area. Hence, if pump delivery is 1 gallon per minute (231 cu. in./min.) the cylinder piston will move at a rate of 20 in./min (231 cu.in. / 12 cu.in./min.)"

So with that being said, do the Steering box mod here
http://westtexasoffroad.homestead.co...rsteering.html
and you should be golden!
you WILL need a larger reservoir tho. If you use a remote reservoir pump, then no problems there.
This valve:
http://www.northerntool.com/webapp/w...70_37216_37216
This cylinder:
http://www.northerntool.com/webapp/w...4000_200394000

This cylinder you posted the link to is it a double acting cylinder? I'm a noob to hydraulics too and I'm thinking about upgrading to hydro on my bender too.
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  #30  
Old 12-17-2009, 02:50 AM
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yes it is. you can just barely make out the ports top and bottom on the side facing the camera.
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  #31  
Old 12-17-2009, 12:08 PM
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when choosing a motor look for a capacitor start type motor which gives the motor an extra kick upon starting

Dave
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  #32  
Old 12-17-2009, 12:17 PM
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Quote:
Originally Posted by idahoaj1 View Post
you can use 24" or even 36" stroke rams if you want. The key is mounting the ram and measuring the amount of travel it will really take. alot of the guys on the pirate thread used 24" stroke rams perfectly. Just because the mfg supplied ram has 14" stroke doesn't mean thats the max.
well if pirate did it then must be true but............ on my Pro-Tools bender mounting the cylinder as they designed the up grade I don't think I could use 24" of travel before the bender hit it self but I shall measure mine cause you got me thinkin and see how much stroke my bender could use

Dave
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  #33  
Old 12-17-2009, 12:33 PM
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look at the ones that ppl have made.. most DO run 24" stroke rams. NOW, not having made one myself yet, I truly have NO idea how much of the stroke you get... but no one has mentioned problems with their setup.
I think most of it is all in how you mount the ram to get the most travel?
Since I have the stock I need for my arms, I will be putting together a set of arms soon, and will be able to have a better idea of how it all works.
I really want a vertical type tho. I think I might have enough stock for 2 sets of arms, if so, i'll build a vertical and horizontal set both.
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  #34  
Old 12-17-2009, 04:12 PM
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OK I am back to correct myself and broke my rule about postin without checkin..........
I looked at the travel on my ProTools bender to see how much stroke it CAN use and I found 30" to be a comfortable max before interference with the die so I am glad for this thread cause I have been lookin for a 14" cylinder but am going to go with a 24" now!
but in looking at the operation once you pass the 14" mark or so the leverage starts to decrease so I'm wondering how it would be but the point I was tryin to make is you would not want to use a cylinder with to much travel cause if a valve was to stick I would not want it being able to hit the cylinder or the die but I shall start looking for a 24" cylinder for sure. I picked up the air/over hydraulic unit from harbo freight so I am just needin a cylinder now but I like the idea about usin a power sterring pump and also the link earlier on how to up the pressure!

Dave
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  #35  
Old 12-17-2009, 05:49 PM
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http://www.harborfreight.com/cpi/cta...emnumber=46169

why not just use this? I love the technical excersize but this seems like it'd fit the bill?

am I wrong?
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  #36  
Old 12-17-2009, 06:24 PM
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that one is nearly identical with the one in this writeup on the subject.
http://www.mindspring.com/~jayk5/bender/
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  #37  
Old 12-17-2009, 07:02 PM
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Quote:
Originally Posted by Sarcastro View Post
http://www.harborfreight.com/cpi/cta...emnumber=46169

why not just use this? I love the technical excersize but this seems like it'd fit the bill?

am I wrong?
Aren't wrong, I mentioned that pump earlier in the thread. The problem with that one is that I don't have 220v power at my place. If they made one that was 120v I'd be set. I haven't found anything economical that is 120v, so if someone knows a similar setup that is for about the same price, I might be interested.

The other thought I had driving around today, was what about other electric ram type things, aka Screw actuators or similar. Dispense with everything but a single part and a switch.

JH
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  #38  
Old 12-17-2009, 09:48 PM
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Haku... are you at all comfortable with electrics?
It really IS stupid simple and easy to hook up 220, once you know what you are doing.
open your fuse panel and see if you got any extra empty spots in it. all you need is 2.
go to home depot and get a 220 breaker that is the same kind as the ones in there.. if you need help with that, shoot some pix and i can help ya.
turn off main power to the box, upen that sucka up and stick it in with some wire out of it, and run it to a plug, etc, etc...
honestly, placing your plug is really the hardest part of the whole thing.
I've done it with big fat 1" diameter extension cord before.. not the best way, but it worked. If this is at all feasible to you, shoot me some pix and a PM and i can help ya out with it. Where its a rental deal, its easily taken out later on down the road when ya move.
most ppl aren't comfortable doing that sort of thing, and some places, only certified electricians are supposed to do it.
"this information is only meant as 'educational' and i am in no way advocating you do something against code or landlords wishes.(cough)"

Last edited by idahoaj1; 12-17-2009 at 09:50 PM.
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  #39  
Old 12-17-2009, 11:13 PM
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Yes, I am fine with electrics. I am lighting designer and Master Electrician by trade, so I deal with stuff like that on a daily basis when I actually have a job (unemployed at the moment). I'm not a certified electrician, but I know all about it. I deal with temporary hook ups for nearly every show, including with generators and the like.

The problem lies in that I am a renter at the moment, and am at the behest of the landlord when it comes to this stuff. As crazy as it is, her Dad is a certified electrician, but how the power is hooked up in this house is completely nuts. Circuits aren't logically split up, and in my opinion the rooms need to split up a bunch more. There is one 15amp circuit for her Kitchen (including the fridge), the Garage, and a bedroom I think. She partitioned a part of the house off to rent, which is where I live, and I also have a RV sized garage. I've asked if we can update stuff somehow, and see if we can install a sub panel or at least a separate circuit for my part of the house and the garage. So far, she hasn't seemed that interested.

So yeah, if it was as easy as just running the wiring and installing a plug, then it would be done already. Until then, I have to deal with popping breakers every 3 minutes when I use my welder. On the plus side, there is a commercial garage space that has been vacant since I moved in like 2 blocks away, and I'm in talks with the rental manager for it to maybe rent one of the bays on a month to month basis. That place has 3 phase power, so it would be trivial to hook this stuff up there.

Thats probably more then you wanted to know about my situation.

JH
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  #40  
Old 12-17-2009, 11:24 PM
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Bandit,

Thank you for your informative response. Part of the reason for wanting this information is that I have considered building a new bender that operates in a different manner. Kind of a poor man's mandrel machine.



Drawing is incomplete but you can get the idea of how it will work.

If I knew what amount of torque my old machine was applying to the tube on the largest material that I might encounter, I should be able to use that in sizing the sprockets and cylinder for a new machine. If I follow what you are saying, the radius of the sprocket would be the effective arm length that the cylinders force would be applied to and it would be constant due to the rotary movement of the sprocket.

Again, thanks for the reply.

George
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