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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 06-20-2016, 05:27 AM
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Hydraulic motor pump and valve specs set up

Hi guys
Iv been reading all these posts in and out for the last few weeks trying to make sure I purchase the right parts for my hydraulic conversion.
Boy can I say this is confusing stuff nearly as confusing as learning about finding and adjusting roll centres on my race car.

A little bit about what I'm trying to do and what I have

I have a pro tools 105 currently manual crank handle
I want to put electric hydraulic on it as the last thing I wanna hear is my air compressor rattling the shed down all weekend while I'm trying to build rollcages

I will pretty much only be bending 38x3mm steel tube or 1 1/2" x.120 wall

I'm in Australia so we don't have habour freight here like so many of the posts relate to but Iv been check the links out to try get the specs and info off them to try find the equvelent here in Aus I'm finding it very difficult as everyone's set ups are great and always full of great info but always seem to be missing one or two vital bits of info to complete the set up

Does anyone PLEASE have a full spec list of your parts used and if possible a link to a video so I can see how fast etc your set up is the last thing I want is something too slow or too fast
Can anyone please help?
So far I'm leaning towards

3"x24" ram 3000psi max

240volt 2.2kw (3hp) 5.8letre per min (1.53US GALLON PER MIN) at 185bar (2700psi) motor has long duty cycle for continuous use.


Directional Control Valve

Brand: Imola AMI-3 (Italy)
Ports: 3/8 BSPP
Spring Centre Cylinder Spool
Approx. 40 - 45 Lt/min
Pressure approx. 250 bar (3650psi)

Any feed back or info please or vids to your hydro set up benders would be awesome
Thanks guys!!
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  #2  
Old 06-20-2016, 06:52 PM
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I suggest getting a longer cylinder (36") because just about any way you mount a 24" stroke cylinder to the end of a PT105, you will not have enough stroke to complete a 90 degree bend (after slop + springback) without repinning. I also think you'll be able to get away with a much smaller cylinder (2" diameter if you mount it properly) to maximize speed, especially if you limit to 1-1/2 x .120.

I ran the numbers on your power unit and it should be more than capable of producing 2,700psi at 1.5gpm with 3hp - you should actually be able to get as much as 3,300psi from that combo. That said, you should respect the labelled limits of the unit as well as the cylinder you connect it to.

I can not find the specification sheet for that valve. Can you post a link? You want a valve that will dump back to the tank normally and hold the cylinders. It's called an "open center" valve and it has the diagram depicted in the image below. In the "center" position, fluid is pumped right back to the tank while the cylinder is "held" (not "floating"). When you move it one direction or the other, it will direct fluid to either advance or retract the cylinder.



How do you imagine you will mount the cylinder or are you looking for suggestions? I can give you my engineer's take on this, but there are lots of ways to accomplish the same thing - as long as you get some of the important geometry correct, you should not have any problems. There are better ways of doing things to maximize speed and minimize forces on the bender.
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Last edited by TheBandit; 06-20-2016 at 06:55 PM.
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  #3  
Old 06-20-2016, 08:14 PM
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I should clarify I will use a 24" stroke cylinder which is 36.25" long
http://www.bareco.com.au/files-hydraul2001-hY17c

Motor and pump

http://m.ebay.com/sch/i.html?_from=R...K&acimp=0&sqp=

Valve option1
http://m.ebay.com/itm/Hydraulic-Cont...UAAOSwSclXLTY0


Valve option 2
http://m.ebay.com/sch/i.html?_nkw=32...p=322150427066
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  #4  
Old 06-20-2016, 08:20 PM
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As for mounting positions I have based my hydraulic specs off the "home brew bender" so wil mount very similar if his works well
http://www.mindspring.com/~jayk5/bender/
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Old 06-20-2016, 10:47 PM
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Do you think this would be more suitable ram?
http://m.ebay.com/sch/i.html?_from=R...K&acimp=0&sqp=

If I went to this size what would the minimum size oil resevour tank be that I would need?
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  #6  
Old 06-21-2016, 12:21 AM
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I haven't bought anything yet or made the stand so I'm open to all ideas.
I was just thinking today as the ram extends and moves the drive arm out which is supporting one end of the ram how do you stop that from getting too heavy causing the die to go off square or tilt as the weight gets heavy as the arm moves
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Old 06-21-2016, 05:19 AM
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I'm in the middle of making a hydraulic conversion and so far I've got the following

50mm ram x 800mm stroke,
Open centre valve as thebandit said.
I've got a hydraulic pack but need to source a new pump as it won't create the desired pressure due to the motor being to low powered,
A home made digital readout,

I've just had some brackets laser cut and am in the process of welding them up. I'm making it similar in principle to the jd2 m32 hydraulic conversion.
I'll post some pictures later on.

Adam
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Old 06-21-2016, 05:43 AM
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The stand

Name:  20160617_174735-800x450.jpg
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The laser cut brackets there are 2 sets of these (top and bottom) and another bracket to triangulate the ram to stop it twisting, these bolt onto the tube bender where the original bolt holes are

Name:  20160510_104344-480x853-768x432.jpg
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A sketch on how I invisage it being

Adam

Last edited by Adam Gardiner; 06-21-2016 at 05:46 AM.
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  #9  
Old 06-21-2016, 07:10 AM
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I was thinking this sorta thing today so the ram is sorta set up diagonally across the back of the bende to push in more of a straighter line rather then parallel and sweeping out into an arc does that sound about right?
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Old 06-21-2016, 07:23 AM
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Ram is mounted between a and b
Pivots on p
Other lines show bender position
B will then swing in an arc keeping the angle better to the bender.



There are a lot of threads on here that give a lot of info.
I'll get some pics of mine up when it's done

Adam
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  #11  
Old 06-21-2016, 10:36 AM
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Quote:
Originally Posted by ducas99 View Post
As for mounting positions I have based my hydraulic specs off the "home brew bender" so wil mount very similar if his works well
http://www.mindspring.com/~jayk5/bender/
I stand corrected regarding the 24" stroke making a 90 degree bend, but the way that cylinder is arranged to achieve that is not without penalty. There is unnecessary internal stress on the bender and the bending time is increased over what's possible for the pump had the system been optimized.

Give me some time and I'll take a stab at optimizing the geometry. I'm sure it would help other folks on here.
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Old 06-21-2016, 12:30 PM
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Disclaimer:
I have not validated or tested the theoretical design presented below nor have I provided any detail on how to safely implement such a system. Even worse, I am human and make mistakes, OFTEN, sometimes with severe financial and/or life threatening consequences. Use of this information is at will and completely at your own risk.

Here is my proposal for optimizing a hydraulic conversion for PT105 style bender.



Design Travel:
I propose designing for 110* of bender arm travel. This should account for any design slop in the dies/bender as well as springback to make 90 degree bends in a single stroke, without repinning.

Cylinder Mounting:
Determine a suitable mounting point near the end of the bender. I propose 22" from the center of the dies because this works out nicely for a 36" stroke cylinder and should work fine on a PT105 or JD2 model 3 bender. You don't have to use this 22" dimension exactly if there is a better mounting point inboard of this, but you will need to scale the flow rate down based on scaling this dimension down (the end result will be the same bending speed, but higher operating pressure). If you go outboard of 22", you will need longer than the suggested stroke or you will be limited to something less than 110* of travel.

Angle the cylinder so it aligns with an imaginary line that runs from the starting point of this mounting location to where the mounting location will end up at maximum bender travel (see image for a visual). For 110 degree design travel, the mounting angle should be 35*. Mount the rear of the cylinder so this angle is achieved in the collapsed position. This mounting angle is what optimizes the conversion of linear movement to rotation when using a fixed displacement pump / fixed linear rate.

You can also use a trunion-style front mount which will reduce the overall size of the bender and may be more convenient for mounting. In this case, you want the same mounting angle with the imaginary line above to pass along the cylinder and the trunion mount.

Cylinder Size:
I suggest using a 2" diameter cylinder. This is the smallest cylinder that is readily available in this stroke length and will operate at very reasonable pressure (max ~1500psi) with this geometry. Alternatively you could use a 2.5" cylinder and up the flow rate per the suggestion in the flow rate section below; there will be no performance drawback in terms of speed or capacity, but a larger cylinder will be heavier and may present a tighter fitment onto the bender; it will also operate at a lower pressure.

Capacity:
The calculations provided assume a maximum capacity of 5,000ft-lb, which I believe will be capable of bending 2"x0.120 DOM or 2"x0.095cromoly. This is based on calculations I did many years ago and scaling some test/measurement values from samples of smaller 1-3/4" tube.

Flow Rate:
Based on the capacity above, for a 1hp power unit, you should be able to use up to 1.13gpm pump. For a 3hp power unit, you should be able to use up to a 3.4gpm pump. If these aren't readily available, consider using a 2.5" cylinder with up to 1.77gpm for 1hp or 5.31gpm for 3hp. If you go with a lower flow rate, the bender will simply operate more slowly and consume less than the available power. If you use a higher flow rate, the motor may be overloaded or stall.

Bend Speed:
Using the numbers above (ether for 2" or 2.5" if you select the pump accordingly), you will be able to do 110* of travel in 26sec for 1hp or 9sec for 3hp.

What makes this an optimized design?
The goal of this design is to fully utilize the available power from a fixed-displacement pump. The biggest challenge to doing so is converting the linear travel of the cylinder to rotational travel of the bender arm. There are many ways to mount a cylinder and get ample torque and rotation out of the bender, but doing so in a non-optimized geometry will leave speed on the table. The same goes for selecting a power unit and pump that flow at a lower-than-optimal rate.

For example, the outstanding hydarulic conversion built by Jay uses a 1hp/1.25gpm power unit with a 3" cylinder and 24" stroke for completing a 90* bend. While this will get the job done, the design is not optimized. At 1.25gpm, it will take about 35seconds to complete 24" of stroke with a 3" ram for that 90* bend whereas the optimized design above will do the same bend, using the same power capacity and overall bend torque capacity, about 10seconds faster. Also because the cylinder in Jay's design is mounted at a shallower angle with respect to the bender arm, it initially requires a much higher force to produce the needed bending torque, which necessitates a larger diameter cylinder and puts increased loads on the bender and it's pins.

Is this the "right answer"?
There is no "right" answer. Some answers are better than others, but there are infinite ways of doing this, many of which will give close to the same performance. This is a system where many different elements may be fixed based on availability of components and one or some other parameter may need to be adjusted to optimize for a given set of equipment, so if you have a particular constraint such as already have a particular cylinder or pump or that only a certain size is available of something, post up and we can try to work through making the most of that component.

Can it go faster with smaller tube?
The design above is based on a fixed geometry and fixed displacement pump. Assuming you are not changing the motor, if you are bending smaller tube, you can trade the lower bending torque required for a faster speed. There are a number of ways to do this. For example, you could provide alternative mounting holes in your bender and frame so the cylinder can be moved closer to the center of the bender (if you do this, be sure to maintain the angles mentioned above). You could also use a variable pulley system between your pump and motor, so you can increase the flow rate when bending smaller tube.

Additional calculations to support above design. msg your email address if you want the Excel file.
Attached Images
File Type: jpg tubebenderhydroconversion_Page_1.jpg (178.1 KB, 199 views)
File Type: jpg tubebenderhydroconversion.jpg (55.3 KB, 192 views)
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Last edited by TheBandit; 06-21-2016 at 02:13 PM.
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  #13  
Old 06-21-2016, 01:59 PM
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Quote:
Originally Posted by ducas99 View Post
what would the minimum size oil resevour tank be that I would need?
There is some good information on reservoir sizing here: http://hydraulicspneumatics.com/200/...eservoirsAcces

Their rule of thumb suggests the reservoir volume to be 3 times the gpm flow rate, so a 1gpm pump would need a 3 gallon reservoir. Keep in mind the level of fluid in the reservoir will go up and down a bit as the cylinder advances and retracts since there is less volume on the rod-side of the cylinder. You'll discover this as you fill and bleed the system, but basically always top off the fluid reservoir with the cylinder fully retracted since this will have the most fluid in the reservoir.
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Old 06-22-2016, 10:15 AM
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Just ordered a 1.6cc pump to go on my 0.75kw motor as this will produce 200bar if required but I have the jd2 m32 and may wish to bend 6mm wall stuff at some point,

I calculated a volume of approx 1.5l for the cylinder and a flow rate of approx 2.25l/min with the pump spinning at 1400rpm, so a time of approx 40s to bend to full extension of the cylinder which is approx 110

Adam
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Old 06-22-2016, 03:52 PM
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How much and where abouts did you order the pump from Iv found heaps on eBay but worried I won't be able to find a coupler the connect to the 19mm shaft of the motors I'm looking at.

Other option is this
http://m.ebay.com/itm/240V-2200W-Car...QAAMXQoiJRgbBZ

Iv read a few posts about other guys using these car hoist set ups it's the exact same specs as the power pack I was looking at before but half the price the only thing is the motor says
" no more then 10% duty cycle" Iv tried ringing them and asking electric motor shops etc to ask what this means and tried google but no one can tell me??? Does this mean the motor can only run for 1 min then needs 9 min to rest/cool down??
Any other thoughts on these specs ?
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Old 06-22-2016, 04:18 PM
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The 1.13gpm flow rated pump how many cc does that work out to be as pumps seem to have cc rating on them rather then a flow rate?
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Old 06-22-2016, 04:59 PM
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Ive bought 1 of these and am only using it for the motor. I didn't get a tank so am making my own.
http://m.ebay.co.uk/itm/HYDRAULIC-PU...%257Ciid%253A2
And bought a replacement pump like this
http://m.ebay.co.uk/itm/HPM-Hydrauli...%257Ciid%253A1

My valve block has a pressure relief valve in it

Hope this helps. I had to use a smaller pump as the hydraulic pack is rated at 55bar due to the motor size. Where as now I can use 200 bar if needed. Not that I will need that much. I'd rather have it slower as I'm only using mine to make the odd cage or truck rather than all day every day in a workshop environment
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Old 06-22-2016, 05:29 PM
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How do you calculate cc to letres or gallons per min?
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Old 06-22-2016, 05:44 PM
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How do you calculate cc to letres or gallons per min?
IIRC 1,000 cc = 1 liter
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Old 06-22-2016, 05:45 PM
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Pumps are usually specified in cubic centimeters per revolution. One cubic centimeter is equal to one milliliter. So multiple the volume in ccs by the RPM of the motor and devide by 1,000 to get liters per minute. For example, 1.6cc x 1400rpm / 1,000 = 2.24 liters per minute.

There are 3.79 liters per gallon, so if you want to convert lpm to gpm, you can divide by 3.79. 2.24lpm / 3.79=0.59 gpm
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