View Full Version : Building a one shot bender
For a while now i've had plans to build a bender. I picked up a 3" double acting hydraulic cylinder and pump a while back for cheap, and after looking at what benders are out there i've decided to make a copy of the Pro-tools one shot.
I have got pretty much everything sorted except for the pin and roller that the follower bar runs on. When bending something this pin is under a hell of a lot of pressure so I want to make sure it's going to be able to handle the pace if you know what I mean. I'm unsure as to what I should make this pin out of. Originally I thought of using something like a 1" high tensile bolt. Can someone help me out? Here is a pic of the one shot bender with the pin in question circled.
http://i7.photobucket.com/albums/y270/Metalfab_101/Linked%20images/hb302a_pinandroller.jpg
Oh, and I know I can buy the pin and roller from Pro-tools. I originally thought I could do it this way but because the hydro cylinder I am using is so big (in diameter) the pin needs to be longer because I have to build the frame bigger to accomodate the cylinder.
Cheers,
Damo.
TheBandit
11-22-2005, 11:28 AM
If I remember right from my conversation with Pro Tools when I started my tube bending project, they use a treated 1018 or 1020 for all their pins.
Because the pin is loaded in double shear, it has a significant strength advantage.
A 1" bolt would work well.
If I remember right from my conversation with Pro Tools when I started my tube bending project, they use a treated 1018 or 1020 for all their pins.
Because the pin is loaded in double shear, it has a significant strength advantage.
A 1" bolt would work well.
What do you think about the roller, I was thinking or pressing a brass bush in the match up with the size of the bolt. Probably machine the surface of the bolt back to get it a nice surface finish & then machine the bush to match.
TheBandit
11-22-2005, 12:25 PM
What size hydraulic cylinder (dia) and what pressure (psi) do you plan to run? Also what is the height of the roller?
If you take the ram force (lb) and divide by the projected area of the bushing (in^2) you can determine the bearing stress. The area of the bushing is the contact diameter times the height (both in inches).
For the slow speeds of a typical bender, I would not worry about the speed rating of the bushing.
For a 3.5in diameter cylinder running at 3,000psi, I get a ram force of about 29,000lb. If your bushing was 1" diameter and 4" long, it would have an area of 4 square inches. The bearing stress would be 29,000lb/4in^2 or about 7,200psi.
The brass bushings listed by McMaster can only take 4,500psi max. However they do have steel backed PTFE coated bronze bushings that can handle 36,000psi.
If you used two McMaster p/n 60695K68 (a 1" ID 1" tall 36,000psi bushing), you would probably be okay. You could press one into the top and one into the bottom of your roller.
What size hydraulic cylinder (dia) and what pressure (psi) do you plan to run? Also what is the height of the roller?
If you take the ram force (lb) and divide by the projected area of the bushing (in^2) you can determine the bearing stress. The area of the bushing is the contact diameter times the height (both in inches).
For the slow speeds of a typical bender, I would not worry about the speed rating of the bushing.
For a 3.5in diameter cylinder running at 3,000psi, I get a ram force of about 29,000lb. If your bushing was 1" diameter and 4" long, it would have an area of 4 square inches. The bearing stress would be 29,000lb/4in^2 or about 7,200psi.
The brass bushings listed by McMaster can only take 4,500psi max. However they do have steel backed PTFE coated bronze bushings that can handle 36,000psi.
If you used two McMaster p/n 60695K68 (a 1" ID 1" tall 36,000psi bushing), you would probably be okay. You could press one into the top and one into the bottom of your roller.
The cylinder I have is 3", as for PSI i'm not sure. The pump is about 25cc/rev from memory. I don't have a motor yet. As for the roller, I haven't finalised the design yet but it will be around 5" long. The longer the better in this case, but the longer you go the more concerned I am about bending the pin too.
TheBandit
11-22-2005, 01:28 PM
The cylinder I have is 3", as for PSI i'm not sure. The pump is about 25cc/rev from memory. I don't have a motor yet. As for the roller, I haven't finalised the design yet but it will be around 5" long. The longer the better in this case, but the longer you go the more concerned I am about bending the pin too.
Once you know the HP and speed of your motor, you will be able to determine the max operating pressure knowing your pump volume.
I would not be concerned about a 5" long pin. Remember the bushing/roller is going to add significant stiffness to the pin (a stiffening sleeve of sorts). This will keep the pin primarily in shear.
Once you know the HP and speed of your motor, you will be able to determine the max operating pressure knowing your pump volume.
How do I calculate that assuming the motor is 1/2 HP and 1440RPM and pump volume is 25cc/rev.
I would not be concerned about a 5" long pin. Remember the bushing/roller is going to add significant stiffness to the pin (a stiffening sleeve of sorts). This will keep the pin primarily in shear.
That's good to know, it hadn't occured to me that the roller (sleeve) would help out.
I am trying to track down some materials specifications for a different types of bronze. From what I have read phospher bronze should be suitable in this application but I need to know what to look for on the material datasheet to determine if it's suitable or not.
TheBandit, thanks for your help so far:D
TheBandit
11-22-2005, 07:53 PM
Looks like your pump is too big for that small of a motor. You will not be able to develop any reasonable pressure unless you drive that pump with a gasoline engine! I think that pump is just plain too big.
With a 1440rpm motor, that pump flows 9.51gpm.
For 1/2 HP, it will only develop 90psi. YUCK!
http://www.pirate4x4.com/forum/attachment.php?attachmentid=216346&stc=1&d=1132712611
Instead, try the Haldex Barne's AC hydraulic power unit many people use. This is available from Northern Tools. Here is a link: http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=6970&productId=30951&R=30951
From their specs, I calculate a rated working pressure of 1,183psi.
http://www.pirate4x4.com/forum/attachment.php?attachmentid=216347&stc=1&d=1132712611
SOMEONE PLEASE CORRECT ME IF MY CALCS ARE WRONG!
Remember these are RATED values (rated for continuous use).
Hmm might have to check the size of that pump (don't have it handy at the moment). Might have to get something a bit smaller and get a bigger motor.
TheBandit
11-23-2005, 02:17 AM
Hmm might have to check the size of that pump (don't have it handy at the moment). Might have to get something a bit smaller and get a bigger motor.
I wouldn't be surprised if it was 2.5cc/rev pump and not 25cc/rev. In that case the flow would be 0.95gpm and your rated pressure would be 900psi for a 1/2hp motor.
If you ran a 1hp motor at the same speed and the pump is actually 2.5cc/rev you would be good to go.
OK, looks like I have the roller and pin figured out.
I was going to use a 1" high tensile bolt but I have found where I can get 1" pins, check it out http://www.bareco.com.au/files/general/g24.htm#pins think that will do the trick?
The roller is going to be mild steel, about 2.5" dia, and it will have a phospher bronze bush pressed in. I also want to drill a hole up the centre of the pin and put a grease fitting on it.
What size hydraulic hose should I be using? 1/4"? 1/2"? 3/4"? I got no fawkin idea :grinpimp: but i'm guessin' 1/2" would do it!?!?
Also, I did up a little diagram to try figure out how many hose end connectors I am going to need. Does this diagram look right??? If so that's 7 hoses, & 14 connectors!
http://i7.photobucket.com/albums/y270/Metalfab_101/Linked%20images/Bender_hydro_diagram.jpg
jstarnes
11-27-2005, 03:00 PM
why dont you just get a control valve with built in relief? saves 1 valve and 2 hoses
some thing like this http://www.surpluscenter.com/item.asp?UID=2005112715562265&item=9-1517&catname=hydraulic
for my bender I used 3/8 (-6) hose I used what ever pipe thread to JIC -6 adapters and ORB/-6jic adapters
as far as fittings post up pic's of the pump inlet/outlet valve in/out and cylinder in/out
then we can help
:flipoff2:
jstarnes
11-27-2005, 03:02 PM
and why dont you just get a power pack like this http://www.surpluscenter.com/item.asp?UID=2005112715562265&item=9-6410&catname=hydraulic it will do 1700psi (the same I used for my bender)
why dont you just get a control valve with built in relief? saves 1 valve and 2 hoses
some thing like this http://www.surpluscenter.com/item.asp?UID=2005112715562265&item=9-1517&catname=hydraulic
for my bender I used 3/8 (-6) hose I used what ever pipe thread to JIC -6 adapters and ORB/-6jic adapters
as far as fittings post up pic's of the pump inlet/outlet valve in/out and cylinder in/out
then we can help
:flipoff2:
I already have the other valve, I got it with the cylinder and pump for cheap. It does flow control as well, I thought it would be cool to be able to slow the ram down as you get to the end of the bend, might make it easier to get things spot on. It has a relief valve built in.
I guess I can just keep it in mind as an option, if I don't want to spring for the extra hoses i'll just leave it out.
I'll grab some photos of the parts later in the week.
and why dont you just get a power pack like this http://www.surpluscenter.com/item.asp?UID=2005112715562265&item=9-6410&catname=hydraulic it will do 1700psi (the same I used for my bender)
Things just seem to cost more over here. For example, the control valve you posted the link to, the cheapest I have found one for is $150. The power packs are even worse.
If the pump that I have already is not suitable I will look into it further, but at this stage it's just not cost effective to do it this way.
ironpig70
11-27-2005, 05:42 PM
for the pin could you use a pin that is used on the 3 point arms on a tractor to pull a scraper or the like.
for the pin could you use a pin that is used on the 3 point arms on a tractor to pull a scraper or the like.
The one's i'll be using are from a tractor supply place, they're likely to be for that purpose or similar. They are 1" diameter. Have a look here (http://www.bareco.com.au/files/general/g24.htm#pins)
ironpig70
11-27-2005, 10:44 PM
The one's i'll be using are from a tractor supply place, they're likely to be for that purpose or similar. They are 1" diameter. Have a look here (http://www.bareco.com.au/files/general/g24.htm#pins)
exactly what i was saying. missed your earlier link. i worked for a dealer and there pretty strong
exactly what i was saying. missed your earlier link. i worked for a dealer and there pretty strong
And cheap!:D
TheBandit
11-28-2005, 11:04 AM
If you can get that pin in the proper length, it should be plenty strong.
Did you verify the flowrate of the pump yet?
If you can get that pin in the proper length, it should be plenty strong.
Did you verify the flowrate of the pump yet?
Won't be home til Thursday so I can't check out the pump til then. I should be able to get the specs off the web. Also, i'll take a few pics of the parts I have too.
Can someone tell me how far the ram extends on the Pro-Tools one shot bender?
ironpig70
11-28-2005, 06:57 PM
And cheap!:D
buy a couple extra:D
I need to figure out the size of the frame so I can build it to allow for the size of the die and enough travel of the ram.
Can someone with a One-shot take a measurement for me? I need to know the distance from the end of the ram tube (where the top plate hinges) to the centre of the roller pin. Like this:
http://i7.photobucket.com/albums/y270/Metalfab_101/Linked%20images/Ram_travel.jpg
EDIT: For those of you playing at home the dimension is 19.25" Thanks to Pair8hd from the Offroad Fabrication Network board for that info.
Apologies for the delay, been working my ass off the last few weeks. Anyway here's what I have.
This ball valve came with the parts I got. I don't really know what i'd need this for, I haven't counted on needing it.
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Ball_valve.jpg
This is the flow control valve. At this stage I won't be using this because I want to cut down on the amount of hoses. And I don't think I really need it anyway.
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Flow_control.jpg
This is the pump. I think it's a Rexroth:rolleyes:
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Hydro_pump1.jpg
Originally I though, OK with all these numbers it should be a piece of piss to figure out the specs. I've been trawling the web and stumbling through the Rexroth web site so far with no luck. If anyone can get me any details that would be great
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Hydro_pump2.jpg
This is the cylinder. It's a big Mofo.
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Cylinder1.jpg
3" bore, 16" stroke. Dunno what the 1.5" refers to. It's kinda overkill for a bender. I think I will only use about 1/2 the length of the stroke but it's what I have and it was cheap so that's why i'm using it.
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Cylinder2.jpg
Clevis takes 1" pins. Those pins I found at the tractor supply place will be perfect.
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Cylinder3.jpg
I spose 3.5" is about standard for a 3" bore cylinder. The two 1/2" plates for the frame will end up being a little over 3.5" apart, so the 5" long pins will be spot on.
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Cylinder_width.jpg
From the measurements I have the 2 plates will end up being about 45" long. So it's not going to be very compact. I might toy with the idea of making it vertical. That should work if I can figure out where to mount the motor, pump & oil tank.
http://i7.photobucket.com/albums/y270/Metalfab_101/Bender/Cylinder_length.jpg
I wouldn't be surprised if it was 2.5cc/rev pump and not 25cc/rev. In that case the flow would be 0.95gpm and your rated pressure would be 900psi for a 1/2hp motor.
If you ran a 1hp motor at the same speed and the pump is actually 2.5cc/rev you would be good to go.
OK, so after much searching I "think" I have the specs on this pump.
Displacement Vg max cm3 11
Operating pressure intermitt. p bar 280
Power at 1450 rpm PAntr kW 8,27
Speed range1) n min-1 500 ... 4000
Weight 3kg
What worries me about this is the power at 1450RPM. 8kW is a LOT. Does this mean it needs 8kW to supply the max pressure of 280bar? (which is about 4000psi). If that's the case then I guess I can get away with a smaller motor because I don't really need 4000psi in the system.
Am I on the right track here or just talking out my ass?:rolleyes:
EDIT: Just found a PDF of the specs of this sucker. I can confirm that it IS 11cc/rev
TheBandit
12-07-2005, 01:34 AM
Displacement Vg max cm3 11
At 1450RPM that's about 4.2gpm, still a very big pump
Operating pressure intermitt. p bar 280
That corresponds to about 4,000psi
Power at 1450 rpm PAntr kW 8,27
That corresponds to about 11hp
I still think you should invest in a smaller pump.
jstarnes
12-07-2005, 04:31 PM
your cylinder looks like american pipe thread OR SAE O ring Boss
take the red plug out and take a pic of the port its self
X 2 on get a smaller pump:D
OK, so it looks like I need a smaller pump.
What size pump should I go for? I haven't bought a motor to drive it yet so that is still open, but I was hoping to stick around 1HP. What do you think?
TheBandit
12-08-2005, 05:43 PM
Have you considered buying a pre-packaged power unit? The Haldex-Barnes unit sold by Northerntool.com is very popular. It has a 1hp motor pushing 1.5gpm, at a rated 1,200psi (see above calculations). With a 3" bore cylinder, you will generate about 8,500lb force (~3.8tons).
jstarnes
12-08-2005, 05:47 PM
Have you considered buying a pre-packaged power unit? The Haldex-Barnes unit sold by Northerntool.com is very popular. It has a 1hp motor pushing 1.5gpm, at a rated 1,200psi (see above calculations). With a 3" bore cylinder, you will generate about 8,500lb force (~3.8tons).
hes already said there $$$$$ downunder
TheBandit
12-08-2005, 06:04 PM
hes already said there $$$$$ downunder
Sorry, I didn't read that.
The northern tool units uses a 1hp 3450rpm motor and a 0.097in/rev pump. You could also use a larger volume pump with a slower motor. Not many pumps are available in that small of a volume from what I've seen.
Sorry, I didn't read that.
The northern tool units uses a 1hp 3450rpm motor and a 0.097in/rev pump. You could also use a larger volume pump with a slower motor. Not many pumps are available in that small of a volume from what I've seen.
Yeah that is a pretty small pump. Might do some sniffing around locally and see wht I can find.
I wonder how much force you need to be able to bend tube. Say 2" .120 wall.
guinea13
12-08-2005, 08:06 PM
I would shoot for a pump that within 1.25 - 3.5 GPM and a pressure within 2000 - 3200 PSI. Loaded GPM should be no lower than 1.25. Otherwise it will be slower than heck.
If you like 12V units you can use one like I am using:
http://cgi.ebay.com/Fenner-12VDC-Single-Acting-Hydraulic-Pump-w-Remote_W0QQitemZ7568196447QQcategoryZ11773QQrdZ1QQ cmdZViewItem
It is double acting and has a built in valve (so you only need two hydraulic lines).
It runs 3.5 GPM unloaded and 1.25 full load at 3200 PSI (says 3000 on site but is actually 3200).
Some pics of my bender before I totally finished it with the pump on it:
http://www.exm.netfirms.com/Bender/BenderPics.htm
Hey TheBandit:
I know, I still owe you some pressure specs on bending tube. Got really busy this past weekend and this week. I am going to try and get this weekend for ya.
jstarnes
12-08-2005, 08:07 PM
My bender with the power pack I posted above will bend 1.750 .120 dom (not chromo) at ~500psi
I can bend 1.750 .120 dom over 1.500 .120 dom (put the 1.5 inside the 1.75) easy but it does take more pressure......
I can say for sure with a JD2 bender a 3" dia cylinder and 1500psi you can bend 2" .120
Im not an engineer, never claimed to be, I didn't work the numbers, but it works :flipoff2:
the power pack I posted pumps slow yes but its fast enough for me :D
guinea13
12-08-2005, 08:11 PM
That must take forever to bend tube at 500 psi. I thought about that pump when I first started looking at making a bender. But it netted less than 3 tons of force for my setup and would be to slow for my taste.
TheBandit
12-08-2005, 08:20 PM
jstarnes what size cyl are you using and what type of bender?
guinea13 - I think your PM was lost in the database crash. I skimmed it and planned to go back, but I don't see it anymore. If you have a sent copy, please resend! I appreciate it. I wont be able to get that Polybot board until next quarter (starts Jan 2). Hope you're not in a hurry.
Pro-Tools say their ram is 15 ton. It look slike about 2" culinder. Single acting with air over hydro. How can that push 15 ton when my 11cc pump + about 8kW will do about 8 ton??? WTF?
TheBandit
12-08-2005, 08:27 PM
Pro-Tools say their ram is 15 ton. It look slike about 2" culinder. Single acting with air over hydro. How can that push 15 ton when my 11cc pump + about 8kW will do about 8 ton??? WTF?
They are using a 10,000psi power unit. It runs small volume, high pressure.
jstarnes
12-08-2005, 08:33 PM
jstarnes what size cyl are you using and what type of bender?
guinea13 - I think your PM was lost in the database crash. I skimmed it and planned to go back, but I don't see it anymore. If you have a sent copy, please resend! I appreciate it. I wont be able to get that Polybot board until next quarter (starts Jan 2). Hope you're not in a hurry.
I had a Mtech (Jd copy) did the "bend-O-matic" conversion, ripped the frame apart (due to the way the B-O-M loads the pin at start of bend, also did it bending double tube) got replacement JD2 main frame (gusseted them)
Im running the 3"dia 24" stroke cylinder http://www.surpluscenter.com/item.asp?UID=2005120821273442&item=9-6070-324&catname=hydraulic
it takes maybe 40 seconds to bend a 90
the max relief is set to 1500-1700 (backed off to just before the motor stalls)
Im in the process of converting it to the JMR stile bender (has the cylinder applying load like a JD/protools Hydro conversion)
guinea13
12-08-2005, 08:33 PM
jstarnes what size cyl are you using and what type of bender?
guinea13 - I think your PM was lost in the database crash. I skimmed it and planned to go back, but I don't see it anymore. If you have a sent copy, please resend! I appreciate it. I wont be able to get that Polybot board until next quarter (starts Jan 2). Hope you're not in a hurry.
What???? I never sent you anything new? What I was telling you was that I didn't get a chance to bend the tubes and take some data. I am going to try to do it this weekend.
guinea13
12-08-2005, 08:34 PM
And no I am not in a hurry. THanks for the update.
jstarnes
12-08-2005, 08:39 PM
http://www.pirate4x4.com/forum/attachment.php?attachmentid=146080&d=1094256486
guinea13
12-08-2005, 08:41 PM
http://www.pirate4x4.com/forum/attachment.php?attachmentid=146080&d=1094256486
And that is why my arms are 3/4 inch thick
http://www.twistedfab.com/modules/coppermine/albums/userpics/10002/normal_Bender6.jpg
They are using a 10,000psi power unit. It runs small volume, high pressure.
OK, so that would work it would just take longer to make the bend right?
jstarnes
12-08-2005, 08:58 PM
OK, so that would work it would just take longer to make the bend right?
yes its slow because the pump is slow BUT you also have to repin the die 2-3 times for a 90
the one shot is a different animal its "one shot"
FWIW Twisted Customs has used a one shot for a long time.........
yes its slow because the pump is slow BUT you also have to repin the die 2-3 times for a 90
the one shot is a different animal its "one shot"
FWIW Twisted Customs has used a one shot for a long time.........
Any idea how long the Pro-Tools takes to do that 90?
New 3.5cc pump is $300 :eek: chasing up some prices on powerpacks, might be a better way to go if I can get a decent price.
guinea13
12-08-2005, 09:18 PM
My JD2 which is similar to a Pro-tools takes about 10 seconds or so to make a 90. It will do about 120 - 130 deg without re-pining
TheBandit
12-09-2005, 12:52 AM
What???? I never sent you anything new? What I was telling you was that I didn't get a chance to bend the tubes and take some data. I am going to try to do it this weekend.
IIRC you have only sent one PM and that's the one I don't have. This would be about a week old now I think.
jstarnes - I assume you are using 500psi at the start of the bend, with it tapering off from there as your ram extends. When the cylinder is in the compressed/start position, what is the approximate offset of your ram from the center pin on the main die? What I am interested in is the perpendicular distance between the cylinder and the main pin. Attached is a drawing. From this measurement and your 500psi I can calculate the bending torque your machine is using to bend the tube. I would like to compare this with the conservative values I have predicted.
guinea13 - I would need the same measurement for your bender to calculate the bending torque
TheBandit
12-09-2005, 12:57 AM
OK, so that would work it would just take longer to make the bend right?
Yes and no. Because they use a higher PSI, they can use a smaller cylinder. Even though they have to reduce their flow rate to get the same PSI from a given HP pump, the size of the cylinder has been reduced so it takes less time to extend.
Make sense?
For a properly sized combination of cylinder and pump and a given torque output, the bend time should only be a function of the pump HP. I went into a detailed explanation on a different forum. Let me know if you are interested.
guinea13
12-09-2005, 07:02 AM
IIRC you have only sent one PM and that's the one I don't have. This would be about a week old now I think.
guinea13 - I would need the same measurement for your bender to calculate the bending torque
I don't have to email anymore either. I can't remember what info I put in it?
Oh, I remember some of the things I told you. It was stats on the ram and pump.
The cylindar is a Prince: 3 inch Bore 24 inch stroke. 1 3/8 rod. 3000 PSI cylindar.
Pump: 3200 PSI 3.5 GPM (unloaded) - 1.25 GPM (loaded)
Moveable bender arm data:
http://www.exm.netfirms.com/Bender/benderarm1.JPG
Fixed bender arm data:
http://www.exm.netfirms.com/Bender/benderarm2.JPG
This is what I remember sending you in the email.
I will get you that measurement for the calculating the bending torque
http://www.pirate4x4.com/forum/attachment.php?attachmentid=218479&stc=1&d=1134114733
jstarnes
12-09-2005, 07:09 AM
Mine would be the same as guinea13's give or take an inch (my old set up)(which is dead now)(:flipoff2: )
Yes and no. Because they use a higher PSI, they can use a smaller cylinder. Even though they have to reduce their flow rate to get the same PSI from a given HP pump, the size of the cylinder has been reduced so it takes less time to extend.
Make sense?
For a properly sized combination of cylinder and pump and a given torque output, the bend time should only be a function of the pump HP. I went into a detailed explanation on a different forum. Let me know if you are interested.
Post up a link or cut & paste in in this thread. I'd be interested in reading it, even if most of it does go over my head:)
Did a bit of chasing around in the last couple of days.
I will have to see if I can find a similar power pack to the ones you guys can get. I have found one available here but it's AUD$1500 (about US$1100) :eek: I might keep looking around just as an excercise but I don't think i'll go this way as it's just too expensive.
I did find a hydraulic supply place just around the corner from where I live. I spoke to the guy there and he can do me a 3.5cc/rev pump for around AUD$300. From what i've been able to find that's about as good as i'm going to do. I can get a 2HP 2880RPM motor for around AUD$200. Factor in the price of fabbing a sheetmetal tank and a couple of hoses and i'll have around half the $ that the power packs costs into it.
This is the way i'm looking at going. I haven't done any math but from what i've read so far I think 3.5cc/rev pump and 2HP 2880RPM motor, on a 3" cylinder should work for me. Can you guys confirm this for me?:D
TheBandit
12-11-2005, 04:04 PM
3.5cc/rev pump and 2HP 2880RPM motor, on a 3" cylinder should work for me. Can you guys confirm this for me?:D
For that pump and motor combination, I calculate the following:
Flow: 2.66gpm or 10.25in^3/sec
Pressure: 1,287.6psi
Cylinder Force: 9,096.6lb
Those are the rated values. For a typicall induction motor, you should be able to load it to 10-20% of the rated load for short periods of time. I am not sure what cylinder force is required for a one-shot style bender, but the worst case scenerio is you would need a larger diameter cylinder.
Post up a link or cut & paste in in this thread. I'd be interested in reading it, even if most of it does go over my head
Here is a copy & paste. The full thread can be found HERE (http://www.bend-tech.com/forum/viewtopic.php?t=171).
couldn't you move the cylinders out a bit (On the die end)and also reduce the force needed to bend the tube? so maybe make it so you can move it to another width so if your bending larger tube it wouldn't work/stress the system so much.
Displacing the cylinders in this way DOES increase the torque generated, but not without a tradeoff. When you do this, the length the ram has to extend is increased, making the bender slower.
Now, this puts you in a bit of a loop for the following reasons. If you need less ram force to generate the same torque, you can now reduce the piston area of the ram, which means for the same volumetric flow rate, the ram will extend more quickly, compensating for the extra distance it has to travel.
In general, a hydraulic power unit is a fixed flow rate machine and you can design to a fixed maximum pressure. These two values are dictated by the mechanical power delivered to the pump. So, for a bigger HP pump (bigger HP motor), you can deliver either a higher maximum pressure or a higher flow rate.
The output of the machine is also a power of sorts. You can bend at a certain torque at a certain speed. To generate more bending torque or to increase speed, you need to increase power. In my case, the bending torque is a fixed value given the maximum rated tube capacity. So the power output of the machine basically dictates the speed you can bend at.
Nothing comes free here - you get the same power out of the machine as you put into the machine (minus some losses due to heat, friction, etc). So when I choose the power of the hydraulic pump, I am dictating the bending power output, which dictates the speed.
The result: a fixed HP pump and bending torque requirement will dictate a fixed bending speed. If I choose to use a smaller ram, it will extend more quickly, but I also have to offset it so that it has further to extend. If I choose a larger ram, it will extend more slowly, but I can offset it less so that it has less distance to extend. Both will have the same bending speed!
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