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Discussion Starter · #21 ·
No grandstanding intended! Sorry for those who haven't taken calculus or mechanics of materials. I just thought the results would be interesting to some even if you don't understand the steps involved to get there.

Goat, no I didn't forget the FBD (free body diagram) or friction - I have them both but they are not scanned. I also have shear and moment diagrams for the tube. I'm not currently showing the layout/kinematics of my machine, but there's a lot more going on behind those Excel cells.

There is a 2x design factor directly placed on the required tube bending moment which should easily account for the effects of friction, strain hardening, and unforseen variables in material. That's shown in the last spreadsheet.

Tomorrow I am going to start some rough solidworks drawings of how I want the machine to look. I think I mentioned above I have a set of 1.75" dies (6" CLR) on their way - three weeks to make them, so I will see them at the end of the month. Once I'm confident in my bending calcs, I will order the two DA cylinders based on dia and stroke requirements.

Anyone familar with hydraulic cylinders? I would like rebuildable units - is there a particular brand that's well known or is easy to get rebuild parts for? I am currently looking at Cheif and Lion, which are similar in price. I may be stuck with what's local since shipping these heavy bastards costs a fortune.
 

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Discussion Starter · #22 ·
WideBody said:
Just had to defend the naturally smart people that feel the confines of formal education are to stifling on intellectual ability.
I don't think education makes you smart, it just makes you educated.

The smartest person I know never graduated high school.
 

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A long follow bar that rides with the tubing would be a great asset to a bender. Getting rid of the gouges that are caused by dragging the tube thru the forming die would help immensely. I realize that that deviates from using the PT105 dies, but it's one of the features that my next bender will have.
 

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Discussion Starter · #24 ·
RawkRash said:
A long follow bar that rides with the tubing would be a great asset to a bender.
I have to agree with you on this one, but I'm really stuck on using the 105 dies. So many of my friends have dies for the 105, it would be hard to justify the cost of buying my own sets or matching follow bars for theirs. Also I want this machine to be as hands free as possible in terms of loading the tube. Thank you for the suggestion though. I am really happy I posted this; you guys are giving me all kinds of good ideas!
 

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I have a pro-tools 105 HD. The one thing I dont like about it is the slop, and lack of rigidity. IMO there should be bronze or oilite bushings in the movable arms, and the pins should fit tighter.
 

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Discussion Starter · #27 · (Edited)
I haven't stopped working on this project, but I haven't been able to put much time into it of late. Based on bending stresses on the main pin, I will have to resleeve the main die so I can use a large main shaft. I am slowly refining things into something workable. I have not designed the follower die swingout or the autostop/degree feature, but the basic design elements are there. Here are some CAD pictures. Any thoughts are appreciated! :)









*EDIT* The above shows a crosspin fixing the spindle to the main frame. Unfortunately, the main die will gall against the spindle while rotating. In a later revision, bearings are installed into the frame so that the spindle can rotate with the main die.
 

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4RnrRick said:
From using my manual protools bender the only quirk that I would like to have is the ability to bend multi axis bends without hitting the ground or the roof of the garage. So if you could design a main pivot on the machine base so you could tilt or angle the whole device say from 0-15-30-45-60-75-90 degrees from the ground that would be a nice feature to have. plus having the hydro power unit on 110 volts would be nice.
Thats why I got mine on wheels.

FWIW neighbors slow down and stare when you are bending tube at 11pm in a snow storm in the driveway :confused:
 

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Discussion Starter · #29 ·
Anyone have any ideas on where I could put a degree wheel? The wheel needs to attach to one of the arms and the pointer has to mount to the other arm (thereby reading the difference, or the angle of the bend). I would like it to be visibile throughout the bend, but I'm having a hard time figuring out where to mount it!

I will be making the wheel myself, so the size and mounting are flexible. I was thinking about adapting a cam degree wheel since they are both large diameter and inexpensive, but I am not afraid to start from scratch.

I do not want to use the cylinder strokes to gauge bend angle.

Any advice/suggestions are welcome!
 

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Most common grade of mild steel dom is gonna probably be 1018 or 1020. Chromo tube is almost always 4130. For the degree ring since it's a project do what's nice. Screw a big ring. Put a gear on the center pivot that'll work a small degree gauge mounted somewhere. Basically like a pair of dial calipers. Make it so you can set your zero.
 

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I hope you have one hell of a shop your going to put this thing in since the tail of the tubing will be swinging almost 90 degrees. I think you may want to do a little tube bending before you go much further since your design doesn't allow for tube gain at any givin point, unless you start the form die cylinder first. I just don't see this design being very accurate from bend to bend, since this is not a draw through style machine it's both types of bending machine in one IE .... draw through and wrap around. wrap arounds suck big hairy balls. :shaking:

I would look at something a with a bit better design like the Ercolina models, these are rotary style machines and the pro tools dies could be machined to except some type of driver pin.

here ya go http://www.ercolina-usa.com/topbender.htm
 

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MAD MAC said:
that thing is nice. I wonder how much one costs?

I agree with Mac on your design. You are sticking to 105 dies cause they are common in garages everywhere. But most of those garages are packed with trucks, parts and whatnot. Not enough room to have two ends swinging around.

I like d.d. machine's idea about he axle chunk. I like it but the springback on the bend will cause the handle to want to spin back all the time. How about using a similar idea, but with a worm drive gear. An electric reversible motor can drive the worm. I imagine you can work in an adjustable stop switch into the degree ring to make repeatable bends.

Gear wear could be an issue. But that is for someone smarter than me to figure out.

I would guess someone else has already figured this out. Probably too expensive anyway.
 

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Discussion Starter · #33 ·
MAD MAC said:
I hope you have one hell of a shop your going to put this thing in since the tail of the tubing will be swinging almost 90 degrees. I think you may want to do a little tube bending before you go much further since your design doesn't allow for tube gain at any givin point, unless you start the form die cylinder first. I just don't see this design being very accurate from bend to bend, since this is not a draw through style machine it's both types of bending machine in one IE .... draw through and wrap around. wrap arounds suck big hairy balls. :shaking:[/URL]
Mad Mac - I really appreciate the feedback! I haven't bent much tubing except for playing around with buddy's 105s, so this kind of feedback is invaluable.

What do you you mean by "tube gain"? Is this the linear feeding of the tubing into the machine, like the model you linked to does?

I agree having the tail end swinging could be a bad idea. Perhaps a couple of valves would be handy so that one cylinder can be stopped.

I don't understand why this machine would be less accurate from bend to bend than the model you listed. Please explain what you mean? The tubing will see the same slip and loading on the follower die. The only difference is how the entire tube's orientation changes as the bend is completed.

I don't plan to measure the angle of either arm seperately, but rather measure the angular difference between the two arms. One way to do this would be to have a degree ring attached to the follower die arm and a pointer attached to the main die arm. Another way would be to attach a potentiometer between the two arms which would measure the same angle.

As for selecting the Pro105 die, this was not the best idea as I've found I have to modify it to make it work. The 1" CL pin is simply overstressed in the cantilevered configuration I am using. I will be resleeving the die to accept a 1.5" CL shaft.

MAD MAC said:
wrap arounds suck big hairy balls. :shaking:
Please explain what you mean. Do you mean it sucks because of the tail end of the pipe swinging around or is there some difference between this and a draw type? :confused:

Thanks again for the feedback. I appreciate negative feedback as much as positive!
 

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What do you you mean by "tube gain"? Is this the linear feeding of the tubing into the machine, like the model you linked to does?
Tube gain is the amount of material that is used to make the bend this is calculated with a percentage of the radius of the form die and the degree of bend being made.

look at a tube bending manuel from a pipefitters handbook.

I ment a wrap around style machine is actually using the slide shoe to do the bending which in turn creates more spring back and also is changing the start point of your bend, so in turn when you change your start or zero mark, then you have lost your start mesurement for you next bend.
 

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Discussion Starter · #36 ·
MAD MAC said:
Tube gain is the amount of material that is used to make the bend this is calculated with a percentage of the radius of the form die and the degree of bend being made.
Thanks for clarifying. I didn't know what the term refered to.

I ment a wrap around style machine is actually using the slide shoe to do the bending which in turn creates more spring back and also is changing the start point of your bend, so in turn when you change your start or zero mark, then you have lost your start mesurement for you next bend.
The start point of my bend will always be the same start point as with a Pro 105 bender. The strap attached to the main die will still fix the tube. Only the follower die will be moving with respect to the tube itself. Maybe I am missunderstanding you, but please clarify if you are saying the tube will be seeing a difference between my bender design and the design of the Pro 105.
 

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Discussion Starter · #37 ·
Pulled the trigger on some parts today: power unit, control valve, two cylinders... some other odds and ends and there goes $700.

I've decided to go digital on the autostop controller. Gonna use a linear pot and a microprocessor so I can have a few seven segment displays. Current angle, desired angle, button for zeroing, knob for adjusting desired angle, and something for calibration. A 12V DC solenoid valve will bypass flow when the desired angle is reached. Lots of details to work out for this controller, but for now I'll just concern myself with the machine components and accomodation of the pot.

Still working on the swingout assembly but I'll be making chips soon :D
 

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Discussion Starter · #38 ·
Does the lack of response mean people like the design, hate it, or just plain don't want to reads this really long thread?

Please tell me you like it, hate it, or what you think I need to change.

Feedback is really appreciated. I am spending a lot of money on this thing and the changes I make now are basically free. Much better to find out something sucks now before I drop coin on all the materials!
 

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TheBandit said:
I've decided to go digital on the autostop controller. Gonna use a linear pot and a microprocessor so I can have a few seven segment displays. Current angle, desired angle, button for zeroing, knob for adjusting desired angle, and something for calibration. A 12V DC solenoid valve will bypass flow when the desired angle is reached.
What for? Other than to make that sucker bling bling you are better off making it simple. No need for fancy stuff other than a simple limit switch. Keep shit like this on the back burner until you have a functioning bender then throw on the bling.

I have yet to see a mention of fatigue...have you evaluated it at all?
 
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