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Need Rod bent and formed

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wdugdale

Swarf
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#1
I want to upgrade an old reloading press and I need 3 parts.... I just don't have the equipment to fabricate these.

Two of them are made from 5/8" STL Rod.... they form a knuckle
Third part is a metal sheet with 2 bends with specific drill holes.

The 3 parts are detailed in the PDF with specifications with the last page showing how they fit together.

Any help fabricating these or pointing me to a source would be appreciated.
 

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Silverbullet

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#2
How much pressure will be put on this ? Wouldn't straight line and roller work instead oh the bends.? Bending rods like that is encouraging breakage. They would more likely be forged . You could get them welded up , still chances of breaking. The only way I see them made is milling from solid , no bending. Even then the 90 degree may need bracing .
Just trying to help not anything else.
 

wdugdale

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#3
How much pressure will be put on this ? Wouldn't straight line and roller work instead oh the bends.? Bending rods like that is encouraging breakage. They would more likely be forged . You could get them welded up , still chances of breaking. The only way I see them made is milling from solid , no bending. Even then the 90 degree may need bracing .
Just trying to help not anything else.
Pressure on the straight rod is usually 35 psi with a max of 100 psi. Based on other data, pressure on specific bends/joint could be more than 10,000 psi based on the Von Mises Stress on Knuckle.

Sounds like welding instead of bending would be easier to fabricate.
 

Tony Wells

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#4
I'm all for machining from solid. You could use flat bar for the 90° bar, and there is a way to machine a "bent" part as you have drawn the 27° off axis part. It's small, compared to what I am used to seeing. In the oilfield, directional drilling in particular, the use of "bent" subs is very common. Some are even built of multiple components in order to be adjustable. Some though are fixed angle. They come in sizes up to around a foot in diameter and 6 feet long, however. But the machining processes would be pretty much the same.

On your 90° part, you have drawn it with no inside radius, which would weaken it and make it impractical to machine, in any case.
 

RJSakowski

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#5
I am curious as to why you designed part#1 as you did. It appears to be a linkage transforming vertical movement of part #5 to horizontal movement of part#3. A straight bar will accomplish the same. Also, why the dog leg in part # 5? One of the great features of SolidWorks is the ability to play around with your designs to make them more construction friendly.
 

Silverbullet

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#6
I am curious as to why you designed part#1 as you did. It appears to be a linkage transforming vertical movement of part #5 to horizontal movement of part#3. A straight bar will accomplish the same. Also, why the dog leg in part # 5? One of the great features of SolidWorks is the ability to play around with your designs to make them more construction friendly.
That's why i suggested straight line and roller to reduce friction and less chance of bending and breakage. He's trying to reload brass shells rifle or pistol. At least by the pictures.
 

RJSakowski

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#7
I was looking at the mechanism wrongly. Parts 2 & 3 are a pneumatic cylinder and it appears that the intent is to operate the press pneumatically. The 1-1/4" bore will develop less than 200 lbs. of force which, in my experience would not be sufficient to operate a reloading press if used for swaging brass. Also, converting the direction of motion from horizontal to vertical will be inefficient. Much better to mount the cylinder vertically, either above or below the press.

If that is not feasible, I would consider using a a double armed crank with a pivot below and to the back of two lines of motion. Linkages would be required on each arm as the motion is through an arc rather than linear.
Crank.JPG
 

Tony Wells

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#8
Mount the cylinder so that it can follow the arc of motion. No need to keep it rigid. Mount on a pivot.
 

wdugdale

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#9
Thanks for the reply all. This will allow the reloading press to be pneumatically controlled as RJ mentioned. Parts #1 and #5 are the main two parts I am trying to bend.

In the completed diagram, Part #2 is Pneumatic cylinder, Part #3 is a threaded linage that attaches to part #2. These two off the shelf parts allow to attach the Pneumatic to the dog leg part #1. This allows there to be motion on both ends of part #1.

Part #5 is the other custom part that will attach to the reloading press's arm to allow for pneumatic control.

RJ: I'll be doing a FL Resize on 9mm and 223 brass..... do you think the force would be sufficient to complete?


I'm all for less chance of breakage and issues.

What I can investigate is using a straight line and roller that Tony & Silver bullet suggests.:
Using a 3/8 or 3/8 X 5/8 flat stock as the straight part.

SilverBullet: How would you connect the flat bar to the reloading press (part #5)

Thanks
 

wdugdale

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#10
One last question: I can also look into positioning the Cylinder under the press in a vertical.

Tony: where on the Cylinder were you suggesting to pivot?
 

Tony Wells

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#11
On the tail end. I have done considerable work with Festo cylinders (and have a few if you haven't acquired yours yet) and built a few things that did need to be articulated. Look at heavy equipment for instance, on the hydraulics. Most all of the cylinders are mounted on the end to allow the body to follow either some linkage, or attachment point to a hinged object i.e. bucket on a hoe or blade on a dozer.
 

RJSakowski

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#12
Thanks for the reply all. This will allow the reloading press to be pneumatically controlled as RJ mentioned. Parts #1 and #5 are the main two parts I am trying to bend.

In the completed diagram, Part #2 is Pneumatic cylinder, Part #3 is a threaded linage that attaches to part #2. These two off the shelf parts allow to attach the Pneumatic to the dog leg part #1. This allows there to be motion on both ends of part #1.

Part #5 is the other custom part that will attach to the reloading press's arm to allow for pneumatic control.

RJ: I'll be doing a FL Resize on 9mm and 223 brass..... do you think the force would be sufficient to complete?


I'm all for less chance of breakage and issues.

What I can investigate is using a straight line and roller that Tony & Silver bullet suggests.:
Using a 3/8 or 3/8 X 5/8 flat stock as the straight part.

SilverBullet: How would you connect the flat bar to the reloading press (part #5)

Thanks
I have an RCBS press and, as I recall, when doing a full length resize, I had to put all my weight into the lever arm. So figure 200+ lbs. at the end of a ft. long lever plus the mechanical advantage of the press at the end of the stroke and you're probably looking at several hundred foot lbs. of torque. I would set up the press with the OEM arm and try a resize to get an estimate of the force/torque required for your press.

SolidWorks has incredibly more use than just drawing parts. I would make a model of the existing press as accurately as possible. It requires some reverse engineering but that's a good exercise for a young and inquiring mind. Model each moving part separately and combine them into an assembly. Mate the parts so that they are constrained to move in a realistic fashion and measure the angle of rotation of the press arm. I would look at just using a straight arm for part #5 and connecting it directly to the cylinder at part #3. The opposite end of the cylinder can be a pivot point, as Tony suggested.

Now you will have to work out the length of the arm, the length of stroke of the piston, and the diameter of the cylinder to allow the development of the required torque with reasonable air pressure. SolidWorks can do much of this for you. The longer the arm, the greater the mechanical advantage but the longer the cylinder stroke has to be. The tradeoff is between stroke length and required cylinder force. Position the cylinder mount so the line of applied cylinder force is as close to a right angle to a line between the pivot point on the arm and the pivot point on the press for maximum force.

It looks like an interesting and fun project. Back to the drawing board!
 

wdugdale

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#13
Thanks to all for the important feedback. I'll use Tony's and RJ's feedback to get back to the design and rework the implementation.
I'll be back with updates in awhile.... along with more questions.

Thanks
 
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