New Tube Bender Design Input
- Thread starter SONICJK
- Start date
The problem with lever arms vs. rotation is that more than 90 degrees at a crack is very hard to achieve. 180 degrees is literally impossible kinematically. Otherwise, the force required becomes too great. Your chain and sprocket scheme solves these issues, but creates some different ones, though not hard to solve. One way would be where the chain needs to be parallel and axial to the ram. This would need some sort of yoke to contain the hydraulics, allowing the ram to pull the chain when it expands - sort of like the arrangement on shock/spring that has to work "backwards" like some setups where the shock is under the engine on a bike. Of course there are any number of other ways to connect the chain through levers, but this way is likely the smallest physically. if you have any sort of side load on the ram, it will eventually fail hydraulically, not to mention the mechanism would be hard to make safe. Otherwise, likely trouble will be in the sprocket connection being able to survive the large torque load. If the sprocket is large enough in diameter, and it's attachment to the die is strong enough (It'll need either a large diameter axle, or a REALLY strong one) it should work fine. You will need to work out how long the half perimeter is for 180 degrees so you know how long the throw of the ram has to be for your sprocket diameter. A better way would be to figure out how much force you need to move your die when the ram is at 90 degrees to the arm that moves it, and calculate backwards from there. The ram you have is unlikely to be strong enough, as you will be essentially asking the ram to do several times the work in the same distance. All depends on the original capacity of your bender, and how close the tube you are bending is to maxing it out. If it can bend substantially larger tubes, then you may have enough force to put more angle on smaller ones. Of course, if you are creating an all new machine you can simply size everything to suite. You can get very powerful and very long throw rams very easily. Certainly chain can be plenty strong. You can always double (triple etc) if needed. That said, you are applying very large forces, and the only way to do so safely is to calculate how strong everything needs to be. "Eagle Eye" engineering (My favorite!) simply will not do for everything, which is why even I get out my calculator for things like this! Looks like a good idea, best of luck!
That's what makes the Hossfeld benders so good I guess, minus the fact that their manual. Have you seen the Rogue tubing bender? It'll at least get you to 90 degrees. They have a second pin mount that pushes it the final 90. What I wonder though... what if you take their design but install a second cylinder at 90 from the first cylinder, then when the first cylinder fully extends, you pull the pin from cylinder 1, pin the second cylinder and complete the cycle. Also, it looks like your running a one way cylinder. If you go with two way cylinders, then you can cycle them closed without having to push them in manually.
Here's a quick and crappy photoshop rendering of what I'm talking about with a pic of the Rogue bender:
Here's a quick and crappy photoshop rendering of what I'm talking about with a pic of the Rogue bender:
Attachments
rockcitycafe
I make things.
SONIC. said:Alright guys as you know I bend seat hoops and stuff.
I use a JD2 Model 3 bender that I just converted to hydraulic with an air over hydraulic ram.
I hate it.
It has to be stopped, disconnected and the ram pushed back in 3 or 4 times for each 180 degree hoop.
Manually this was no big deal but with the ram it makes each hoop take forever, the opposite of why I "upgraded" the stupid thing.
SO with this in mind I have been designing a new bender based on the JD2 M3 die set.
This is what I have come up with and I would like you guys input here on any glaring flaws you see in the design
Basically the through bar through the bender and die now is connected at the bottom to a sprocket, the sprocket is engaged in a chain that is connected to the ram. When the ram is actuated the sprocket turns, turning the die and bending as a result.
There's a spring attached to the other end of the chain so that when you release the hydraulic pressure it will spring back to neutral position on its own.
This effectively makes the bender capable of doing 180 degrees in one shot.
The bottom section with the chain would be enclosed with some sort of chain guard to prevent injury if the chain were to snap, keep your fingers out, etc.
What are your thoughts here?
I think that chain would jump off the sprocket, have you looked at hydraulic motors instead of a cylinder?
if you're going to go chain, it really needs to loop around at least 180 degrees of the sprocket... maybe even getting a rack and pinion instead of chain would work better, or even welding the chain to a steel bar and using it and the sprocket as a rack and pinion?
SONICJK
Reminds me of...me No, I'm sure of it. I hate him
Roc City Cafe said:
My first thought was rack and pinion, but for the cost of the one I would need is very prohibitive.
Welding a chain to a bar is a really good idea though, I wonder how strong it would be? I guess worst thing that could happen is the chain breaks off the bar?
Your design with the two sprockets solves the side load problem, but halves the power of the ram: (for every inch the ram moves, the chain moves 2). The ram would also require a sprocket (teeth not required, but effectively a pulley). I suggest you think much larger sprockets. You will have space, and the mechanical advantage of larger diameter will be hugely valuable, allowing wimpier chain and wimpier sprockets for any given load. I think the chain "rack and pinion" will not be practical, as the chain will requires a lot more wrap around to work, not to mention you would only be loading 1 + tooth at a time vs many with some wrap. Think 180 degrees for reasonable power transmission.
Is there a reason you couldn't just get Rack and Pinion gears from McMaster-Carr instead of using a chain? Mount the gear rack on the hydraulic cylinder.
SONICJK
Reminds me of...me No, I'm sure of it. I hate him
What about this?
180 degree sprocket wrap, minimal side loading if its centered on the chain and the chain is 1/8" or so above the ram.
Do we think the side load will still be an issue?
And a larger sprocket would be fine, I just don't feel like drawing one up at the moment
180 degree sprocket wrap, minimal side loading if its centered on the chain and the chain is 1/8" or so above the ram.
Do we think the side load will still be an issue?
And a larger sprocket would be fine, I just don't feel like drawing one up at the moment
