modeling tosional spring

[2ms1]

Below is a joint that, as you can see, has a torsional spring acting upon it. The problem is I haven't the slightest clue how to make the spring actually operate as a spring in the model. I've made a helix sweep combined with a couple long cylinders to come up with a solid part that looks like a torsional spring, however I have no idea how to make at behave as one in the model.

This joint needs to be able to function as a joint as part of a larger assembly. Thus, each of the two sides will need to be able to rotate about the center pin part. I think I've got the proper constraints for that, however the spring is a solid, so the joint can't move.

Please help.

View attachment 3156

 

[2ms1]

uh oh. Does the fact that no one has responded mean that it's likely that it is not possible to model a torsional spring like this? If so, I'm in trouble.

 

[wensink]

I think it's possible. It will be a little complex to keep the windings the same. And the 2 legs of the spring ahs to be only related to the windings, and not to any planes.


If i have a little time. I will try to make a model.





good luck

 

[2ms1]

That would be great. Yes I have no idea whatsoever right now so any help at all would be greatly appreciated.

 

[CPiotrowski]

The problem I am seeing is the functionality of the hinge. It looks to me that both sides of the hinge can move freely away from the spring. If their being held by something then you will need to use some kind of external reference or relation to get it to respond the way you want it to. I'm sure its possible but I would have to mess with it to get it to work. This isnt really something you can give verbal direction on. Are you looking to animate this or simply change a value to get the spring and hinge to update in another orientation? One is much easier than the other. From a quick glance tho. I would model the spring as you did. Then, create an additional curve at the ends of the spring not related to datum planes. This will allow the long ends to move with the spring position. Assemble the spring into the assembly first and assemble the hinge in second. Use insert thru the center of both, align the centers to their planes and hold the rotation of the hinges to tangent on the long parts of the spring. That will allow the hinge to update with the position of the spring.
Edited by: CPiotrowski

 

[2ms1]

I left the spring unattached to the two side of the hinge for now because I figured until I figure out how to get the spring to "flex", then attaching its ends makes the hinge completely fixed which is even worse than not having spring there for now just because I want to be able to move it around to test kinematics. I do need to get the spring functioning though.


I'll certainly contrain the spring to "attach" to the two sides of joint, but first I need to have the spring not be an infinitely rigid solid as it is right now (by default), if I'm not mistaken. I am new to CAD and do not know anything about giving solids properties like flexibility.

 

[CPiotrowski]

This is a pretty complex spring for a new cad user. You need to explain what you will be using this for and what results you are looking to get. Are you just looking to modify the rotation of one end of the spring and get the hinge to follow it?

 

[2ms1]

It's a torsional spring that is designed to "fold" in one direction. It's actually a standard steel wire torsional spring sold by mcmaster.com, for which I have the exact strength of, dimensions, etc.(unfortunately I can't lookup andshare alink bc this computer setup to only be able to access this forum). Right now, as shown in picture, the spring is under no tension. The spring will be opposing the action of an actuator that is attached to each of the two links the joint will be connecting (it's a robot arm). So the actuator will be able to move the joint such that the joint rotates from its current base position (call it 9:00,3:00), through to a second position of about 45° down on each side (to roughly 7:00, 5:00), and then its the spring's job to return the joint to its base position as shown.


I do want it to animate, unfortunately.


I actually found another torsional spring in download section of this site. I've attached it here. Doesthis modelhave properties that allow it to "flex" in the way that torsional springs are supposed to?


2007-02-16_133713_torsion.ziphttp://www.mcadcentral.com/proe/forum/uploads/2ms1/2007-02-16_133615_torsion.zip
Edited by: 2ms1

 

[2ms1]

Ok here's someone else's model of a torsional spring. It seems to have a couple 'curve' elements in the model tree which I do not understand the funtion of. I am guessing they may be there to impart the flex capability? Please look:


View attachment 3177


View attachment 3178





Below isthe torsional spring I am trying to make flex. The base position of this spring is different of course, but the function is otherwise identical -- one leg needs to rotate about the axis through middle of coil by 90 degrees. These kinds of spring are designed to apply even amount of torque throughout thisrange of motion, and so I will be modeling it that way.


View attachment 3179
Edited by: 2ms1

 

[mcgowanp]

hey 2ms1, so I had a look at this but could not find the files that I was looking for so I had a go at it again using the same method.


You'll see that I did the spring main body and the added in a helical cut to take away some of the spring to give me the correct angle for the moving spring arm. I used simple figures in my component and found the block angle and the profile length of the helical cut (x) where the two figures that I needed to make this work. i found out that when y=0 x=8 and y=45 x=7 and y=90 x=6. Plotted this in excel and this was straight line curve. I used the first 2 sets of values of x and y in the equation for a straight curve (y=mx-c) to do simultaenous equations and changed object to be the x value since I found this most convienent and used the following x=(y-360)/(-45) in the assy to give me the result I needed. Its sounds a bit long winded I know but thats just the way I am explaining it, I'm sure that i am as clear as mud

.


Here's the assy anyway, edit the component block2 (the red component) and change the angular dim to what ever angle you require and you will see the reulting updated geo. Its not a true reflection of the way that spring should behave but it will provide a sense of what will happen.


Hope this helps. Paddy.


2007-02-20_140033_torsional_spring.rarhttp://www.mcadcentral.com/proe/forum/uploads/mcgowanp/2007-02-20_135137_torsional_spring.rar