Flexible Extension Spring

[missa]

I am having trouble designing a flexible extension spring.  I am following this video here: Creo Parametric - Adding Flexibility in Assemblies - YouTube  but I can't figure out how to create the "Length between two defining points" when making the part flexible. 

Just a side note, I tried making the hooks using the intersect method (3/4 circle placed above end of spring with an arc connecting the end of the spring to top of circle), and I also tried creating the hooks using the sweep&curve method (create a half circle on top of end of spring, sweep it, then create a curve from the sweep line to the end of the spring and tweak the curve).

I also tried going into Tools>Relations and defining the changing variables so that the pitch does not change when the length of the spring is extended or compressed.

My biggest problem is creating the length between two defining points.  When I try to make it flexible, and click the spring to select the Section&Profile, the only length dimension I get is from each end of the spring, not from the top point of the hooks.

I can attach more pictures if you need.

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[RonSt.Pierre]

check out this spring

[missa]

I did, but I can't figure out how it would answer my question.  Could you please elaborate how the spring you uploaded applies?

Thanks

[RonSt.Pierre]

sorry, I kinda dropped it and ran...

after you open the part, go into the parameters

here you have the options for the spring (if designed right, it will work, put garbage in, you will get that)

  total coils

  wire diameter

  free length (spring alone)

  spring length (to contact points between the hooks)

  outside diameter

  hook 2 angle (angle relative to the first hook, "0" is parallel, 90 is 90, 180 opposite, and so forth)

try changing the values to:

tc=10

wd=.05

fl=3

sl=4

od=.75

hook=0

then change the value of sl=3 and regen

play around, see if this helps

we have this spring wrap around a cylinder and hook onto itself

the flexibility can then be applied to the spring length

[dschenken]

The flexible capability can only change characteristics of the part or assembly component that already exist. In the example video the spring was modeled to have the distance between two points be the primary characteristic that drove the rest of the spring.

Flexibility does not allow selecting random things from a part or assembly to alter them - the characteristic has to exist and has to be modeled to act the way the user builds them to act.

[missa]

Yeah, I thought so.  I am having difficulty creating those two points on the spring.  How can I define the length between two points on the spring at the hooks so that I can select them as a primary characteristic for the flexibility option?

EDIT: If you check out the image I initially uploaded on my OP, you'll see the defining points for the length dimension are on the end of the helical sweep (coil) and not on the hook itself.  I created datum points on the hooks in hopes of selecting them in the "Make Flexible" option, but it doesn't work like that.  I can't seem to figure out how to set a length and make it aprimary characteristic.

[Kevin]

For the spring extension or compression you want the pith to change, not sure if that was a typing mistake. What's not changing is the number of coils. If you leave the pitch unchanged you end up adding coils to the spring when it regenerates. You also might want to try a construction for the spring using a curve from equation.

[missa]

I figured out how to do it.  Please reply if you would like me to explain the details.  I have uploaded an extension spring that can easily be modified.  Change the "DO_NOT_EDIT" sketch dimension to manipulate the entire length (including hooks), change the helical sweep profile to change the spring length, change the helical sweep section to change the outer diameter, and go into relations and change the divisor where it says pitch=length/coils (except they're not variables, I labeled it in a comment though, something like "change number of coils").

Let me know if this is good or not.  It worked for my purposes, I was able to flex the spring and when it regenerates it looks correct.  Sometimes the number of coils can mess up one of the hook's sweep sections, I don't really get why it does that (I don't think it should mess up), but yeah if you can figure that one bug out that would be nice.

[missa]

I should mention that I was able to figure this out by applying most of the concepts I learned from "Creo Dunwright" 's YouTube video on flexible compression springs.