# Spring reaction force **URL:** \ **Category:** General Questions\ **Tags:** results\ **Created:** [June 21, 2023, 8:59pm UTC](https://prepomax.discourse.group/t/spring-reaction-force/952 "2023-06-21T20:59:55Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![andnee](https://avatars.discourse-cdn.com/v4/letter/a/87869e/32.png) [@andnee](https://prepomax.discourse.group/u/andnee)\ **Post date:** [June 21, 2023, 8:59pm UTC](https://prepomax.discourse.group/t/spring-reaction-force/952/1 "2023-06-21T20:59:55Z")
Hello, I tried a simple linear elastic analysis and added a couple of spring constraints to a reference node. It appears to me: 1. spring constraints are always assumed to connect to the ground (i.e. the spring is fixed at one end), whereas I’d rather have the spring be connected between two nodes; 2. I am unable to obtain the reaction force in the spring. Can somebody confirm and explain how I get the spring constraint reaction force ? Also, I fail to see any possibility to include rotational springs, although a node is endowed with rotational DOFs. Therefore I had to apply a BC and block those rotation. Personally I feel some consistency may be missing here. Is it a problem with Prepomax not supporting the feature or it is altogether missing in Calculix ? Thank you, Andrea ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [June 22, 2023, 7:21am UTC](https://prepomax.discourse.group/t/spring-reaction-force/952/2 "2023-06-22T07:21:36Z")
> [@andnee](#): > > spring constraints are always assumed to connect to the ground (i.e. the spring is fixed at one end), whereas I’d rather have the spring be connected between two nodes; Indeed, this was already requested here but has to wait for its turn: [Spring between two nodes](https://prepomax.discourse.group/t/spring-between-two-nodes/116) > [@andnee](#): > > I am unable to obtain the reaction force in the spring. > Can somebody confirm and explain how I get the spring constraint reaction force ? With this type of spring element (spring to ground) you can only request the reaction forces for the node to which the spring is attached. > [@andnee](#): > > Also, I fail to see any possibility to include rotational springs, although a node is endowed with rotational DOFs. Therefore I had to apply a BC and block those rotation. Personally I feel some consistency may be missing here. Is it a problem with Prepomax not supporting the feature or it is altogether missing in Calculix ? It’s a CalculiX limitation but there are potential workarounds: [Torsional Spring - SPRING2? - CalculiX](https://calculix.discourse.group/t/torsional-spring-spring2/889) ---
**Author:** ![andnee](https://avatars.discourse-cdn.com/v4/letter/a/87869e/32.png) [@andnee](https://prepomax.discourse.group/u/andnee)\ **Post date:** [June 23, 2023, 2:35pm UTC](https://prepomax.discourse.group/t/spring-reaction-force/952/3 "2023-06-23T14:35:53Z")
Got it, clear. But unless I am much mistaken, my spring is attached to a reference node and there is a forum that I skimmed through which discusses the fact that ref nodes have variable node numbers (each time the model is run) and it is therefore hard to request at the output stage that particular node reaction force, that is basically what I need. My desire would be to have all the reaction forces collected in one place at post-proc, including the springs, as a form of output from calculix. Leaving aside, of course, the option to manually click the node in prepomax, which is also difficult because, if I am correct again, reference node disappear from the model at post processing. Any good idea ? On a lesser note, the fact that rotational springs are not supported is very surprising, as I cannot see any technical difficulty more than reproducing linear spring code yet with respect to rotational degrees of freedom. Was this left behind in Calculix for some reason I fail to understand ? ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [June 23, 2023, 3:06pm UTC](https://prepomax.discourse.group/t/spring-reaction-force/952/4 "2023-06-23T15:06:50Z")
If the spring is attached to the reference point of a rigid body, you can request the RF output for it by switching the Region type to Reference point name. ---
**Author:** ![synt](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/synt/32/4658_2.png) [@synt](https://prepomax.discourse.group/u/synt)\ **Post date:** [June 23, 2023, 8:35pm UTC](https://prepomax.discourse.group/t/spring-reaction-force/952/5 "2023-06-23T20:35:34Z")
In addition to the discussion, it can be useful to do further calculates of contact pressure based on spring reaction and tributary arras.