Why is there a gap between my panels when I pull on the frame panel?

The question:

I am concerned that when the fastener is pulled in tension that the two parts that it fastens together will create a gap between them. I am concerned about this because the fastener spring appears to me to be in the load path of the fastener. If that is the case then I need to be able to calculate that gap and make sure that we don’t violate any of our design requirements.

Further information:

I need to understand how much the panel will "lift" during operation. I know that my tension force will be greater than the minimum bolt preload (15 pounds) but significantly less than the tension working load (200 pounds). Can you tell me the spring stiffness of 2700 fasteners? Do you have anything that calculates gaping under load with these fasteners

Target: Evaluation of the maximal gap between panel and frame during operation due to tension forces (sheet separation).

Configuration: Calculation for part no. MTHTLC-10Z and MTHR33Z
Minimal grip of 7,60mm (worst case)
All calculations in nominal dimensions and forces

 configuration of the quarter turn fastener

Description: The worst case (max gap) appears for the
minimum grip situation.

locked position minimum grip

The spring has a preload of 40N in  this condition.

 maximum gap configuration

The spring load at block condition is 50 N.

The force is  not 40 N but is more falling into a range of just 34N – 60N (but the effect in terms of “travel” is minor due to the small grip-range)  After “consuming” the 1,45mm, the system is in block condition. In this condition it can withstand 1330N (900N work-load) –with a static load.

Conclusion:

A gap is possible if the load is higher then 40N(200 lbs = 890 N)

How much significantly less?

The gap is reduced with 0,8mm if the system is in maximum grip condition.

Looking at your design, you need to design in such way so that you have a 8,4mm thick panel and frame. It is recommended to go to the max. grip condition.

If you require a smaller gap, or have issues that you have difficulty in operating a MTH series due to the gap being big, change to a longer stud length or transfer to the HGR series.

The springs in this series are stronger, we also recommend to compress the spring with the tool ISTP-1Z a first time, prior to installation.