Gas Lift Strut Problem

[Gene Michael]

I recently purchased a pair of Kessebohmer 380n struts for a project that's a gift. They look great, but there are no mounting instructions. Getting the hardware properly positioned is critical. Kessebohmer is a German company, but they do have a local distributor in Wilmington, North Carolina. They don't have mounting instructions and advise that this model has probably been discontinued. My goal is to provide lift support for a cabinet with a lifting top - very much like bench seat with a heavy seat/lid. The lid is 22" by 70" and weighs about 40 pounds.

Can anyone offer suggestions for mounting? Kind of like flying by the seat of my pants on this as I have zero experience with lift struts. Any and all suggestions will be appreciated.

[Jerry Thompson]

Have you tried YouTube? I have found instructions about many tools and procedures there.

[Malcolm McLeod]

You'll have to experiment, mostly - but as a starting point, determine what you know about the install geometry:
1) the extended length of the strut,
2) the compressed length (add a 1/2" or so, so that you don't close it against the limit stop)*,
3) the distance from the strut mounting point on the seat/lid to the hinge,
4) the 'down' position of the seat (and so it's strut mounting stud),
5) the intended 'up' position of the seat (and mount).

Draw the above layout at full size on a suitable surface (or use CAD/scale it if you're comfortable with such).
From the 'up' strut mounting stud position, scribe an arc of radius equal to the extended length of the strut.
From the 'down' position of the same stud, scribe an arc equal to the compressed length (+1/2") of the strut.
The two arcs should intersect at two points (or maybe only one?); this will be the required position for the strut's fixed mounting stud. If there are 2 intersections, use your best judgement about which is most suitable.

At this point, I'd mock up a test rig of scrap with similar dimensions and use it to determine if the loading and spring force are suitable. Make sure the simulated lid will stay closed with just it's own weight (you can approximate with a paint can, a dumbbell, your arm, etc). Make sure the strut force is not so strong that the lid flies up too fast.

If something doesn't feel right - Try the 2nd intersection; Get new struts? Some struts have adjustable dampening.

If you experiment enough, you can generally find a 'over-center' position, so that the struts actually 'pull' the lid closed (as well as provide lift assistance). Tho' this generally requires a relatively tall 'stand-off' mount on the lid (maybe 2-3", if I am correct in the assumed scale of your cabinet), AND depends on the strut length.

If it works as expected, transfer the location(s) to the cabinet top.

* If the strut has a 'zero force' position near it's compressed length, use the length of the strut at this point.

[Andy Giddings]

Did you try contacting the parent company in Germany via their website (also in English) http://www.kesseboehmer.com/en. They also have a section for downloads, support etc where you might find some info on the struts