Thread: Maths guru required. Anyone know how to calculate the position of Gas Struts?

it can be worked out but being lazy like I am....

I simply make up a dummy strut from some dowl and conduit, mark and measure it so it moves the same lengths as the strut you have and then place a plastic clip over the rod. temp up some mounts for it and open then close it, If you dont exceed the min/max travel of the strut then you're good to go.

I prefer hinging as per the red diagram but dont forget to extent the mount point away from the hinging door so that when closed the mount point goes
"over center" and helps to close the door.

you can also simply draw it up with a compass.

to a scale mark up your closed door position and your open door position. Draw an arc from the hinge point across the position of the mount point on the door in the open and closed position.

Now using the scaled size draw 2 arcs from the pivot point of the gas strut, one from the fully compressed length of the strut and one for the fully open length.

so long as the arc of the doors mounting point stays within the 2 arcs (compressed and extended) of the strut as drawn from its pivot point then you are good to go.

with some scaled drawings or Dave's dowels you can work it out. I tried using trig and did not see my way through.

not sure if it will be possible/necessary to have the strut fully closed when the window is closed. However I expect that the strut needs to be fully open when your window is at 30*

On this diagram you need to move point A which is a hinge point out until the point at C is at the point as per length B. C is the other hinge point, the point at B and C will be coincidental for the strut to be fully closed.

Yeah - I have been scratching my head and trying to recall my university maths, but it is probably only high school trigonometrics really.

I guess I could try the triangle sine rule, where the length of a side divided by the sine of the opposite angle equals any other combination. No wonder my brain hurts when I think about it Too many years between my maths theory and now.

I was hoping someone else had tackled this before me and perhaps found some sort of calculator to do it on the web.

Looks like I'll be trying Dave's conduit and dowel technique!

Thanks for the help and the diagrams though.
David

heres how I usually work them out...

the black is the door/window frame, the top image shows how to extend the pivot point so that the strut over centers.

the red is the arc that the pivot point follows as the door opens.
the dark blue is the radius that the head of the strut follows when fully compressed (which would be 400mm for the strut you've provided)
the Green is the radius that the head of the strut follows when fully extended.(700mm)
light blue represents the attachment point on the door in the open and closed position and
the purple/brown is the point on which the strut pivots.

to make the guess in process a little quicker.

draw up your door/frame in the fully open position and add in radius lines at a scaled interval of about 1cm.

make a template that provides the center of rotation and the max/min radius arcs and slide that up the frame until you find a radius line thats completely covered by the template then mark the center. Done and dusted theres the plan.

On slugburners diagram, points A and C can be in any number of different positions so you can't figure it by using maths. If you knew either A or C then you can figure all the rest including B

I've fitted struts to a few different applications in the course of my work, and usually get the engineering done by the supplier. they charge $25 for the figuring and you end up with 50 newtons of hand force to close the door. I'm sure they'd work it out for you if you want to get it spot-on. You need to provide a diagram with the weight of the door in it's open position, The length of the door back to the fulcrum, how many degees of action you require, and in your case, the power of your struts if you already have them. By the way they must always be fitted with the cylinder part uppermost. Good luck with it
Aussie Gas Strut Company - Design - Manufacture - Supply
Don.

This may help, it is from the AL-KO website. www.alko.com.au/

mikehzz wrote,...

On slugburners diagram, points A and C can be in any number of different positions so you can't figure it by using maths.

Sorry, but have to completely disagree with that comment. Mathematics can be used to pretty well solve anything.

Ron.