Building a fold down door with torsion gas spring calculation

[Robert C]

I'm building a wall mounted cabinet, with a fold down door. It is for my grandson's slot car track, in his bedroom. The door is 3x7 feet and weighs approximately 40 lbs. It is mounted length wise, on the wall. I think I need tension or torsion gas springs, which pull instead of push. I don't want the door to drop down and hit him and I want it to be easy to open and close. The door will open 90 degrees and rest on the floor. I can mount the two springs, wherever needed, as I have no set point which needs to used. I have tried several gas spring manufacturers and they have not been of any help. I just need to use a stock spring and mount it accordingly, but I don't know how to figure what I need. Can anyone help me with this?
Thank you,
Robert

 

[billy_joule]

I would go to an auto wreckers and salvage some gas springs from hatchbacks. I've paid less than $10 a pair in the past.
Make sure you get ones with suitable mounts so you can screw then straight on.

 

[Robert C]

The only problem with them is they hold the weight up and in this case it's opposite. The weight comes when closing or lifting the door. I need a torsion gas spring, that pulls.

 

[billy_joule]

I know. That's a better solution IMO.
The door is held closed with a latch, release the latch and the door glides open (to rest on the floor). Force is needed to close the door, lean on the door while engaging a latch 3 feet from the floor.
Just like a hatch back really.

The alternative seems less user friendly:
Force the door open (down to the ground) then latch it down - Presumably you don't want a hole or something on the floor for the latch, how will you engage the latch and also keeping the door down? with a latch at ground level while standing on the door? Sounds awkward.

 

[CWatters]

How about a pulley and 40lb weight?