Calculating gas spring (strut) size

I recently picked up a Bantam trailer and would like to build a hinged frame to go over the top and bolt a roof top tent to the frame, similar to the one featured in the "trailers in action" thread in Jeep Trailer Tech forum. The tent weighs 140 pounds and with frame would be in the neighborhood of 200 pounds, thus the need for gas springs to assist lifting the frame and tent. Is there an easy or practical way to calculate the size and force of gas spring needed, or do I have to hire the services of an engineer/ math major? Thanks.

 

How far does it need to lift? Would some suv tailgate shocks work like what they sell at the parts stores?

 

Give me some dimensions of the frame and were you want the struts mounted. Its an easy calculation.

 

The lid frame to which the tent will be attached is 4' x 6' and will sit directly on top of the 4 x 6 trailer tub. It will be hinged on one of the long sides (passenger side). The struts are mounted to each end of the trailer and the frame that will hold the tent (picture a giant toy box with hinged lid and a tent bolted to the lid). The total weight of the lid frame and tent should be between 200 and 225 pounds. The trailer tub is about 17" deep. Thanks for your help.

 

Two of these mounted on each end 1.5 feet from the hinge should open the lid and keep it open. You will need to have some latch. to keep it closed.
http://www.marinersdirect.com/shorts/details.php?ProdClass=Hardware&ITEM=4817145

heres my calc

220lbs x 2 feet (centered) from hinge = 440 foot-lbs

440foot-lbs / 300lbs = 1.46 feet for balanced load.

since you want it to open and stay open on its own i extened the mechanial advanage to 1.5 feet.

This sould get you REAL close might need some minor tweaking.

 

Let me also add that I am assuming it struts will be mounted vertical.
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Thanks very much for your help. I think I get it, but the followup post has me a little confused. Is your calculation based on a perfectly vertical mounting angle? Since I am fabricating this setup from scratch, I have total flexibility as to mounting angle.

 

Yes my calculation was with struts mounted vertically. Sorry for any confusion.

heres a diagram of what i was thinking.


i would drawn it up in cad but the university still hasen't given me the licence file for my cad package yet