Which Struts for a steel M416 Lid?

[jeepfreak81]

I am trying to figure out which struts to buy. I expect the lid to weigh about 160 lbs (hopefully lighter) and will be hinged on the long side of the trailer. I am planning on 2 struts. Do I split the weight of the light across 2 struts? I figure I am going to have to add the weight of the tent as well. So add another 100 lbs or so as well. How do you size the length as well?

 

[tripc]

I would go with atleast 2 150 lb. That should give you enough. Might need a little more but not much..

 

[Woods]

Check post 245 on THIS THREAD

There may be a shortcut though. Your configuration sounds like something Adventure Trailer would have some experience with. If they can tell you which gas spring to use, then pay them double what they ask and you'll be getting a bargain.

 

[DonBeasley]

I have two 175 struts for my steel lid from Sierra 4x4. I may go up to 200 as it is a little hard to open but I think it is mostly from the tight gasket seal.

There is an ARB Simpson III tent on top so that is about another 100+lbs.

 

[jeepfreak81]

I have two 175 struts for my steel lid from Sierra 4x4. I may go up to 200 as it is a little hard to open but I think it is mostly from the tight gasket seal.

There is an ARB Simpson III tent on top so that is about another 100+lbs.

What is the extended length of those? That is how I was planning on mounting mine. Also where can you find the ends to mount on the trailer for the struts to mount to? Grainger was $$ and Ebay looks like an option if these will work?

http://www.ebay.com/itm/Gas-Spring-...ies&hash=item5194bc773a&vxp=mtr#ht_5659wt_998

 

[New Horizons Overland]

Go to Mcmaster Carr's website and search Gas springs. It has all the instructions on what mesurements to take. I got mine from them and the drawings were spot on.

 

[DonBeasley]

Go to Mcmaster Carr's website and search Gas springs. It has all the instructions on what mesurements to take. I got mine from them and the drawings were spot on.

That is the place to go. Gas struts are center mounted in lid and 8" from edge on tub. Part is "9416K385. Ball ends are 9416K76. Bracket for strut is 9512K91.

 

[jeepfreak81]

That is the place to go. Gas struts are center mounted in lid and 8" from edge on tub. Part is "9416K385. Ball ends are 9416K76. Bracket for strut is 9512K91.

Thank you, I went with the same measurement model you used only in a 200# lift. I am going to have the tent, as well as the tent lift mech and I bet that extra is going to be needed.

 

[Kiddmen57]

I am designing my lid right now, and the gas spring thing is a tough one. The way most of us have them set up means that the springs do not provide a constant force as lift for the lid. I found this website that tells you how to determine the force in each direction from your spring.

http://dev.physicslab.org/Document.aspx?doctype=3&filename=Dynamics_ForcesActingAngle.xml

Basically, My lid at 36 degrees open the way I have the spring mounted will result in an angle of the shock at 57.5*. Taking the sin (57.5*)x200(lbs force on the shock) nets you 168.67 lbs of lift for each spring (200lb spings). This results in 168.7x2= 335.34 lbs of lift. My lid weights 200lbs with the RTT, so I have an extra 135 lbs to overcome to shut the lid.

On the closed side of things, I have a net resultant angle of 18.6 degrees. Using the same calculation sin(18.6)x200 = 63.8 lbs of lift each. 63.8 x 2 = 127.6 lbs of lift. This means I have to lift up ~72.4 lbs to raise the lid. This is why a lot of lids are difficult to open at first, because the angle of the spring when closed pushed all the force laterally, not vertically. If I go to a 175lb spring, then I have less force to overcome pulling the lid closed, but I have even more weight to lift at opening. Also, because of this, at one angle through the opening range of the lid, it will become neutral (force of springs equals the weight of the lid etc).

Ideally the spring would travel equally on either side of vertical through its range. This requires pretty long stroke shocks, which have a compressed length of nearly 20". My trailer tub is not that tall.

Essentially, having the spring as close to vertical as possible is the best for minimizing the variances in lift force.

This design was my initial, but I will be changin it to locate the spring more vertical in the closed position.

 

[Kiddmen57]

Here is the re-designed location. Centered on lid, and centered on tub. Theoretically, this should allow me to use my load/2 (200lbs/2 = 100lb) springs. I will likely choose just over this as hardware, weld beads, sleeping gear, etc are not factored in. I may use a 150lb strut on the taller side of the tent and a 100lb spring on the shorter side. That will provide just about the right load. I may also go with 2 150lb springs (unfortunately 125lb is not an option). The heavier springs will mean i have load to overcome closing the lid, but over time, the struts will lose some force.

EDIT: this arrangement would only work with the combined spring force of the struts EQUAL to the lid weight. THis will likely never happen in the real world. So I went back to the drawing board again.

 

[Woods]

I designed my gas spring location, so the lid would stay closed in the down position and up in the up position. Your current design (assuming the lid will stay up in the up position) will not allow your lid to stay closed in the down position.

 

[Kiddmen57]

I designed my gas spring location, so the lid would stay closed in the down position and up in the up position. Your current design (assuming the lid will stay up in the up position) will not allow your lid to stay closed in the down position.

Yup, just discovered that. Now I am going to attempt to design the angles such that the same springs will provide roughly 15-20lbs less force than the total weight when closed, and ~35lbs (?) more force when open. Thus having the desired effect. The vertical position would work if the springs could perfectly balance the load (not practical).

This is a fun learning experience though, and I'm lucky to have access to CAD that will allow me to make mistakes in the computer rather than in steel.