How heavy do you think the trunk is?

[whitecastle]

I upgraded the stereo in my '65, and in order to fit the new 6x9s under the rear deck lid, I decided to remove the torsion bars. I plan to install a pair of gas struts to replace the torsion bars, but need to know what kind of weight to expect. I don't really have any way to properly weigh the trunk.

Because the length of the strut depends on its weight rating, I have to make sure I get the right weight rating to determine my mounting location.

Has anyone else done this who might have a ballpark for the trunk weight?

I have a pair of of Stabilus 56lb struts - giving me support for 112lbs. Do you think that is enough to support the trunk?

[defrang]

I had my 1965 trunk lid off and painted. My guess 60-70lbs.

[Dan Szwarc]

Where you put the pivot for the gas strut will make ALL the difference in the strut needed. You may just want to buy the longest strut you can get and a few other sizes and just return the ones you don't use.

[darrylqmiller]

Saw this on FB and saved it for future use. Haven't tried it myself so can't say how good it works.


Good luck

[bd94s10]

Yeah good stuff Darryl. I used actuators on my other project for a HEAD piece in my bed that covers the rear suspension. They work awesome. They are from Digital Dakota. My suspension cover is WAY heavier than a trunk lid off a slab. I used 2 though.

[whitecastle]

So I finally got around to adding some gas springs to my trunk set up.

I rigged up and installed two 56lb gas springs, and they turned out to be nowhere near adequate to compensate for the weight of the trunk. I chose them because I thought that would be enough to deal with the weight, but also because they where nice and short - fully compressed was around 13", allowing for nice, discreet mounting.

So anyway, looks like I'm going to have to step up the weight rating. I picked up another two that are 87lbs each, but they are longer.

I'm going to have to rethink my mounting scenario also.

More to come.

[Steve K]

You have to keep in mind the physics of the situation in addition to the weight. With the trunk pivoting up and down on the factory hinges, gravity will be enhanced by the inertia of the dropping lid requiring much more support than just the dead weight of the trunk lid. Think of the old teeter totter as a kid and how much it was influenced not only by the weight of the fat kid on the other end, but how far up you choked up the length of the lever to compensate for that. I am neither an engineer or a physics expert, but I bet there are some out there that can tell you exactly what you need by the weight of the lid, the location of the pivot points, and the distance of the drop from fully open to closed. You will also have to factor in how fast (or slow) you want it to close and whether you want it to hold the trunk open which I am sure you do. Then you'll have to consider whether you want to be able to give it a gentle nudge to begin closing or whether you need to put downward pressure on it the whole way down before you latch it shut. Here's where my "expertise" comes from. I built a utility trailer using a modified truck topper to enclose it. It had the original short window on gas closers, but I extended the length of the tail gate the full height of the trailer from top to the bed of the trailer. It took a fair amount of trial and error to get it right. In the end, a mechanical engineer brother asked me dimensions, weight, height and desired functional characteristics and told me exactly what to get in terms of length and compression.

[zinctwentyone]

I upgraded the stereo in my '65, and in order to fit the new 6x9s under the rear deck lid, I decided to remove the torsion bars. I plan to install a pair of gas struts to replace the torsion bars, but need to know what kind of weight to expect. I don't really have any way to properly weigh the trunk.

Because the length of the strut depends on its weight rating, I have to make sure I get the right weight rating to determine my mounting location.

Has anyone else done this who might have a ballpark for the trunk weight?

I have a pair of of Stabilus 56lb struts - giving me support for 112lbs. Do you think that is enough to support the trunk?

66 Deck lid shipping weight is 106lbs.

[Bill Prince]

As per what I remember from my Statics and Dynamics class of 40 yrs ago, and a sanity check:

If the trunk lid weighs 75 lb, and if the length is 45" (front to back), and the center of gravity is at 22" from the front.

Then the in-lbs of torque required to balance the trunk lid at the center of gravity and hinged at the front, is 1,650 in-lbs, for a balance lifting of 75 lbs at the center.

So, if the lifting point is at 11" from the front of the trunk lid, then the force required to balance (more to lift), is 150 lbs.

However this is perpendicular to the trunk lid. If the angle of the lifting cylinders is 45 degrees, (150 lbs divided by the sin of 45 degrees) then the balance lifting weight is 195 lbs.

Therefore, I would estimate that the lifting force would need to be something in the order of magnitude of 200 lbs.

Or 100 lbs per cylinder. Way more than say, lifting from the rear on each edge, which would be about 19 lbs. (no help from springs)

[JonW]

Any updates on this?

[Steve K]

No help with the question that was asked, but I found the correct sized speakers that were flat enough to fit under the package tray using the factory mountings without touching the torsion bars. They sound great. I believe they were Pioneer speakers and the key difference from a lot of speakers is the tweeter cone is flush with the rim of the speaker rather than extending beyond it.

[whitecastle]

Any updates on this?

My Lincoln went up on blocks a while back and this got demoted on the to do list. So sadly I have no updates.