Gas Struts

[Wavery]

Has anyone given any thought to adding gas struts to the roof lift arms.

I'm thinking of putting 2 or 4, 200#, 20" gas struts on each roof. I'm just wondering if anyone has tried it or has any thoughts on it. If they were properly designed and un-tragically placed, a person should be able to lift the roofs with one finger.

https://www.amazon.com/Struts-Suppor...jaz10cnVl&th=1

[Shane826]

Where would you put them? And wouldn’t that make it even harder to close?

[Wavery]

Originally Posted by Shane826

Where would you put them? And wouldn’t that make it even harder to close?

I'd have to weld brackets to the frame. Not a big deal.

That's the beauty of the gas struts. They can lift a lot of weight but are easy to retract. Same concept as most cars have on their trunk lids and SUVs have on their tailgates. Our last motorhome had them on our king sized platform bed. That bed was heavy as heck but you could lift and lower it with with one finger. We stored a lot of stuff under there.

Auto manufacturers abandoned the torsion rod technology about 40-years ago. I've often wondered why TM hasn't gone with gas struts a long time ago. There MUST be a reason. I'm just not seeing it. That's why I'm posting this thread. Maybe someone knows and save me a lot of time and $.

[rickst29]

Bill's picture shows show the compressed strut completely vertical (with maximum lifting power), but I think that there isn't ground clearance to provide for that. That placement would also probably run out of working distance in the vertical position. (The 8" limit for maximum motion provides a total of 20" from the connection point). I assume that we're talking about a connection to the existing struts, and not a completely new structure. That makes this a 2D "math problem ", rather than a 3D situation.

I looked at the front-most struts of my 2619 with a tape measure (in the garage, closed. The gas strut is only effective for lifting the shell (a twisting when its own lowered position contacts the the lift arm at an angle. The limiting factors on placing the lower fixed" connection seem to be as follows:

1. The maximum length of the extended strut is 19.7 inches. This creates a limit (in the shape of an arc) for the maximum distance from the strut lower mounting point.
2. The compressed strut also attaches the lift bar at a distance not less than 12" minimum from it's lower mounting point.
3. In closed position, the strut should have the largest possible angle from the horizontal bar.

Rule #1 creates a limit in "open" position, while rule #2 limits the "closed position. The pair of curves, and the desire to keep the fixed mounting point low, seem to land together at a point about 3-1/2 inches below the "lower" screw of the inner pair of screws which anchor the lift bar to the torsion arm. the torsion bar. The lift bar attachment would be about 14" from the very end. I attach photos, holding the socket extender end in the air at the approximate mounting spot. The second photo shows a black twist-tie at the location of the other end.

[rickst29]

In closed position, and at the beginning of motion, a majority of the pressure (the cosine of the angle, IIRC) is trying to push the lift bar out from its joint with the torsion bar, in a sideways direction. This worries me a bit.

As the shell becomes lifted, the weight of the shell pushes in the opposite direction, somewhat balancing that. But the very end of motion, the strut begins to "pull in" (rather than push out) adding to the weight on the lift arm. To the extent that the strut has not reached 90 degrees, this "pull-in" pressure also affects horizontal motion a bit - trying to pulling the shell "inwards" from full open position, which may or may not be completely desirable.

In my own "guessed at" positions for installing these, the angle for the initial lift seems to be 15-20 degrees, so about 30% of that rated power would be working in the vertical direction. The 200 lb bars would be maybe 50-60 lbs of assistance in the desired vertical direction.

Anyway, the lower mounting structure "in empty air" might be difficult for me to build and install, I have no welding experience.

[Larryjb]

Originally Posted by Wavery

Has anyone given any thought to adding gas struts to the roof lift arms.

I'm thinking of putting 2 or 4, 200#, 20" gas struts on each roof. I'm just wondering if anyone has tried it or has any thoughts on it. If they were properly designed and tragically placed, a person should be able to lift the roofs with one finger.

Hmmm.... an accident just waiting to happen....

Hee hee. Couldn't resist this one.... I know you meant strategically placed. I assume it was predictive typing!

[jagizzi]

McMaster Carr has quite a selection of struts. We built our teardrop trailer and placed 100# struts to lift it and hold it open. I can tell you that placement is critical. I aimed for less than fully compressed at close so that if I was off a millimeter or two I could still get the hatch closed.

Heck, now that I'm thinking about it, in this instance it's pretty simple to figure mounting points. I know that struts are used in some of the A-Frame popups. Now if I could only weld, dang.

[Wavery]

Originally Posted by Larryjb

Hmmm.... an accident just waiting to happen....

Hee hee. Couldn't resist this one.... I know you meant strategically placed. I assume it was predictive typing!

Good catch Larry........ I fixed it to be more appropriate.

[Bill]

Wavery -

I'm very interested in this concept. The initial lift of my front shell is very hard, the torsion bar adjustments are maxed out, and I'm not looking for another trip to South Dakota. Can you give me a little more detail in your thinking?


My mental picture says that when the front shell is down, the strut is compressed, so presumably it is mounted in such a way that it is 12 inches (more or less) long. Then, as I release the latches and begin to lift the shell, the strut helps me for the first 8 inches of strut expansion, after which it is fully extended. Then what? The strut is fully extended, but the shell still has to move several more feet. To me this means that the top of the strut can't be attached to the shell itself. You are apparently thinking that in some way it would push on the lift arm at a point where the total motion of the lift arm is 8 inches - in other words, somewhere near the hinge point?

Second part of the question. Once I get the shell up about halfway, the remaining lift is very easy, and I don't need any further help. I don't want the strut to continue helping me, because I don't want it to slam the shell into the end stops at the end of the shell travel. Is the plan to mount the strut where it produces full force when the lift arm is horizontal, and then as the lift arm rotates toward vertical, the strut keeps pushing, but is no longer pushing in the direction of rotation?

In other words, something like the attached sketch?

Thanks

Bill

[Wavery]

Bill, go out to your SUV and lift the t/gate. You'll see how the struts are mounted near the hinge on the body and on the t/gate less than 50% of the distance.

If situated properly, the strut will be fully extended when the t/gate is fully opened. Most of the energy of the strut is exhausted in mid stroke (depending on the strut valving).

I don't have all the math worked out and it's just an idea at the moment. I didn't want to wear out my brain (or $) until I find out if someone has been successful (or not) with the concept. My intent is not to have the strut do all the work. Just be an assist. As you well know, after 60-years-old, humans loose about 10% of our muscle mass per year (all things being equal). My wife and I are in our late 70's and each year that roof gets heavier. All I'm trying to do is extend the amount of time that we will be able to lift those roofs without hurting ourselves. I no longer want my wife to even try to lift the roofs, where last year, she could do it on her own, if she had to.

I love your drawing by the way. Is it OK if I use it?

I seem to remember that TM tried using electric lifts at some point. Do you remember that?