Gas Struts

[rickst29]

Although this could theoretically go into the floor's street side "corner sideways, I don't remember that wood wall brace being very tall - and it would have all of the lift bar's stress going through that one screw. I think that a length of 90 degree angle stock, maybe 3" x 3", is still desirable to provide for more screw connections to the TM floor. (That length and width can also probably provide for a second screw between the "countertop" bar and the vertical side of the 3x3 sheet stock.

After considerable search time, I settled on this set of counterop supporting bars: https://www.amazon.com/Countertop-Su...dp/B0B393B1GJ/

The individual bars are rated for 250 lbs. The 2-2/2" width is the "biggest" which amazon has, and the 3/16 thickness makes for a good cross section. With no angled support bar included, only the cross section (at the 90 degree bend) resists distortion. That would seem to be a good match for gas struts rated at 120 or 150 lbs maximum. "200 lbs" is possibly too much for these cheap mounting bars, and maybe also too much for the "hanger" from the floor.countertop support brackets above.
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The other items in my shopping list could be: one of these on angled mounts on each lift bar (using 5 screws each), https://www.amazon.com/Angled-Suppor...dp/B074R6GT2W/. Along with one of the "large outside mount brackets" https://www.amazon.com/Angled-Suppor...dp/B074R6GT2W/ from the same listing (using only 3 screws, but that's probably enough, and I could drill out to a slightly large screw size). These are only galvanized, and a bit prone to rusting over time. For the shocks themselves, I'm not going to pay $$$ for stainless before I'm sure of the strength to buy. Mut my first guess is this pair, at 120 lbs each: https://www.amazon.com/ARANA-C16-080.../dp/B08B3Y7Y7W

The attachment to the lower box of the TM should probably be made with angle bar, at least 12" long, to provide for an adequate number of screws into the floor. My first guess is a pair of these (one per front corner) at about $15 each. https://www.ebay.com/itm/224412511327 Those are stronger, but need to be painted. 3" height (vertical) allows for 2 bolts into the angled mount brackets, and prevents changes in the angle of that mounting bracket.

A 2x2x12 stainless steel angle bar is available for only a few $ more, but the 2" height probably provides for only one screw into the angled mounting bracket. When the shell is rotated up and forwards, the fully extended gas strut will probably create some amount of compressive force at the at the strut attachment end. That force (at maybe 70 degrees of angle to the bar, almost perpendicular will try to rotate the end of the mounting bracket up and into the trailer. Such movement would tend to loosen a mounting bolt at the opposite end (into the angle bar), with possibly bad results. A second bolt at the other end (into the angle bar) prevents that motion. SS is also a lot weaker than cold-rolled.

[Wavery]

1/4" x 1 1/2" Steel flat bar is pretty easy to find at scrap metal yards. Drilling it on a drill press is pretty straight forward too.

I would (heat and) bend it to a 90* angle "L" so that the longest part extends from the frame to just beyond the outer box wall. The short side of the "L" would be about 3" long and bolt to the frame with 5/16" self drilling/tapping bolts. I would weld a gusset to close the "L" for maximum support. The long side of the "L" would through bolt through the box floor frame with "T" nuts on the inside of the box (inside the cabinet). Might even have to weld some ears onto the "L" bracket so that 3 bolts could go up through the floor (about 1.5" apart).

S/S is soft and bends bends easily. If using S/S one would need to increase the bar thickness by about 50%. It would be prettier but not necessary unless one plans to use it in sea water.

[rickst29]

We agree that "304" SS is a lot weaker, and would possibly need either 1/4" or 5/16 thickness (becoming much more expensive).

I could have complications with the interior floor "nuts" for those hanger bolts, likely being underneath the the 40 gallon fresh water tank on the street side. (The curb side has a slight complication with batteries on top - the floor underneath the batteries needs to be flat, although I could add some 3/4 plywood as "riser" for the batteries to rest on, with holes/gaps for the nuts.

The bigger problem is having only 1-1/2" of width, from TM front to TM back, for mounting the two screws at the end of the "counter support". In raised position, considerable torque may be applied by the strut to the opposite end of the counter support, with its full length as the "perpendicular arm" apply that twisting force. The rear-most screw is the pivot point, the second screw (less than one inch away) receives about 10x more twisting force than the force being applied by the strut. The ratio of their moment arm lengths is about 10:1) This is a bit tough on the bolt, and also tries to twist the forward side of the bar away from the TM floor. Under the TM floor, the plate is effectively only 1-1/2" wide (with a 3/4" moment arm trying to pull away from the floor in front, and a 3/4 moment arm trying to twist into the foor along the rear.

Those problem get reduced by more bar width, but a single bar with a lot more width becomes harder to bend. An alternate "solution" would be to add TWO of your L bars for each strut, separated by some amount of distance. The "forward bar" would have a slightly longer descending portion, the "rear bar" could descend by as little as 1".

My purchased angle bars costs more money (mostly for shipping), but provide a full 12" of length along the floor edge for several screws to resist both the tension/compression forces AND the torque. I'm inclined to use 6, maybe even 7 screws per bar. Much better than your welded tabs, and I have no welding experience.

[rickst29]

Originally Posted by FlyboyTR

I was getting ready to post this when I saw mickmanor's post about the Aliner. Way back, we played with an Aliner for some rough off-road adventures. I ended up installing four gas struts which helped in raising the roof panels. They also use a torsion spring system.

I followed the info provided in this attachment. The author goes into great account as to the physics as to placement, etc. Maybe there is some info here that can help push the thoughts of adding gas struts to the TM.

Thanks for the attachment, this was great information. to have.

[rickst29]

Originally Posted by larsdennert

Probably better to take it to a dealer and have them adjust the bars. If the bars are worn out, get new ones.

Bill and I have our bars at maximum adjustment already.

Bar replacement is a non-trivial job, requiring the shell to be supported on side platforms which my HOA will not allow me to build in the street-visible driveway. My problem is limited to the front-most pair on the front shell, so the rear support arms of the front shell could probably remain attached. But the platforms probably need to prevent both front-to-back AND side-to-side motion, because the hinged clamping pins are to weak to prevent disasters in those directions.

My nearest dealer is about 400 miles away, and that dealer might not have much experience with this job. (There's another one at slightly longer distance with more experience, but it's 12-14 hours eachway to reach either of those dealers) The job might not get done in a single day, adding overnight hotel expenses. The cost of bars to the dealers is high (truck freight) unless coordinated with a new TM delivery.

Only after that (maybe $700 for travel and the overnights in expensive towns, and maybe $450 of the pair of shipped torsion bars, can I begin to plan for hourly shop costs. Maybe 5 hours at $180?

I'm at or above $2000 for the long trip and "proper" repair costs.
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Parts for the struts would be $50 for the "counter support brackets", less than 20$ for the strut mounts, $30 for the "first guess" 120-lb struts, and about $40 for a pair of those 3" x 2" x 12" angle brackets. Adding another $50 for some "fresh" 5200 sealant, some "fresh" paint and primer, and and a whole bunch of bolts and nuts and washers, I'm still under $200 in parts and supplies. I can drill a bunch of holes and and assemble the parts for only a few beers.

If I ever need to use stronger struts in the future (maybe supporting new and heavier solar panels) the struts are replaced for only about 30$ per pair.

[Wavery]

Then, there is the reinforcing of the lift arm itself. It's EZ enough to to, it just need to be done. Putting that much force on those flimsy lift arms could cause them to bend.

Now that I think of it, The upper attachment of the lift arm to the roof could be problematic. It isn't designed to have much force on it at all. In fact, that could be the hardest problem of all.

[rickst29]

Originally Posted by Wavery

Then, there is the reinforcing of the lift arm itself. It's EZ enough to to, it just need to be done. Putting that much force on those flimsy lift arms could cause them to bend.

Now that I think of it, The upper attachment of the lift arm to the roof could be problematic. It isn't designed to have much force on it at all. In fact, that could be the hardest problem of all.

They already support "pretty high" torque from the torsion bar at the bottom. Although the attachment is supported by multiple bolts and possibly an inner sleeve, the bar itself carries a pretty heavy bending force already, with the twist at the torsion bar and and weight of the shell working in poposite directions along it's length. (The forces begin as a bending stress on the "width" of the bard (the 2" width, not the 1/2" depth), and shift to become a vertical weight from the top. The additional bending forces are not a lot different than those which would be applied by more powerful torsion bars. My 2619 came with the weakest "front" bars which TM stocked at that time. The lift arms themselves handle heavier shells in longer TM models, but I think they are all the same. (AFAIK, my less loaded "2619 lift arms" are not different than "3124" lift arms).

The struts would add new tension at the beginning, but the lift arm can handle that. It would also add new bending stress (that's what we WANT TO GET out of all this) with initial lifting force being the sine of something between 20 - 30 degrees times the maximum force of (for example) 120 pounds on each side. For 120 lbs at 20 degrees, the vertical lift would be 0.34 * 120 lbs (almost 40 lbs from each bar, which is maybe more than I should choose to apply.) The tension into the torsion bar end is completely new at the start, and big (94% of 120 lbs is 113 lbs). This sideways force must be resisted by the screws (front to back) along the 12" frame mount plate, that "feels" OK for at least 5 screws.

Near the end of lifting with the struts pulled out to nearly maximum length, I'm not sure whether the gas strut still wants to "push" a tiny bit more, or have become "overextended" and desire to pull inwards by a bit. In either case the force is probably quite small (in comparison to that "120 lb" rating for pushing power when fully compressed. The vertical component would seem to be a lot harder on the TM box corner mounting bracket, starting out at maybe 40 lbs of "lift" per side for # 120 struts. After lifting motion begins, the vertical power is increased due to the angle of the strut, but decreases as the strut "power" falls with increasing length. (I don't see any information about the ending "power" to either push or pull when the struts are fully extended.)

The countertop support is rated for up to 250 lbs, spread evenly along its 12" long dimension. The average "moment" of torque being applied is 6 inches, that's a slightly longer distance than I will have sticking out from the trailer box in a horizontal arrangement. (I'm building with at least twice the strength I need along the countertop support).

The bigger issue is the lifting force trying to pull my frame-attached L bar, down and away from the trailer body along the length of the screws. (The vertical component strut force will be primarly focused , primary focused on the forward-most screws of my L-bar.) That's a lot of downwards force for only a couple of screws to handle. The L bar itself spreads this force along the length of the bar, it appears as torque - but the moment arm on the forward-most screws is LONGER than the moment arm on the screws towards the rear. For $40, I could buy a 36 inch segment of 3x2 angle iron and spend most of a day sawing it in half to yield tow 18 inch segments - or I could special order a pair of 18" long bars, and then mount them below and inside the existing very thin plates with the torsion bar guide holes, with additional new screws mounting the overlap of both plates into the edge of the TM wall. More cost, but more mounting screws.

[rickst29]

Originally Posted by Wavery

Now that I think of it, The upper attachment of the lift arm to the roof could be problematic. It isn't designed to have much force on it at all. In fact, that could be the hardest problem of all.

With my TM closed in the garage (it's snowing AGAIN), I can't inspect that upper attachment roller bearing mount. But if the length of mount back plate plate (front to back, against the shell) is short, without an adequate number of screws to resist the new front to back horizontal forces, I could maybe put in a new and longer "metal strip" against the shell underside, providing a steel-to-steel connection between the mount and the new back plate. The presumably weaker "strip to-shell" screws could be then be added in a larger number, providing better resistance against those additional front-to-back sliding forces.

[Wavery]

That could work but I'd use pop-rivets. You know how these TMs puke screws.

[EZCAMPER]

Waverly, my wife and I will soon be in our 70s. It is getting more difficult for us to open. We have recently discovered that using the tongue jack to assist. We lower the tongue to open the front and then raise the tongue to open the back. Then level out. It makes a huge difference. Closing is the reverse, just remember to raise the corner jacks before you close!