lifting the tent rack questions

colorado matt

Adventurer
ok i need a bit of guidance .... i have a telescoping rack on my trailer and want to use compressed gas spring things... i can not for the life of me find what i want .... mostly because i dont know what to search for .... keep finding threads on lifting the truck or vehicle ..... need 4 of them on the corners and be able to lift about 160 lbs total .... little less or a little more and i will just have to use some effort to lift or push it back down for travel ...i think ...thats how i have it in my mind .... need to expand about 20 inches past their closed position and when closed be less than 36 inches .... and again ...does it exist and what is it called?...where can i get them?.... are there options for how they mount and where would i find those mounts?...preferably weldable ...thanks for any direction, advice or link .....Matt
 

high-and-dry

Active member
mc master carr. they are pricey. they sell the mounts too


they sell this one a little cheaper
4528" extended 25.59" compressed 19.69" stroke 562 force open 873 for closed 1.1" body die 0.55" rod dia 6465K98 part number $162.87. these are reducable force


Product Detail 3D CAD models available

Reducible-Force Gas Spring, 45.28" Extended Length



Each
ADD TO ORDER
In stock

amazon sells gas struts. the issue is it looks like a 20 inch stroke is going to be hard to find. they seem to max out on amazon at 15 inch stroke.
 
Last edited:

Recommended books for Overlanding

The Longest Line on the Map: The United States, the Pan-A...
by Eric Rutkow
From $16.72
Overlanders' Handbook: Worldwide route and planning guide...
by Chris Scott
From $23.74
Cycling the Great Divide: From Canada to Mexico on North ...
by Michael McCoy, venture Cycling Association
From $9.99

NatersXJ6

Explorer
Something to consider, if you mount the gas spring in the right orientation, and have the right type of frame, you can probably lock the frame in place with pins and have a much more solid platform.

I just went through a minor battle finding the right springs and calculating the lifting force for my trailer lid after adding a massive amount of weight to it. It took me back to basic static’s and dynamics, but it was fun, and nice to do math and have it work out. I haven’t written it up yet...

BTW, my gas springs from McMaster-Carr were $65 or $70 per pair, shipped, 150 lb each 17” approx stroke.

If you need specific selection help, a picture would be useful, or a basic drawing.

lifting straight up in the corners with gas springs might not work out very well, due to balance and force and bending issues. using the spring to move a linkage can work very well.
 

colorado matt

Adventurer
sorry to here that it may have issues....I cant even picture what a linkage set up would look like ..... have spent hours on mcmaster carr lately..... and yes rack legs will get lock in place with pins..... 4 posts 1.5 inch square 11 gauge .... rack is 1.25 ..14 gauge .... trailer is at the welder and hope to have some pics soon...Matt
 

NatersXJ6

Explorer
Gas springs inside of a telescopic tube with pins will be much better. When you think about the amount of side loading on a rooftop tent from wind, climbing, moving around, it would become pretty easy to bend the 3/8” or so rod in the spring if that was the only thing holding it up.

Probably better yet would be horizontally (actually angled) gas springs that both lift and push outward on the top of your tubes from a center point, and tubes mounted on lockable pivots so that you can lower one end then the other.

I know others have done this 4 corner vertical lift thing, and I haven’t, but I can see binding issues as you aren’t able to push all 4 corners down simultaneously with similar amounts of force.

As far as “linkage” setups, take a look at something like a scissor jack or a stand-up desk. They have an x-shaped linkage to raise a stable platform in a level plane. Some use gas springs. That may or may not work for you. I strongly considered building something like that last time around but decided just to build a fixed rack with a cargo basket under it.

As a final thought, take a look at the individual specs for gas springs. It is fairly common for the closing force requirement to be 20-25% above the opening force. You might want to make sure you have good handles near the springs so you can pull them down effectively.

Have fun, and share some pictures when you can!
 

colorado matt

Adventurer
ok looking at reducable force spring mentioned earlier in the thread .... add in corrosion resistent and end with mounts and "pricey" is putting it mildly .... and now closing force vs opening force has me confused ..... the reducable force ones have a bleed screw to release pressure but no way to add it back if you go to far.... in the future if i add a awning or ??? and all that work is changed....more bedding in the winter.... my mind is now wandering towards linear actuators...

and the welder and i have done our best to anticipate final height of trailer and travel needed for rack to hit a target height ideal for the annex .... wondering if 4 inches will make that much of a difference and 15 to 16 inch ish travel would save a good chunk of money.....

and the four corners and having to push the 4 corners down at the same time is another worry that could be eliminated by actuators ..... hope to have a frame on wheels and will know more by the end of the week ..... thanks so much for your all your comments and help....Matt
 

NatersXJ6

Explorer
My suggestions, skip the corrosion resistance, the factory coatings are pretty decent, and will probably last longer than you own the trailer. My trailer was a 2007, lived in Colorado for about 8 years; then Arizona and California, original gas springs out in the weather and mud and no noticeable corrosion.

I waffled on the reducible force, but ultimately decided that calculating my best estimate of high and low forces then picking the mid range and hoping for the best was in my favor with respect to cost, buying a second pair seemed better than reducing too far... but I only needed 2. Also, the odds or reducing them all the same without some sort of balancing tool seem really low.

I looked up some SAE documents that seemed to indicate a best practice of designing SUV hatches for 16 lb opening and 20-24 lb closing forces. I assumed I’m a bit stronger than a soccer mom (that depends on the day) and have myself a 30 lb open and 50 lb closing (I do have weight on my side in closing) window. It worked out okay, but I made a mistake in mounting, and without some more bracket fab and welding I’ve sort of limited my opening distance.

With respect to the annex, I think you will find that 4” low isn’t the worst thing in the world. Ground is rarely perfect anyway. I set mine up so my wife and kids should generally be able to walk under it, but I can’t quite, so it is like 68” off the ground in most situations. It seems about right, but sometimes the annex rumples a bit at the bottom. I know I got the height right because it is right above my sight line, and I hit my head on it a lot during building!

All things considered, for a straight-up lift, I would look to linear actuators... but I think a high cost tolerance is helpful there.
 

colorado matt

Adventurer
telescoping rack for the tent.... target is 6'8" .... trailer is 24 inches off the ground with wheels and springs.... 30" tall box .... 6" between box top and tent rack for table and/or solar panel storage .... leaves 20" of movement upwards to hit my target height ..... plan is to run the rack down for travel and lift at campsite for annex .... Matt
 

Hoghead

Observer
If it helps you at all, I use these.

https://www.ebay.com/itm/2PCS-1500N-330lbs-18-Stroke-12V-DC-Linear-Actuator-for-Auto-RV-Home-Application/123550717709?pageci=6c71d6e4-396e-4565-ac66-b36f76958fd9

not saying they are perfect, but when I started pricing gas springs and then these, I thought these would be easier. That and all of the things you are thinking about with binding and so forth. You will need power though, it does require more wiring too. I don’t store my trailer outside, I don’t know if these would stand up to long term outside storage.
 

colorado matt

Adventurer
thanks ...had some in my wish list but they are now not available ..... traiiler got put on the axle today.... quick rough measurements tells me that i may only need about 15 inches of lift ...so that opens up more and cheap to well priced options...most pushing about 225 lbs .... I will see if i can get a pic up ...MattIMG_20201008_165721407.jpgIMG_20201014_104845.jpgIMG_20201014_104848.jpgIMG_20201014_131450729.jpgIMG_20201008_165721407.jpgIMG_20201008_165721407.jpgIMG_20201008_165721407.jpgIMG_20201014_131450729.jpgIMG_20201008_165721407.jpgIMG_20201008_165721407.jpgIMG_20201015_121116023.jpg
 

Attachments

Recommended books for Overlanding

We Will Be Free: Overlanding In Africa and Around South A...
by Mr Graeme Robert Bell
From $17.87
Long Way Round: Chasing Shadows Across the World
by Ewan McGregor, Charley Boorman
From $16.69
Don't Go There. It's Not Safe. You'll Die.: And other mor...
by Jared McCaffree, Jessica Mans, Kobus Mans
From $19.99
Overlanders' Handbook: Worldwide Route & Planning Guide: ...
by Chris Scott
From $29.95
Top