Clearance question for those that have built telescoping racks with squre tubing

jays0n

Adventurer
My trailer has a rack that is currently built out of 1.5" square tubing. The rack is too tall for much offroading, the CG is just too high. I knew this might be an issue when I built it but figured I'd tackle it when it became a problem. Well, it's a problem so here I am. I will be using linear actuators to raise and lower it and have all that figured out. What I'm not sure about is what size to use for the tubing. My plan is to keep the lower parts of the legs and add the larger size tubing to the rack so as to not have to worry as much about water getting into the legs, plus it will be easier to modify the existing rack this way. The OD of the existing rack with a fairly heavy coat of paint that will be removed from the telescoping sections is 1.516" and I found telescoping tubing (no inner weld protrusion) in 2" OD and 1.75" OD, both 0.105" wall. The clearance calculations are below but my question is how much clearance is too much (rack will rattle around) and how much is too little (rack binds)?

2" OD x 0.105" Wall Square Tubing with 1.516" OD Square Tubing Telescoped Inside

2 - 0.105 - 0.105 = 1.79 ID

1.79 - 1.516 = 0.274 total space between tubes

0.274 / 2 = 0.137 space on each side of inside tube


1-3/4" OD x 0.105" Wall Square Tubing with 1.516" OD Square Tubing Telescoped Inside

1.75 - 0.105 - 0.105 = 1.54 ID

1.54 - 1.516 = 0.024 total space between tubes

0.024 / 2 = 0.012 space on each side of inside tube

It seems obvious to me that the 1-3/4" OD is going to be too tight, even with the paint removed and the surface greased so that means I'm probably going to have to go with the 2" OD instead. That leaves me with a bit more than 1/8" of clearance around the inside tube. Is that more than I want or just right?
 

1store

Banned
When you weld up they will not mach. You are not using a jig . So it will have natural bind. You have divide 1/8 by two . If all fails tap for a bolt are two that can be tightened when down
 

Eaglefreek

Eagleless
Maybe you can find some or have some nylon bushings made that fit into the top of the inside tubing and protrude out a little bit and on the bottom of the outside tubing that goes in a little that will allow it to slide but take up some of the space to keep it from rattling.
 

meental

Observer
Agree with eagle, try to get some sort of bushing that can be used to help minimize binding and rattle. This would probably work best with the 2" tubing, the bushing could be 1/8"

Sent from my rooftop tent while stargazing
 
I have not tackled this yet, but I definitely plan on at least .125 of slack. Trying to keep everything square on four post and exact, good luck. I'm a good fabricator and am scared about accomplishing this feat. Tack, and try. Nothing is more discouraging then grinding down all your welds, after everything is welded up. With the additional contact points of the actuators, i think your rattles will be kept at bay.
 

jays0n

Adventurer
The 1/8 is the divided by two number so it's 1/8 all around. I should be able to weld it pretty straight as I do have a jig of sorts. I'm going to cut the legs off at the desired height while still bolted to the frame. Then I'll cut the enough off the legs still attached to the upper square to leave only 6" stubs attached to the square. I'll slide the sleeves down onto the remaining legs and then slide the stubs of the top section into the top of the sleeves, this should keep everything pretty straight for welding. I'm hoping you're right and the actuators will help keep it tight. Looks like I'm going with the 2" then, unless anyone thinks that I should go with the 1-3/4 ?
 

1store

Banned
GO with the 2'' after you get it done see if it makes sounds. No need to look for something to go wrong. If so you can make spot welds bumps ever 6'' are so then file to have tight . lots of luck. A old welder over 50 years in the union trick use door shims to center. When it binds no need to get mad it's a easy fix a very light coat of pant some use oil it make a big mess . See where it rubs.
 
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jays0n

Adventurer
It probably would but I'm trying to keep as much of the existing rack intact and it's made from 1-1/2" square tubing.
 

dstock

Explorer
I went with 1 1/2" telescopic tubing for the outer legs and 1 1/4" telescopic tubing for the inner. My rack is made from 1 1/4" square tubing. If it were me, not knowing exactly what your rack looks like, I would get telescopic tubing for both inner and outer legs and cut off the square tube legs. In my opinion you don't want any extra movement in the legs then needed, things will bang around which can cause breakage. In your case, 1 3/4" telescopic outers with 1 1/2" telescopic inners you should be golden.

I just switched to linear actuators on mine and it's awesome!!
 

shack

Adventurer
when we did mine, we pulled the legs towards the innermost corner and did a spot weld to hold them in place. The we added the upper crossmembers and the rack. When everything was finished, we ground the spot welds off the legs. The result was that the legs stayed somewhat tight to the larger tubing when the rack traveled up or down and at rest.
 

Nd4SpdSe

Adventurer, eh?
My rack is made using 2" ID trailer hitch tubing for the supports and 2" OD tubing of varying thicknesses depeding on there and that they're doing. It may be big, but I wanted the electric actuators inside the tubing, and the 2" ID tubing has one side cut out to accomodate the actuator. It welded the racking while it was down to have it hopefully stay where it needs to be.

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Nd4SpdSe

Adventurer, eh?
nd4spdse
That the cleanest set up I have saw in a long time. Less for a tree to hang on.

Thanks! I have a tonneauu cover that goes on top of it, and the tent mounts to the OEM roof rack from a Frontier, that mounts to that racking underneath.

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jays0n

Adventurer
I'm not normally a truck bed trailer fan but THAT is awesome, well done! I've thought about it and went with replacing the entire leg. I ordered 1-3/4 for the upper sections and 1-1/2 for the lower (telescoping tubing so I know they will fit). I also ordered my actuators today too so hopefully in the next few weeks when work quiets down a bit I'll be doing some cutting! The upper square of the rack is 1-1/2 so I'll leave 6" or so of the legs attached to it, cut the existing gussets off, sleeve it into the new upper portion of the leg, plug weld it, weld around the top and replace the gussets with new ones. Once that's done I'll attach the actuators and hopefully I'll be all set. I'm adding shocks as well so this is going to handle like a completely different trailer when I'm done, cant wait to get it out and see how much more stable it is.
 

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