Roadie's Birthday RTT

[The Roadie]

OK, it's up. While putting it away, I was wicked tired, and tried to use my Engel fridge to put maybe 50 pounds on to assist a reach. The Engel protested this mistreatment and promptly fell over. Leaving me in free fall sideways. Nothing broken (I'm a bit fluffy and I might have bounced.) But I've got a big rib bruise and an bunch of fluid on my left elbow. Ick. Not ER-worthy, but it does point out a risk of a deployed RTT while out solo and you injure yourself and have to drive yourself out (assuming you don't have a SPOT beacon to call for help). You have to be ready and able (while injured) to pull some bolts and ditch the tent. Another reason to not go solo.

Anyway, here ya go.

Bottom of the 14 gauge Superstrut, with holes enlarged to match the rivnuts on the vehicle. 4 out of five are in a row, the extreme front one is out of line.



Double stick tape applied



1/8" neoprene warming up in the sun



Neoprene applied and razor trimmed



On the vehicle



Cross struts cut



Struts installed with shims so they won't hit the roof. 1/4" in front. 1/2" in rear.



Another angle



Tent up



Tent rails installed



Cover off



Starting to deploy



Deployed!

[The Roadie]

A tour. The overhang is enough to keep you out of the rain while you throw stuff up there. I didn't have the time to spend another half hour to zip on the changing room that goes down to the ground if you aren't in a remote place and the wife wants some privacy. But the tent itself only took me ten minutes to deploy,and another ten to pack up. With practice, I'm sure it's a five minute deal. Weight, about 90 pounds.

[fishsticks]

Love it. Is that permanent fixture now? Or will you be modifying the rack so you can switch?

Glad you're OK after the spill.

[djthumper]

Looks nice! I am also glad you are ok from the spill.

[The Roadie]

Thx for the thoughts. The tent is a PAIN to attach to the crossbars, but the crossbars only use 4 3/8" stainless bolts to attach to the fore/aft rails. That's where I'll disconnect it. I'm too tall to get in my garage, but I have tall drive-in bays in the warehouse at work. So I'll throw up a pulley system there to get it off when I need to swap back and forth. And if I don't get the pulley in right away I have access to many strong guys, some of them tall, some of them Filipino.

[Trail X]

Quite a setup Bill!

How is their travel cover? If I recall, their design zips on, right?

What's the big seatbelt inside the tent for?

[The Roadie]

Excellent questions, as always.

1) The cover is very heavy coated fabric, designed to be dust-resistant. Velcro flaps on two corners for tightness. Zipper goes around three sides, and the side where the tent opening is (passenger side of the vehicle) has an extrusion like boats use on sails. The cover has a rope sewn into the edge, and it inserts into the extrusion so it can be totally removed if desired. You can do a quick setup and leave it attached to the tent. But then it obscures the passenger doors front and rear. The rear passenger side door is where my fridge slides out. This way the changing room, if attached, could also be the rainy day kitchen. (Like I ever knowingly camp in the rain anymore? I paid my dues for rainy tenting in Maine and New Hampshire for 20 years.....) The Camping Lab awning I didn't install yet, will be on the driver's side.

2) The webbing belt I had to call the seller to find out - there's one from each of the honkin' u-hoop triplex hinge fittings, they have loops in the ends, and they're safety reassurance straps for descending the ladder. My wife's just over 60 now (I'm just under.) so that's actually pretty important. I can pee in the middle of the night using proven technology at the bed level. She would need to descend, and was never happy about the prospect. A happy wife is a frisky wife.

[Philberto]

Excellent idea on the side rails, where'd you get the SuperStruts from? Now I know that I'll need shims for my roof rack when I finally get it setup... Was sitting on the roof the other day, denting it, and more motivated than ever to at least get a platform up there. Nice RTT! And belated happy birthday, I assume?

[The Roadie]

Lowes and Home Depot both carry the Superstrut line, but it's near the electrical conduit, not the metal fabrication supply section. Home Depot has more accessories, at least in my market. Wholesale electrical stores carry FAR more accessories, and even have powder coated and other finishes on the channels. But I was in a hurry, and didn't want to wait for Monday to access the wholesalers or Grainger.

Search for T&B Superstrut.

I considered taking the crossbars to work and arching them in our 30-ton hydraulic press, but then I said. WTF. OEM crossbars are curved, and useless to carry 4X8 plywood on. Why would I perpetuate THAT insanity when I have a chance to do it up industrial-like?

[bgwolfpack]

Looks Fantastic! The Superstrut system is smart, well done. In your first post you said this tent is 2 years old. Doesn't look 2 years old or ever used!

[Trail X]

Bill, a quick question. Do your mount nuts have serrations in them or something to increase the friction? Metal on metal doesn't have much of a friction factor, and the more I think about your mount the more I worry about it moving around while the truck is bouncing and thrashing around. In my experience, I've had my entire rack scoot about 6" forward on me after a trail ride, and my jerry can mounts similarly moved about 6" left on the rack (though they were limited by a cross bar). I just don't want your tent scooting out over the side of your vehicle during a particularly rough trail.

I now ensure I tighten my roof rack down with my impactor, and my jerry can mount now has a "hook" that allows it to hold on to one of the cross braces.

Personally I'd make sure you put something that can limit the tent's movement (laterally and longitudinally) - maybe some self tapping screws on either side of the mounts, just to make sure the mounts don't move on you.

Added: You can actually see my jerry cans swinging left-right in the beginning of this video... just shows the forces at work up there. This was before I added the hook.

[The Roadie]

Bill, a quick question. Do your mount nuts have serrations in them or something to increase the friction?

Oh, yeah. Do they ever! One of my non-negotiable requirements before I chose this system.

One of the worst rides in my life was when I was provisioning a group of 8 people at the upper end of Coyote Canyon, and my first mount solution for the Surco rack used flat rectangular nuts with very wussy serrations (knurled, actually). The entire 200-250 pounds of rack was sliding back and forth and threatened to come off! I blocked the trail for a half hour while ratchet strapping everything down, including THROUGH the open rear windows!

Look at these serrations, baby!

SuperstrutNylon cone channel nut. For use with Superstrut metal framing and hanger systems. Goldgalv electroplated zinc finish on case hardened steel. Extreme resistance to pull out and side slip. Unique design of alternate teeth provides a wedging action that increases with the load. Pliable nylon cone secures the nut in place. Fits all 1-5/8" channel.

[BSalty]

Did you use the 4' channel? I may be using this stuff as well for my rig plan. However I need the rail to come forward closer to the windshield for what I have planned. Just trying to get a feel for the dimensions once it is mounted.

[Trail X]

What about the actual tent mount/stirrup?



Was the serrated channel nut used somehow in this location too?

[The Roadie]

I bought a ten foot length of each. The vehicle rails are five feet long, the two crossbars are four feet.

The tent side channel nuts aren't serrated, but they're about two inches long. And the aluminum channel overlapping area is wider than the 12 or 14 gauge steel thickness (edge on) that is the contact patch on the Superstrut side. I'd estimate the aluminum area at 2" X1/4" per side of each channel nut, for one square inch per nut. Times eight nuts. 8 square inches. Clamping force given the torque I put on the bolts is at least 200 PSI. So let's say 1600 pounds equivalent of force. Static coefficient of friction of clean aluminum is about 1.3? So maybe 2000 pounds of static friction. And it weighs around 100 pounds so it should withstand a fore or aft accel or decel force of 20 G's? Oh, professional M.E., am I doing the back of the envelope calculation about right?

For side to side, it's about the same eight square inches, but one alum/steel interface and one steel/steel.

BUT, compared to a channel nut with a very short screw, this design has longer bolts that would tilt if there's any start of movement. And that would increase the clamping force. I bet the ultimate limit is the tensile strength of the 8mm stainless bolts or the tear-out strength of the aluminum channel tabs.

The cool thing I never looked up before was the coefficient of friction for aluminum. It's always been intuitive that aluminum sticks better to itself than steel sticks to steel. But the numbers support that feeling.

[Trail X]

Sounds fairly sound, except friction isn't really related to contact patch, just the normal force (you can find that related to your nut torque here: http://www.engineersedge.com/calculator ... e_calc.htm). However your assumptions otherwise seem reasonable - even if 20 Gs sounds immensely high.

It'd still be interesting to study it... make a reference mark with a sharpie, then see if it moves after a trip.

[cbbryan]

I am curious; our roof bearing max load capacity is 250-300lbs right? With a 90lbs tent, 180lbs man, 130lbs woman, and unknown gear are you not worried you are exceeding the limits? Or is the limit given only apply to our factory crossbars?

[The Roadie]

Everybody with a RTT has the same question, and I've heard it discussed that the factory rating is for dynamic loads that are bouncing around as you drive. The static load of stuff up there when you're parked won't bend the support structure. It has to be designed to not collapse on your head in a rollover accident, so I'm not worried.

Won't be the first time we've exceeded factory recommendations for things. The manual actually says 220 lbs / 100 kg, for the curious. Heck, I'm over that by myself, fluffy one that I am.

[cbbryan]

So what you are saying is that if/when I get a roof basket to toss the plastic cross bars cause they are weak?

[fishsticks]

So what you are saying is that if/when I get a roof basket to toss the plastic cross bars cause they are weak?

That's not what he said.... but that pretty much goes without saying.