121 replies to this topic

[ETAV8R]

Welcome!

For me I'd be putting on the fuel can holder on after taking the jacks off. My camper does not stay on my truck full time. I also don't always carry extra fuel. It would free up room in the camper and lessen the worry of fuel getting out of the can. Seems like it would be pretty easy to fab up. The cost for materials is pretty minimal but finding a non-carb jerry can is pricey part.

Edited by ETAV8R, 16 May 2017 - 07:31 PM.

[Kinsey]

Josh41,

Sorry for not posting these pics sooner. I just got back from a trip and pulling the camper off and putting stuff away. Here is the Roto Pax can mount.

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[Wandering Sagebrush]

Josh41,
Sorry for not posting these pics sooner. I just got back from a trip and pulling the camper off and putting stuff away. Here is the Roto Pax can mount.

Nice solution!!!! I assume you made the mount, well done.

[Josh41]

Thanks for posting the pics, I'm really struggling with the idea of drilling holes in my new Fleet, that looks like a nice solution.  Any reason you went on the side and not the rear?  

Josh

[nikonron]

Personally, I would rather mount to the rear, I don't like anything hanging out on the sides if it doesn't have to be there. Ron

[ntsqd]

I get wanting to use the jack brackets, but large masses cantilevered into space make me real nervous. I know such a bracket would fail for me.

 

If you're not using your tail-gate I'll suggest tying onto those mounting points instead. I did this with our spare tire swing-away.

Edited by ntsqd, 23 May 2017 - 01:38 AM.

[Kinsey]

The weight of a 3 1/2 gallon fuel can cantilever is nothing. It is visible in my mirrors and sticks out less, about the same as the awning. The camper has the passenger side rear window and I don't want to block it and the driver's side has the LP and I don't want to block that either.

[ntsqd]

I get roughly 23.8 lbs of liquid (6.8 lbs/gal for most liquid fuels), so guessing about 25-26 lbs for the fuel and the can. Really, really rough Rule of Thumb for Dynamic Loadings is 3 times the static weight, so around about 77 lbs swinging up and down and fore to aft and back on every bump. My NATO cans measure 13" wide by 6.375" deep, so that puts the centroid of the weight (mass actually), in the horizontal plane, ~14.5" from any corner.

 

That makes the Moment on the jack bracket something like: 77 lbs X 14.5" = 93 lbs-ft (can think of a Moment as a torque). What this means is that every bump that equals or exceeds 3 times the pull of Gravity is exerting at least 93 lbs-ft of torque on the jack bracket. This doesn't include any Impulse loading from the can not being completely full. That can drive the actual, extremely brief duration loading significantly higher (think: like hitting the end of that 14.5" long lever with a 3.5 lbs or less hammer).

 

Because I know all of this I know it would fail for me. It is the curse of an Engineering education. Hopefully my outlining it all doesn't mean it will fail for you too.

 

EDIT: DOH! moment (no pun intended). I calc'd the diagonal of the whole can, not the centroid location. I kept looking at that number thinking it was too big. So, the actual leverage length is roughly 7.25" which makes the Moment 46.5 lbs-ft instead of 93 lbs-ft. Still quite a large number, but it will increase the fatigue life over the 93 lbs-ft number.

Edited by ntsqd, 25 May 2017 - 01:54 AM.

[ETAV8R]

^^^Mind Blown^^^

 

Thank you for the indepth analysis.

[craig333]

Of course it will fail, the question is when. So far I think I have three years on mine and its holding up great. I'm not an engineer but I'll be surprised if mine fails in the campers expected lifetime.