So I made a DIY mount for my waterport 3.8 gallons. I'm not much of an engineer lol. But can someone chime in and let me know if my mount is safe? Or is it too much stress applying on the side of the roof rails?
DIY WaterPort 3.8 Gal OEM Roof rack mount. Will it hold? Safe enough for overlanding? (1 Viewer)
- Thread starter KraziAzn
- Start date
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That’s about 32 lbs. of twisting force on the aluminum extrusion. The cross bars on either side of the mount will minimize the twisting, but take it for a bumpy drive and see if it whacks against the car body.
Asking for trouble there, especially w/r fatigue.
- Thread starter
- #5
Please explain. what do u mean by w/r fatigue?
Is there any way to improve on this design?
awesomeissquid
SILVER Star
I think you are going to run into trouble since it is just clamped around the track. Without doing any calcs I feel like the bracket is going to rotate. I think a better design would be to include a nut that runs in the roof track that your plates can bolt to. That will keep the whole assembly from rotating. That said, I am not sure the stock bars can handle that amount of rotational moment especially if you go off-road. Might want to replace the two plates on the inboard side with one larger plate. Here’s some sketches of what I would start with if I was designing this.
If the water can is resting on the body, which it looks like it is, you’ll likely be fine. It’s definitely not overbuilt, but my technical guess is “s***’ll hold”
If you’re really concerned about it, turn the container to be on the inside of the frame rail. Then it’ll fully rest on the roof, and the mount will just restrain it from moving around. Pad the bottom obviously
It would really concern me that movement in the container could possibly dent the panel just above the window on any off road situation.
- Thread starter
- #10
Wow! Ty for the sketch! This is really helpful! I'm going to remake it
Yes, I agree. I added some spacers so it clears the body.
awesomeissquid
SILVER Star
Excited to see version 2.
Fatigue happens when there are very small movements within metal coupled w a micro defect in the metal grain. think of the micro defect as a crack seed...known as a stress concentration. The seed initiates a micro crack which grows over time such that the metal area taking the load shrinks. Once the area becomes too small...failure.
This is exasperated by load dynamics coupled w structural natural frequencies which, if in the sweet spot (structure harmonic) will magnify the apparent load up to 10x. Look up Verrazano Narrows Bridge. Could happen if road surfaces dynamically matches vehicle/mount dynamics (think saline valley road in dv) at certain speeds.
I just saw reference that the bottom edge of the tank rests on the roof panel. This will improve things, though not eliminate as the structure can move away from the roof (negative loading). Basically buys you more time before failure.
Taking all this and more into account, this is one reason why correctly designed products cost (designing Outreach law suites).
That's all the news not fit to print ✌
This is exasperated by load dynamics coupled w structural natural frequencies which, if in the sweet spot (structure harmonic) will magnify the apparent load up to 10x. Look up Verrazano Narrows Bridge. Could happen if road surfaces dynamically matches vehicle/mount dynamics (think saline valley road in dv) at certain speeds.
I just saw reference that the bottom edge of the tank rests on the roof panel. This will improve things, though not eliminate as the structure can move away from the roof (negative loading). Basically buys you more time before failure.
Taking all this and more into account, this is one reason why correctly designed products cost (designing Outreach law suites).
That's all the news not fit to print ✌
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