ticki2 wrote:
While that calculator is helpful for some things it is not applicable to your tie downs . It is a simple beam calculator . What is needed is a cantilever beam with a fixed end and concentrated load at the end . The same would apply to a hitch extension .
I am.not an engineer , just enough knowledge to be dangerous . If you have access to engineers check with them . I would be interested how they would calculate dynamic loads ie , bouncing down the road , most all of these formulas only calculate static loads .
BTW , your tie downs look more than adequate .
Yes, the calculator is a fixed load, I also took the specs from the advertised material from a product one trailer.com and ran it through the calculator for comparison as it was actually a smaller tube size. I think a good comparison of what you're referring to would be the Companies that sell personal fall restraint equipment and do demonstrations.
Our harnesses are rated for a man weighing up to 350 pounds. OSHA requires that any tie off point be capable of holding a static weight of 5000 pounds. The reason being the force generated from an object in motion for 3 ft. (person falling) and then an abrupt stop. If my memory recalls somewhere around 2500 to 3000 pounds, which is why the safety lanyards have some sort of shock system built in, to lessen the felt impact. Myself and a lot of other employees have went to the lanyards with the retractable automatic locking strap (like a seat belt). The same test weight put on their machine and allowed to free fall had the values significantly lowered because of the less distance traveled (inches) before stopping. There are a lot of variables and I’m not endorsing a particular
size and weight tube, but only what I feel comfortable with for my own DIY project, and experiences in the field. BTW, we do build a lot of load bearing equipment using I beams and hoist trolleys and I have a couple tables for that as well and they all take into account the beam specs (height, width, weight (thickness) , span, load travel, bouncing of load, beam deflection. As an example I have a 17’ 8” I-beam down at my shop right now- I have ran it through 5 or 6 calculators and confirmed with engineering, the load isn’t very high due to the span. Thanks for the reply Ticki2, there are a lot of things in play. All things being equal I’m sure the weak link is the truck camper itself, I can’t remember how many posts I’ve read, using all sorts of tie downs, that there’s a danger of ripping the eyelets in the camper loose.
In the market to buy a T/C
2002 F350 4wd CC DRW 8’ box
Load Lifter 5000 rear air bags, front Timbrens
Rancho 9000 shocks
Brighton, Illinois
