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Old 06-04-2016, 05:42 PM   #57
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Uh-oh. You just validated every engineering reservation my husband ever had on these products. The reservations that got us into "no" territory on any potential off-the-shelf purchase.

We are still committed to building our own, or hiring out for it if we can identify a source with skill, availability, and a price we can live with. I found another contender on Insta last night... a Sprinter off-road upfitter named Vancompass, which posted a vid loop of this tire mount that they designed (screengrab below). I sent a feeler email but it's the weekend so I have not heard back, and they may turn out to be like Aluminess (not taking new orders for X amount of time) or Back Country Box (not yet with a design on the table).

Meanwhile, as we follow potential new vendor leads, we continue to investigate local welding suppliers, and large custom-ordered components of heavy steel show up in the our mail clusterbox. By one pathway or the other, this will get completed eventually.
Interblog,
Tell LB3 to build one like the Johnny Cash song...one piece at a time. He can "borrow" some time on the CNC plasma cutter at work, take a piece out in his lunch box every day, and weld it together at home!
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Old 06-04-2016, 07:46 PM   #58
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Please let us know what they tell you. When I talked to a customer rep on the phone a couple of weeks ago it sounded like they had just built a number of them recently but had been backordered. Hopefully they didn't cut corners on material or workmanship to get caught up. I'm headed north in a few weeks and I'd like to ensure that it is roadworthy before we load it up. Good luck with your travels.

I sure will, I have not had a moment to sit and call since I left Florida.. We are now in our vacation rental in San Clemente for 10 days.. Now I can sit for a few and make some calls and work on a solution as we still have a long trip ahead of us, and having a broken storage box is not going to cut it..
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Old 06-04-2016, 08:09 PM   #59
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Had a bit of a mishap.. The gearbox started to bend.. I tightened everything up and put some ratchet straps around it.. Not sure why this happened, there is no way I had more than 250 lbs and it's supposed to hold 300.. Attachment 263824Attachment 263825
This is the problem when you've got a heavy weight balanced at the center like a teeter-totter. Hit a bump or a pothole, and the box will rock side-to-side, applying bending moment to the crossbars, which may be either undersized or too few in number for the capacity of the box. The box may be capable of supporting a 300-pound static load, but that doesn't necessarily translate to a 300-pound dynamic load.

The important things about loading one of these boxes are: (1) center the weight of the load as much as possible, and (2) secure the load inside the box so it can't shift side-to-side. The same rules apply to any hitch-mounted carrier.

I know one guy who has a cargo box on the back of his SUV, who fills the void spaces in his box with inflatable kayak float bags to keep his load from shifting in transit. But that's probably an expensive option. Inflatable beach balls might do the same thing at a lower price.

Also, check the fit of the carrier in the hitch receiver. If it's not a snug fit, you might use some thin wooden wedges to shim the carrier into the receiver more securely so it fits tightly and there's less wobble-room. Shims on the bottom and one side should do it.
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Old 06-04-2016, 09:05 PM   #60
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Interblog,
Tell LB3 to build one like the Johnny Cash song...one piece at a time. He can "borrow" some time on the CNC plasma cutter at work, take a piece out in his lunch box every day, and weld it together at home!
I'm a country oldies fanatic so you really made me laugh.

I have this hinge in a box on the floor of my office:
My first choice is to buy a commercial box but I've been nonplussed by all of them.
My second choice is to commission one built but quality and availibility are elusive in the market right now.

If I have to build, I should have the major parts next week but I'm worried about the weight. A 6ft long 4x3 beam is about 100 pounds all by itself.
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Old 06-04-2016, 09:23 PM   #61
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The rear box would block sensors and interfere with blind spot assist system in the newer Sprinters thus completely disabling it on the entire period of accommodation in the rear hitch. Therefore, the second benefit of a small rear trailer is up. Btw, the price of a good new one is under two thousand.
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Old 06-05-2016, 07:18 AM   #62
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...The box may be capable of supporting a 300-pound static load, but that doesn't necessarily translate to a 300-pound dynamic load.....
BINGO. Or anything close to the forces that might be generated by 300 lbs. or less in the wrong dynamic situation.

When I first saw the off-the-shelf boxes, I said to myself, "I'd like to see one of those suckers survive IH-10 from Baton Rouge to the Neches River. I think it would be done for by Laf." My husband and I had our first exposure to just how bad a bad freeway can be on that stretch - while on our maiden voyage back to Houston from Memphis, where we purchased our Interstate. The 2500 Sprinter is not as rough as the 3500, but on a wretched freeway in an advanced state of disrepair, it makes little difference. I was sitting in the back as he was driving through Louisiana and I swear that my bottom left that seat countless times (I wasn't joking in previous threads about being catapulted into lower earth orbit). I was belted in but I felt the breeze beneath.

And what goes up must come back down - with tremendous force (with the number of engineers here, I'm betting that someone proposes some reasonable equations for this scenario).

In our case, on that freeway, I told my husband something along the lines of, "In these conditions, you just have to slow waaaay down to minimize the impact on the rear end - there's nothing else that can be done. Otherwise the cabinets might come loose and I might lose some teeth if I continue to sit back here."
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Old 06-05-2016, 08:30 AM   #63
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That's what happened, I 10 west Florida to California is not all smooth, tons of bumps and pot holes. I'm really surprised I didn't lose it and cause a bad wreck.. They should at least have a safety strap that is attached to the box and the hitch.. Four small brackets and 8 small nuts and bolts is not much to hold 300 lbs..
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Old 06-05-2016, 09:29 AM   #64
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Mr. B,

Looks like you could fit that motorcycle in that trailer. You need to head to the Cabot Trail.
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Old 06-05-2016, 12:04 PM   #65
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Mr. B,

Looks like you could fit that motorcycle in that trailer. You need to head to the Cabot Trail.
Thank you ). Actually yes, it fits there alright
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Old 06-05-2016, 09:28 PM   #66
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I'm one of those internet engineers and the cargo box in the first photo looks like it was assembled improperly to me.



The bent flange on the bracket that wraps around the square post should not be used to support that silver bar since it doesn't even come flush with the edge of the square post. Any rocking load from an uneven weight distribution in the cargo box then creates a bending moment on the flange instead of applying a shear force on the base of the flange which is orders of magnitude stronger.
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Old 06-06-2016, 10:57 AM   #67
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As a recovering retired EE, it appears from the photo that the square(?) tubing is not stout enuf or there needs to be more of them. While I can think of several ways to beef it up, will leave that to the MEs.
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Old 06-06-2016, 11:09 AM   #68
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Here is the response I received:

Thanks for the sending the image of the ‘Hat Brackets’ on your GearSpace where you added another nut.

This bracket, the Hat bracket, is designed to have its ‘ears’ or ends deflect up when the locking nut
is tightened, so just letting you know that the Hat brackets have a slight upward bend
by design.

The upward deflection of the Hat both puts tension on the nut so be doubly sure it does not back up and this
deflection also centers the female tube inside the hat bracket.

Please feel free to call me to visit more if you like.

Best,


Not sure if he knows his own product very well.. The brackets were flush when I left and I don't think the nuts are supposed to almost fall off..
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Old 06-07-2016, 05:01 AM   #69
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Here is the response I received:

....

Not sure if he knows his own product very well.. The brackets were flush when I left and I don't think the nuts are supposed to almost fall off..
Road conditions can, and do, produce strange results at times. Driving on rural highways southward to Abilene back in March, some of the roads were so rough in a particular fashion that all of our rear flap windows shook open. I would not have thought this possible, but I watched the rear view mirrors as it transpired. The infamous Texas plains winds were extremely high that day and that might have been a contributing factor. The windows never shook open on rough freeways before. Apparently I needed certain state highways for that to occur.

So, nuts are not supposed to almost fall off but windows are not supposed to shake open either. Products must be designed for the entire range of foreseeable real-life conditions, not just average conditions, or they will not necessarily behave as expected or represented.
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Old 06-07-2016, 06:27 AM   #70
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It appears that we are dealing with another excised thread here. I’m still not sure what the opposing poster’s specific complaint had been, but in the interest of clarification, it might be beneficial to articulate the difference between engineering and science, with the intention of perhaps avoiding future misinterpretation of the type that can sometimes result in thread excising.

The practices of engineering and science are intended to complement each other, and in fact, they only serve us properly when they do. As an a propos illustration of this, given historical comparisons of the Interstate to a space shuttle, Columbia’s failure mode was confirmed conclusively using science, not engineering. The engineering calculations strongly pointed toward a particular failure mechanism, but calculations are just calculations – they are not real life – and some key decision-makers initially would not take them at face value because calculations alone can inadvertently underweight or overlook the contributions of key variables such that the results become misleading. It took rigorous and repeated applications of the scientific method to back up the engineering, and it did so in a manner that was so elegant that I don’t think anyone predicted that aspect of the outcome, neither engineers nor scientists (hence the hyper-educated onlookers’ collective and startled cry of, “Whoa!” at the final moment of experimental truth).

This Forum appears as if it may contain a disproportionate number of engineers, but I have a Master’s degree in science. Rather than roughly applying physical theory and running approximated calculations through my head, I instead view much the world through a de facto lens of null and alternative (alternate) hypotheses. With respect to the issue on the table that had become contentious, which was Mjgman’s experience with the GearSpace, it is entirely possible to confirm its failure mode (and thus its future potential for additional failure) every bit as rigorously and conclusively as was done with Columbia. The null hypothesis is that the consumer product known as GearSpace performs as represented. The alternative hypothesis is that it does not. If I were designing an experimental regime intended to prove or disprove the null hypothesis, I would be going about it very differently from how I might comment on a Forum. But I don’t have that luxury, because however interesting such testing would be, it’s not likely to happen given the practicalities involved. That being the case, we are left with guesses that are based on the available information. Those types of guesses may be at best only semi-educated out of necessity, but they are not random, not the product of any ulterior motives, and they do have a basis, however rough it may have to remain. And in this case if I were compelled to predict, my money would be on the alternative hypothesis.
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