Early stages of planning to cut a BFH in my van.

[Road]

RE: Self-Built Long-Bed Pop-Top on Vannery O'Connor:

Been spending more hours out under moonlight mind-guessing approximate dims, structural bulkheads, and potential failure points as I contemplate an outdoor build and creating something durable and efficient for extended travel.

I've spent lot of time with exact-dims planning on paper, too, as well as research into a variety of methods. Thank you all for suggestions and ongoing encouragement.

I'm enjoying this challenge. I find it especially invigorating during this Big Pause of 20-21 and having spent all the last year in one place.

New: Just scored a cool pair of hard-to-find hardware pieces I've been searching for, for ages. I got the last pair they had (usually available only from the UK):

They are reman'd out of stainless after an original of one of several designs used over the years.

Often hard to get in the states new. The particular bend at the top of the struts at the lower end--easy enough to do in a decently-equipped shop--and the fact that these are ready-made and proven, and at a price less than my figuring dims and manufacturing on my own for endless hours, feels like a score.

I know exactly what I want to do with them and how they will be used.

10 pts to anyone who knows what they are and has personal hands-on experience in installing them.
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2nd Note:

Been getting some helpful inspiration and technique tips on self-built wedge-style from online details of Michael Gorski's build of a pop-top (he built the support camper too):

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https://roaddude.com

 

[Herbie]

10 pts to anyone who knows what they are and has personal hands-on experience in installing them.

I'll take those points. Hell, I've done it twice, since I transplanted the original ones to my van back in 2010, then upgraded to a more stout set in 2014. (One side of the original pair was slightly bent and binding in the arc, hence the replacement.) The geometry is almost the same. Near enough to work.

 

[Road]

View attachment 55515

I'll take those points. Hell, I've done it twice, since I transplanted the original ones to my van back in 2010, then upgraded to a more stout set in 2014. (One side of the original pair was slightly bent and binding in the arc, hence the replacement.) The geometry is almost the same. Near enough to work.

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Ten Points to @Herbie!

They're really interesting, clever pieces of hardware, aren't they. I'm fascinated by the differences over the years and how some have the knuckle and extra pivot point and others don't. I'd love to have a pair of each to compare lifting angles and such.

The way they work, as you know--lifting the low end clear of the roof when the high end is raised--solves the problem of having a piano or other hinge arrangement at the actual edge of the pop top. Also allows less overall length to get the same headroom at the high end. It'll be fun figuring out just where to place them and how to install them.

 

[Herbie]

Yep, they're very tricky. The hard part is that they're kind of a precision piece. The 4-bar linkage with the sliding segment is more forgiving, but the 6-bar linkages like I have are VERY sensitive that all the bar-lengths have to be just right, or else you get binding. This isn't a problem for mass-manufacturing, but it makes it hard to "DIY" a set unless you either copy existing dimensions exactly or have access to the kind of simulation software it takes to move everything through their arcs before you get a working set of dimensions.

A mechanical engineer friend of mine really blew me away, though: Even with the 6-bar linkage, despite all the complicated ranges of motion, you can basically model it as if you'd taken a "slice" out of regular piano-hinged roof where the hinge point is like 4-5 feet behind the vehicle. As you say, though, the real key is just that they solve a bunch of fitment problems that come from a regular pin/piano hinge. Finding a way to create a lid that seals on the roof is much easier if you don't have to deal with a "pinch" point where the gap between top-of-vehicle and the moving roof is only 1/4"!

 

[Road]

Yep, they're very tricky. The hard part is that they're kind of a precision piece. The 4-bar linkage with the sliding segment is more forgiving, but the 6-bar linkages like I have are VERY sensitive that all the bar-lengths have to be just right, or else you get binding. This isn't a problem for mass-manufacturing, but it makes it hard to "DIY" a set unless you either copy existing dimensions exactly or have access to the kind of simulation software it takes to move everything through their arcs before you get a working set of dimensions.

A mechanical engineer friend of mine really blew me away, though: Even with the 6-bar linkage, despite all the complicated ranges of motion, you can basically model it as if you'd taken a "slice" out of regular piano-hinged roof where the hinge point is like 4-5 feet behind the vehicle. As you say, though, the real key is just that they solve a bunch of fitment problems that come from a regular pin/piano hinge. Finding a way to create a lid that seals on the roof is much easier if you don't have to deal with a "pinch" point where the gap between top-of-vehicle and the moving roof is only 1/4"!

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That's a great way to think of it, and a point I hadn't thought of yet; to see it as a section however far in from the point the planes would intersect if continuing. I see scale templates being made of mat board in my future to help determine how far back or forward to place these clever hinges.

Thanks, man.

 

[Dave]

Well, is there a BFH yet?