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Thread: Mechanical hardiness of arches

  1. #1
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    Default Mechanical hardiness of arches

    So first off, hi. This is my first post here.

    We just pulled off a successful drive-through arch tunnel using 3/4" PVC. 100 feet long, each arch was 34 feet circumference. On a $500 budget (we are a non-profit). I'd like to do better next year.

    Two areas where we fell short:
    1). The lights tend to break a lot, because they are tied to the outside of the pipe. If I can put them inside a transparent pipe, they'll last longer.

    2). The tunnel could hold up to 35mph winds, but it fell in 55mph. It was pretty spectacular.

    I have never tried your solutions with PEX and HDPE, but I keep seeing pictures of pipe all curled up in a ball. Can a 34-foot arch of that hold up under its own weight? I would also kind of like to hang icicles off the top, and I have a hard requirement that I have to drive passenger vans through it. I can probably get more budget next year, but not like $36,000.

    What kind of frame is needed and/or required at that size, for those kinds of translucent pipes you use?
    Thanks!

  2. #2
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    Default Re: Mechanical hardiness of arches

    My experience is with 2" HDPE. It would not have been able to be uncurled to cover 34' without of a bunch of cross bracing. And it would not have liked it. But a drive through tunnel of that size probably needs cross bracing anyway. It would be an expensive experiment to find out. Besides the cost of the product, shipping on the big size HDPE is horrible.

    I am not sure how it would work out if you used straight sections of larger sized HDPE. I would think they would be hard to bend. A smaller diameter might be more bendy.

    What kind of lights did you use and why did they "break a lot"? If they were secured to the pipe, you should have had few failures.

    The wind is all about engineering a solution to keep the base in place and having sufficient guying. It would be hard on a DIY budget to get a standalone structure that will sustain the wind loads you are talking about. A solid base structure, cross bracing between arch and guy wires on the start and end arches would help a lot. Did you analyze how they fell in the high winds?

  3. #3
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    Default Re: Mechanical hardiness of arches

    Hi hi,

    I used store-bought C3's--mostly because I was on a tight schedule. The breakage was during transport and assembly/disassembly--and, of course, the catastrophic windstorm damage. Not during the static display itself. I was thinking that if I put the lights inside of the pipe, I could just let the storm blow it down. I have some China-made, $2-per-10m LED strips and fairy lights on order right now. I don't have the budget for WS2815's, but with that size tunnel I also figured I have enough channels to play with that I don't need pixels, anyway.

    The arches also serve a hidden, practical purpose: power routing. I've got traffic driving through a commercial parking lot. So rather than have hundreds of cars drive over my wiring, I route over the arch. Unfortunately, that comes with yet another challenge: I'm on a hard parking lot, that is not mine. Hammering rebar stakes into the ground is almost never an option. What killed the tunnel in wind was when the wind direction went directly along the length of the tunnel. It lifted all of our 50-pound buckets holding it down at once, then...crash!

    Instead of guy wires, I opted to use PVC cross-couplers to connect twin PVC spines going down the length of the tunnel. This stopped compression and twisting action along the tunnel, but it came at the expense of making the whole thing top-heavy. To negate that threat, I devised a suspension-bridge system of ropes, much like you see on yard inflatables or a suspension bridge. Which got it to 35mph, but 55mph overpowered all the buckets. (p.s. I probably shouldn't say "instead" of guy wires--there were plenty of lights going along the length of the tunnel)

    Now I'm thinking I need an aluminum frame with a truss on the sides, with clamps welded on to mount transparent piping. The thing is: 1. expense. 2. how to make a drive-through arch out of it. 3. the strongest aluminum is a hollow, circular rod anyway. And 4. the transparent piping is untested (where I thought this forum might know more).

    Fortunately, I am able to experiment on just one arch section at a time. If I can make an arch out of one, then I can probably repeat. Also, not every arch section may need its own aluminum frame. But I would like to hang some icicles from 15-feet in the air on them all, if I can help it, and that adds some top-heavy force.
    Last edited by 1pet2_9; 01-16-2021 at 12:44 PM.

  4. #4
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    Default Re: Mechanical hardiness of arches

    You say the Arch has a 34' circumference, how wide and how high does it need to be?
    2012 - 1st year 64 Channels - 7500 LED lights - 5 sequences
    2013 - 128 Channels - 10,000 LED lights - 7 sequences (2 New)
    2014 - 201 Channels - upgrading 8 Arches to dumb RGB - 8+ sequences (1+ New)
    2015 - 240 Channels + 8 Universes - sequences TBD
    2016 - No Display
    2017 - Back in the Game - 240 Renard Channels + 12 Universes
    2018 - 256 Renard and 9 Falcon Outputs of Pixels - 16 sequences shown over 2 nights
    2019 - 256 Renard and 9 Falcon Outputs of Pixels - 16 sequences shown over 2 nights
    2020 - Emergency Conversion to Falcon F48 with limited wireless

  5. #5
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    Default Re: Mechanical hardiness of arches

    We got 15 feet height (at the zenith) out of the 34-foot arches (which consisted of 2x 12-foot PVC sections, each coupled with a 10-foot section in the middle). With that, we were able to clear all of our traffic. We had a volunteer dedicated to checking each vehicle's clearance, but in the end we didn't have to turn anybody away. Although we did have one van who had a bunch of stuff on their roof, who came close. I made pure arches for aesthetic reasons, so if I do the math, that gave us about 22 feet width (only the 10 feet in the middle of which would have been driveable, in the worst-case). I did look at other shapes that could have been structurally stronger, but I just didn't like the way they looked. Except for one: there was a gumdrop shape that I liked, which looks kind of like an arch with a curved steeple up top. I achieved that by using these brand new (but a bit expensive) PVC couplers, which could bend at any angle. I opted against that because I felt we needed two couplers on the arch--not one. Wind tends to blow diagonally on the arch, and that creates a twisting motion.

    I don't know what options in the way of transparent tubing couplers are even available.
    Last edited by 1pet2_9; 01-17-2021 at 03:05 PM.

  6. #6
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    Default Re: Mechanical hardiness of arches

    I have a 20ft by 20ft canopy over my pool. it uses 1" steel pipe and standard couplers like used for the canopie at swap meets.

    Maybe frame this with taller verticals and secure the arches to it along the way.

  7. #7
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    Default Re: Mechanical hardiness of arches

    Absolutely, but how much did the canopy run? Thanks for chiming in. If there's a good way to bring in steel that's not $10,000, I've got a bunch of kids who will be very grateful. I know a guy who is a recent grad from welding school, if I can come up with the materials and the drawings.

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