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I'm creating a light up dancing pole. This requires a translucent material that is strong enough to support the weight and force of a human being, even when it's hollowed out to so LEDs can go inside. The material must also be reasonably affordable, so something like diamond is out of the question. I figured that polycarbonate was my best bet.

I did some searching and found a polycarbonate tube with the right dimensions (8ft length, ~45mm outer diameter). Here are the exact specs:

  • Length: 8 ft
  • Outer Diameter: 1.750 in.
  • Inner Diameter: 1.500 in.
  • Wall Thickness: 0.125 in
  • Weight: 0.332 lb/ft

My question is whether this pole can support the torque of an average-strength 150lb human dancer. Not someone who is using all their bodily strength to destroy the thing, but apply force at different angles and forces.

It will be secured to the ground by bolting it to a weighted platform. My concern is whether the pole could potentially break.

dcorking
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Ben Greenberg
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    Are you going to bolt it in at the bottom and the top, or just at the bottom? (Bolting at the top as well should help, it'll cut the max torque arm on the bolts in half essentially) – Trevor Archibald Mar 20 '15 at 03:20
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    @TrevorArchibald Unfortunately I can't bolt at the top as this is in a courtyard are without a roof. I'm building a stage pole ala instructables.com/id/Mobile-Stripper-Pole-no-need-to-attach-to-ceiling/ – Ben Greenberg Mar 20 '15 at 07:11
  • Do you have a material data sheet, can you get one for the pipe? – mart Mar 20 '15 at 16:28
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    @mart http://www.eplastics.com/Lexan_Polycarbonate_Tube and http://www.eplastics.com/Clear-Polycarbonate-Rigid-Tubing1-5-8-ID-x-1-3-4-OD-x-1-16-Wall-x-8ft is what I could find – Ben Greenberg Mar 20 '15 at 20:41
  • Honestly, if this is an "I need one of these" question and not a, "This is fun, but there's no immediate need" question, I'd be shocked if somebody doesn't already make something like this. I'm at work now though and I don't want "Light up dancing pole" on my search history. – cKrug Mar 23 '15 at 19:24
  • cKrug: I've already searched intensely for it, it doesn't exist for sale – Ben Greenberg Mar 24 '15 at 19:36
  • Consider using a steel rod that supports the lighting and the polycarbonate tube. Also, get a thicker wall tube - 1/8" isn't going to work well for the loads described. Maybe a 1" steel bar with spacers out to a 1.25" inner diameter, 1.75" outer diameter, 0.25" wall tube. There's a 1/8" gap between the steel and the plastic, fill that with flexible PCB substrate loaded with surface mount LEDs and spacers so the tubes are mechanically connected. Note that a one inch steel bar will still experience significant deflection, but it won't break. – Adam Davis May 21 '15 at 18:53
  • Have you considered composite materials? You can get a pretty clear material with composites, and they can be built in such a way that they could withstand the loading. The material may have to be thicker than you are first thinking, but 2" OD probably would be an option. – Mark Sep 03 '15 at 23:40

2 Answers2

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CAVEAT: I do not have any design experience in plastic, but by using first principle, this is how I would tackle the problem.

The first thing we need to know is what are the typical forces exerted on a pole during pole dance. Assuming that the dancer is spinning at not more than 45 degrees from the axis of the pole, then the maximum centripetal force acting on the pole would be equal to the weight of the dancer (150lb or 68kg). Given that the pole is 8ft or 2.44m in length, the maximum bending moment induced at the base of the free cantilevering pole would be:

m = 68kg, a = 9.81m/s², L = 2.44m
M = F x L
  = m x a x L
  = 3.3 kNm

Polycarbonates, in general, have ultimate tensile strength in the range of 55-75MPa. This is one-fourth of the tensile strength of structural steel. From the technical specifications in eplastic.com, the polycarbonate material specified has an ultimate tensile strength of 9500psi or 65.5MPa. Assuming this is also the yield strength for the plastic material, then the elastic section modulus can be calculated as follows:

Do = 44.5mm, Di = 38.1mm, py = 65.5MPa
Z = π(Do⁴ - Di⁴)/32Do
  = 3.97cm³

And the moment capacity of the pole can be conservatively calculated as such:

Mc = pyZ
   = 0.26kNm
   < M

Based on the above, the polycarbonate dance pole would not be strong enough to support the force generated by a dancer.

Question Overflow
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    And note that this is even without considering a factor of safety. The material is likely brittle, so a very large factor is safety would be in order. – hazzey Mar 21 '15 at 15:23
  • Question Overflow-- how much force could it actually sustain? – Ben Greenberg Mar 21 '15 at 20:52
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    @BenGreenberg, the moment M generated must be lesser than its capacity Mc, which means the lateral force on the pole must be smaller than 100N to be sustainable. Will be even lesser if you consider a factor of safety, say 1.6, as pointed out by hazzey. You should also consider shear and buckling failure for designing the pole. – Question Overflow Mar 22 '15 at 02:52
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    You'd also need to think about deflection criteria. I don't know the specifics of pole dancing, but I'd imagine the deflection on the pole can't be all that high. You'd have to think about the ease of dancing, as well as the dancer's confidence in the pole. – cKrug Mar 23 '15 at 19:11
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Given the variables involved and the relatively low cost of polycarbonate tubing, I'd be tempted to just buy a length and test it. Use a fairly chunky dancer to build in a factor of safety.

Polycarbonate isn't brittle and so catastrophic failure is unlikely. However, it scratches easily, which might degrade its light transmission over time. Stress corrosion cracking can be a long-term problem but I don't imagine any corrosive materials would be involved in the application you describe.

If the top of the pole can't be built-in, think about guy-lines ('shrouds' in yacht-speak), possibly with a spreader to give more room for the dancer.

rdt2
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