6
$\begingroup$

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.

Improve this question
$\endgroup$
8
  • 1
    $\begingroup$ 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) $\endgroup$
    – Trevor Archibald
    Mar 20, 2015 at 3:20
  • 1
    $\begingroup$ @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/ $\endgroup$
    – Ben Greenberg
    Mar 20, 2015 at 7:11
  • $\begingroup$ Do you have a material data sheet, can you get one for the pipe? $\endgroup$
    – mart
    Mar 20, 2015 at 16:28
  • 1
    $\begingroup$ @mart eplastics.com/Lexan_Polycarbonate_Tube and eplastics.com/… is what I could find $\endgroup$
    – Ben Greenberg
    Mar 20, 2015 at 20:41
  • $\begingroup$ 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. $\endgroup$
    – cKrug
    Mar 23, 2015 at 19:24

2 Answers 2

Reset to default
6
$\begingroup$

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.

Improve this answer
$\endgroup$
4
  • 5
    $\begingroup$ 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. $\endgroup$
    – hazzey ♦
    Mar 21, 2015 at 15:23
  • $\begingroup$ Question Overflow-- how much force could it actually sustain? $\endgroup$
    – Ben Greenberg
    Mar 21, 2015 at 20:52
  • 2
    $\begingroup$ @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. $\endgroup$
    – Question Overflow
    Mar 22, 2015 at 2:52
  • 1
    $\begingroup$ 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. $\endgroup$
    – cKrug
    Mar 23, 2015 at 19:11
0
$\begingroup$

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.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.