When building your own telescoping pole out of EMT conduit, it can be useful, if not outright necessary, to predict how the pole with perform in your application, namely: Will it hold its weight? This article is meant to provide technical guidance to help answer this question, written by Austin Allen - an engineering professional and the founder at Elation Sports Technologies LLC.
Context
When making a telescoping pole out of EMT conduit, the project use case and scope should first be identified. Consider the following questions:
Will anything be mounted/attached to the end of the pole? If so, what is its weight?
Will the pole be held at an angle, or positioned vertically, or horizontally?
Will the pole be exposed to sunlight, wind, rain, or other weather conditions?
Question 1: Will the Pole Hold its Weight?
A telescoping coupling (split collar clamp) should be used to allow your two pieces of EMT conduit to:
Slide relative to one another
Lock their position
Elation Sports Technologies offers clamping couplings to pair 1/2" to 3/4" EMT conduit, and 3/4" to 1" EMT conduit. Each coupling comes with a press-fit adapter sleeve to minimize mechanical stresses and reduce rattle. This article will assume that the reader is using this type of coupling to create their telescoping pole.
Ultimately, friction is what holds the EMT conduit in place and keeps it from slipping when the telescoping coupling is tightened down. If the weight of the object attached to the end of the pole is larger is larger than the friction force between the coupling and the conduit, the pole will slip. Tightening the hand knob on the coupling increases the friction force, which makes the pole less likely to slip.
We performed a set of tests to answer the question: how much do I need to tighten the hand knob of the telescoping coupling to hold X amount of weight? That is, how much torque do I need to apply to the hand knob to prevent the pole from slipping? In our tests, an adult was able to comfortably turn the hand knob with up to 9 lb-inch of torque, which means an adult user can expect our larger coupling to hold up to about 57 lbs, and our smaller coupling to hold up to about 52 lbs. (Note that these are estimates for performance, which depend on surface treatment, grip strength, and other case-specific factors.) Someone with less hand strength can expect their telescoping pole to hold the weight according to the trends shown in Figure 1 below. Remember that this maximum load weight includes the weight of the conduit itself, so if your sliding piece of conduit weighs 10 lbs, and your end-mounted object weighs 5 lbs, then your total load that pole must withstand is 10 + 5 = 15 lbs.
Figure 1. Maximum Pole Slipping Load vs. Hand Knob Torque.
EMT conduit surface preparation is recommended to maximize the holding strength of your telescoping pole: Wipe down the conduit with isopropyl (rubbing) alcohol with a paper tower and wait for it to dry, in order to remove oil, dirt and other contaminants. This will increase the holding force of the telescoping couplings.
If your telescoping pole will be held at an angle instead of vertically, it becomes easier for the pole to keep from slipping. As the pole is held closer and closer to horizontal, it becomes increasingly unlikely that the pole will slip along its axis. Let us answer the question: if I hold the telescoping pole at an angle of (30, 45, 60, etc.) degrees, how much weight can the pole hold without slipping? Add the weight of the mounted object to the weight of the sliding conduit, and then multiply that number by an "angle factor" to calculate the effective weight that the pole must withstand. That angle factor is shown in the following Figure. Say I want to hold the telescoping pole at 45 degrees; the corresponding angle factor value is 0.71. If the weight of the sliding conduit on my pole is 10 lbs, and my mounted end object is 5 lbs, and I hold the pole at 45 degrees, then the effective weight is (10 + 5) * 0.71 = 10.6 lbs.
Equation 1. Effective weight equation.
Figure 2. Angle Factor for the Effective Weight that the Pole Must Hold.
Takeaway:
Calculate the effective weight on your telescoping pole and compare it to the chart in Figure 1 to estimate if your telescoping pole will slip or not. If you have any questions about applying these calculations to your project, reach out to us at any time, and we would be happy to help advise you on your project!
Question 2: How Does the Weather Affect the Pole's Performance?
If your telescoping pole will be used outdoors, you should use a telescoping coupling that is explicitly UV-resistant - this is important due to how the ultraviolet (UV) light present in sunlight degrades plastics over time. To protect against UV light damage, UV stabilizer material is added to plastic. Without this added stabilizer, when exposed to sunlight, plastics tend to become:
Brittle (more likely to crack/fracture when under load)
Chalky in appearance
Discolored
All EMT conduit telescoping couplings from Elation Sports Technologies include UV stabilizer, to mitigate the harmful effects caused by exposure to UV light present in sunlight.
If you will be using your telescoping pole in hot summers or cold winters, expect the following changes in the mechanical behavior of your plastic telescoping coupling:
Cold - Increased brittleness, i.e. the coupling will be easier to break if impacted.
Hot - Reduced material stiffness, i.e. your telescoping pole will be more flexible.
Also note that EMT conduit is made from galvanized steel - this helps to protect it against rust. For further protection against rust, anti-rust spray coating can be applied to the conduit before assembling it with your telescoping coupling.
Takeaway: If you are using a plastic telescoping coupling to make a DIY telescoping pole out of EMT conduit, choose one which advertises resistance to UV light.
Question 3: How Else Can I Improve the Pole's Performance?
In addition to the tips already mentioned, you can further improve the performance of your DIY telescoping pole by using an inner adapter sleeve. All Elation Sports Technologies EMT conduit telescoping couplings come packaged with an inner adapter sleeve, and the benefits include:
Reduced pole rattle - If no inner adapter sleeve is used, the inner (smaller and sliding) EMT conduit's base can bang against the inside of the larger segment of conduit when the pole is moved.
Reduced pole flexing - Using an inner adapter sleeve reduces the lateral load on the plastic coupling, so that the inner sleeve carries some of that load. This reduces unwanted flexing of the pole, and helps to mitigate breakage.
For a given length, a pole made from 2 x couplings and 3 x EMT conduit segments will have a smaller collapsed length than a pole made from 1 x coupling and 2 x EMT conduit segments, which will make your telescoping pole easier to transport!
Figure 3. Expansion/Compression Diagram for Two-Piece vs. Three-Piece Telescoping Pole.
In addition, it is advised that you do not extend your telescoping pole further than 90% of its total potential length. Including this overlap between each pair of EMT conduit segments will maximize the strength and stability of your telescoping pole.
Takeaway:
To maximize the performance of your DIY telescoping pole, do the following:
Utilize an inner adapter sleeve to reduce rattle, and reduce the chance of breakage.
Using a 3-piece pole with 2 x couplings will allow your telescoping pole to be more compact for transport.
Extend your telescoping pole to no further than 90% of its total potential length.
Conclusion
With all the above tips in mind, you will be well on your way to creating your own DIY telescoping pole out of EMT conduit! All telescoping couplings from Elation Sports Technologies are engineered for maximum performance for your next big project. Check out our other blog posts for more assembly instructions and project ideas!
Thanks for reading! Come and check out our available products now at www.elationsportstechnologies.com/shop!
Austin Allen
Founder and Owner
Elation Sports Technologies LLC
