Can you really 3D print trekking poles?! Some of the best ideas come from making ridiculous concepts happen. And yes, you can indeed create trekking poles with only a few dollars' in aluminium tubing and some rubber chair feet... and a 3D printer!

Read on for the rationale and features of the design, or skip ahead to the printing and assembly instructions...

A FEW DESIGN GOALS:

• * Adjustable length. This is the bit that makes things complicated. The pole needs to support the weight of a person down the long axis without being compressed to a shorter length, but while still being easy to adjust.
• * Robust feet. It should be possible to fit standard rubber feet onto the poles, and have force distributed evenly across the feet.
• * Ergonomic handles. The handles should look like handles, and not just tubes.
• * Strong straps. The handle straps, which take the majority of force, need to be anchored firmly.

IN-DEPTH IN DESIGN

From a pure printing perspective, it goes without saying that all parts are designed for easy printing without supports. But, let's get into the functional aspects of the design, and the problems they're intended to solve!

Adjustment mechanism. Let's start with this, because it's the most important element of the entire design! Conceptually, this works by using a screw attached to the outer to push wedges down against the inner pole, and thus hold it in place with friction. It took a few different designs to refine the design to be tough enough, provide enough friction, and still be easily printable (and tolerant of print variances).

You'll notice that the two wedges are attached to a kind of half-ring. This gives the screw knob more surface area to push against. However, the two are separate so that they can move inwards (and towards each other) against the inner pole, without the ring working against that, and without having to rely on assumptions about the amount of flexibility in the materials used.

Early prototypes used three wedges rather than two. However, using two wedges meant the screw thread sections could be larger and stronger. It also meant that the wedge pieces could be larger, and easier to handle.

Now, the feet! The important part here was ensuring that the bottom of the pole wouldn't cut through the rubber feet like a cookie cutter, and so the adapter is really just a thick chunk of plastic with reinforcement outside and inside the pole.

Last, but not least, the handle! The most important consideration here is the strap attachment. As mentioned below in the assembly instructions, the strap needs to be looped around the metal pole itself, for maximum strength. It's possible to print a handle that's strong, but it won't ever be as reliably tough as the metal pole. The pole is deliberately off-centre inside the cavity for the strap, so that there's room for a knot or sewn section of the loop.

GATHERING COMPONENTS

Poles: I bought 2x 1m lengths of 16mm (outer diameter) aluminium tubing, and 2x 1m lengths of 12mm (outer diameter tubing), both of which had 1mm walls. It was cheap and they're nice and rigid. I cut each tube down to 70cm because that suited the range of adjustability that worked for my height (I usually use 120cm poles). These tubes cost me a total of $12 here in Australia - I'd expect them to be much cheaper elsewhere in the world!

Feet: Good old 16mm chair feet from the hardware store. Very cheap for a pack of 4.

Printed parts: Now, these parts are likely to take abuse, if not directly then from being dropped and bashed around. So, you'll probably want to use a high infill percentage. I used 100%, but I also printed in PLA. There are obviously plenty of tougher materials that might do better. No supports required.

Straps: I cut some webbing from an old bag strap and sewed simple loops.

ASSEMBLY

Most of this will be obvious! The only thing that could really cause a problem would be putting the feet onto the lower poles before running it through the upper pole from the top, as the foot is intentionally too large to fit, to prevent it getting lost inside when collapsing the poles for transport. Anyway, follow the steps, and Nothing Can Possibly Go Wrong:

1. Cut poles to length, as discussed above. If in doubt, 70cm for each length is probably reasonable for most average heights. Take care to smooth off the cut surfaces, or else the printed bits won't fit!

2. Fit the main adjustment bracket to the bottom of the outer (upper) poles. Glue them in place and let the glue dry.

3. Fit the inner guides to the inner (lower poles). Glue those in place, too, and let that dry.

4. Put the straps through the hole in the handle, and then put the handle onto the top of the outer pole. Make sure the strap goes around the pole, inside the handle, so that it's anchored around the metal, not just wedged into the plastic. That way, the strap strength depends solely on the strap itself, and not on anything plastic. Glue the handle into place so that the pole is just below the top of the handle - remember, we'll be screwing down the cap over the top, so don't let the pole stick out and obstruct that.

5. Drop the inner pole into the outer pole via the handle end so that the inner guide is at the top. The guide stops the loose end of the inner pole rattling inside the outer pole. The bare end of the inner pole will protrude from the bracket we glued to the bottom of the outer pole. Pull it through a little way!

6. Take the adjustment wedges, and slot them into the adjustment bracket. Then, take the adjustment knob and screw it into place. The middle section is now complete.

7. Screw the caps onto the handle tops - we're finished with the handle end, now too, which just leaves the feet.

8. Push the foot adaptors onto the bottoms of the inner poles. If you like, glue them on, though if it's a tight fit they should be fine. Push the rubber feet over the top of the adaptors, and we're done!

Now you're good to go! Happy trails!

This object was made in Tinkercad. https://www.tinkercad.com/things/7b8j5J1bBPg

Uploaded to the #Tinkerfun contest, too!