Wood-Only Kart Race Inspires Fancy Wooden Bearings

The mountainous Italian town of Artena holds an annual soap box derby for wood vehicles – and they mean 100% wood, not a speck of anything else. Fierce competition led [Alessio] to engineering and CNC fabricating these gorgeous wooden roller bearings for the wheels to give him an edge.

Thousands in costume attend the renaissance faire known as “Palio delle contrade di Artena”, and the popular wood-only race is called “La Carettella.” The karts are operated by a two-man team: one in front who brakes, the other in the rear who hops on and off to push as needed throughout the course. There appears to be no steering from the wheels** so turning is also a two-man effort. The wooden levers dragging on the pavement provide some steering from the “driver”, and the push-man often manhandles the entire rear end, drifting where necessary.
HAD - Carettella2The course also includes full-width obstacles like hay bales. Teams are divided by community or “contrada”, and it was [Alessio]’s team captain who came to him with the special request of roller bearings. Unable to find evidence of other wooden bearings, [Alessio] knew he would have to invent them himself – so he did.

HAD - Carettella1The roller bearings are built into the wheel hub and look just like ones made from hardened steel. [Alessio]’s cellulose of choice was Lignum Vitae, a self-lubricating wood that is also the hardest grown and available for sale (among those labelled “ironwood”). After drafting the wheels and bearings in Rhino they were cut using a 3-axis CNC milling machine and assembled.

Sadly, during the race [Alessio]’s driver managed to crash the kart – twice, maybe it was all the extra speed – so they did not win this year’s Carettella. [Alessio] has his eye on victory next year – enough that he is keeping the actual specs of the design to himself.

Below are 11 magnificent seconds of [Alessio]’s kart run, and some footage of the Artena festival. (Skip to 1:40 for the racing).

** Update – As several astute readers have pointed out, there is clearly steering. The front wheels are mounted to a plate that pivots in the middle of the kart, as controlled by the driver’s feet. Oops.

*** Update – One of our Italian readers has translated that the official rules allow only for a metal steering pin, likely to prevent teams from kartwheeling if a wooden one snapped. Also, while metal parts are not allowed, fasteners like nails and screws are, as subject to judge’s inspection.

47 thoughts on “Wood-Only Kart Race Inspires Fancy Wooden Bearings

          1. … Not until I looked it up.

            Apparently the wiki used to say it means “Sit on my phallus.”

            Apparently this is only in the region of Sardinia. Not all of Italy.

            Apparently many people from Sardinia have never even heard of this.

            Apparently in modern culture everyone is well aware that it’s a sign of approval, it’s on Facebook, everyone watches Hollywood movies and TV.

            What a delightfully obscene double-entendre coincidence I wish I could take credit for.

    1. It’s possible that I was wrong, but I looked, and I couldn’t see evidence of it. I watched a handful of other races and I don’t see the wheels turning at all, either individually or on a central pivot.

      I’m curious now, where do you see them pivoting?

    2. Never been to Artena, I’m from north italy, anyway, I checked the Game Rules here: http://www.artena.wli.it/palio.htm
      “La carettella dovrà essere costruità interamente in legno, mentre il perno anteriore di giunzione in legno o in ferro, inoltre chiodi, bulloni e viti in ferro…. Sulle carettelle si effettueranno dei controlli…”
      … Summarizing: The “carettella” must be built all in wood, the only part that could be iron is the steering pivot, and also nails, bolts and screws. The “carettella” will be chececk by judges.
      My 2 cent ;)

      1. I’ll trust you. Update #2 made to point out about the steering bolt. Had a suspicion about that one.

        More importantly: Does a thumbs up gesture in Italy have obscene, sexual connotations or do people know what it means in America? :)

    1. My town has an old granite quarry! Construction and machining issues aside however, I suspect there would be practical and legal issues involved in racing multi-ton brittle vehicles down a steep road lined with onlookers XD

    1. To be honest, it was a stretch to interpret my google-translated Italian with their not-as-a-first-language English.

      Maybe we should have met in the geographical middle and communicated in more passable French or German.

      “Not a spec of anything else” might have been an overreach on my part. I mean, they’re clearly painted for one. But then they are “only wood” enough to necessitate machining bearings from exotic timbers so.. *shrugs*.

      Now that I see that the front wheels steer I have to wonder if that pivot pin is also wood or whether they made an exception for something that would kartwheel the team down the pavement if it snapped. The helmets aren’t wood either if that counts.

      The important part in context is that renaissance constraints led to some modern/classical engineering blends we all appreciated :)

          1. I was joking. We’ve already seen that the steering pivot can be made from metal, and the rules allow for minor fasteners like nails and screws. You might be right.

      1. Since his website is down you can’t see, but, one of the big reasons for choosing Lignum Vitae was because it is naturally self-lubricating. Part of what makes me think that grease is not allowed or it wouldn’t’ve mattered.

    1. Lignum Vitae was (is?) used for the bearings for submarine prop shafts. Knowing that, I wouldn’t even consider another species.

      It is CITES protected, though, but I remember seeing a few “surplus” piles of Vitae. Probably from submarine prop shafts…

  1. The original caged roller bearing used appears in H3 – John Harrison’s third chronometer (The chap who won the Longitude Prize, and also credited for the invention of the bi-metallic strip – so two inventions in one item!). This fine timepiece can be seen in the Royal Observatory Greenwich http://collections.rmg.co.uk/collections/objects/79141.html
    I believe the rollers are made in Lignum Vitae.
    Ergo, we seem to have gone full circle (excuse the pun!)

    1. The problem I foresee is tyres/wheels splitting along the grain if the streets are too bumpy or uneven.
      I would hazard a guess that long strips of veneer glued around the rim could form a functional tyre, at least that way there wouldn’t be any directional grain which could fail.

  2. I love the wheels you made. Do you mind sharing how you imbed the bearing into it so securely?

    Would you be open to sharing your cad drawing as well? I can pay if needed. I am wanting to make a similiar project.

    Thanks

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