3D printed rim Joiner

 

The Platonic Solids, image courtesy of https://commons.wikimedia.org/wiki/File:Platonic_solids.jpg

Setup of joiner for cube - see line 2 of diagram below

Cube (table without tabletop) with one side missing. This is sturdy enough but it rocks a bit. Any bigger and it wouldn't fit through the door!

I thought this would be ok but it was a bit flimsy

Tetrahedron with now very rusty steel joiners

New joiners with internal washer spacers set up for cubes. This was not the final design for the bolts. The final design is in the pic below.

Joiner schematic

Some time ago now, I started experimenting with joining circular waste objects together to make mathematical objects like Platonic solids. The principle is that, aided and abetted by 3d printing or other joiners, circles can be made to act like regular polygons (squares, equilateral triangles, regular pentagons) in models and other constructions. Initial work started with beer cans and cds where joiners form a free-to-move hinge between the circular faces. Eventually I managed to publish a maths education paper on the subject.

Bike wheels are circular objects too, and for several years I've been using them in sculptures, however when this article was written, the joiners I'd used were timber or steel.

All that changed a few weeks ago, after I had gathered the time and energy to complete a bike rim icosahedron.  Although the build was successful, the parts had taken a considerable amount of work (sourcing, cutting, drilling, deburring, painting) to complete, and the results still weren't safe for my grandkids to play with, so it was back to the drawing board, or  rather, back to the laptop PC and 3d printer.

 A 3d printed part that would do the same thing as the steel icosahedron joiner could have lots of advantages compared to the steel parts:

* Able to make one part that's versatile for different platonic solids and prisms without extra effort

* Rustproof.

* Could most commonly be made from strong PLA+ material

* No need for deburring as 3d printing is with a 0.6 nozzle and edges are not sharp.

* Able to be resized during printing so steel or plastic or other pipe fits inside. This leads to greater strength and the possibility a pipe connecting 2 joiners together as per the photo below.

Construction showing plastic pipe used in a tetrahedron

However on the other side, 

* May not be as strong as steel, so care needs to be taken with assembly, and it is recommended to use rims without spokes or hubs in the structures. This is because full bike wheels may be too heavy for the 3d printed joiners.

* Resistance to UV rays is really not known. 

* Resistance to heat, ie 45C ambient temperatures is really not known.

* Extra care needs to be taken with building the full icosahedron, as without careful extra support, the structure weight may overwhelm the 3d printed joiners. To get around this, try building a yurt! In this case, it  is an icosahedron with 5 sides lopped off as shown below. The 5 rims touching the ground can be pegged to the ground for extra stability.

Just add a cover and you have a yurt or cubbyhouse!

For builds with this part, I started on a cube, and then built the icosahedron cubby house. Along the way, I refined the fasteners used for the construction, so that the bolt ends are inside the joiners. This makes the construction safer. The idea of a printed pad for the washers in the assembly worked well right from the start. 

Here is the list of parts needed for each join (see photos below) . This assumes you are using a rim which is like the ones I usually use, a 27" steel rim which is not hollow and has a low profile. High profile, aero 700c rims might need longer bolts.

3d printed rim joiner                   1

3d printed washer spacer             2

6mm hex head screw, 30mm       2

6mm washer approx 17mm od    4

6mm nyloc nut                              2

6mm spring washer                     2

 

 

The next shape I plan to build is an octohedron in the front yard.

Regards Steve Nurse

In this photo, the bolts are positioned about 138 degrees apart. This angle is set in the way the joiner is made, and matches the icosahedron angle and bolt positions shown in the table above

 Update Jan 27, 2025

I have put both the joiner and washer pad up on thingiverse as downloadable files. Here is the link, https://www.thingiverse.com/thing:6927455 

Regards Steve Nurse

2024 Icosahedron

 

Icosahedron at its current site

On the road

Et voila

Next step

Work in progress

Building in front yard

Drilling jig, drilled joiner, and painted joiner the single thru bolt.

Deburring inside using lathe

Dodecahedron made with the same techniques

Bringing home the wheels

Dumpster at a local environment park's bikeshed

Late last year I attempted to make an icosahedron sculpture from old bike wheels and failed but was not put off! I had tried to make joiners from cheap, weak wood, and also did not bother despokifying the wheels I was using. All this combined to make the thing collapse under its own weight.

So this year, when I was ordering some cut steel tube for shelving, I also ordered some tubes for icosahedron building. As well as getting the steel cut, the parts had to be drilled, but were also deburred, degreased, dried, primed and painted. The drilling was at the dihedral angle for the icosahedron of 138.2 degrees, and I 3d printed a jig that let me mark out and then drill the holes. Quite early on I realised a shortcut was possible and used a single bolt (instead of 2) in each of the 30 joins between rims.

When all the parts were ready including wheels with spokes removed, I started in, and managed to build an icosahedron in my front yard before Christmas (complete with lights and dangly things and windmill) . Then I transferred it to M's house in time for Christmas lunch. For short distances it can be busted into 3 rings of 5 with 5 loose wheels, and the rings fit (rather conspicuously) on the top of my small car. Not great for longer distances though!

With this success under my belt, I changed the icosahedron into a smaller "glamping" hut which seems to be quite good and could be slept in.  My grandkids were amused by the structure, but the general consensus was that the joiners were still too sharp for kids to play with it as a cubby house. It was back to the drawing board again but this time it wouldn't take a year!  I've been gathering bike wheels again, and a new design is almost ready! More in next post.

The Cleveland Connection

 

For the last year or so I have been clearing out my mum and dad's house in Kew, as my mother died last year after a short stay in care, while Dad is in aged care due to physical weakness. My brother-in-law John and his wife Lynn helped me significantly with removing items from the house and taking them to Op Shops (Thank-You!). This included a large number of books.

Long after I thought all the books were gone, and amid a family kerfuffle about who was to attend a Christmas gathering (if you want to start organising something do it by email and not by word of mouth!) Lynn rang me to say she had rescued a few photos and personal items from Mum and Dad's stuff. I was volunteering at the Wecycle bike shed at the time and Lynn offered to drop everything off at my place, which she subsequently did. I stashed most of the photos in with the large box of other photos that came from Mum and Dad's place, but a ring bound booklet attracted my attention.

It took a while to work out what it was - really it seemed like a series of curriculum vitae and recollections from a group of Melbourne doctors called The Cleveland Fellows. It is full of source material from doctors without much connecting narration, but after taking it to Dad to read (he had forgotten its existence), then discussing it with him and reading it again myself, I can fill in the gaps a bit.

The story goes back to the Second World War where a US Army medical unit called the fourth general hospital established itself in Melbourne. A wikiPedia page devoted to this unit is at https://en.wikipedia.org/wiki/4th_General_Hospital_(United_States_Army)  , and this page along with its references were part of my research. The unit arrived in Melbourne at the end of February 1942 and on 12th of May 1942 the unit moved into the Royal Melbourne Hospital building. The booklet I have was compiled by the physician Tom Hurley for a 60th anniversary dinner to commemorate the unit’s occupation of the Royal Melbourne Hospital.

Subsequent to the fourth general Hospital unit returning to Cleveland, Melbourne doctors applied for and were sponsored to leave and work in Cleveland for a year. These exchanges took place between 1949 and 1991. Doctors were of my dad's generation (Born 1931) or slightly older through to the most recent visitors who were not much older than me (born 1960) .

 The organizer of the dinner was the physician Tom Hurley (Dad recalls endocrinologist Ian “Skip” Martin was also an organiser) and the dinner was held on 9th of May 2002. Tom had requested curriculum Vitae and recollections of Cleveland from all who attended and compiled the replies in a booklet, presumably distributed to attendees. Contributions range from curriculum vitae only to single page letters with a paragraph or two of Cleveland recollections to 2 or 3 pages of Cleveland recollections. Most interesting were accounts about cultural life in Cleveland including playing and hearing music, and in Melbourne, where one doctor laments AFL club Essendon’s lack of form!

On the Melbourne side of the exchange Pincus Taft is mentioned often and I recall Dad was an associate of one of his relatives,  the dermatologist Eric Taft. On the Cleveland side Max Miller who was concerned with diabetes is mentioned often, but I couldn't find him in the list of officers in the unit's history which is here https://web.archive.org/web/20120718035458/http://www.med-dept.com/unit_histories/4_gen_hosp.php  

It has been interesting and fun to read this book and to unravel the small mystery about it. It's been a good way to connect with my Dad. My son is a  medical researcher with overseas contacts and I plan to pass the “Tale of two hospitals” on to him soon. He had previously snapped up several medical histories and medical biography from Mum and Dads collection.

 

By Stephen Nurse, eleventh of November 2024

Icosahedron Sculpture

 

Hi

For a few months, I have been working on a bike rim icosahedron  (20 sided figures which nominally use triangles as sides), with the starting point gathering enough 27" bike rims to do the job. Before Christmas, I started putting one together in my girlfriend Mary's back yard, my own backyard having too much cr&p (junk in the form of other bike sculptures mostly) in it! 

As well Mary was having a Christmas lunch, this could be the star attraction - along with Mary's excellent cooking of course!

To join the bike rims, making edges was the first step, and I did this by drilling wooden joiners at the dihedral angle using a 3d printed jig. These were put away for a few weeks till I had time to build anything. Finally, close to Christmas, all the wheels and tools and edges were bundled in the car.

Assembly was only partly successful and partly done before Christmas, the bike wheels weigh enough to rip apart the joiners. But Christmas lunch was a complete success with Mary, me and 5 guests laughing and eating and reading the daggy Christmas Cracker jokes almost continuously for several hours. 

Graham had arrived completely soaked by the rain on recumbent bike and was given a new set courtesy of Mary. Later he rode home in the rain again and even later still returned the clothes, dry washed and ironed to Mary!

I will work on another joiner for the icosahedron, this time from steel tube and wing nuts, and may remove the spkes and hubs from the donor wheels.

PS 3 wheels make quite a neat unit, but when the units are joined up using spoke holes, they act like dodecagons. I've made a pic of this using 20c pieces.Will report further progress.

This link is for a completed sculpture made with 1 rim per side.

This link is for a completed sculpture made with 3 rims per side.

Bike Rims Article

 

Cycling is about staying fit and using resources wisely. Recumbent bike makers can even reuse old bike parts to make new machines – its been very satisfying for me since about 1987!  Recently I’ve branched out to use old bike wheels in non-recumbent things.

 I have a 3D printer and a few years ago developed some designs to join CDs together  to make geometric shapes (see article here). CDs are round just like bike wheels, and so I've gone on to use CD joining techniques to make bike wheel versions of the mathematical shapes called platonic solids. These include tetrahedrons and dodecahedrons and I am working on a 20 sided icosahedron.

 

                 

 

Inspiration for the shapes comes from the bike dome at Ceres in suburban Brunswick– I don’t anticipate building anything that big and my designs might be a bit more orderly, but the dome shows what can be done. The Trisled newsletter recently featured a similar community-built dome at Meeniyan in Eastern Victoria.

 

A few weeks ago, I gave my small tetrahedron table away to my friend Simon for his 60th birthday and was able to transport it to his place by bike. That was on the way to the Wecycle bike shed where we volunteer. At his party later that evening, it was set up in his garden, staked to the ground as its base is not very big and its prone to tipping.

 

 

 

A larger tetrahedron I made uses a raft of 3 bike wheels bolted together to form a side of the 4 sided tetrahedron. I’ve had this for quite a while and have transported it by trike and trailer. I’m not sure if it qualifies as a road train or pantechnicon, but this is a 14 wheeled vehicle!

 

From Heidi "Here

That’s a fun story – made me chuckle. Here’s a pic from the day.

Thanks for letting me use the sculpture!

Cheers

Heidi

Once I took it to a community bike day and it was noticed by Heidi Marfurt who is the Darebin Council’s sustainable transport officer. Just a few weeks ago Heidi wanted to use the sculpture at another community bike day, The Rezza Bike Day.

 

The sculpture uses the wheel centres as axles for small windmills which also use cds as blades and a 3d printed hub. That is just a fun thing but shows what can be done with recycling. When Heidi asked me to loan the bike sculpture I decided to extend it and worked out I could make something quite high (about 1.8m) without using only 6 extra bike wheels.  The pattern is shown in the picture – as long as there is part of a wheel on an edge, then the outer triangle shape can be made, even if the outer triangle is not completely filled in. I needed 2 goes of putting it together to get the pattern right.

 

                 

 

 

Actually loading the sculpture sides into the Heidi’s car involved Tetris-like manipulative skills and in the end only the smaller tetrahedron would fit in. A few days later Heidi came back to my house with the sculptures and they were festooned with ribbons and a couple of the CDs had broken off. I was thinking it's a bit like those stories where a garden gnome gets kidnapped and sends postcards from Queensland and then turns up months later with a suntan and tattoos! Heidi was quite sick of loading and unloading the sculpture in cars by this time, but the whole event went well and the sculpture was appreciated.

 

Most recently, I used the frame for painting a crank arm on a Wecycle repair bike. This was to turn a silver right hand crank black, as the original black one had a stripped thread. The other hanger in the back yard is the dodecahedron, used as my regular clothes line.

 

Sofar I’ve been making wheel joiners (they act as platonic solid edges) from steel tube, pvc pipe or wooden dowel. When there’s a narrow angle (ie on tetrahedrons), the large steel tube seems better, and the drilling can be marked out with dividers and a centre punch. For larger angles like on a dodecahedron, I use the dowel, and drill with the help of a 3d printed jig. This wikepedia page  

https://en.wikipedia.org/wiki/Table_of_polyhedron_dihedral_angles  gives the relevant angle between faces, it is called dihedral angle in geometry-speak.

 

 

 

I plan to go on building the bike wheel sculptures, and mostly use 27 inch steel bike wheels. The 27 inch bikes are now of an age with the are often being thrown out and are not worth restoring - or are only worth restoring if the wheels are swapped out - so they end up in the recycling dumpster at Ceres. I can load up about 4 wheels at a time on the back of my bike, even more if the spokes have been removed. Also I know Serge, the volunteer who does most of the stripping of unwanted bikes at Ceres. We stop and have a chat while I’m there, and swap notes about the Wecycle and Ceres Sheds and our bikes.