Tensegrity Prisms etc 3

Basic car using Yakult straws as axles and frame.

Avant Garage

Car in Avant Garage

How the other half live, 4 wheel steering car and deluxe long 2-card garage

4 wheel steering car.

A couple of towers made from 4 sets of capped rods.  The one on the right has the rod ends close coupled making it stable, while the one on the left has the coupling rubber bands stretched very long and near the edges making it unstable. I made 2 videos showing how they react, here  is #1, and here is #2.

Some details. There is a flower at the top.

A tree.  I had to tone down the colour on this one, with multicolour rubber bands it was a bit over the top.

Self propelling rubber band car, here is the video.

Solidworks model showing basic hole size which can be adjusted for whatever rod you use (ie 3mm fibreglass, 3mm wood, Yakult straw, cotton bud) when printing the free downloadable model from CGTrader

Hi, I don't have many words to add here, but have made new versions of the models shown in my previous post, and this time used the more solid, free, downloadable model.  I added one or 2 tweaks, especially to the tower models.  Last night I made another type of self-propelling car, and plan to show that in my next post.

Regards

Steve Nurse

Tensegrity Prisms etc. 2

Hi, last time I wrote on this topic I'd gotten this far, making some tensegrity prisms using 3d printed parts and rubber bands, but ....

after a bit of random fiddling with the parts, I made this thing, and realised the tensegrity struts could also be wheel axles, if only the slots in the side were changed to the right diameter.

So by changing the part, I was able to make this basic car, and

........ this 4 wheel steering car, and

....... going back to the tensegrity prism designs, this tree, and

...... this tower.

Add a roof to the first prism, and you have an avant-garage, or at least an avant-carport, as in "Buckminster, where did you park the Dymaxion?"  "In the avant -garage of course".

Double garage

All together now!

Self-propelling car from the newer, larger, stronger version of the part.

On Your Marks, get set, go, here is the video!

Part in Solidworks showing centre diameter.

Hi, not much to say here, in pics above and on video, here are the results of further research, ok, playing around with my 3d printed tensegrity rod ends.  I plan to put a version of the part up on the net for free download shortly. Part 3 is here .

Regards

Steve Nurse

Asymmetric Surfboard

My asymmetric surfboard .....

started life as a carbon-fibre reinforced Trigger Brothers windsurfer.

At Spout Creek

Quite an old photo!

The half-template

The Asym bit. Rectangle marks the finbox position.

Hi

For more years than I care to remember, I have been a surfer, and have spent many holidays and weekends by the beach bobbing about in the water.  My family is very lucky to have access to a house at the coast, and for a long time Howard Hughes ran the local surf shof and I got boards through him.

Alan Atkins used to surf one of the local breaks and I admired his style, and he surfed these big long surfboards, up around the 8' mark and it helped his big wave surfing look effortless, so I bought a similar thruster surfboard from Howard.  Some time later I broke that board at Johanna, and I had broken a series of boards before that, and I was really sick of it so decided to use old windsurfers for my surfboards.  I bought one or two cheaply off Howard (from free for a creased one to $100 for some others, and I was sort of used to their size and floatation, having surfed 8' mals.

So old windsurfers have been my boards for the last 25 years or so (my son was in creche when I broke the board at Johanna, now he is married and buying a house ) and I still look out for them on ebay, and they are still quite cheap craftspieces from surfboardmakers of the 1980s.

My last board was a Trigger Brother's windsurfer with carbon fibre reinforcement and it worked well but was getting long in the tooth and leaking and going brown, so started looking for a replacement, and after reading articles like this one on Swellnet,  thought that I could get a Swallow tail board, and get it modded to be an Asym to suit me, a goofy cum switchfoot.  And that's just what I did, taking the board to Zak Surfboards in nearby landlocked Thornbury for the mod which cost me about $150, the same as the board cost me in the first place.

After a little bit of practice I got used to it and really like it now. But would now like to take the thing further.  My particular Asym only suits a goofy, but I am keen to take the idea further, making a double ended Asym with one end that suits a goofy and the other end that suits a natural footer.

So until a few days ago I'd done nothing about it but I was down the coast a few days ago, and had walked to the cliff with surfboard and wettie. It was too cold to be outside, let alone contemplate going out in the surf which was ok but a bit small, so after checking out the surf, then turning back without going in, walked along the cliff for a bit, lingering on the clifftop for a bit longer  to get a few more ocean glimpses.  And when I'd stopped to check out the surf again, I started chatting to a lady who turned out to be legendary surfer Gail Cooper, and we were talking all about windsurfers and asymmetric surfboards and even that I also design bicycles. 

So I got inspired, and started on the making path for the surfboard.  At the next opportunity, I traced the planshape for the Trigger Brothers asym and will get working on a double ender asym.  Zak's recommended Akushape software, and I will probably use that but first I plan to make a model of the board and fin using Solidworks and my 3d printer.  I will report on how it goes here at the design blog.

Regards

Steve Nurse.

Tensegrity Prisms etc.

Diagrams from Hugh Kenner's Geodesic Math....

show a few tensegrity prisms with 3, 4 and 5 sides: not all that clearly!

My 1st prism based on Kenner's instuctions, 9" timber struts with string 2/3 times as long.... and

The same thing with my printed version from

printed rod ends with fibreglass rod. 

Setting up a model.

Peeling the model off the tin

Result

Rod size

Model hole size, when you print, the whole model can be adjusted in size up or down to suit rods from about 7 - 10 mm.

The prisms can be imagined in a rolled-out form, it ends up a bit like a rope ladder without ropes joining rungs on the diagonals...

and then put into diagram form on 2d cad, the progression A to F shows fewer and fewer joining parts as the same rubber bands take the place of more tension members.

The struts started to look oversize on this model, so..

I made a different rod end.  This shows setting up a model on an empty plastic turps bottle....

with this result.

After a bit of tweaking, it looked like this,

and this,

and finally this!

Hi

For about a year and a half, I have been experimenting with 3d models and shapes, and somewhere along the line came across a reference to the late Hugh Kenner's book "Geodesic Math and How to Use It" (link is to google books).  My supervisor at Monash uni, Mark Richardson had incorporated geodesics and tensegrity into some designs for 3d printers and velomobiles, so even before hearing of Kenner's book I had some vague knowledge of geodesics and tensegrity, and their inventor, Buckminster Fuller.

So I thought I should know more, and lashed out and bought a copy (web link , but it may be possible to find pdf versions free online) and then put it away for a while, until my friend George came to visit to pick up a bike, and we somehow got talking about geodesics and I dug it out and showed it to him and said "I really should read it", and so I started.

But really the book calls for involvement, and on page 6 says the reader should start building models of the things. And so I did, but really, it was a bit tricky and fiddly using the recommended timber dowel and string, and I thought I could do better, so I sussed out some old hollow fibreglass tent poles from the shed, and measured them, and then designed some 3d printed rod ends to suit the diameter.  The resulting 3d printable file helps make tensegrity prisms but needs rods and rubber bands to complete them. The stl file is free and can be found free through Cgtrader here . Once you make a prism using the models, you realise that you can use fewer and fewer rubber bands to come up with the same result.

So results including an attempt to make a sort of system of reducing the number of rubber bands are shown above.  Eventually I started making models where the rods were clashing in the middle, so decided to redesign, this time using (back to the shed, which yes, has enough spare junk to build a moonrocket) 3mm or thereabouts solid fibreglass rod. The bottom 5 photos show the results, including (ta-da!) the wonderful application of holding a beer can.

This topic hasn't been exhausted by a long way, firstly, there are 166 more gobbledigook-filled pages of Mr. Kenner's book to plough through with models to build, and secondly, I have already diverged off with some rod-end inspired designs.  More next time, part 2 is here.

Regards

Steve Nurse

Upcycled Spool Clock

With me in the kitchen. Time for a cup of tea?

Detail from one of the clocks

Clock Numbers on the printer

Mounting the 3d printed numbers on the clock.

This is the printer spool with the clock and white painted hands. 

This setup includes an m8 bolt, nut and washers, and holds numbers between the spool edge and the centre hub bolt.  It can be used to teach basic mathematics such as counting and ordering the numbers from 1 to 12.

Config 1 shows (6 + 2 x 3 = 12)

Config 2 shows (2 x 2 + 2 x 4 = 12)

Config 3 shows 4 sets of 3

Config 4 shows 6 set of 2

The clockface can be left on a spool in the printer.  If the spool is feeding into the printer at 10cm / min and the filament is coming off at a diameter of 150mm, how long does it take for the spool to rotate once?  A bit later (you are printing an oversize pokemon-themed fidget spinner) the filament speed is the same but the filament is coming off at a diameter of 125mm.  How long to rotate now?

Pic from Thingiverse.

Hi!

Every roll of 3d printer filament comes with a spool, and unless you do something with it when its useful life comes to an end, it gets thrown away, or at best recycled into other plastic products.  But a filament spool can be quite a fine thing, and it’s good to at least try to reuse it by making it into something else. 3d printing provides opportunities to do this. If items made with the spool can be sold for more than the costs of the filament  and other parts, then your 3d printing pays for itself almost immediately.  One filament seller who has embraced this idea of reuse is Eumaker who have prehacked their spools so they can be made into coffee capsule stands, coathangers and other items.

 

So here is something you can make with your printer using a filament spool.  The filament I get comes from 3dfillies, if you get filament on different spools, you will have to adapt the designs I have uploaded here on Thingiverse. The 3dfillies spool can be broken down into 3 parts, there are 2 sides and a central cylinder.  Breaking down the spool into 2 sides can be done using a screwdriver to press the locking tabs on the sides away from the holes in the cylinder so the tabs can be moved away from the holes and disengaged.

 This project is a clock which can be made in different ways and used as an education tool. The clock numbers hook over the edge of a spool side, and are held in place by rubber bands.  In the middle there is a round adapter piece which holds a clock mechanism.  These are available for about $16.00 each from Jaycar in Melbourne, but they can be much cheaper (from $1.00 each) from ebay, ali-express and other online sites.  The mechanism I bought only included black minute and hour hands, which made it hard to read the clock because of a lack of contrast, so I used liquid paper to paint the clock hands white.  A clock that you can tell the time from!  Wow!

 

The 4 clock configurations shown above can be used to teach students about factorisation, sub factorisation and counting. All factorisations of 12, ie 1 x 12, 2 x 6, 3 x 4 can be demonstrated, and 4 sets of numbers on 3 rubber bands is different to 3 sets of numbers on 4 rubber bands.

12 is a highly divisible number and it would be interesting to make a clock with 11 numbers filling the 360 degree clockface.  The "11" clockface can be divided into number sets, but only by addition, not by multiplication.

Permutations and combinations can be demonstrated as well.  If you look at Config 4, the numbers can be assembled on the spool in 12! or 12*11*10*9*8*7*6*5*4*3*2 different ways and the colour arrangement can be put together in 6! or 6*5*4*3*2 different ways. 

This will be the first of several posts about my 3d print designs coming up in the following weeks.  My designs will mostly be free, but I'd like to make money from them somewhere along the line, so will be charging for key designs through Cgtrader .