Peter Nolan

Thanks for the suggestions, but even when you delete the image (both the inline version and the attachment) it just reappears after you accept the edit.

A little while ago I became interested in some slightly unusual gear ratios (for a few reasons covered below). More recently though, I gained access to a laser cutter, and hence the ability to make custom lego gears. With this in mind, I decided to work out all the possible custom gear combinations that will fit on a standard technic beam (ie all the combinations where the centre-to-centre axle distance is a whole number of studs). I found the website https://www.cailliau.org/en/Alphabetical/L/Lego/Gears/Dimensions/ handy for figuring out the meshing. I'm not sure if this is of interest to anyone else, but here is what I found: One custom gear with one standard gear (Standard gear, Custom gear, Ratio) 12 52 3/13 16 32 1/2 16 48 1/3 20 44 5/11 20 60 1/3 28 52 7/13 36 44 9/11 36 60 3/5 Two custom gears where both have a prime number of teeth (Custom gear, Custom gear, Ratio) 11 53 11/53 11 37 11/37 17 47 17/47 17 31 17/31 23 41 23/41 37 59 37/59 19 29 19/29 13 19 13/19 43 53 43/53 37 43 37/43 53 59 53/59 There are also plenty of 'loose running' combinations where the centre-to-centre distance between axles is only 0.5 mm off an integral number of studs. I tried one of these, and it seemed to work fine. Loose-running combos (standard gears in bold) (Gear 1, Gear 2, Ratio) 8 23 8/23 8 39 8/39 8 55 8/55 11 20 11/20 11 36 11/36 12 19 12/19 12 35 12/35 12 51 4/17 15 16 15/16 16 31 16/31 16 47 16/47 19 28 19/28 20 27 20/27 20 43 20/43 20 59 20/59 23 24 23/24 23 40 23/40 23 56 23/56 24 39 8/13 24 55 24/55 27 36 3/4 28 35 4/5 28 51 28/51 36 43 36/43 36 59 36/59 39 40 39/40 39 56 39/56 40 55 8/11 55 56 55/56 SO the big question is, why would I be interested in such things? The first is that a while back I built a 'phase revival' machine (video below). In this situation I wanted a ratio close to, but not exactly 1:1. In the video I used 20:24, which means that the first cog has to rotate 7776 times before all the parts line up again. If I used a custom ratio of 39:40, and had 11 modules instead of 5, it would take 10 billion years (rotating the left-most gear at 1 revolution/second) before all the pieces realigned! I'm not quite sure why, but the idea of a machine that takes the entire lifetime of our sun to reset is appealing! And now for the prime numbers... I've been interested in making lego spirographs recently, and the key to interesting patterns is the lowest common multiple of the two gears. If you have a gear with a prime number of teeth, you are pretty much guaranteed of getting lots of 'knots' in the design. In the second video below, I used a 43 tooth gear meshed with a 36 tooth gear. To actually make the gear profile, I used https://www.festi.info/boxes.py/Gears?language=en with a modulus setting of Pi (3.14) to make lego compatible gears. You also need to tweak the burn correction depending on the cutter and material. I also set 'profile_shift' to zero. I suspect that a little more fine-tuning would be required to get the best result, but this is a good starting point. I hope that someone else finds this interesting! Ahhhrrgh. I can't delete the table below! Please ignore....

Just worked out some more gear combos--haven't figured out how to post html though... Also haven't figured out how to delete comments--please ignore this one.

Hello! I'm a first time poster in the Technic forum, but thought that my inverted spirograph might be of interest. Rather than move the pen, I used a planetary gear setup to move the paper. Different gear combinations give different results, as does the pen position. The pen-holding frame is made up from a lot of 2 x 4 bricks, but the guts of the machine is a hard plastic wheel with internal gear teeth (I'm not sure of the correct name, but this is the part I used: http://www.bricklink.com/v2/catalog/catalogitem.page?id=83393&idColor=11#T=C&C=11). Sadly the spirograph has now been dismantled--my son needed the parts for a Chima vehicle... Enjoy!

Hi Everyone, seeing these comments got me thinking about what the different gear ratios would do. I've put together a table of all the possible gear combinations and the resultant number of points in a spirograph pattern. I've treated the 14 tooth gear combinations separately, since these can only mesh with double bevel gears (as far as I know). The maximum number of points is 18, when you rotate a 36 tooth gear around a fixed 14 tooth gear. Apologies for low quality image--I had to resort to a low-res jpeg to get the filesize small enough.

Thanks for the feedback--yes, the linework was quite wobbly! The pens were Lego brand (with a cross-section almost the same as a 2x1 brick) but unfortunately they were a little undersized, which resulted in some play in the pen holder. If I was building it again I'd probably include some kind of locking mechanism to hold the pen. Cheers, Peter

Yes, you can buy replacement pinions. I did this for a couple of trains using plastic replacements. Looking on ebay it seems that only brass ones are available at the moment.You could try http://www.ebay.com/itm/Pinion-gear-Replacement-Gear-for-Lego-Duplo-Intelli-Locomotive-Module-0-4-9-/201444974931?var=&hash=item2ee70e6153:m:mYQEmFvY5iw4Oeq_D7I26Cg (no affiliation with me). As for how to actually get the pinion off, you could try looking at: http://www.papa-mach-ganz.de/pdf/PapaMachGanz-LEGO-Duplo-Intelli-Lok-Zahnrad-wechseln.pdf. It is in german, but the pictures are useful. Good luck!

Hi Jonathan, nice to see some more duplo ideas :-) My advice is to work quickly--before you know it, your daughter will be onto Lego...

Mike--I tried to send you a PM, but it failed for some reason. If you send your details to me by email or PM I'll organise postage. Cheers, Peter

Hi Mike, I think that component is actually an infrared transmitter or receiver. When you connect a smart carriage, it communicates with the engine via infrared. Will snap a photo when I get a chance... BTW presumably you are in Australia. If so, I'd be happy just to post you the circuit boards as spare parts--I suspect the chances of me doing any repairs on my engine are slim to none...

Hi everyone, Mike: you didn't buy that train off ebay in Australia by any chance? I recall seeing an item for sale that matched your description. As it happens, I have an open (non-working) intelli-train somewhere on my workbench at the moment. The problem with mine is a stripped gearbox, so the circuit board may still be OK. If you like I could take a photo of the circuit board for reference. Legogal: I'm pretty sure that all the different types of Duplo track fit together. I think that the main problem is that with the different lengths making a closed layout can be a bit tricky. On the other hand, having a variety of different length straight tracks gives you more flexibility.

Nice one Guy--I admire you dedication! Sadly I don't have enough crossovers to build these layouts, but it is interesting to see them and consider how they would work.

That looks really interesting. Seeing the physical layout, it looks somewhat modular. I wonder what would happen if you duplicated everything to the left of the rightmost loop (i.e. everything from the right-hand points inclusive) and connected it in place of the left-most loop? Or perhaps replaced the right-most loop with a mirror image of everything to the left?

Nice one!

Great, thanks for that--I'll pass it on.

Nice work Guy. I have a feeling that a Turing-complete layout is only a matter of time... Robert--my son too has been playing with regular lego a lot lately. He's very keen on the Lego Cargo train set, but he'll have to wait for some time yet for that one. As for whether the kids whose train sets we've been playing with will appreciate the finer details of APR, APV and computational duplo track layouts, who can say? However, the 11-year-old brother of my son's friend was rather taken with the binary counter layout. He is an aspiring coder, as well as a lego fan, so the whole concept was rather appealing to him. I've been thinking of a couple of new symmetrical Duplo track layouts that should be APV. When I next have the time (and the floor is free of lego) I'll try to make another video.

Thanks for that Guy

Thanks :-) It was quite a satisfying layout, especially with the train visiting all parts of the track without any intervention. I'm trying to think of my own (non-computational) layout that also visits all points. Ideally I'd like to come up with something symmetric--I'll post another video if I come up with something interesting.

Hi all, I've successfully made the 3-stage binary counter. I've put together a video which shows it in action: Enjoy :-)

A kids playground that doubles as a computer would be great--perfect for a science and technology centre. We have Questacon (http://www.questacon.edu.au) here in Australia, but yes, the child labour aspect may be problematic ;-) Back to Duplo though, I picked up three second-hand packs of the original sprung switches yesterday (6 switches in total). Once I get a couple more of the new switches I'll have enough to make the three-stage counter track. I made a two stage counter yesterday, but it has since been disassembled by my son... I'll make a video when I get a chance to put together a new layout (probably in a weeks time).

Wow, I haven't checked this thread for a while, and things have certainly progressed... Guy, I reckon there is an Ig Nobel in this for you... (http://www.improb.com/ig/ig-top.html). I don't have quite enough switches, but if I come across some on eBay I'll try making a counter layout.

Hi Sarah, I also tried my son with a mixels set recently and he really liked it. My son is still young, so Duplo is more developmentally appropriate. However, he really enjoys the extra play value of the Lego sets. At the moment a good solution is that do most of the building if he gets a new Lego set, which he then incorporates it into his imaginary play. He also likes tinkering with, and repairing, the sets even if he can't build one from scratch. Oddly I found that the Technic motocross bike (42007) to be really good--it was an interesting build for me, but a good sturdy toy for my son (since all the technic pins hold it together very securely).

I was interested to see the new design for the 24-tooth gear in section 5 of 'Evolution of shapes'. I remember that the centre portion of the old design often broke--I guess that is why the design changed. The advantage of the old design though was that you could fit an axle in the offset position to make a crankshaft.

Wow--that's a lot of work. Interesting reading. You are right about the required tolerances for a good fit. I made a few custom pieces of Duplo on a CNC mill, and it was quite tricky to get a good fit. Too close a tolerance and the parts bind, and too loose and they won't stick at all.

Hi Robert, Thanks for looking over my diagram. Yes, that is correct--I had assumed that the main layout was APR, but forgot to explicitly state it In that case I think I am happy with my contribution to the Duplo train track layout/design field of study Yes, I see your point. Although if only one type of trapping loop exists, and only one such loop is found in a layout, then the rest of the layout would have to be APR. In practice I suppose the difficulty would be finding the trapping loops in the first place--I think it would be much easier to use your LiveCode program. However, if you wanted to make certain that any loop is APR you could add a section like this: This arrangement of three switches all joined output-to-output is one of the aesthetically pleasing things you can do with Duplo track. That does sound like an interesting approach. Since there are only three types of connections between switches (input<-->input, input<-->output, output<-->output) I wonder if simply counting the different types of connections would tell you much about a layout? I suppose that the direction of travel of the train would be important too, which would complicate things.