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.

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

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!

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.