by LoboCNC Apr 11, 2015
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If anyone needs spare or replacement o-ring this company has them https://www.alliedmetrics.com/seals/o-rings/

Amazing and so cute walking :))
Thank you very much :)

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Yes, the hole in the side of the flywheel is for a 4-40 set screw that may be needed if you don't already have a tight fit of the flywheel on the shaft.

The remix for 1p coins works for NZ 10c coins as well.

Great item, very detailed instructions. Please update the parts list to mention 'nuts' for the screws. Seems like it was implied for everybody else except me - I thought the groves for the screws will be in the 3d printed parts.

This design does not use nuts. The screws thread directly into the printed parts. Note that 4-40 threads are much to small to 3D print, but the holes are sized so that if you force the screw into the hole, it will form its own thread in the plastic.

Great. Makes sense now that you explained. Thanks.

I have no pennies, can I substitute with cents?
The diameter of the cents should be 19mm

A penny diameter is 19.05mm, so your 19mm dia. coins will probably work fine.

No Pennies in Canada :( we ditched them.

Might be time for a border run.

I made it, that's why I am here, Not going back EVER.

What is the groove for on top of the flywheel running from the centre to the edge....?

There is a hole in the hub part of the flywheel for a set screw to secure the flywheel to the shaft. The groove is for allen wrench access.

I see, thank you for your quick reply. Am building one but made some slight adjustments. I have 4mm ID bearings and 4mm steel shafts so will make it fit them. (from RC motors) Also designing a flywheel for Australian 2c pieces. It will take 88 coins and should come out at around 480g. Will keep you informed....

Looking forward to seeing your "make"

The flywheel part file includes a conical hollow. Is there a reason for this geometry?

The hollow part is just to reduce the mass in the center of the flywheel, which in turn, maximizes the ratio of the rotational inertia to the overall mass.

That's what I thought, but wanted to make sure. My system filled that in with support material, which is a pain to dissolve (and I didn't want any leftover small plastic chips rattling around on the inside). I instead adjusted the interior to be "solid" with a bit of a gap for axle clearance, and am rebuilding the part at low interior density but thick wall. Should provide the same outcome.

Hi, the pdf-file is empty. Do You know why?
Do I something wrong?

The PDF file is a 3D PDF - you need to use a PDF viewer that supports 3D files.

Thank you for uploading this fantastic little toy...

But!!.....when you designed this, why did you use a currency as your weight ??? ... could you not have used something a bit more widely accessible to the rest of the world? Say... a stack of washers??? or better yet..maybe ball bearings ?

Check out the remixes - there are a number of adaptations for different coins around the world.

Or you could try putting 3/4" (19mm) dia steel balls in the coin slots. I haven't tested this, though, so it may not work.

I decided to use coins because they are much more consistent than washers and they have a better packing density than spheres. And if you are in the right country, they are more commonly available than either.

where do I find the pdf file?

The file gyroman3d.pdf is in the Thing Files, 4th from the bottom.

Thanks very much, LoboCNC! I just made one and I love it! I added a little pulley wheel and it can gain much faster speed. Initially it can hardly walk, now it can do a fine job :D https://www.youtube.com/watch?v=Y-aFRy1UGOM&feature=youtu.be

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Hello, LoboCNC

Mine went together perfectly, and it runs well, but i'm bummed out that it doesn't keep speed anywhere like yours, and doesn't even have enough to take a step :/ This bums me out a lot! Are your bearings greased or ungreased? Mine came greased and i feel this may be taking a lot of the energy away?


It's more typical for small, high speed bearings to have a very light oil rather than grease. If they seem gummed up, you could try soaking them in something like WD40 and see if that loosens them up. There's not much of a load on them so they don't really need much lubrication. You should also check to make sure that nothing is binding or rubbing anywhere (you shouldn't hear any scraping).

Super cool!!!!

In step 3 we put all the bearings in all the pieces, but then in step 10 it mentions putting bearings in again. I tried it the first way, putting bearings in on step 3 and found step 9 to be very hard. I measured the rod that McMaster sent and it measures 2.99-3.02 (depending on how firm I am with the calipers) and the bearings measure 2.99mm so it's possible McMcaster just sent me a rod that's a little too big. Would that 0.02mm be enough to make it impossible to use this rod and slide it through the bearings on the side piece?

Yes, you can definitely get problems with the shafts not sliding smoothly onto the bearing, both from the shaft being oversized and the bearings being undersized. (I had one set of 3mm bearings that wouldn't slide over the same shaft that worked fine with a different set of 3mm bearings.) Usually, though, it is pretty easy to reduce the shaft diameter by a tiny amount with some 400 grit emory paper. I'll put the shaft in a drill and then sand a bit and then test with a bearing until the bearing will just slide over the entire length.

I sanded them down, but I still don't quite understand what happens in step 10. My side of the eccentric is only deep enough for 1 bearing on the side (2 are in the middle - the ones put in on step 3), but it sounds like step 10 wants you to put 2 bearings on the side as well?

In step 10, you have one bearing that rides in the slot in the eccentric, and the second bearing rides in the slot in the side piece. The two bearings end up side-by-side, but they are sliding in slots in different parts. If this is not clear, look at the Gyroman3D.pdf file. With the 3D PDF, you can selectively hide some parts (or even make them transparent) so that you can see what's going on inside the assembly.

Side note for anyone outside the United States:

McMaster Carr do not ship anywhere outside the US unless you are an established business. This means that anyone from countries other than the US won't be able to source any parts from McMaster Carr. Unfortunately I can't find the gaskets anywhere on Ebay and such websites, so I'll be improvising with something.

You can now collaborate on a thing and get help on customizing a thing with this App:http://www.thingiverse.com/app:796

I just remixed this for any Aussies who want to make one with 1 cent coins! http://www.thingiverse.com/thing:858508

Gyroman - AU 1c Coin Compatible Flywheel

Quick, someone try to get this to work with LEGO bricks! - Brilliant build and design. Perfect video too.

Be careful selecting your pennies.

  • Mass of a solid "copper" (95% copper, 5% zinc from 1962 to 1982) penny = 3.11g
  • Mass of a clad penny (97.5% Zinc clad with copper from 1982 to present) penny = 2.5g

That's a significant difference. Note the overlap year; 1982 had a mix of the two in production. Make sure you distribute the old pennies evenly, if you have them.
These numbers are for the U.S. cent.

Thanks so much. SCIENCE!

Could you please upload the coins flywheel in dxf or another editable format? Thanks!!!

I've just added the Solidworks files flywheel.sldprt and retainingring.sldprt for those wanting to adapt this for other types of coins. Note that the total mass of pennies I used is 260g. Generally, the more mass the better.

+1, I'd like to do this with Israeli currency :)

It would probably run for months if you sent it on a Mars expedition.

Super cool. Even just swaying back n forth was fun.

are those coins the same size as 0.01 euro?

The US pennies are actually closer in size to the 0.02 euro coins, and I've just added a version of the flywheel with a slightly smaller diameter so the 0.02 euro will fit snugly. Also note that RobertCL has done a flywheel remix for 1p UK coins (http://www.thingiverse.com/thing:794106).

Gyroman - UK 1p Compatible Flywheel

You mention 4 O-rings 1/16" thick x 1 7/8 OD but the o rings on the foot don't look the same size as the two used on the flywheel mechanism. Is this an error or do they stretch that much?

No error - all the o-rings are all the same size. The ones used for the belt drive reduction are stretched quite a bit. You may be able to use larger ones for the belt drive that are not stretched so tight, but the 1 7/8" ones were the largest available in my local hardware store, and they seem to work. They are pretty cheap, so you could try some different sizes and see what works best.

Didnt know o-rigns could be stretched that much, i guess its not the same kind I use on my pool

Thanks for clarifying! and Thank you for the model!

That's a brilliant design! And great job on making it printable

Excellent !!!! Love it!